Red Knot (Calidris canutus): COSEWIC assessment and status report 2020

Official title: COSEWIC assessment and status report on the Red Knot Calidris canutus, islandica subspecies (Calidris canutus islandica), roselaari subspecies (Calidris canutus roselaari) and rufa subspecies (Calidris canutus rufa) in Canada

Committee on the Status of Endangered Wildlife in Canada (COSEWIC)
islandica subspecies – Not at risk 2020
roselaari subspecies – Threatened 2020
rufa subspecies (Tierra del Fuego / Patagonia wintering population) – Endangered 2020
rufa subspecies (Northeastern South America wintering population) – Sspecial concern 2020
rufa subspecies (Southeastern USA / Gulf of Mexico / Caribbean wintering population) – Endangered 2020

COSEWIC Assessment summary

Assessment summary - November 2020 - Red Knot - islandica subspecies

Common name

Red Knot - islandica subspecies

Scientific name

Calidris canutus islandica

Status

Not at Risk

Reason for designation

This medium-sized shorebird breeds in the northeastern Canadian High Arctic and migrates across the North Atlantic Ocean to overwinter in coastal Europe. About 120,000 birds breed in Canada and make up 40% of the global population. Winter surveys in Europe indicate that populations have been stable or fluctuating slightly over the past three generations. Individuals congregate at many sites in winter, where they may be exposed to threats such as disturbance and effects of shoreline stabilization. Risks from exposure to storms and severe weather during trans-oceanic migratory flights may increase with climate change. However, as past population declines have been halted, and former threats from shellfish harvesting in Europe are much reduced, the status of this population has improved since the last assessment.

Occurrence

Nunavut, Northwest Territories

Status history

Designated Special Concern in April 2007. Status re-examined and designated Not at Risk in November 2020.

Assessment summary - November 2020 - Red Knot - roselaari subspecies

Common name

Red Knot - roselaari subspecies

Scientific name

Calidris canutus roselaari

Status

Threatened

Reason for designation

This medium-sized shorebird breeds in northwestern Alaska and on Wrangel Island in the eastern Russian Arctic, overwintering on the Pacific coast of the Americas. The global population numbers about 22,000 mature individuals, most of which likely migrate through Canadian airspace, although only small numbers are recorded annually on coastal islands of British Columbia on spring migration and in winter. Migration and winter counts indicate a long-term population decline of 39-64% over three generations, although trend estimates have low precision. Habitat quality is declining in areas used throughout the year. Population and habitat declines are anticipated to continue. Individuals congregate at key sites on migration in Alaska, Washington, and California, making them vulnerable to localized threats. Threats include disturbance from recreational activities, coastal development, aquaculture, and shoreline stabilization, as well as over-fishing of grunion (small fish whose eggs are an important food source) in coastal Mexico. Exposure to storms and severe weather during long migratory flights may increase with climate change.

Occurrence

British Columbia, Yukon

Status history

The species 'roselaari type' was considered a single unit (which included three groups) and designated Threatened in April 2007. Based on the Designatable Unit report on Red Knot (COSEWIC 2019), a new population structure was proposed and accepted by COSEWIC; two groups previously assessed under the ‘roselaari type’ were transferred to the rufa subspecies (Northeastern South America wintering population, Southeastern USA / Gulf of Mexico / Caribbean wintering population). The remaining unit now includes only the roselaari subspecies. The roselaari subspecies was designated Threatened in November 2020.

Assessment summary - November 2020 - Red Knot - rufa subspecies (Tierra del Fuego / Patagonia wintering population)

Common name

Red Knot - rufa subspecies (Tierra del Fuego / Patagonia wintering population)

Scientific name

Calidris canutus rufa

Status

Endangered

Reason for designation

This medium-sized shorebird breeds in the central Canadian Arctic and overwinters in Tierra del Fuego at the southern tip of South America, with migratory round-trips of over 30,000 km each year. Annual winter surveys indicate that the population of about 7,500 mature individuals has declined by 73% over the past three generations. Habitat quality is declining in areas used for breeding, migration stopovers and in winter. Population and habitat declines are anticipated to continue. The population congregates at a few key sites on migration on the east coasts of North and South America, and on the wintering grounds, making it highly vulnerable to threats. Threats include human harvesting of Horseshoe Crab (whose eggs are an essential food source for northbound migrants) in Delaware Bay, disturbance and predation from recovering falcon populations, oil development, and disturbance from recreational activities. Risks from exposure to storms and severe weather during very long trans-oceanic migratory flights may increase with climate change.

Occurrence

Nunavut, Northwest Territories, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador

Status history

The rufa subspecies was considered a single unit (consisting solely of southern wintering birds from Tierra del Fuego / Patagonia) and designated Endangered in April 2007. Based on the Designatable Unit report on Red Knot (COSEWIC 2019), a new population structure was proposed and accepted by COSEWIC; two groups previously assessed under the 'roselaari type' were transferred to the rufa subspecies (Northeastern South America wintering population, Southeastern USA / Gulf of Mexico / Caribbean wintering population). The Tierra del Fuego / Patagonia wintering population of the rufa subspecies was designated Endangered in November 2020.

Assessment summary - November 2020 - Red Knot - rufa subspecies (Northeastern South America wintering population)

Common name

Red Knot - rufa subspecies (Northeastern South America wintering population)

Scientific name

Calidris canutus rufa

Status

Special Concern

Reason for designation

This medium-sized shorebird breeds in the central Canadian Arctic and migrates long distances to overwinter on the northeastern coast of South America, centred in northern coastal Brazil. Overall numbers appear to be stable, with an estimated wintering population of about 19,800 mature individuals. During migration, the population congregates at key sites on the eastern seaboard of the United States, where it is vulnerable to threats from human harvesting of Horseshoe Crab (whose eggs are an essential food source for northbound migrants) in Delaware Bay, disturbance and predation from recovering falcon populations, and disturbance from recreational activities. Risks from exposure to storms and severe weather during long migratory flights may increase with climate change.

Occurrence

Nunavut, Northwest Territories, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador

Status history

The species 'roselaari type' was considered a single unit (which included three groups) and designated Threatened in April 2007. Based on the Designatable Unit report on Red Knot (COSEWIC 2019), a new population structure was proposed and accepted by COSEWIC; two groups previously assessed under the 'roselaari type' were transferred to the rufa subspecies. The Northeastern South America wintering population of the rufa subspecies was designated Special Concern in November 2020.

Assessment summary - November 2020 - Red Knot - rufa subspecies (Southeastern USA / Gulf of Mexico / Caribbean wintering population)

Common name

Red Knot - rufa subspecies (Southeastern USA / Gulf of Mexico / Caribbean wintering population)

Scientific name

Calidris canutus rufa

Status

Endangered

Reason for designation

This medium-sized shorebird breeds in the central Canadian Arctic and overwinters along the coasts of southeastern United States, Gulf of Mexico and islands in the Caribbean Sea. Migration and wintering surveys indicate that the population has experienced steep declines, in the range of 33-84% over three generations, with no evidence of recovery. The current population is estimated to be about 9300 mature individuals. During migration it congregates at a few key sites on the eastern seaboard of the United States, making it vulnerable to threats from human harvesting of Horseshoe Crabs (whose eggs are an essential food source for northbound migrants) in Delaware Bay, disturbance and predation from recovering falcon populations, and disturbance from recreational activities. Risks from exposure to storms and severe weather during fall and winter may increase with climate change.

Occurrence

Nunavut, Northwest Territories, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador

Status history

The species 'roselaari type' was considered a single unit (which included three groups) and designated Threatened in April 2007. Based on the Designatable Unit report on Red Knot (COSEWIC 2019), a new population structure was proposed and accepted by COSEWIC; two groups previously assessed under the 'roselaari type' were transferred to the rufa subspecies. The Southeastern USA / Gulf of Mexico / Caribbean wintering population of the rufa subspecies was designated Endangered in November 2020.

COSEWIC executive summary

Red Knot

Calidris canutus

Wildlife Species Description and Significance

Red Knot (Calidris canutus) is a medium-sized shorebird with a typical “sandpiper” profile: medium-long bill and smallish head, longish legs, and long tapered wings giving the body an elongated streamlined profile. In breeding plumage, the face, neck, breast and much of the underparts are rufous red. The upperparts are dark brown or black spangled with rufous and grey. In winter plumage, knots (used throughout to refer to Red Knots in general) have white underparts and pale grey back.

Six subspecies of Red Knot are currently recognized worldwide, each with distinct biogeographical populations that differ to varying degrees in distribution, in scheduling of the annual cycle, and genetically. Three subspecies occur in Canada: C. c. islandica, C. c. roselaari, and C. c. rufa. The taxonomy of North American Red Knot populations has been revised since the 2007 COSEWIC Status Report, with the populations wintering in Tierra del Fuego, as well as those wintering in northern Brazil and in southeastern USA / Gulf of Mexico / Caribbean, which were formerly assigned to C. c. roselaari, all now regarded as part of C. c. rufa. These three populations of rufa are also treated here as separate designatable units (DUs). The following five Red Knot DUs are considered here:

• DU1 - islandica subspecies (C. c. islandica): breeds in the northeastern Canadian High Arctic, and winters on the European Atlantic seaboard.
• DU2 - roselaari subspecies (C. c. roselaari): breeds in northwestern Alaska and on Wrangel Island in the Russian Eastern Arctic, migrates through Canadian airspace to overwinter on the Pacific coast of the Americas, and occurs in small numbers in coastal British Columbia on migration and in winter.
• DU3 - Tierra del Fuego / Patagonia wintering population (C. c. rufa in part): breeds in the central Canadian Arctic, and winters at the southern tip of South America, in Patagonia, Argentina, and Tierra del Fuego.
• DU4 - northeastern South America wintering population (C. c. rufa in part): breeds in the central Canadian Arctic, and winters on the northeastern coast of South America, centred in the Maranhão district of northern Brazil.
• DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population (C. c. rufa in part): breeds in the central Canadian Arctic, and winters along the coasts of the southeastern United States, Gulf of Mexico, and Caribbean Sea.

Red Knot is a “flagship” species for shorebird conservation, with long, inter-continental migrations and high vulnerability to threats, as it concentrates in large numbers at a few key sites on migration and in winter. It crosses many international boundaries and is symbolic of the need for international cooperation for successful conservation. Conservation of sites used by knots also benefits many other shorebird species.

Distribution (see wildlife species description and significance above)

Habitat

Red Knot nests in barren habitats in the Arctic, such as windswept ridges, slopes, or plateaus, with little vegetation cover. On migration and wintering areas, knots use coastal areas with extensive sandflats, mudflats and rocky flats, where birds feed on bivalves and other invertebrates. Along the mid-Atlantic coast of the eastern United States, they use sandy beaches and feed on high-energy Horseshoe Crab eggs. They also use salt marshes, brackish lagoons, mangrove areas, mussel beds, peat banks, rocky intertidal platforms, inland saline lakes, and agricultural fields.

Biology

Red Knot is monogamous, with pairs usually laying a single clutch of four eggs in the latter half of June, and the eggs hatching about mid-July. Females depart soon thereafter, leaving the males to accompany the young until they fledge. Breeding success varies considerably, depending on weather and the abundance and impacts of predators. Red Knot has comparatively high adult annual survival, ranging from 0.62-0.92 (mean 0.80), which varies in response to foraging and weather conditions on wintering grounds and during migration. Red Knot has a generation time of about 7 years, and most individuals start breeding at age two years.

Red Knot undergoes significant physiological changes during migration, to increase flight efficiency and permit rapid accumulation of body stores after reaching the breeding grounds. Organs and tissues involved in flight increase in size, while digestive organs and leg muscles decrease. Stores of fat and protein remaining on arrival on the breeding grounds are then used to regrow the latter organs in preparation for the breeding attempt.

Population sizes and trends

• DU1 - islandica subspecies. Recent counts and mark-resighting estimates of C. c. islandica birds wintering in Europe suggest a Canadian population of about 128,000 mature individuals. Annual winter surveys in coastal Europe show a stable or slightly fluctuating population trend over the past three generations.
• DU2 - roselaari subspecies. Mark-recapture studies on the US Pacific coast suggest a population size of about 22,000 mature individuals of C. c. roselaari, including birds that breed in both northwest Alaska and on Wrangel Island. Very small numbers are seen in Canada in most years, although satellite tracking suggests that most of the population migrates through Canadian airspace on spring migration, and many may stop briefly on the British Columbia coast. Repeated migration and winter surveys in the United States indicate that this DU has experienced a long-term population decline, equivalent to about 39-64% over three generations, with no evidence of recovery.
• DU3 - Tierra del Fuego / Patagonia wintering population. The C. c. rufa population wintering in Tierra del Fuego numbered over 50,000 birds in 1982 and 2000, including mature individuals, subadults and juvenile birds, but declined by over 80% to <10,000 birds in 2011 and 2018. This reflects an actual population reduction rather than a redistribution of birds to different areas, as few knots now winter at peripheral sites along the Patagonia coast which formerly held up to 21% of the wintering count. The Tierra del Fuego / Patagonia wintering population (DU3) is now estimated to be about 7,500 mature individuals and is estimated to have declined by about 73% over three generations (1999-2020), with no evidence of recovery.
• DU4 - northeastern South America wintering population. Some 32,500 Red Knots of all ages were found on the northeastern coast of Brazil during aerial surveys in 2019. This total was considerably higher than on previous surveys, although the difference likely reflects improved methodology designed specifically for Red Knots. Numbers overall appear to be relatively stable or fluctuating slightly, with an estimated population of about 19,800 mature individuals wintering in northeastern South America.
• DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Recent estimates based on population modelling indicate that a total of about 10,400 Red Knot of all ages winter in coastal areas of the southeastern United States, with at least 5,000 additional knots likely wintering on islands in the Caribbean, for a total of about 15,400 birds. Adults likely make up about 60% of these totals, resulting in an overall southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) estimate of 9,300 mature individuals. The weight of evidence from migration and wintering surveys indicates that the population has experienced steep long-term declines, in the range of 33-84% over three generations, with no evidence of recovery.

Threats and limiting factors

Many of the key threats to Red Knot are associated with its long-distance migrations and physiological changes that maximize flying efficiency and breeding success. Its relatively inflexible life history strategy makes Red Knot particularly sensitive to the effects of human interventions and changing climate and habitat conditions. Threats affecting all five DUs to varying extents include ecosystem modifications/biological resource use which affect food resources needed at critical times of the year (e.g., Horseshoe Crab harvest in Delaware Bay, Grunion fishery in Mexico), habitat shifting and alteration (e.g., climate change effects on habitat conditions and predator relationships on the breeding grounds), and changes to coastal habitats resulting from sea-level changes. Significant disturbance from human activities occurs in many areas, and most DUs are affected by increased predation or disturbance from increasing falcon populations. Oil spills pose a threat to all DUs. Increased frequency and intensity of storms on the breeding grounds, and hurricanes in migration areas, may periodically cause significant mortality, especially for those DUs that undergo long trans-oceanic migratory flights.

• DU1 - islandica subspecies. Overall threat impact: Low-Medium. Shoreline stabilization and dredging for cockles (now much reduced) in coastal wintering areas of NE Europe has reduced the quality of foraging and roosting habitats. Changing climate may affect breeding habitats and cause increased predation on breeding grounds and lead to reduced habitat quality at migration and wintering sites owing to sea level rise and ocean acidification.
• DU2 - roselaari subspecies. Overall threat impact: Medium-High. Over-fishing of Grunion in Upper Gulf of California, Mexico reduces availability of their eggs which are a key food resource for Red Knot in the critical period before spring migration. Coastal development, aquaculture, and shoreline stabilization on the Pacific coast may degrade foraging and roosting habitats used on migration and in winter. Changing climate may affect habitats and lead to increased predation on breeding grounds, and reduced habitat quality at migration and wintering sites owing to sea level rise and ocean acidification.
• DU3 - Tierra del Fuego / Patagonia wintering population. Overall threat impact: High-Very High. The Tierra del Fuego / Patagonia wintering population (DU3) had the highest overall threat impact of all DUs, likely related to its having the longest migration. Major threats include ongoing issues with Horseshoe Crab abundance in Delaware Bay, increased predation and disturbance from increasing falcon populations throughout its range, disturbance from recreational activities, and possible effects from climate change, including increasing storm frequency, on breeding grounds (habitat alteration, predation) and on migration and wintering areas (e.g., sea-level rise).
• DU4 - northeastern South America wintering population. Overall threat impact: Medium-High. Major threats include ongoing issues with Horseshoe Crab abundance in Delaware Bay, increased predation and disturbance from increasing falcon populations, and possible effects from climate change, including increasing storm frequency on breeding grounds (habitat alteration, predation) and on migration and wintering areas (e.g., sea-level rise).
• DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Overall threat impact: Medium-High. Disturbance by recreationists significantly affects quality of foraging and roosting areas on wintering and migration areas in eastern North America. Major threats include ongoing issues with Horseshoe Crab abundance in Delaware Bay, increased predation and disturbance from increasing falcon populations, and possible effects from climate change, including increasing storm frequency on breeding grounds (habitat alteration, predation) and on migration and wintering areas.

Number of locations

As Red Knot from all DUs nest at many widely distributed sites, across the high Arctic in Canada, Alaska, or eastern Russia, the number of locations for each DU during the breeding season is much greater than 10, as geographically distinct nesting areas are likely exposed to differing risks from key threats, such as ecosystem modifications and climate change. However, fewer locations are often used on migration or in winter. Non-breeding season estimates for the number of locations are: DU1, islandica subspecies, likely >10 in winter; DU2, roselaari subspecies, likely >10 on migration; DU3, Tierra del Fuego / Patagonia wintering population, likely 5-10 in winter; DU4, northeastern South America wintering population, likely >10 on migration; DU5, southeastern USA / Gulf of Mexico / Caribbean wintering population, likely >10 on migration.

Protection, status and ranks

Red Knot is protected in Canada under the Migratory Birds Convention Act (1994). It was listed on Schedule 1 of the Species at Risk Act in 2012, as follows: C. c. rufa Endangered (the southern Tierra del Fuego / Patagonia wintering population, now DU3); C. c. roselaari Threatened (including present DU2, the northeastern South America wintering population in northern Brazil and the southeastern USA / Gulf of Mexico / Caribbean wintering population, DU4 and DU5, now believed to be C. c. rufa), and C. c. islandica (now DU1) Special Concern (the previous DUs reflect earlier taxonomic designations). Red Knot (C. c. rufa) is also listed under species-at-risk legislation in Ontario, Quebec, New Brunswick, Nova Scotia, and Newfoundland and Labrador. C. c. islandica and C. c. roselaari are not listed under provincial or territorial species-at-risk legislation.

Red Knot (C. c. rufa) is listed federally in the United States as Threatened, and as Threatened in New Jersey and as of Special Concern in Georgia. C. c. rufa was added to Appendix 1 of the Convention on Migratory Species in 2005. Red Knot was listed as Critically Endangered on the Brazilian list in 2014 and categorized as Endangered in Argentina, Chile and Uruguay. France declared the species to be protected in Guadeloupe and Martinique in 2012 and in French Guiana in 2014. C. c. roselaari has been designated as Endangered in Mexico and as a species of management concern in the United States.

NatureServe lists C. c. rufa globally as G4T1, nationally in Canada as N1B and N1N, and nationally in the United States as N1N. It ranks C. c. rufa as S1 to S3 in Northwest Territories, Ontario, Quebec, Saskatchewan, Prince Edward Island, Nova Scotia, New Brunswick, and Newfoundland in Canada, and in Virginia in the United States. C. c. islandica is ranked N3B nationally and S2B in Northwest Territories.

Technical summary: islandica subspecies (Designatable Unit 1)

Calidris canutus islandica

Red Knot islandica subspecies

Bécasseau maubèche de la sous-espèce islandica

Range of occurrence in Canada (province/territory/ocean): Nunavut, Northwest Territories

[Populations breeding in Northeastern Canadian High Arctic and wintering in Europe]

Threats (direct, from highest impact to least, as per IUCN threats calculator)

Was a threats calculator completed for this Designatable Unit? Yes, on 11-12 February 2020, by Guy Morrison (writer), Richard Elliot (Birds SSC co-chair), David Fraser (facilitator), Marie-France Noel (COSEWIC Secretariat), Rosanna Nobre Soares (COSEWIC Secretariat), Yves Aubry (CWS), Louise Blight (SSC member), Mike Burrell (SSC member), Amanda Dey (New Jersey), Scott Flemming (CWS), Marcel Gahbauer (SSC co-chair), Patricia González (Argentina), Andy Horn (SSC member), Jessica Humber (Newfoundland and Labrador), Kevin Kalasz (USFWS), Amie MacDonald (Trent University), Ann McKellar (CWS), David Newstead (USA), Larry Niles (USA), Hayley Roberts (CWS), Paul Smith (SSC member), Don Sutherland (Ontario NHIC), Wendy Walsh (USFWS), Greg Wilson (British Columbia), Paul Woodard (CWS)

islandica subspecies: The assigned overall threat impact is Low-Medium. The following contributing threats were identified, listed in decreasing order of impact:

11.1 Habitat shifting and alteration (Medium-Low)

7.3 Other ecosystem modifications (Low)

9. Industrial and military effluents (Low)

1.1 Housing and urban areas (Negligible)

1.2 Commercial and industrial areas (Negligible)

1.3 Tourism and recreation areas (Negligible)

2.4 Marine and freshwater aquaculture (Negligible)

3.1 Oil and gas drilling (Negligible)

3.3 Renewable energy (Negligible)

5.1 Hunting and collecting terrestrial animals (Negligible)

6.1 Recreational activities (Negligible)

6.3 Work and other activities (Negligible)

7.2 Dams and water management/use (Negligible)

8.2 Problematic native species/diseases (Unknown)

9.1 Domestic and urban waste water (Unknown)

9.3 Agricultural and forestry effluents (Unknown)

9.5 Air-borne pollutants (Unknown)

11.4 Storms and flooding (Unknown)

What additional limiting factors are relevant?

Key factors limiting the productivity and survival of Red Knot islandica subspecies relate to its long-distance, trans-oceanic migration between the Canadian High Arctic and Europe, and the associated physiological changes it undergoes to maximize flying efficiency during migration. This relatively inflexible life history strategy makes islandica subspecies Red Knots sensitive to the effects of human interventions and changing climates and habitat conditions.

Status history

COSEWIC Status history: Designated Special Concern in April 2007. Status re-examined and designated Not at Risk in November 2020.

Status and reasons for designation:

Status:

Not at Risk

Alpha-numeric codes:

Not applicable

Reasons for designation:

This medium-sized shorebird breeds in the northeastern Canadian High Arctic and migrates across the North Atlantic Ocean to overwinter in coastal Europe. About 120,000 birds breed in Canada and make up 40% of the global population. Winter surveys in Europe indicate that populations have been stable or fluctuating slightly over the past three generations. Individuals congregate at many sites in winter, where they may be exposed to threats such as disturbance and effects of shoreline stabilization. Risks from exposure to storms and severe weather during trans-oceanic migratory flights may increase with climate change. However, as past population declines have been halted, and former threats from shellfish harvesting in Europe are much reduced, the status of this population has improved since the last assessment.

Applicability of criteria

Criterion A (Decline in Total Number of mature individuals): Not applicable. Number of mature individuals in the population is not declining.

Criterion B (Small Distribution Range and Decline or Fluctuation): Not applicable. EOO of 1,084,949 km² and IAO of 327,212 km² are both higher than threshold levels.

Criterion C (Small and Declining Number of mature individuals): Not applicable. Population estimate of 128,000 mature individuals is higher than threshold levels.

Criterion D (Very Small or Restricted Population): Not applicable. Population estimate of 128,000 mature individuals is higher than threshold levels.

Criterion E (Quantitative analysis): Not applicable. Analysis not conducted.

Technical summary: roselaari subspecies (Designatable Unit 2)

Calidris canutus roselaari

Red Knot roselaari subspecies

Bécasseau maubèche de la sous-espèce roselaari

Range of occurrence in Canada (province/territory/ocean): British Columbia, Yukon

[Populations wintering mainly on the Pacific coast of North and Central America]

Threats (direct, from highest impact to least, as per IUCN Threats Calculator)

Was a threats calculator completed for roselaari subspecies?

Yes, on 11-12 February 2020, by Guy Morrison (writer), Richard Elliot (Birds SSC co-chair), David Fraser (facilitator), Marie-France Noel (COSEWIC Secretariat), Rosanna Nobre Soares (COSEWIC Secretariat), Yves Aubry (CWS), Louise Blight (SSC member), Mike Burrell (SSC member), Amanda Dey (New Jersey), Scott Flemming (CWS), Marcel Gahbauer (SSC co-chair), Patricia González (Argentina), Andy Horn (SSC member), Jessica Humber (Newfoundland and Labrador), Kevin Kalasz (USFWS), Amie MacDonald (Trent University), Ann McKellar (CWS), David Newstead (USA), Larry Niles (USA), Hayley Roberts (CWS), Paul Smith (SSC member), Don Sutherland (Ontario NHIC), Wendy Walsh (USFWS), Greg Wilson (British Columbia), Paul Woodard (CWS)

The assigned overall threat impact for Red Knot roselaari subspecies is Medium-High. The following contributing threats were identified, listed in decreasing order of impact:

7.3 Other ecosystem modifications (Medium-Low)

11.1 Habitat shifting and alteration (Medium-Low)

1.1 Housing and urban areas (Low)

1.2 Commercial and industrial areas (Low)

2.4 Marine and freshwater aquaculture (Low)

6.1 Recreational activities (Low)

8.2 Problematic native species/diseases (Low)

9.2 Industrial and military effluents (Low)

1.3 Tourism and recreation areas (Negligible)

3.1 Oil and gas drilling (Negligible)

5.1 Hunting and collecting terrestrial animals (Negligible)

6.3 Work and other activities (Negligible)

8.1 Invasive non-native species/diseases (Negligible)

3.3 Renewable energy (Unknown)

7.2 Dams and water management/use (Unknown)

9.1 Domestic and urban waste water (Unknown)

9.3 Agricultural and forestry effluents (Unknown)

9.5 Air-borne pollutants (Unknown)

11.4 Storms and flooding (Unknown)

What additional limiting factors are relevant?

Key factors limiting the productivity and survival of Red Knot roselaari subspecies relate to its trans-oceanic and coastal migration and the associated physiological changes it undergoes to maximize flying efficiency during migration. This relatively inflexible life history strategy makes roselaari subspecies Red Knots particularly sensitive to the effects of human interventions and changing climates and habitat conditions.

Status history

COSEWIC Status history:

The species 'roselaari type' was considered a single unit (which included three groups) and designated Threatened in April 2007. Based on the Designatable Unit report on Red Knot (COSEWIC 2019), a new population structure was proposed and accepted by COSEWIC; two groups previously assessed under the ‘roselaari type’ were transferred to the rufa subspecies (Northeastern South America wintering population, Southeastern USA / Gulf of Mexico / Caribbean wintering population). The remaining unit now includes only the roselaari subspecies. The roselaari subspecies was designated Threatened in November 2020.

Status and reasons for designation:

Status:

Threatened

Alpha-numeric codes:

A2bc+4bc

Reasons for designation:

This medium-sized shorebird breeds in northwestern Alaska and on Wrangel Island in the eastern Russian Arctic, overwintering on the Pacific coast of the Americas. The global population numbers about 22,000 mature individuals, most of which likely migrate through Canadian airspace, although only small numbers are recorded annually on coastal islands of British Columbia on spring migration and in winter. Migration and winter counts indicate a long-term population decline of 39-64% over three generations, although trend estimates have low precision. Habitat quality is declining in areas used throughout the year. Population and habitat declines are anticipated to continue. Individuals congregate at key sites on migration in Alaska, Washington, and California, making them vulnerable to localized threats. Threats include disturbance from recreational activities, coastal development, aquaculture, and shoreline stabilization, as well as over-fishing of grunion (small fish whose eggs are an important food source) in coastal Mexico. Exposure to storms and severe weather during long migratory flights may increase with climate change.

Applicability of criteria

Criterion A (Decline in Total Number of mature individuals): Meets Threatened, A2bc and A4bc. Estimated rate of reduction in number of mature individuals of 39-64% over the past three generations (21 years), based on migration and winter surveys, is higher than the threshold levels, and habitat quality is declining. Population and habitat declines are likely to continue into the future based on assessed medium-high overall threat impact, indicating a likely population decline >30% over a three-generation period spanning past and future.

Criterion B (Small Distribution Range and Decline or Fluctuation): Not applicable. EOO of 167,016 km² is higher than threshold levels, and IAO of 500-2000 km² is lower than the threshold level for Threatened, but the population is not severely fragmented, occurs at more than 10 locations, and does not experience extreme fluctuations.

Criterion C (Small and Declining Number of mature individuals): Not applicable. Population estimate of 22,000 mature individuals is higher than threshold levels.

Criterion D (Very Small or Restricted Population): Not applicable. Population estimate of 22,000 mature individuals is higher than threshold levels.

Criterion E (Quantitative analysis): Not applicable. Analysis not conducted.

Technical summary: rufa subspecies (Tierra del Fuego / Patagonia wintering population) (Designatable Unit 3)

Calidris canutus rufa

Red Knot rufa subspecies (Tierra del Fuego / Patagonia wintering population)

Bécasseau maubèche de la sous-espèce rufa (Population hivernant dans la Terre de Feu et en Patagonie)

Range of occurrence in Canada (province/territory/ocean): Nunavut, Northwest Territories, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador

Threats (direct, from highest impact to least, as per IUCN Threats Calculator)

Was a threats calculator completed for the Tierra del Fuego / Patagonia wintering population of Red Knot?

Yes, on 11-12 February 2020, by Guy Morrison (writer), Richard Elliot (Birds SSC co-chair), David Fraser (facilitator), Marie-France Noel (COSEWIC Secretariat), Rosanna Nobre Soares (COSEWIC Secretariat), Yves Aubry (CWS), Louise Blight (SSC member), Mike Burrell (SSC member), Amanda Dey (New Jersey), Scott Flemming (CWS), Marcel Gahbauer (SSC co-chair), Patricia González (Argentina), Andy Horn (SSC member), Jessica Humber (Newfoundland and Labrador), Kevin Kalasz (USFWS), Amie MacDonald (Trent University), Ann McKellar (CWS), David Newstead (USA), Larry Niles (USA), Hayley Roberts (CWS), Paul Smith (SSC member), Don Sutherland (Ontario NHIC), Wendy Walsh (USFWS), Greg Wilson (British Columbia), Paul Woodard (CWS)

The assigned overall threat impact for the Tierra del Fuego / Patagonia wintering population is High-Very High. The following contributing threats were identified, listed in decreasing order of impact:

7.3 Other ecosystem modifications (High-Low)

8.2 Problematic native species/diseases (Medium)

6.1 Recreational activities (Medium-Low)

11.1 Habitat shifting and alteration (Medium-Low)

11.4 Storms and flooding (Medium-Low)

1.1 Housing and urban areas (Low)

1.2 Commercial and industrial areas (Low)

1.3 Tourism and recreation areas (Low)

2.4 Marine and freshwater aquaculture (Low)

7.2 Dams and water management/use (Low)

9.2 Industrial and military effluents (Low)

3.1 Oil and gas drilling (Negligible)

3.2 Mining and quarrying (Negligible)

6.3 Work and other activities (Negligible)

2.3 Livestock farming and ranching (Unknown)

3.3 Renewable energy (Unknown)

5.1 Hunting and collecting terrestrial animals (Unknown)

9.1 Domestic and urban waste water (Unknown)

9.3 Agricultural and forestry effluents (Unknown)

9.5 Air-borne pollutants (Unknown)

What additional limiting factors are relevant?

Key factors limiting the productivity and survival of the Tierra del Fuego / Patagonia wintering population of Red Knot relate to its long-distance, trans-oceanic migration between the Canadian Arctic and Tierra del Fuego, and the extreme physiological changes it undergoes to maximize flying efficiency during migration. This relatively inflexible life history strategy makes knots in the Tierra del Fuego / Patagonia wintering population particularly sensitive to the effects of human interventions and changing climates and habitat conditions.

Status history

COSEWIC Status history:

The rufa subspecies was considered a single unit (consisting solely of southern wintering birds from Tierra del Fuego / Patagonia) and designated Endangered in April 2007. Based on the Designatable Unit report on Red Knot (COSEWIC 2019), a new population structure was proposed and accepted by COSEWIC; two groups previously assessed under the 'roselaari type' were transferred to the rufa subspecies (Northeastern South America wintering population, Southeastern USA / Gulf of Mexico / Caribbean wintering population). The Tierra del Fuego / Patagonia wintering population of the rufa subspecies was designated Endangered in November 2020.

Status and reasons for designation:

Status:

Endangered

Alpha-numeric codes:

A2bc+4bc

Reasons for designation:

This medium-sized shorebird breeds in the central Canadian Arctic and overwinters in Tierra del Fuego at the southern tip of South America, with migratory round-trips of over 30,000 km each year. Annual winter surveys indicate that the population of about 7,500 mature individuals has declined by 73% over the past three generations. Habitat quality is declining in areas used for breeding, migration stopovers and in winter. Population and habitat declines are anticipated to continue. The population congregates at a few key sites on migration on the east coasts of North and South America, and on the wintering grounds, making it highly vulnerable to threats. Threats include human harvesting of Horseshoe Crab (whose eggs are an essential food source for northbound migrants) in Delaware Bay, disturbance and predation from recovering falcon populations, oil development, and disturbance from recreational activities. Risks from exposure to storms and severe weather during very long trans-oceanic migratory flights may increase with climate change.

Applicability of criteria

Criterion A (Decline in Total Number of mature individuals): Meets Endangered, A2bc and A4bc. Estimated rate of reduction in number of mature individuals of 73% over the past three generations (21 years), based on wintering population surveys, is higher than threshold levels, and habitat quality is declining. Population and habitat declines are likely to continue into the future based on assessed “high-very high” overall threat impact, indicating a likely decline >50% over a three-generation period spanning past and future.

Criterion B (Small Distribution Range and Decline or Fluctuation): Meets Threatened, B2ab(iii,v). IAO of 1100-1300 km² is lower than the threshold level of 2000 km², the population exists at <10 locations in winter, and there is a projected continuing decline in quality of migration and winter habitat, and an observed continuing decline in the number of mature individuals.

Criterion C (Small and Declining Number of mature individuals): Meets Threatened, C2a(ii). The population estimate of 7,500 mature individuals is lower than the threshold level of 10,000 mature individuals, and there is an observed continuing decline in the number of mature individuals, all of which occur in the same subpopulation.

Criterion D (Very Small or Restricted Population): Not applicable. Population estimate of 7,500 mature individuals is higher than threshold levels.

Criterion E (Quantitative analysis): Not applicable. Analysis not conducted.

Technical summary: rufa subspecies (Northeastern South America wintering population) (Designatable Unit 4)

Calidris canutus rufa

Red Knot rufa subspecies (Northeastern South America wintering population)

Bécasseau maubèche de la sous-espèce rufa (Population hivernant dans le nord-est de l’Amérique du Sud)

Range of occurrence in Canada (province/territory/ocean): Nunavut, Northwest Territories, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador

Threats (direct, from highest impact to least, as per IUCN Threats Calculator)

Was a threats calculator completed for the northeastern South America wintering population of Red Knot?

Yes, on 11-12 February 2020, by Guy Morrison (writer), Richard Elliot (Birds SSC co-chair), David Fraser (facilitator), Marie-France Noel (COSEWIC Secretariat), Rosanna Nobre Soares (COSEWIC Secretariat), Yves Aubry (CWS), Louise Blight (SSC member), Mike Burrell (SSC member), Amanda Dey (New Jersey), Scott Flemming (CWS), Marcel Gahbauer (SSC co-chair), Patricia González (Argentina), Andy Horn (SSC member), Jessica Humber (Newfoundland and Labrador), Kevin Kalasz (USFWS), Amie MacDonald (Trent University), Ann McKellar (CWS), David Newstead (USA), Larry Niles (USA), Hayley Roberts (CWS), Paul Smith (SSC member), Don Sutherland (Ontario NHIC), Wendy Walsh (USFWS), Greg Wilson (British Columbia), Paul Woodard (CWS)

The assigned overall threat impact for the northeastern South America wintering population is Medium-High. The following contributing threats were identified, listed in decreasing order of impact:

7.3 Other ecosystem modifications (Medium-Low)

8.2 Problematic native species/diseases (Medium-Low)

11.1 Habitat shifting and alteration (Medium-Low)

11.4 Storms and flooding (Medium-Low)

1.1 Housing and urban areas (Low)

2.4 Marine and freshwater aquaculture (Low)

6.1 Recreational activities (Low)

7.2 Dams and water management/use (Low)

9.2 Industrial and military effluents (Low)

1.2 Commercial and industrial areas (Negligible)

1.3 Tourism and recreation areas (Negligible)

3.1 Oil and gas drilling (Negligible)

3.2 Mining and quarrying (Negligible)

6.3 Work and other activities (Negligible)

3.3 Renewable energy (Unknown)

5.1 Hunting and collecting terrestrial animals (Unknown)

9.1 Domestic and urban waste water (Unknown)

9.3 Agricultural and forestry effluents (Unknown)

9.5 Air-borne pollutants (Unknown)

What additional limiting factors are relevant?

Key factors limiting the productivity and survival of Red Knot in the northeastern South America wintering population relate to its long-distance, trans-oceanic migration between the Canadian Arctic and northeastern South America, and the physiological changes it undergoes to maximize flying efficiency during migration. This relatively inflexible life history strategy makes knots in the northeastern South America wintering population particularly sensitive to the effects of human interventions and changing climates and habitat conditions.

Status history

COSEWIC Status history:

The species 'roselaari type' was considered a single unit (which included three groups) and designated Threatened in April 2007. Based on the Designatable Unit report on Red Knot (COSEWIC 2019), a new population structure was proposed and accepted by COSEWIC; two groups previously assessed under the 'roselaari type' were transferred to the rufa subspecies. The Northeastern South America wintering population of the rufa subspecies was designated Special Concern in November 2020.

Status and reasons for designation:

Status:

Special Concern

Alpha-numeric codes:

Not applicable

Reasons for designation:

This medium-sized shorebird breeds in the central Canadian Arctic and migrates long distances to overwinter on the northeastern coast of South America, centred in northern coastal Brazil. Overall numbers appear to be stable, with an estimated wintering population of about 19,800 mature individuals. During migration, the population congregates at key sites on the eastern seaboard of the United States, where it is vulnerable to threats from human harvesting of Horseshoe Crab (whose eggs are an essential food source for northbound migrants) in Delaware Bay, disturbance and predation from recovering falcon populations, and disturbance from recreational activities. Risks from exposure to storms and severe weather during long migratory flights may increase with climate change.

Applicability of criteria

Criterion A (Decline in Total Number of mature individuals): Not applicable. Number of mature individuals in the population is not declining.

Criterion B (Small Distribution Range and Decline or Fluctuation): Not applicable. Although IAO of 1000-1600 km² is lower than the threshold level for Threatened, the population is not severely fragmented, occurs at more than 10 locations, and does not experience extreme fluctuations.

Criterion C (Small and Declining Number of mature individuals): Not applicable. Population estimate of 19,800 mature individuals is higher than threshold levels.

Criterion D (Very Small or Restricted Population): Not applicable. Population estimate of about 19,800 mature individuals is higher than threshold levels.

Criterion E (Quantitative analysis): Not applicable. Analysis not conducted.

Technical summary: rufa subspecies (Southeastern USA / Gulf of Mexico / Caribbean wintering population) (Designatable Unit 5)

Calidris canutus rufa

Red Knot rufa subspecies (Southeastern USA / Gulf of Mexico / Caribbean wintering population)

Bécasseau maubèche de la sous-espèce rufa (Population hivernant dans le sud-est des États-Unis, le golfe du Mexique et les Caraïbes)

Range of occurrence in Canada (province/territory/ocean): Nunavut, Northwest Territories, Alberta, Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador

Threats (direct, from highest impact to least, as per IUCN Threats Calculator)

Was a threats calculator completed for the southeastern USA / Gulf of Mexico / Caribbean wintering population of Red Knot?

Yes, on 11-12 February 2020, by Guy Morrison (writer), Richard Elliot (Birds SSC co-chair), David Fraser (facilitator), Marie-France Noel (COSEWIC Secretariat), Rosanna Nobre Soares (COSEWIC Secretariat), Yves Aubry (CWS), Louise Blight (SSC member), Mike Burrell (SSC member), Amanda Dey (New Jersey), Scott Flemming (CWS), Marcel Gahbauer (SSC co-chair), Patricia González (Argentina), Andy Horn (SSC member), Jessica Humber (Newfoundland and Labrador), Kevin Kalasz (USFWS), Amie MacDonald (Trent University), Ann McKellar (CWS), David Newstead (USA), Larry Niles (USA), Hayley Roberts (CWS), Paul Smith (SSC member), Don Sutherland (Ontario NHIC), Wendy Walsh (USFWS), Greg Wilson (British Columbia), Paul Woodard (CWS)

The assigned overall threat impact for the southeastern USA / Gulf of Mexico / Caribbean wintering population is Medium-High. The following contributing threats were identified, listed in decreasing order of impact:

6.1 Recreational activities (Medium-Low)

7.3 Other ecosystem modifications (Medium-Low)

8.2 Problematic native species/diseases (Medium-Low)

11.1 Habitat shifting and alteration (Medium-Low)

11.4 Storms and flooding (Medium-Low)

1.1 Housing and urban areas (Low)

1.3 Tourism and recreation areas (Low)

2.4 Marine and freshwater aquaculture (Low)

7.2 Dams and water management/use (Low)

9.2 Industrial and military effluents (Low)

1.2 Commercial and industrial areas (Negligible)

3.1 Oil and gas drilling (Negligible)

3.2 Mining and quarrying (Negligible)

5.1 Hunting and collecting terrestrial animals (Negligible)

6.3 Work and other activities (Negligible)

3.3 Renewable energy (Unknown)

9.1 Domestic and urban waste water (Unknown)

9.3 Agricultural and forestry effluents (Unknown)

9.5 Air-borne pollutants (Unknown)

11.2 Droughts (Unknown)

What additional limiting factors are relevant?

Key factors limiting the productivity and survival of Red Knot in the southeastern USA / Gulf of Mexico / Caribbean wintering population relate to its migration between the Canadian Arctic and the US Gulf States and Caribbean Sea, and the physiological changes it undergoes to maximize flying efficiency during migration. This relatively inflexible life history strategy makes knots in the southeastern USA / Gulf of Mexico / Caribbean wintering population particularly sensitive to the effects of human interventions, changing climates and habitat conditions, such as loss of stopover sites.

Status history

COSEWIC Status history:

The species 'roselaari type' was considered a single unit (which included three groups) and designated Threatened in April 2007. Based on the Designatable Unit report on Red Knot (COSEWIC 2019), a new population structure was proposed and accepted by COSEWIC; two groups previously assessed under the 'roselaari type' were transferred to the rufa subspecies. The Southeastern USA / Gulf of Mexico / Caribbean wintering population of the rufa subspecies was designated Endangered in November 2020.

Status and reasons for designation:

Status:

Endangered

Alpha-numeric codes:

A2bc+4bc

Reasons for designation:

This medium-sized shorebird breeds in the central Canadian Arctic and overwinters along the coasts of southeastern United States, Gulf of Mexico and islands in the Caribbean Sea. Migration and wintering surveys indicate that the population has experienced steep declines, in the range of 33-84% over three generations, with no evidence of recovery. The current population is estimated to be about 9300 mature individuals. During migration it congregates at a few key sites on the eastern seaboard of the United States, making it vulnerable to threats from human harvesting of Horseshoe Crabs (whose eggs are an essential food source for northbound migrants) in Delaware Bay, disturbance and predation from recovering falcon populations, and disturbance from recreational activities. Risks from exposure to storms and severe weather during fall and winter may increase with climate change.

Applicability of criteria

Criterion A (Decline in Total Number of mature individuals): Meets Endangered, A2bc and A4bc. Inferred rate of reduction in number of mature individuals of 33-84% over the past three generations (21 years), based on migration and winter surveys, is higher than threshold levels, and habitat quality is declining. Population and habitat declines are likely to continue into the future based on assessed medium-high overall threat impact.

Criterion B (Small Distribution Range and Decline or Fluctuation): Not applicable. EOO of 1,500,261 km² and minimum estimate of IAO of 2,548 km² are both higher than threshold levels.

Criterion C (Small and Declining Number of mature individuals): Meets Threatened, C2a(ii). The population estimate of 9,300 mature individuals is lower than the threshold level of 10,000 mature individuals, and there is an observed continuing decline in number of mature individuals, all of which occur in the same subpopulation.

Criterion D (Very Small or Restricted Population): Not applicable. Population estimate of 9,300 mature individuals is higher than threshold levels.

Criterion E (Quantitative analysis): Not applicable. Analysis not conducted.

Preface

The status of Red Knot (Calidris canutus) was assessed in 2007 (COSEWIC 2007) and listed on Schedule 1 of the Species at Risk Act in 2012, on the basis of three designatable units (DUs) that aligned with three subspecies as then described: C. c. rufa Endangered; C. c. roselaari Threatened, and C. c. islandica Special Concern. Red Knot taxonomy has since been significantly revised, on the basis of genetic, moult, and movement studies (Baker et al. 2012a,b, 2013, 2020). The two populations that overwinter in the southeastern United States/Gulf of Mexico/Caribbean and on the northeastern coast of Brazil, which were formerly regarded as part of C. c. roselaari, are now considered to belong to C. c. rufa (Baker et al. 2013, 2020; Burger et al. 2020). Only those Red Knot wintering on the west coast of the Americas are now considered to be C. c. roselaari (Carmona et al. 2013), while those wintering in Europe are still considered to be C. c. islandica, as in COSEWIC (2007). C. c. rufa is further subdivided here into three populations, based on widely disjunct wintering areas, namely those wintering in extreme southern South America including Tierra del Fuego (formerly the only group included in C. c. rufa) and the two wintering groups noted above (Baker et al. 2013, 2020; Verkuil et al. 2017).

The COSEWIC Birds Specialist Subcommittee examined lines of evidence for discreteness and evolutionary significance of these Red Knot populations, to determine the appropriate number and delineation of DUs, and proposed five DUs based on the wintering areas described above (COSEWIC Birds Specialist Subcommittee 2019). In November 2019, COSEWIC approved the five proposed Red Knot DUs for use in the present status assessment (COSEWIC Birds Specialist Subcommittee 2019).

There is a considerable amount of new information available on many aspects of the biology of Red Knot (summarized in Baker et al. 2013, 2020; Niles et al. 2010a; USFWS 2014a). New population size estimates are available for most DUs, based on mark-resighting data from flagged birds and from ground and aerial surveys (e.g., Lyons et al. 2016, 2018; Morrison et al. 2020a,b,c). Population trends have been reassessed for most DUs, based on analysis of International Shorebird Survey data, extensive ground-based counts, and aerial surveys (e.g., USFWS 2014a; Morrison 2018; NJA 2020). Migratory connectivity and degree of mixing on wintering areas has been assessed through observations of knots marked with coloured flags, radio-tags, geolocators, and GPS units (e.g., USFWS 2014a; Baker et al. 2020; Burger et al. 2020). Important new migration stopover areas have been identified through geolocator records and aerial surveys (e.g., McKellar et al. 2015; Burger et al. 2020; Johnson pers. comm. 2020; MacDonald 2020).

A Species at Risk Recovery Strategy and Management Plan for Red Knot, which incorporated a preliminary threat assessment for each of the three subspecies, was produced in 2017 (Environment and Climate Change Canada 2017), based on the three DUs identified in COSEWIC (2007).

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2020)

Wildlife Species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)^*

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)^**

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)^***

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

^* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
^** Formerly described as “Not In Any Category”, or “No Designation Required.”
^*** Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.

Wildlife species description and significance

Name and classification

Scientific name: Calidris canutus (Linnaeus 1758) (C. c. islandica, C. c. roselaari, C. c. rufa)

English name: Red Knot

French name: Bécasseau maubèche

Other names: Qajorlak (Inuktitut), Sitjariaq (Inuktitut from Nunavik), Playero rojizo (Latin American Spanish), Correlimos Gordo (Spanish), Maçarico-de-papo-vermelho (Portuguese)

Classification: Class: Aves

Order: Charadriiformes

Family: Scolopacidae

Subspecies

Globally, Red Knot is classified into six subspecies, each with distinctive morphological traits, breeding areas, migration routes, wintering areas, and annual cycles (Piersma and Davidson 1992; Tomkovich 1992, 2001; Piersma and Baker 2000; Piersma and Spaans 2004; Buehler and Baker 2005; Baker et al. 2013; Figure 1). Three subspecies occur in Canada: Calidris canutus islandica, C. c. roselaari, and C. c. rufa.

C. c. islandica (DU1) breeds in the northeastern Canadian High Arctic, probably as far west as Prince Patrick Island and south to Prince of Wales Island (Godfrey 1992; Morrison and Harrington 1992; Baker et al. 2013), and in the High Arctic of Greenland from the northwest around the north coast to about Scoresby Sound on the east coast. It winters in the United Kingdom, the Netherlands and other coastal areas of the European seaboard, and migrates to and from the breeding grounds through Iceland and northern Norway.

C. c. roselaari (DU2) breeds in northwestern Alaska and on Wrangel Island in Russia, and winters along the Pacific coast of the Americas, particularly on the coasts of southern California and northern Mexico. It migrates northwards via the Pacific coast of the United States and Canada, and southwards more directly from staging areas in Alaska to wintering areas from southern California to northwest Mexico (Buchanan et al. 2010; Carmona et al. 2013; Bishop et al. 2016; J. Johnson pers. comm. 2020).

Figure 1. Worldwide distribution of the six recognized subspecies of Red Knot. Arrows connect non-breeding (= wintering) areas identified by dots (scaled to relative population size) with breeding areas (purple shading). For this report, islandica populations represent DU1 and roselaari populations represent DU2. For rufa wintering populations, dots in Tierra del Fuego represent DU3 (the Tierra del Fuego / Patagonia wintering population), those on the north coast of South America represent DU4 (the northeastern South America wintering population), and those in the southeastern United States and central America represent DU5 (the southeastern USA/Gulf of Mexico/Caribbean wintering population). Map by Hugo Ahlenius, GRID-Arendal 2010.

C. c. rufa breeds across the central Canadian low and middle Arctic, and has three distinct and widely separated wintering populations (Baker et al. 2013, 2020), in (a) southern South America, primarily in Tierra del Fuego (Chile and Argentina), with some birds in the coastal Patagonia region of Argentina (DU3 - Tierra del Fuego / Patagonia wintering population); (b) on the northeastern coast of South America, principally in the area of Maranhão, Brazil (DU4 - northeastern South America wintering population); and (c) in the southeastern United States and Gulf of Mexico, including areas in coastal Texas and adjacent areas of Mexico, as well as on islands in the Caribbean Sea (DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population).

Morphological description

Red Knot is a medium-sized shorebird with a typical calidridine sandpiper profile (cover photograph), with a proportionately small head, and straightish bill tapering from thicker base to thinner tip and slightly longer than the head. It has a short neck, short tibia, stout tarsus, and long tapered wings giving an elongated streamlined profile to the body (length 23-25 cm, mass about 135 g although highly variable; Baker et al. 2013).

Red Knot is distinctive in breeding, or alternate, plumage, with face, neck, breast, and much of the underparts coloured rufous red. The lower belly and vent behind the legs tend to be lighter, especially in rufa, and some whitish or brownish feathers may be scattered through the breast (Baker et al. 1999). Feathers on the upperparts have dark brown-black centres edged with rufous and grey, giving the bird a spangled appearance that provides effective camouflage on the sparsely vegetated High Arctic breeding grounds. Flight feathers range inwards from dark brown or black in the primaries to grey in the secondaries and tail feathers, and there is a narrow whitish wing bar. Males tend to be more brightly coloured than females, with more extensive rufous on the underparts (Prater et al. 1977; Cramp and Simons 1983; Roselaar 1983; Hayman et al. 1986; Baker et al. 2013, 2020).

Red Knot is much plainer in winter, or basic, plumage, with white underparts and a pale, un-patterned grey back. The upper breast has greyish or brownish streaking, extending laterally along the flanks, and the head has dull greyish patterning with a whitish supercilium (Cramp and Simmons 1983).

Juveniles have similar plumage to winter adults but can be distinguished by dark subterminal bands on the feathers of the mantle, scapulars and coverts, giving the bird a characteristic scaly appearance (Prater et al. 1977). Juveniles may also have a pale dull buffish colour suffusing the breast (Baker et al. 2013).

Population spatial structure and variability

The six subspecies of Red Knot that occur globally (Figure 1) are generally differentiated by the relative depth and extent of reddish colour on the ventrum, darkness of markings on the dorsum, bill length and body mass, as well as by differences in scheduling of migration and moult, and by geographic separation (Piersma and Davidson 1992; Tomkovich 1992, 2001; Piersma and Baker 2000; Piersma and Spaans 2004; Buehler and Baker 2005; Buehler and Piersma 2008, Baker et al. 2013, 2020). Recent genetic studies conducted by Verkuil et al. (2017) using 15,000 genome-wide single-nucleotide polymorphisms (SNPs), showed that all six subspecies can be differentiated genetically.

These subspecies likely diverged after the glacial maximum of the Wisconsin glaciation, 22,000-18,000 years BP, through eastwards expansion from a single Red Knot population that survived the glaciation by breeding in unglaciated regions of central and eastern Eurasia (Buehler and Baker 2005). The North American group is thought to have diverged from a Siberian ancestor about 12,000 BP, and split into the three North American subspecies within the past 5,500 years (Buehler and Baker 2005; USFWS 2014a), perhaps as recently as the last 1,000 years (Buehler et al. 2006).

Recent research on population genetics, migratory strategies and connectivity has resulted in the reassignment of some Red Knot populations to different subspecies than were considered in the previous COSEWIC Status Report (COSEWIC 2007). Those birds wintering on the Pacific coast of North and Central America, along southeastern USA / Gulf of Mexico / Caribbean coasts, and on the northeastern coast of South America, were formerly considered to be C. c. roselaari and were treated as such by COSEWIC (2007). However, C. c. roselaari is now considered only to comprise birds breeding in northwest Alaska, and Wrangel Island in Russia, and migrating to wintering areas on the Pacific coast of the Americas, centred in Mexico, with some birds in Panama and farther south (Buchanan et al. 2010; Baker et al. 2013; Carmona et al. 2013). All Red Knot wintering in the southeastern United States, Gulf of Mexico and Caribbean, as well as those in northeastern South America, are now considered part of subspecies rufa (Baker et al. 2012a,b; 2013; 2020; Verkuil et al. 2017; Burger et al. 2020).

The three Red Knot wintering populations now referable to rufa (Tierra del Fuego, northeastern South America, and southeastern USA / Gulf of Mexico / Caribbean) all migrate north to breeding areas in the low- and mid-Canadian Arctic islands (Niles et al. 2010a, 2012a; Burger et al. 2012a, 2020; Baker et al. 2013, 2020; Newstead et al. 2013). Movement studies using radio-telemetry, geolocators, and coloured leg bands indicate that most knots wintering in Texas, west Florida, the Gulf of Mexico, and the Caribbean migrate north in spring through central North America and likely nest in the westerly portions of the Canadian breeding range (Newstead et al. 2013). Birds from east Florida, northeastern Brazil, and Tierra del Fuego pass up the Atlantic coast of the United States in spring and likely nest in the more easterly part of the range (Niles et al. 2008; Newstead et al. 2013). However, details of where birds from each of these wintering populations breed within this area have yet to be determined.

Designatable units

Revisions to the taxonomy of North American Red Knot populations since 2007, and the results of research on population genetics, morphometrics, migratory connectivity, and moult and migration scheduling, have necessitated a reconsideration of the delineation and number of Red Knot DUs. In November 2019, COSEWIC approved the use of five Red Knot DUs in this status assessment, based on information presented by the COSEWIC Birds Specialist Subcommittee (2019), and key points from that report are presented here.

DUs are considered by COSEWIC to be “discrete and evolutionarily significant units of the taxonomic species, where “significant” means that the unit is important to the evolutionary legacy of the species as a whole and, if lost, would likely not be replaced through natural dispersion” (COSEWIC 2017a). A population (or group of subpopulations) is recognized by COSEWIC as a DU if it has attributes that make it both discrete and evolutionarily significant, relative to other populations. COSEWIC recognizes three different lines of evidence for discreteness and four for evolutionary significance and uses a weight of evidence approach that builds on them (COSEWIC 2017a). At least one of the following lines of evidence from each should be met to justify a DU designation:

Discreteness:

• D1. Genetic distinctiveness, including inherited traits (e.g., morphology, life history, or behaviour) and/or neutral genetic markers (e.g., allozymes, DNA microsatellites, DNA RFLPs, or DNA sequences);
• D2. Natural disjunction between substantial portions of the species’ geographic range, such that past and future movement of individuals between regions is severely limited, and where disjunction likely favours evolution of local adaptations;
• D3. Occupation of differing eco-geographic regions that reflect historical or genetic distinction. Although some dispersal may occur between regions, it is insufficient to prevent local adaptation.

Evolutionary significance:

• E1. Evidence that the discrete population differs markedly from others in characteristics that reflect relatively deep phylogenetic divergence. Differences could be manifested by fixed differences in functional genes, or in stable cultural behaviour, or indicated by qualitative genetic differences at relatively slow-evolving markers;
• E2. Persistence of the discrete population in an unusual or unique ecological setting that is likely or known to have given rise to local adaptations;
• E3. Evidence that the discrete population represents the only surviving natural occurrence of a species that is more abundant elsewhere as an introduced population;
• E4. Evidence that loss of the discrete population would result in an extensive disjunction in the range of the species in Canada, where disjunction is defined as regions of species’ occurrence widely separated geographically by regions of non-occupancy, such that natural dispersal among such regions is unlikely to occur.

The previous COSEWIC assessment of Red Knot recognized three DUs, corresponding to the subspecies occurring in Canada as then delineated (COSEWIC 2007). Although the populations assigned to two of these subspecies have been revised (see Population Spatial Structure and Variability), the three subspecies currently recognized in the Americas meet criteria for recognition as distinct DUs, based on the body of evidence from studies of population genetics (Verkuil et al. 2017), migratory connectivity (Morrison 1975; Niles et al. 2010b, 2012a; Wilson et al. 2011; Burger et al. 2012a, 2020; Carmona et al. 2013; Newstead et al. 2013; Baker et al. 2020), and morphometrics and moult patterns (Morrison and Harrington 1992; Engelmoer and Roselaar 1998; Harrington et al. 2007, 2010; Baker et al. 2013).

Red Knot of the subspecies C. c. rufa breed exclusively in Canada, nesting in the low to mid-Canadian Arctic (Figure 2). There are three distinct and widely separated rufa wintering populations: (a) in extreme southern South America, primarily in Tierra del Fuego, with some birds in the coastal Patagonia region of Argentina and small numbers on Chiloé Island, Chile; (b) on the northeastern coast of South America, principally in the area of Maranhão, Brazil; and (c) in coastal areas of the southeastern United States, Gulf of Mexico, including areas in coastal Texas and adjacent areas of Mexico, as well as on islands in the Caribbean Sea (Baker et al. 2013).

Figure 2. Breeding range of Red Knot in the Canadian Arctic. C. c. islandica breeds in the High Arctic regions of northeastern Canada and Greenland. C. c. roselaari breeds in northern and northwestern Alaska, and on Wrangel Island, Russia (not shown). C. c. rufa breeds entirely within Canada in the central Canadian Arctic. (Map created by the COSEWIC secretariat, COSEWIC 2007).

These three major wintering populations of C. c. rufa are also separable genetically (Baker et al. 2012a,b; Verkuil et al. 2017; Verkuil pers. comm. 2019), with an analysis of AFLP markers showing separation of individuals among the three populations (Baker et al. 2012a), with F_ST estimates of 0.16 - 0.20 (Verkuil pers. comm. 2019). While there are no strict thresholds for estimates of genetic differentiation in avian systems, F_ST >0.1 reflects strong genetic distinctiveness that is highly suggestive of evolutionary divergence (Toews pers. comm. 2019). As this genetic analysis does not show strong differences in slow-evolving neutral genetic markers, nor evidence of multiple fixed nuclear markers, these genetic data only indirectly support the use of criterion E1 to differentiate among DUs 3, 4 and 5, and suggest a more recent evolution of differences reflected in the genome-wide AFLPs.

Baker et al. (2012a,b) concluded that the three genetically distinguishable wintering populations of rufa (DUs 3, 4, and 5) must show high fidelity to their wintering sites for the observed level of population structure to have evolved. They also indicated that these populations would likely be isolated on their Arctic breeding grounds, as gene flow and dispersal would otherwise swamp these genetic differences (Baker et al. 2012a). There does appear to be overlap of breeding areas used by these populations within the low- and mid-Canadian Arctic, e.g., Southampton Island (Smith pers. comm. 2019) and elsewhere (Burger et al. 2020; Porter pers. comm. 2020). However, details of where each of these discrete wintering populations breeds, and the mechanism(s) by which these DUs maintain their genetic separation on the breeding grounds, remain unclear.

The five Red Knot DUs are described below with reference to relevant lines of evidence for discreteness and evolutionarily significance.

DU1 - islandica subspecies

This DU includes islandica Red Knot, which breed in the northeastern Canadian High Arctic, probably as far west as Prince Patrick Island and south to Prince of Wales Island (Godfrey 1992; Morrison and Harrington 1992; Baker et al. 2013, 2020; Figure 2). They winter in the United Kingdom, the Netherlands and other coastal areas of the western European seaboard and follow northward migration routes through Iceland and northern Norway (Godfrey 1992; Wilson 1981; Wilson et al. 2011, 2014). The delineation of this DU is unchanged from that previously assessed by COSEWIC (2007). Significant interchange of individuals between islandica and rufa breeding populations is unlikely, given their different migration systems, genetic separation (Verkuil et al. 2017), and largely non-overlapping breeding ranges (Godfrey 1992).

DU1 - islandica subspecies meets the following lines of evidence: D1, D2, D3, E2, E4.

• D1: Studies have shown varying degrees of genetic variation that support genetic distinctiveness of islandica and other Red Knot subspecies, with small differences in the frequency of different mitochondrial DNA sequences (Buehler and Baker 2005) but significant differentiation in single-nucleotide polymorphisms (Verkuil et al. 2017).
• D2: The breeding range of islandica in the northeastern Canadian High Arctic is thought to be largely disjunct from the breeding areas of rufa in the low- and mid-Canadian Arctic (Godfrey 1992), although the breeding range may overlap at mid-Arctic latitudes, for example around Somerset, North Baffin, Prince Patrick, and Melville Islands (USFWS 2014a; 2019). Its migratory pathways between nesting areas and wintering areas in western Europe are unique and disjunct, and these natural disjunctions likely favour the evolution of local adaptations related to migration and foraging strategies.
• D3: Birds of the islandica subspecies winter in coastal areas of northern boreal eco-geographic regions of Europe, over 5000 km from the nearest coastal wintering areas of rufa, and in very different ecoregions from those used by Red Knot wintering in southern North America and South America (Niles et al. 2006; Verkuil et al. 2017). They are thus exposed to different ecological conditions both on migration and in winter, which likely favour the evolution of local adaptations.
• E2: Red Knot of the islandica subspecies are unique in migrating from the Canadian High Arctic across the North Atlantic Ocean to western Europe. The disjunct nature of this discrete wintering population and its long-term persistence, likely since the end of the last Pleistocene glaciation (Buehler and Baker 2005), have led to adaptations involving considerable physiological transformation of internal organs and muscles during and after migration related to flight and breeding requirements (Piersma et al. 1999; Morrison et al. 2007).
• E4: Despite some areas of possible overlap of nesting rufa and islandica, current evidence suggests that all Red Knot breeding north of approximately 76°N are of the islandica subspecies (USFWS 2014a). Loss of this subspecies would eliminate this large and distinct portion of the Canadian breeding range.

DU2 - roselaari subspecies (C. c. roselaari; 2007 status report - C. c. roselaari and present DUs 4 and 5).

This DU includes roselaari Red Knot, which breed in northern and northwestern Alaska and on Wrangel Island in Russia (Figure 2), and migrate down or over the Pacific coast of Canada and the northwestern United States to coastal wintering grounds in California and the Pacific northwestern region of Mexico and parts of Central and South America (Buchanan et al. 2010; Carmona et al. 2013; Bishop et al. 2016). This delineation of roselaari differs significantly from that considered by COSEWIC (2007), which also included those populations now considered part of subspecies rufa, that overwinter in northeastern South America (DU 4) and southeastern USA / Gulf of Mexico / Caribbean (DU5; below).

C. c. roselaari is genetically distinguishable in genome-wide SNP variation from the other five Red Knot subspecies, including rufa (Verkuil et al. 2017). It is effectively isolated, with no indication of recent interchange with other groups of Red Knot and is most closely related genetically to C. c. rogersi, the subspecies that breeds farther west in eastern Russia (Verkuil et al. 2017). C. c. roselaari uses very different migration routes from other subspecies, moving between breeding areas in Alaska and Wrangel Island and wintering areas on the Pacific coast of North America (Carmona et al. 2013), although some birds of both roselaari and rufa may occur in Panama and Chiloé Island in winter (Navedo and Gutierrez 2018; Newstead and LeBlanc 2018), and Texas in spring (USFWS 2014a). Birds from the roselaari subspecies normally occur in Canada only in small numbers (hundreds or fewer) on the Pacific coast of British Columbia during spring and fall migration (e.g., Campbell et al. 1992; eBird 2019). Recent GPS tracking studies indicate that some roselaari Red Knot may stop regularly on isolated offshore islands off the coast of British Columbia during northward migration (Johnson pers. comm. 2020), and a few individuals may over-winter in some years (eBird 2019).

Verkuil et al. (2017) also identified genetic differentiation between roselaari breeding in Alaska and Wrangel Island. Emerging genetic evidence suggests that these differences might be as significant as other divisions in the Red Knot population structure (Conklin pers. comm. 2020). Observations of northward knot migration along the northwest Pacific coast of the United States suggest passage of two populations with slightly different timing and habitat use (Buchanan et al. 2017). However, with no ability to discern which individuals stopover in Canada during migration, there is currently insufficient information to warrant further subdivision of roselaari into two DUs.

The roselaari subspecies (DU2) meets the following lines of evidence: D1, D2, D3, E2.

• D1: C. c. roselaari is genetically distinguishable from the other five Red Knot subspecies, based on thousands of genome-wide SNPs (Verkuil et al. 2017).
• D2: The breeding range of roselaari in Alaska and Wrangel Island is disjunct from those of the rufa and islandica subspecies in the Canadian High Arctic (Portenko 1981; Godfrey 1992; Buehler and Piersma 2008). Its Pacific migratory pathways are unique and largely disjunct, although a few roselaari may overlap with rufa in Panama and Texas (USFWS 2014a). These natural disjunctions likely favour the evolution of local adaptations related to migratory flight and foraging strategies.
• D3: Birds of the roselaari subspecies winter in coastal areas of Pacific eco-geographic regions of western North America, in quite different ecoregions from those used by rufa Red Knot wintering in southeastern North America and northeastern and extreme southern South America. The major wintering areas of the two subspecies are at least 2000 km apart, although a few birds of these two subspecies may overlap in Panama and Texas (USFWS 2014a). Most are thus exposed to quite different ecological conditions both on migration and in winter, which likely favour the evolution of local adaptations.
• E2: Red Knot of the roselaari subspecies are unique in migrating from nesting areas in Alaska and Wrangel Island in Siberia down the Pacific coast of North America. The disjunct nature of this discrete breeding and wintering population, and its apparent long-term persistence, probably since the end of the last Pleistocene glaciation (Buehler and Baker 2005), has likely led to local adaptations to this ecological situation.

DU3 - Tierra del Fuego / Patagonia wintering population

This DU includes those rufa Red Knot that winter principally in Tierra del Fuego, with a few birds wintering along the Patagonian coast of Argentina and at Chiloé Island, Chile (USFWS 2014a), and it aligns with the full subspecies rufa as previously assessed by COSEWIC (2007). Birds from this population are unique in migrating much farther south than other populations, to distinct wintering areas that are disjunct by over 5000 km from the next nearest areas in coastal Brazil (USFWS 2014a). The wing moult schedule of this population differs from those wintering in more northerly areas, as it occurs entirely on the wintering grounds (Harrington et al. 2007, 2010a,b; Baker et al. 1998, 2013, 2020). Red Knot in the Tierra del Fuego / Patagonia wintering population (DU3) differ from those in DUs 4 and 5 in being smaller (e.g., in bill length and mass; Niles et al. 2008, Baker et al. 2013, 2020), and apparently in the degree of physiological changes on migration, as these longer-distance migrants likely undergo more reduction in their digestive apparatus and augmentation of flight muscles prior to migration (Baker et al. 2004; Atkinson et al. 2006, 2007).

The Tierra del Fuego / Patagonia wintering population (DU3) meets the following lines of evidence: D1, D3, E2.

• D1: This population has been differentiated from other wintering rufa populations based on an analysis of genome-wide AFLP markers (Baker et al. 2012a; Verkuil pers. comm. 2019). The degree and significance of this genetic differentiation is the subject of ongoing study (Conklin pers. comm. 2020).
• D3: Tierra del Fuego / Patagonia wintering population (DU3) individuals winter in coastal portions of the Southern Andes Ecozone in extreme southern South America, over 5000 km from birds from the northeastern South America wintering population (DU4) that winter in coastal areas of the equatorial Amazonian Orinocan Lowland Ecozone (Griffith et al. 2019), likely reflecting both historical and genetic distinctions. They thus over-winter in quite different coastal ecosystems. Although some birds from the Tierra del Fuego / Patagonia wintering population (DU3) pass through areas of coastal Brazil used by the northeastern South America wintering birds (DU4), any interchange has been insufficient to prevent local adaptation (see E2 below), and there are no records of individually marked birds changing wintering regions between years.
• E2: Birds in the Tierra del Fuego / Patagonia wintering population (DU3) are unique in migrating long distances (some 15,000 km in each direction) from the Canadian Arctic to extreme southern South America, with most overwintering in relatively harsh coastal climates of Tierra del Fuego. The disjunct nature of this discrete wintering population has led to local adaptations arising from their different ecological situations as compared to other rufa knot (northeastern South America wintering population - DU4, and southeastern USA / Gulf of Mexico / Caribbean wintering population - DU5), including moulting on the wintering grounds rather than at migration stopover areas in eastern North America (Baker et al. 1998, 2013; Harrington et al. 2007, 2010a,b), and being smaller and lighter (Baker et al. 2013; USFWS 2014a). These birds are also thought to undergo more pronounced physiological changes that facilitate their long migration, including accumulating large fat stores, undergoing substantial changes in metabolic rates, reducing the size of leg muscle, gizzard, stomach, intestines and liver, while increasing the size of pectoral muscles and heart (Baker et al. 2004; Atkinson et al. 2006; Niles et al. 2008).

DU4 - northeastern South America wintering population

This DU includes those rufa Red Knot that winter along the northeastern coast of South America, especially in the states of Maranhão and Ceara in northeastern Brazil, and occasional birds may winter in adjacent French Guiana and Suriname. This population was considered part of the roselaari DU in the previous status assessment (COSEWIC 2007). These Red Knot appear to be genetically distinguishable from the other wintering populations (Baker et al. 2012a; Verkuil pers. comm. 2019) and differ in using a disjunct geographical wintering area, morphometrics (measurements and weights; heavier than Tierra del Fuego / Patagonia wintering population (DU3) birds), and flight feather moult schedules (some of the northeastern South America wintering population (DU4) birds start but do not complete moult on migration in the eastern United States, while others undertake the entire wing moult on their South American wintering areas; Baker et al. 2013).

While birds from this population may co-occur with other rufa populations in Delaware Bay during northward migration, and at other east coast US sites during southward migration, their migration and moult schedules appear to be different (Baker et al. 2013; Lyons et al. 2017; Burger et al. 2020), and genetic studies indicate that the populations can be distinguished through high-resolution genetic techniques (Baker et al. 2012a; Verkuil pers. comm. 2019). Although some Tierra del Fuego / Patagonia wintering population (DU3) birds may occur on migration in northern Brazil, there are no observations of colour-marked birds from either of the Tierra del Fuego / Patagonia wintering population (DU3) or the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) there during the winter (Fedrizzi et al. 2016).

The northeastern South America wintering population (DU4) meets the following lines of evidence: D1, D3, E2.

• D1: This population has been differentiated from other wintering rufa populations based on an analysis of genome-wide AFLP markers (Baker et al. 2012a; Verkuil pers. comm. 2019). The degree and significance of this genetic differentiation is the subject of ongoing study (Conklin pers. comm. 2020).
• D3: Birds in the northeastern South America wintering population (DU4) winter in coastal areas of the equatorial Amazonian Orinocan Lowland Ecozone (Griffith et al. 2019), over 5000 km from birds in Tierra del Fuego / Patagonia wintering population (DU3) that winter in coastal portions of the boreal Southern Andes Ecozone, and over 2000 km from those that winter in coastal areas of the Eastern Temperate Forest and Tropical Wet Forest Ecoregions of southeastern US and Caribbean, likely reflecting historical distinctions supported by genetic differentiation (Baker et al. 2012a). They thus over-winter in different coastal ecosystems. Although some Tierra del Fuego / Patagonia wintering population (DU3) birds migrate through areas of coastal Brazil used by wintering birds from the northeastern South America (DU4), interchange appears to have been insufficient to prevent local adaptation within the northeastern South America wintering population (DU4; see E2 below), and there are no records of birds changing wintering areas.
• E2: Birds in the northeastern South America wintering population (DU4) have a variable moult schedule that differs from other rufa populations (Baker et al. 1998, 2013; Harrington et al. 2007, 2010a,b). Birds in this DU have slightly different morphometrics (Baker et al. 2013), and likely undergoing less pronounced physiological changes linked to migration strategies, especially compared to Tierra del Fuego / Patagonia wintering birds (DU3; Atkinson et al. 2006; Niles et al. 2008).

DU5 - Southeastern USA / Gulf of Mexico / Caribbean wintering population

This DU includes those rufa Red Knot that winter in the southeastern United States, including coasts of Florida, the Gulf of Mexico coasts of Louisiana and the Texas/Mexico coastal border region, and islands in the Caribbean Sea. This population was considered part of the roselaari DU in the previous status assessment (COSEWIC 2007). These birds are genetically distinct from wintering populations in northern Brazil (the northeastern South America wintering population - DU4) and Tierra del Fuego / Patagonia wintering birds - DU3; Baker et al. 2012a,b; Verkuil pers. comm. 2019). While Red Knot that winter in the southeastern United States (eastern Florida and Georgia) appear to migrate northwards along the Atlantic coast through Delaware Bay, the birds wintering along the Gulf Coast (western Florida, Louisiana, Texas) migrate north in spring through central areas of the United States and Canada and likely nest in the more westerly parts of the Arctic breeding range (Newstead et al. 2013). The genetic separation that has been observed suggests that mixing does not occur with other rufa populations on the breeding grounds (Baker et al. 2012a).

The southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) meets the following lines of evidence: D1, D3, E2.

• D1: This population has been differentiated from other wintering rufa populations based on an analysis of genome-wide AFLP markers (samples involved Florida birds; Baker et al. 2012a; Verkuil pers. comm. 2019). The degree and significance of this genetic differentiation is the subject of ongoing study (Conklin pers. comm. 2020).
• D3: Birds in the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) winter in coastal areas of the Eastern Temperate Forest and Tropical Wet Forest Ecoregions of southeastern US and Caribbean, over 2000 km from those that winter in the equatorial Amazonian Orinocan Lowland Ecozone (Griffith et al. 2019), likely reflecting historical distinctions supported by genetic differentiation (Baker et al. 2012a). They thus over-winter in different coastal ecosystems.
• E2: Birds in the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) are relatively short-distance migrants, migrating only from the Canadian High Arctic to overwinter in coastal climates of the Gulf of Mexico and Caribbean Sea. The disjunct nature of this discrete wintering population appears to have led to local adaptations to this ecological situation, including a moult schedule that differs from other rufa populations that migrate longer distances, as they likely undertake their complete wing and body moult at migration stopover areas in eastern North America (Baker et al. 1998, 2013; Harrington et al. 2007, 2010a, 2010b); they also undergo less pronounced physiological changes linked to migration strategies (Baker et al. 2004; Atkinson et al. 2006; Niles et al. 2008).

Special significance

Red Knot has long been considered a flagship species for shorebird conservation, owing to its long trans-hemispheric migrations, dependence on a relatively small number of key wintering and stopover areas, and its vulnerability to a range of environmental and climate-related factors (Morrison et al. 2004; Morrison 2018). Conservation of the habitats for Red Knot brings benefits to many other species of shorebirds and waterbirds. At some sites, knots and other shorebirds are economically important in attracting eco-tourists and birdwatchers (Karnicki 2016). Red Knot is one of the most studied shorebird species, and has served as a focal research species for development of conservation strategies for long-distance migrants (Myers et al. 1987; Harrington and Flowers 1996; Piersma and Baker 2000). It has been a focus of conservation efforts in Delaware Bay, and one individual knot (known as B95 from the inscription on his flag) was the subject of a popular book, Moonbird (Hoose 2012). This individual survived for more than 20 years through the major population crash of the Tierra del Fuego population and would have flown the distance to the Moon and back over the course of its lifetime (Hoose 2012). Conservation concerns surrounding knots and Horseshoe Crabs (Limulus polyphemus), in Delaware Bay have been featured in newspaper articles, documentary films, and the award-winning book The Narrow Edge (Cramer 2015).

Aboriginal Traditional Knowledge was not identified for the Red Knot. However, this species is part of ecosystems that are important to Indigenous people who recognize the interconnectedness of all species within the ecosystem.

Distribution

Global range

The global distribution of the six currently recognized subspecies of Red Knots is shown in Figure 1 and described in the Subspecies section.

Canadian range

The breeding range of Red Knot in the Canadian Arctic and likely breeding ranges of the three subspecies are shown in Figure 2.

Most C. c. islandica (DU1) breed in High Arctic areas of Greenland (Salomonsen 1950, 1967), with about 40% of the global breeding population nesting on the islands of the northeastern Canadian High Arctic (based on numbers in Whitfield et al. 1996; Morrison et al. 2006; COSEWIC 2007; Andres et al. 2012). The precise division between the ranges of C. c. islandica and C. c. rufa is uncertain, and birds nesting on either side of marine waters separating the mid-Arctic islands from the Queen Elizabeth Islands may be either subspecies (Godfrey 1992; Morrison and Harrington 1992).

Breeding grounds of C. c. roselaari (DU2) are found in north and northwestern Alaska and on Wrangel Island off northeastern Siberia in eastern Russia. This subspecies migrates through Canadian airspace in spring, and is usually observed in Canada only in small numbers on migration in coastal British Columbia (eBird 2019) and sometimes as far inland as Whitehorse, Yukon (Sinclair pers. comm. 2019). A few birds occasionally overwinter on the coast of southern British Columbia (eBird 2019). It is not known whether the birds occurring in Canada breed in Alaska or Russia, but is likely that both populations migrate through Canadian airspace.

The breeding range of C. c. rufa (Tierra del Fuego / Patagonia wintering birds (DU3), northeastern South America wintering population (DU4), and southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5)) falls entirely within the central and southern parts of the Canadian Arctic archipelago. Suitable habitat is not continuous in this region, resulting in discontinuities in occupancy (Figure 3). Rufa breeds on Coats and Mansel islands in northern Hudson Bay, Southampton Island, the east coast of Foxe Basin (Godfrey 1986; Gaston 2019), some islands in Foxe Basin (e.g., Prince Charles Island, Rowley Island, but not on Air Force Island; Johnston pers. comm. 2015), the west coast of Baffin Island (Morrison unpublished data; Niles et al. 2005, 2008, 2010a), probably across the Boothia Peninsula, King William Island, and southern Victoria Island (Parmelee et al. 1967). There seems to be no suitable habitat between northern Hudson Bay and the Rasmussen Basin (Niles et al. 2005), and Red Knot was not recorded there (Godfrey 1986, 1992) or in the Rasmussen Lowlands (Johnston et al. 2000). Although rufa appears to breed on the west side of the Boothia Peninsula and on King William Island (Niles et al. 2005), it is believed to be replaced by islandica on Prince of Wales Island to the north (Manning and Macpherson 1961; Godfrey 1992). Although there appears to be suitable habitat on Banks Island in the western Arctic archipelago, Red Knot has not been recorded breeding there (Manning et al. 1956; Johnston pers. comm. 2015) (see Figure 3; Habitat).

Figure 3. Known breeding range, distribution of preferred nesting habitats, and distribution of surveys and sightings of Red Knot (REKN) in the Canadian Arctic (from Rausch and Smith 2013).

Figure 3 was compiled by Rausch and Smith (2013) using the Circumpolar Arctic Vegetation Map (CAVM) and sightings of Red Knot in the Canadian Arctic, to determine the nesting habitats most used by the species (see Habitat). Overlaying the preferred habitats on a recent range map (Ridgely et al. 2007; CWS 2009) suggests that the current range likely includes large areas of unsuitable habitats, and that further surveys may reveal Red Knot breeding in areas with suitable habitat not included in the current range, such as the Brodeur Peninsula (Lathrop et al. 2018).

Extent of Occurrence (EOO) and Index of Area of Occupancy (IAO)

Little specific information is available on where Red Knot from each DU breed across the high Arctic, and the smallest area essential at any stage to the survival of knots from the Tierra del Fuego / Patagonia wintering population (DU3), northeastern South America wintering population (DU4), and southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) occurs outside Canada. Knots from the roselaari subspecies (DU2) only occur in Canada during the non-breeding period. As a consequence, different approaches and data sources were used to calculate the extent of occurrence (EOO) and index of area of occupancy (IAO) for each DU, as described below.

DU1 - islandica subspecies

The EOO for C. c. islandica in Canada was estimated as 1,084,949 km², calculated as a minimum convex polygon that encompasses its known breeding range within the northeastern Canadian Arctic, with an assumption of Prince of Wales Island as the southernmost limit (Figure 4).

The IAO for islandica was estimated as 327,212 km² (Figure 4), determined using a 2 x 2 km grid drawn over the Canadian breeding range (Figure 2), based in part on the distribution of preferred nesting habitats (Figure 3).

As different methods and data sources were used in the previous status report (COSEWIC 2007) to determine the EOO and IAO for DU1 - islandica subspecies, it is not possible to assess trends in these parameters.

Figure 4. Extent of occurrence (EOO) and index of area of occupancy (IAO) for Red Knot C. c. islandica (DU1) in Canada, based on the known breeding range within the northeastern Canadian Arctic (from Figure 2; map prepared by R. Nobre Soares and S. Allen).

DU2 - roselaari subspecies

The EOO for C. c. roselaari in Canada was estimated as 167,016 km², which encompasses areas along the Pacific coast of British Columbia where Red Knot have been recorded on migration or during winter during the 10-year period 2009-2018 (eBird 2019), together with records of GPS-tagged birds made during spring migration in 2017 and 2018 (Johnson pers. comm. 2020) (Figure 5).

Figure 5. Extent of occurrence (EOO) and that portion of the index of area of occupancy (IAO) for Red Knot C. c. roselaari (DU2) that occurs within Canada, based on records of Red Knot on migration or in winter (2009-2018) from eBird (2019), shown by black dots, and records from GPS-tagged birds during spring migration in 2017 and 2018 (Johnson pers. comm. 2020), shown by blue dots (map prepared by S. Allen).

In some cases (e.g., crucial feeding sites for migratory taxa), the relevant area of occupancy is the smallest area essential at any stage to the survival of the taxon (IUCN Standards and Petitions Subcommittee 2017; COSEWIC 2019), and in such cases, this area need not occur within Canada. As stopover sites used on spring migration likely represent the smallest essential areas used during the annual cycle by roselaari Red Knots (Johnson pers. comm 2020), IAO was calculated for this DU during spring migration. A minimum estimate of the Canadian portion of the IAO during the spring migration period is 356 km², based on the same migration records in coastal British Columbia used to estimate EOO (Figure 5). However, IAO calculated for this life stage should account for other undocumented sites in British Columbia, as well as coastal sites in Alaska and the Pacific Coast of the contiguous United States, in order to reflect the smallest area essential during spring migration for this DU. As these sites are together estimated to total an additional 200-800 km of coastline, it is probable that overall IAO is between 500 and 2000 km² during spring migration.

As EOO and IAO for this DU were not delineated the same way in the previous status report (COSEWIC 2007), it is not possible to assess trends in EOO and IAO.

Tierra del Fuego / Patagonia wintering population (DU3), northeastern South America wintering population (DU4), and southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5)

The size of the EOO for C. c. rufa, which comprises these three DUs, was estimated as 1,500,261 km², calculated as a minimum convex polygon that encompasses the breeding range of these three DUs within the central Canadian Arctic (Figure 6).

Figure 6. Extent of occurrence (EOO) for Red Knot C. c. rufa (DUs 3, 4, and 5) in Canada, based on the known breeding range of the subspecies within the central Canadian Arctic (from Figure 2; map prepared by R. Nobre Soares and S. Allen).

Although there is some recent information available on breeding sites of individuals from these DUs, no consistent patterns have emerged (Burger et al. 2020; Porter pers. comm. 2020). Although there appears to be significant overlap of the EOO of all three DUs within the central Canadian Arctic, the finding that genetic markers can differentiate among the wintering populations (DUs) suggests some degree of genetic isolation on the breeding grounds (Baker et al. 2012a,b). As the portion of the total EOO of C. c. rufa assignable to each of the Tierra del Fuego / Patagonia wintering population (DU3), the northeastern South America wintering population (DU4), and the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) is thus unknown, each is assigned the same value of 1,500,261 km², equal to the EOO for all C. c. rufa, based on the breeding distribution shown in Figure 6. This is clearly a maximum value, although considering the abundance estimates of each DU and the scattered breeding dispersion of Red Knot across much of the Canadian Arctic, it is very likely that the actual EOO for each far exceeds 20,000 km² and other EOO thresholds used in applying assessment criteria.

As Red Knots from the Tierra del Fuego / Patagonia wintering population (DU3), the northeastern South America wintering population (DU4) and the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) breed in a dispersed fashion over relatively large areas of the Canadian Arctic, but are concentrated in smaller areas at migration stopovers or on the wintering grounds outside Canada, IAO was calculated for these DUs at these latter sites.

A minimum estimate of IAO for the Tierra del Fuego / Patagonia wintering population (DU3) of 1072 km² was calculated by overlaying a grid with a cell size of 2x2 km on regularly occupied sites within the concentrated wintering range on the coasts of Tierra del Fuego and southern Patagonia, where Red Knot has been recorded during the 10-year period 2009-2018 (eBird 2019; Morrison et al. 2020a; Morrison unpubl. data) (Figure 7). Up to 5% of the total population (maximum of 375 mature individuals) may occur in winter at sites outside this area (Morrison pers comm. 2019). If each individual occurred in a separate 2x2 km grid square, they could account for an additional portion of the IAO of up to 1500 km². However, given the tendency of wintering Red Knots to cluster in flocks, the additional portion of the IAO occupied by the peripheral birds is likely 100-200 km² at most, suggesting that the actual IAO used by Red Knot from DU3 in winter is probably 1100-1300 km².

Red Knot from the northeastern South America wintering population (DU4) also concentrate in coastal South America during winter, where IAO was calculated. The area of the core IAO of 684 km² was calculated by overlaying a grid with a cell size of 2 x 2 km over regularly occupied sites within the wintering range on the coasts of northeastern Brazil, where Red Knot has been recorded during the 10-year period 2010-2019 (Morrison, Ross, Mobley, and Mizrahi unpubl. data; eBird 2019; NJA 2020; Morrison et al. 2020c) (Figure 8). However, some birds from this DU overwinter in small groups at other scattered coastal sites in adjacent French Guiana and Suriname. If these birds represent about 5% of the population, or about 1000 individuals (Morrison pers. obs.), they likely occupy an additional portion of the IAO roughly equal to about 300-600 km², suggesting that the total IAO used by Red Knot from DU4 in winter is probably about 1000-1600 km².

Figure 7. Primary areas included in the index of area of occupancy (IAO) for Red Knot C. c. rufa Tierra del Fuego / Patagonia wintering population (DU3) on its wintering grounds in southern Argentina and Chile, based on the distribution of regularly occupied wintering sites (2009-2018) on the coasts of Tierra del Fuego and Patagonia (eBird 2019; Morrison et al. 2020b; Morrison unpubl. data; map prepared by R. Nobre Soares and S. Allen).

Figure 8. Primary areas included in the index of area of occupancy (IAO) for Red Knot C. c. rufa northeastern South America wintering population (DU4) on its wintering grounds in northeastern Brazil, based on the distribution of regularly occupied coastal wintering sites (2010-2019) in the states of Maranhão and Ceara (eBird 2019; Morrison, Ross, Mobley and Mizrahi unpubl. data; Morrison et al. 2020c; map prepared by R. Nobre Soares and S. Allen).

The IAO for the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) of 2,548 km² was calculated by overlaying a grid with a cell size of 2 x 2 km over migration stopover sites along the coast of Hudson Bay in Manitoba and extreme northwestern Ontario, near the mouth of the Nelson River, where all or most of the birds in the DU are thought to occur during spring migration, during the 10-year period 2009-2018 (McKellar et al. 2015; Burger et al. 2020; eBird 2019) (Figure 9). This value is considered to be a minimum estimate, as it is likely that small numbers may occur in coastal Hudson Bay outside the survey area in spring.

As different data sources, areas, and DU delineation methods were used to determine the EOO and IAO of the Tierra del Fuego / Patagonia wintering population (DU3), the northeastern South America wintering population (DU4), and the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5), compared to the 2007 Status Report (COSEWIC 2007), it is not possible to assess trends in these parameters for these DUs.

Figure 9. Primary areas included in the index of area of occupancy (IAO) for Red Knot C. c. rufa southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) at migration stopover sites on the coast of Hudson Bay in Manitoba and Ontario, near the mouth of the Nelson River (2009-2018), where all southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) knots are thought to occur during spring migration (eBird 2019; McKellar et al. 2015; Burger et al. 2020; map prepared by R. Nobre Soares and S. Allen).

Search effort

For the islandica subspecies (DU1), the Tierra del Fuego / Patagonia wintering population (DU3), the northeastern South America wintering population (DU4), and the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5), information from Arctic nesting grounds has come from targeted regional and local surveys, such as the Arctic Program for Regional and International Shorebird Monitoring (Arctic PRISM) (Bart and Johnston 2012; Government of Canada 2018), and the Northwest Territories - Nunavut Bird Checklist Survey (CWS 2009), as well as from historical avifaunal surveys (e.g., MacDonald 1953; Parmelee and MacDonald 1960; Parmelee et al. 1967; Godfrey 1986). In Europe, counts of islandica subspecies (DU1) Red Knot on the wintering grounds are coordinated by Wetlands International (Wetlands International 2018).

For the Tierra del Fuego / Patagonia wintering population (DU3), the northeastern South America wintering population (DU4), and the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5), information on numbers and distribution of Red Knot in Canada south of the breeding grounds comes from ground counts and aerial surveys. Ground counts include surveys conducted by biologists (e.g., in Quebec) and volunteer survey schemes such as the Atlantic Canada Shorebird Survey scheme (ACSS, formerly Maritimes Shorebird Survey scheme, MSS) and the Ontario Shorebird Survey (OSS). These volunteer programs are coordinated through PRISM (Bart et al. 2002; U.S. Shorebird Conservation Plan Partnership 2018). Aerial surveys conducted by the Canadian Wildlife Service of Environment and Climate Change Canada (CWS) have provided important information from James Bay (Morrison and Harrington 1979; Friis 2017; Friis and Morrison 2018) and Hudson Bay (McKellar et al. 2015), and the Mingan Islands, Quebec (Buidin et al. 2010; Lyons et al. 2017; Aubry pers. comm. 2019). For the roselaari subspecies (DU2), historical records from the west coast of Canada (Campbell et al. 1998) have been supplemented with records from eBird (2019), which also provides information on records from all DUs from all parts of the Americas.

Internationally, coastal aerial surveys have provided much information on shorebird distribution at migration stopover areas and wintering sites, involving roselaari subspecies (DU2), Tierra del Fuego / Patagonia wintering population (DU3), the northeastern South America wintering population (DU4), and the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5). ECCC-CWS conducted “Atlas” surveys covering the coasts of South America in the 1980s (Morrison and Ross 1989) and further “Atlas” projects were conducted in Panama (Morrison et al. 1998) and Mexico (Morrison et al. 2009). For the Tierra del Fuego / Patagonia wintering population (DU3), the key areas in Tierra del Fuego have been surveyed annually since 2000 (Morrison 2018; Morrison et al. 2020a), with additional coverage of the coastline of Patagonia in 2002, 2003, 2004 and 2012 (Morrison et al. 2004, 2020b; Morrison 2018). For the northeastern South America wintering population (DU4), aerial surveys of the northeastern coast of South America (covering the Guianas and north and northeastern Brazil) have been conducted in various years between 2008 and 2019. These ongoing surveys provide regular monitoring of the most important wintering areas (Morrison et al. 2012, 2020a,b,c; NJA 2020). For the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5), ground and aerial surveys have provided information from the southeastern United States (Niles et al. 2006). Further information on search effort is given in Sampling Effort and Methods and Population Sizes and Trends.

Habitat

Habitat requirements

Red Knot uses different habitats for breeding, migration, and wintering. In the Arctic, knots nest in exposed barren habitats, such as windswept ridges, slopes, or plateaus (Pleske 1928; Parmelee and MacDonald 1960; Nettleship 1974; Baker et al. 2013). Nest sites are usually on dry, south-facing sites, often near wetlands or lake edges which may be used for feeding and where the young are led after hatching (Whitfield and Brade 1991; Tomkovitch and Soloviev 1996). Using the Circumpolar Arctic Vegetation Map (CAVM), Rausch and Smith (2013) found that preferred nesting habitats for Red Knot were “cryptogam, herb barren”, “graminoid prostrate dwarf-shrub, forb tundra”, “rush/grass, forb, cryptogam tundra”, and “prostrate dwarf-shrub, herb tundra” habitats which are widely distributed across the Arctic (Figure 3). Nesting densities are usually low, with nests often 0.75-1 km or more apart (Nettleship 1974; Niles et al. 2010a). An analysis of breeding habitat characteristics of C. c. rufa, based on 21 nests on Southampton Island and relocations of radio-tagged birds over a wider section of the central Canadian Arctic, indicated that birds generally nested within 150 m of sea level, within 50 km of the coast, and in areas with less than 5% vegetation cover (Niles et al. 2005, 2008; Lathrop et al. 2018). Foraging habitats may be considerable distances from nests (up to 10 km) and are usually in damp or wetland habitats, or barren areas (Whitfield and Brade 1991; Niles et al. 2010a; Baker et al. 2013; Morrison unpubl. data).

On migration and in winter, Red Knot favours coastal areas with extensive intertidal flats, usually sand although sometimes mud, where the birds feed on bivalves and other benthic invertebrates (Schneider and Harrington 1981; Piersma et al. 1993; Baker et al. 2013). The most important wintering habitats of birds from the Tierra del Fuego / Patagonia wintering population (DU3) are the massive intertidal sand and mudflats at Bahia Lomas, Chile, and Bahia San Sebastian, Argentina, in Tierra del Fuego. Knots also forage on restinga habitats, rocky intertidal platforms that support a variety of invertebrates, at Rio Grande on the Atlantic coast of Tierra del Fuego, Argentina, and on migration stopover areas on the coast of Patagonia (Morrison and Ross 1989; González et al. 1996). Similar rocky intertidal habitat is used in the Mingan Archipelago, Quebec, during southward migration (Baker et al. 2013). During spring migration in Delaware Bay, knots forage on sandy beaches used by nesting Horseshoe Crab, feeding on crab eggs (Botton et al. 1994; Tsipoura and Burger 1999). Red Knot also use eroding peat banks along the shoreline of the eastern United States on northward and southward migration, where they feed on mussel spat (Niles et al. 2010a; Baker et al. 2013). They sometimes forage within the tide wrack on beaches, salt marshes, brackish lagoons, mangrove areas, and mudflats on migration and in winter, in the southeastern United States and northeastern Brazil (Niles et al. 2005, 2010a; Cohen et al. 2009, 2010). Knots moving through the interior of North America may use inland saline lakes and agricultural fields (Gratto-Trevor et al. 2001; Beyersbergen and Duncan 2007; Baker et al. 2013).

An important aspect of habitat quality for Red Knot on migration and wintering areas is the proximity of suitable roosting areas that provide an undisturbed area safe from ground or aerial predators and human disturbance (Ferrari et al. 2002; Peters and Otis 2006; Rogers et al. 2006).

Habitat trends

Habitat trends for the DUs are summarized in Table 1, based on the following assessments.

It is unlikely that major changes in the extent of breeding habitat have recently occurred in the Canadian Arctic, although long-term changes resulting from climate change will likely affect Red Knot (all DUs), probably in a negative fashion (Meltofte et al. 2007). Lathrop et al. (2016) assessed likely future habitat changes in the Canadian Arctic under three climate change scenarios - full (islandica and rufa - DU1 and DUs 3,4,5), islandica-only (DU1), and rufa-only (DUs 3,4,5). Their modelling results: (1) predicted a widespread decrease in breeding habitat suitability in the southern portion of the rufa breeding range, while the rufa-only (DUs 3,4,5) model suggested increasing habitat suitability in selected areas in the central portion of the rufa range; (2) the islandica-only (DU1) model suggested an increase in suitable habitat area extending across the southern section of the High Arctic Islands; (3) in both cases, a significant portion of the new habitat areas predicted by the models occurred at the spatially distant end of the subpopulation breeding ranges, requiring each subspecies population to travel farther to utilize new habitat; and (4) results suggest that the rufa subpopulation would be more vulnerable to effects of future climate change than islandica. Scenarios presented by Wauchope et al. (2016) under different climate change models are less optimistic. Whereas the amount of “climatically-suitable breeding conditions” increased for about half of 24 shorebird species analyzed in the North American Arctic, for Red Knot few such areas would remain by 2070; 12% and 5% compared to present under “optimistic” and “pessimistic” emission scenarios, respectively. The percentage of suitable habitat remaining by 2070 was 6-36% and 1-18% under the two scenarios.

There have been significant (>50%) historical wetland habitat losses in North America (Dahl 1990a,b) and elsewhere globally (Davidson 2014), including coastal wetlands (Li et al. 2018), potentially affecting birds from all DUs on migration and wintering areas. These losses mean that shorebirds have fewer alternative sites should they encounter problems at current sites in migration or wintering areas, potentially limiting their options for successfully completing the annual cycle. In the United States, ongoing losses and changes in coastal habitats resulting from coastal protection measures are expected (USFWS 2015). Potentially, the most significant losses to coastal habitats are anticipated from sea level rise resulting from warming climates (Galbraith et al. 2002, 2005, 2014). In Europe, populations of C. c. islandica (DU1) are likely to be affected by reductions in habitat through projected sea level rise. In the Wadden Sea, degradation of feeding habitats through commercial shellfisheries has affected islandica subspecies (DU1) and may still be affecting this subspecies (Blew et al. 2017).

For roselaari subspecies (DU2), Glick et al. (2007) estimated that 44% of the tidal flats at 11 sites in the Pacific Northwest of the United States would be lost by 2100, based on a model forecasting a sea-level rise of 0.69 m. Galbraith et al. (2002, 2005) modelled sea level rise impacts at five major shorebird sites in the United States, which predicted losses of 20-70% of current intertidal areas. For roselaari subspecies (DU2), four sites on the Pacific coast of the United States were forecast to lose between 14.1% and 38.9% of their intertidal habitat by 2050 and 2100, respectively, under a 2°C warming scenario. Under the same scenario, the respective losses would be 19.8% and 57.4% for the Tierra del Fuego / Patagonia wintering population (DU3), the northeastern South America wintering population (DU4), and parts of the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) passing through Delaware Bay (Galbraith et al. 2005). The Bolivar Flats in Texas, used by the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5), were estimated to lose 19.8% and gain 1.8% of the area of intertidal flats by 2050 and 2100, respectively. Galbraith et al. (2005) concluded that if their 50% probability predictions occurred, San Francisco Bay and Delaware Bay sites “could not possibly support shorebird numbers that are even only fractions of their current sizes”.

However, such predictions of habitat changes are complicated, both technically and in interpretation. For instance, modelling by Glick et al. (2008) predicted increases in tidal flats in Delaware Bay (15-fold), though decreases in most other areas in the Chesapeake Bay area (47-96%). They mostly forecast increases in beach habitats in Delaware Bay and elsewhere the region, but it is unknown whether such beaches would support Red Knot and Horseshoe Crab populations as in their present relationship.

The likely effect on habitat was a fundamental element in the assessment by Galbraith et al. (2014) on the vulnerability of Red Knot to climate change. Vulnerability was increased from a Risk Level of 4 (High Concern) to 6, a new category reflecting an assessment of “Critical” under the risk categories described in the United States Shorebird Conservation Plan (Brown et al. 2001; Galbraith et al. 2014).

Biology

The information in this section is drawn mostly from the species account for Red Knot in Birds of North America (Baker et al. 2013) and Birds of the World (Baker et al. 2020), the United States Red Knot status assessment (Niles et al. 2008), and the Red Knot Conservation Plan for the Western Hemisphere (Niles et al. 2010a), as well as from the writer’s personal experience (Morrison pers. obs.). Most information presented here applies to all five DUs, except as noted.

Life cycle and reproduction

Red Knot has a monogamous mating system (Parmelee and MacDonald 1960). Males often arrive first on the breeding grounds (Whitfield and Brade 1991), with pair bonds forming soon after arrival, although display songs may be heard during northward migration (Piersma et al. 1991; Morrison unpubl. data; Baker et al. 2013). Mating occurs on the breeding grounds and pair bonds remain intact until shortly after the eggs hatch (Whitfield and Brade 1991; Niles et al. 2008). Egg-laying occurs after a period of physiological reorganization within the bird’s body following arrival on the breeding grounds, with eggs formed from local food resources rather than from body stores brought from migration areas (Morrison and Hobson 2004). Clutches are laid over a six-day period (Nettleship 1974). There is normally only one clutch per year, although a replacement clutch may be laid if the nest is lost early in the season (Whitfield et al. 1996). Clutches normally consist of four eggs (Parmelee and MacDonald 1960; Nettleship 1974; Niles et al. 2007; Baker et al. 2013), although three-egg clutches have been recorded on Ellesmere Island (Nettleship 1974). The latter may be a result of a re-nesting attempt after loss of the first clutch (in Alaska, Johnson pers. comm. in Baker et al. 2013).

Nests are usually simple scrapes placed in small patches of vegetation, which may be lined with pieces of lichen or other vegetation (Pleske 1928; Nettleship 1974). Incubation takes 21-22 days and is shared by males and females (Bird in Salomonsen 1950; Nettleship 1968). Territories are large and hence nest densities are low, with nests typically widely separated (0.75-1 km apart in Parmelee and MacDonald 1960; Nettleship 1974; Niles et al. 2010a; Baker et al. 2013). Estimated regional densities for C. c. islandica (DU1) in the Canadian Arctic and in Greenland varied between 0.13 and 2 pairs/km², with densities in local study areas on Ellesmere Island ranging between 0.4 and 12.7 pairs/km² (Whitfield et al. 1996). Although territories are defended from other conspecifics, off-duty birds tend to feed away from their territory in communal feeding areas (Parmelee and MacDonald 1960; Flint 1972; Nettleship 1974). Male Red Knots are highly faithful to the same breeding area from year to year (Baker et al. 2020). One islandica Red Knot bred at a site near Alert, on the north coast of Ellesmere Island, over a period of at least 11 years between 1992 and 2002 (Morrison unpubl. data).

Hatching generally occurs in the first half of July in the Canadian Arctic (Parmelee and MacDonald 1960; Nettleship 1974), and up to two weeks earlier for C. c. roselaari (DU2) in Alaska and northern Russia (Loktionov et al. 2015; Johnson 2018). The young leave the nest within 24 hours of hatching, and the brood begins to wander large distances across the tundra within 1-2 days, often travelling several kilometres (Morrison 1992; Morrison unpubl. data; Baker et al. 2020). The female departs a few days after hatch, leaving the male to care for the brood, and fledging takes place at approximately 18 days (Parmelee and MacDonald 1960; Nettleship and Maher 1973 Nettleship 1974). Males depart following fledging and are followed by the juveniles 1-3 weeks later (Morrison 1992). Nesting success may vary considerably from year to year, depending on weather conditions and predator cycles, affecting population numbers in the following wintering season (Boyd and Piersma 2001).

Longevity and survival

Red Knots can live for more than 20 years, and most start breeding at age two (Baker et al. 2013). The oldest known islandica was about 25 years old (COSEWIC 2007) and the iconic rufa Red Knot known as B95 was about 21 years old when last observed in Tierra del Fuego in January 2014 (Morrison 2018, unpubl. data).

Mendez et al. (2018) reviewed annual survival estimates of shorebirds and reported values for Red Knot from eight studies ranging from 0.62 to 0.92, with a modelled overall adult survival rate (corrected for methodological biases) of 0.801 ± 0.011. Annual survival rates of knots on southward migration in James Bay averaged about 0.70 over the period 2009-2018 (MacDonald 2020) and were not time-dependent, while annual survival at Mingan during 2006-2016 also averaged about 0.70 (0.46-0.86), but was time-dependent and apparently lower in more recent years (Aubry pers. comm. 2020). Given that the most current apparent survival estimates from Delaware Bay are about 0.90 (Smith pers. comm. 2020), an overall value for adult survival of 0.80 seems appropriate.

Generation time calculated using the online IUCN Generation Length Workbook spreadsheet (IUCN Standards and Petitions Subcommittee 2017) is 7 years, based on adult (>2 years) survival of 0.80 and fecundity of 1.5, juvenile survival of 0.25 and fecundity of 0, and sub-adult survival of 0.65 and fecundity of 1.5 (Appendix 1). Method 2 in the IUCN guidelines (Generation Time = 1/adult mortality + age at first reproduction) also produces an estimate of 7 years. Note that assuming the age of first reproduction as 2 years is defensible, as IUCN guidelines indicate that a lower value would encompass age of first breeding as less than 2 years (between 12 and 24 months), and some knots may not breed until older than 2 years (Azpiroz and Rodríguez-Ferraro 2006; Martínez-Curci et al. 2020; see Baker et al. 2013, 2020), and Watts et al. (2015) used age of first reproduction as 2-3 years.

The calculated generation time of 7 years is similar to that of 6.9 years recently estimated by Bird et al. (2020) and is used here for all five DUs. This value is considerably higher than the generation time of 4-5 years given in the 2007 status report, which suggested that very few knots live for more than about 7-8 years (COSEWIC 2007), and it is now known that some live at least 20 years (Baker et al. 2013).

For the rufa Tierra del Fuego / Patagonia wintering population (DU3), Baker et al. (2004) estimated knot survival as 0.85 when conditions were good in Delaware Bay, and 0.56 in years with little food there, producing generation times of 8.7 and 4.3 years, respectively. The McGowan et al. (2011) estimate of survival for Red Knot in Delaware Bay of 0.92, implying a generation time of 14.5 years, seems unrealistically high, but may be possible when conditions are particularly favourable. Rakhamberdiev et al. (2015) noted that winter and summer survival of C. c. islandica (DU1) can vary considerably, sometimes in a compensatory manner. Population matrix analysis suggests that substantial population increases may be possible when conditions are particularly favourable (Wilson pers. comm. 2018; Appendix 1).

Much less is known about survival of juvenile birds during their first two years of life. Annual survival of juveniles at Mingan, Quebec, during 2006-2016 was estimated as 0.12-0.42, but was time-dependent and apparently lower in more recent years (Aubry pers. comm. 2020). Juvenile survival has been estimated as 0.25 (Mendez et al. 2018 and see Appendix 1; Boyd and Piersma (2001) for C. c. islandica), or as half adult survival (Baker et al. 2004), but field estimates are lacking for most DUs. Little information is available on where young birds spend their first summer before breeding at age two, and how their movements and habitats used affect their survival and recruitment into the breeding population (Martínez-Curci et al. 2020).

Physiology and adaptability

Red Knot undergoes many significant physiological changes during migration, especially during the final stopover on northward migration (Piersma et al. 1999; Baker et al. 2004). These changes increase flight efficiency to enable birds to reach the breeding grounds and involve accumulating sufficient additional body stores to breed successfully. Fat deposition continues towards the end of the migration stopover, while the “flight machinery” that will power the flight - e.g., heart, flight muscles, fat deposits - increases in size (Piersma et al. 1999). In contrast, the digestive organs and muscles that will be used less or not at all during the flight - e.g., leg muscles, gizzard, gut, liver - decrease in size (Piersma et al.1999). Thus, by the time the bird departs, it is well-prepared for the long flight to the Arctic. The stores of fat and protein that remain when knots arrive on the breeding grounds are then used to enable gut, gizzard, heart (which decreases in size during flight), liver, gonads, etc. to be regrown in preparation for the breeding attempt (Morrison et al. 2005; Morrison 2006). Failure to accumulate the needed stores and undergo the complex physiological transformations before migration and breeding would have severe survival consequences (Baker et al. 2004; Morrison et al. 2007; see Threats section).

The ability to undergo physiological changes that reduce the mass of the digestive apparatus before long flights is likely most critical for long-distance migrants, such as islandica Red Knot (DU1) en route from European wintering grounds via Iceland to the Canadian Arctic, and the long-distance rufa (DU3) migrating from Tierra del Fuego via Delaware Bay to the Arctic (Atkinson et al. 2007). The availability of easily digestible and energetically rich Horseshoe Crab eggs in Delaware Bay is thought to be of greater importance during northward migration for long-distance rufa migrants from the Tierra del Fuego / Patagonia wintering population (DU3) than for populations from closer wintering areas (northeastern South America wintering population DU4, southeastern USA / Gulf of Mexico / Caribbean wintering population DU5), and the latter may undergo less extensive physiological changes during migration. Restoration of Horseshoe Crab populations in Delaware Bay is therefore thought to be critical for future recovery of the Tierra del Fuego / Patagonia wintering population (DU3; Niles et al. 2009).

Dispersal and migration

Recent studies of Red Knot tagged with coded flags, geolocators, or radio nanotags have provided much new information on migration routes used by birds in all five DUs (Burger et al. 2020). Light-level geolocators provide relatively continuous information on the birds’ position, based on day-length and date, but require the recapture of the bird to download data from the geolocator (Porter and Smith 2013). The 24-hour daylight in Arctic breeding areas often precludes an accurate position fix, but recorded periods of light and dark do provide information on incubation schedules (Burger et al. 2012b). The development of an automated MOTUS radio telemetry tower network, to detect the presence and movements of birds carrying VHF ‘nanotags’, is increasingly enabling the tracking of migrating Red Knot in both North and South America (Taylor et al. 2017; Motus 2018).

DU1 - islandica subspecies

It is well-established that the Red Knot populations breeding in the northeastern Canadian High Arctic (DU1) migrate to European wintering grounds (e.g., Morrison 1975; Davidson and Wilson 1992; Baker et al. 2013, 2020). Two major routes are used on northwestward migration from Europe, via Iceland and via northern Norway, and birds have occasionally been detected switching between stopover sites on different routes in subsequent years (Wilson et al. 2011). On fall migration, knots from the northern parts of the Canadian breeding range are likely able to fly directly to Europe, as judged by departure weights and stable isotope patterns (Morrison unpubl. data; Dietz et al. 2010; Baker et al. 2013, 2020).

Conditions at final spring stopover sites play a key role in influencing survival and reproductive success. Only those knots departing in good condition from Iceland stopover sites were later detected alive after a series of difficult summers on the breeding grounds, and departure condition from Iceland appears to be directly related to length of survival, even during normal summers (Piersma 1998; Piersma et al. 1999; Morrison 2006; Morrison et al. 2007).

There are three records of individual Red Knot using different flyways in different years: (1) a bird captured at the Mingan Archipelago in August 2008 during southward migration seen in northeast Iceland in May 2010 on northward migration, (2) a bird captured in northern Norway on northward migration in May 2009 and seen at the Mingan Archipelago in July 2009 on southward migration; and (3) a bird banded in eastern England in March 1971 and found on Barbados in August 1972 (Wilson et al. 2010). It is interesting to note that islandica and rufa have the lowest degree of genetic differentiation amongst Red Knot subspecies (Verkuil et al. 2017), perhaps reflecting their evolutionary history (Buehler and Baker 2005; Buehler et al. 2006). However, such records appear to be very uncommon.

DU2 - roselaari subspecies

Movements from the breeding areas in Alaska and Wrangel Island to the main wintering areas on the Pacific coast of California and Mexico, through the four major stopover areas on the Pacific coast (Grays Harbor and Willapa Bay, Washington, and Copper River and Yukon-Kuskokwim Deltas, Alaska) have been documented through observations of flagged and radio-tagged birds (Buchanan et al. 2010; Carmona et al. 2013; Bishop et al. 2016). High site-fidelity has been found at Pacific stopover sites (Buchanan et al. 2012). Knots are thought to make long-distance flights between the main areas during northward migration (Carmona et al. 2013; Bishop et al. 2016), and very few Red Knot (generally <100) are seen on the coast annually in British Columbia (Campbell et al. 1998; eBird 2019).

Although many roselaari Red Knot fly directly from stopover sites at estuaries in Washington to those in Alaska during northward migration, results from recent GPS tracking studies have shown that many (27 of 47; 54%) stopped for 1-5 days on small islands or rocky islets on the coast of British Columbia, perhaps to rest or avoid headwinds or predators rather than to refuel (Johnson pers. comm. 2020; Figure 5). In the autumn, GPS tracking indicates that knots fly from staging areas in Alaska directly to wintering areas from southern California to northwest Mexico (Buchanan pers. comm. 2020; Johnson pers. comm. 2020). Red Knots seen in British Columbia (generally <100 annually; Campbell et al. 1998; eBird 2019; although note GPS tracking results) can be referred to these populations of roselaari.

Most roselaari Red Knot appear to fly directly from spring migratory stopover sites on estuaries in Washington to Alaskan stopover sites during northward migration (Buchanan pers. comm. 2020; Johnson pers. comm. 2020), presumably flying between them in a relatively direct line, unless deflected by weather conditions. The most direct “Great Circle” route from Gray’s Harbor and adjacent Willapa Bay in Washington to the Copper River Delta in southeast Alaska passes directly over Haida Gwaii in British Columbia (Google Earth 2019), well within Canada’s 200 mile EEZ (Exclusive Economic Zone). Flying in a straight line from these Washington stopover sites to the Yukon-Kuskokwim Delta in southwest Alaska would take a route slightly farther west, likely missing Haida Gwaii but well within Canada’s 200 mile limit (Google Earth 2019). Virtually all roselaari Red Knots (DU2) thus likely travel through Canadian airspace when migrating northwards between Washington and Alaskan stopover sites. Indeed, many of these birds likely stop briefly in Canada, as evidenced by the sample noted above, in which 54% of 47 GPS-tagged northbound roselaari knots stopped on remote islets in British Columbia (Johnson pers. comm. 2020; Figure 5).

June records indicate that the northeast coast of the Gulf of California, Mexico is important for one-year-old knots summering south of the breeding grounds, the only such area known for the DU (Soto-Montoya et al. 2009).

There is some indication that birds breeding on Wrangel Island are genetically distinct from those in northwest Alaska (Verkuil et al. 2017) and may migrate northwards on different schedules (Buchanan et al. 2018), at least in some years (Buchanan pers. comm. 2020). Much less is known about southward migration, and few large concentrations of knots have been detected between breeding and wintering areas (Carmona 2013).

DU3 - Tierra del Fuego / Patagonia wintering population

Southern-wintering rufa knots (Tierra del Fuego / Patagonia wintering population DU3) make their way north from their main wintering grounds in Tierra del Fuego, up the coast of Patagonia, stopping at several key sites (Morrison and Harrington 1992) including San Antonio Oeste (González et al. 1996, 2001), Bahia Blanca (Petracci pers. comm. 2019), Punta Rasa (Martínez-Curci et al. 2015, 2020), and Lagoa do Peixe in southern Brazil (Baker et al. 1998). Studies of weight gain and geolocator tracking suggest that some knots leave on a long flight from the more northerly of these stopover sites, crossing Amazonia directly to the east coast of the United States (Niles et al. 2010b; Burger et al. 2020). However, many birds stop on the north coast of Brazil (Morrison and Harrington 1992; Rodrigues 2000; Rodrigues and Lopes 2000; Fedrizzi et al. 2016; Mobley pers. comm. 2019) - some 83% of geolocator birds from southern South America stopped here during northward migration (Burger et al. 2020). It is likely that most Red Knot from the Tierra del Fuego / Patagonia wintering population (DU3) then pass through the Delaware Bay system in spring (88% of geolocator birds) (Niles et al. 2010b; Burger et al. 2020).

Rates of weight gain of Red Knot in Delaware Bay are amongst the highest recorded for the species globally (Atkinson et al. 2007). The birds feed principally on the eggs of the Horseshoe Crab, which provide an easily digestible and energy-rich food source. Several studies have shown that failing to reach adequate body condition before leaving the last spring stopover area may have severe survival consequences for Red Knot (Baker et al. 2004; Morrison et al. 2006). When knots were unable to reach optimal departure weights in Delaware Bay in the early 2000s, owing to reduced availability of Horseshoe Crab eggs, their survival rates fell from about 85% to 56% (Baker et al. 2004). The modelled declining population trajectory closely matched that observed during aerial surveys in Tierra del Fuego over the same period (Baker et al. 2004; Morrison et al. 2004, Morrison 2018). Recent tracking of radio-tagged knots departing from Delaware Bay has shown that birds in better condition departed later, arrived on the breeding grounds earlier, and migrated south later than individuals in poor condition, indicating they were more likely to have bred successfully (Duijns et al. 2017). In addition, these studies indicated that birds in poor condition were less likely to be subsequently observed in autumn, suggesting higher mortality.

Geolocator studies have shown that knots departing from Delaware Bay and other east coast US sites fly directly to more northerly areas in Canada (Niles et al. 2010b). Many pass through southern James Bay in late May (Morrison and Harrington 1992; Morrison pers. obs.). Many (92% of geolocator records) of the Tierra del Fuego / Patagonia wintering population (DU3) knots use the recently (re)discovered stopover site near the mouth of the Nelson River on Hudson Bay, where over 4,000 birds have been counted in late May and early June (McKellar et al. 2015; Burger et al. 2020). It is unknown how long knots may have been using this site, though 3,500 were reported from the area in spring 1974 (Morrison et al. 1995; IBA 2013).

Although the easterly migration route taken by birds from the Tierra del Fuego / Patagonia wintering population (DU3) suggests that they might occupy the more easterly parts of the breeding range, geolocator results show that birds thought to be from DU3 are found in many parts of the Arctic (Porter pers. comm. 2020). Banded Argentinian rufa knots have been found nesting at both eastern and western extremes of the Canadian Arctic breeding range, and 100 randomly selected rufa knots from Delaware Bay were tagged with radio transmitters and later relocated, scattered across the whole breeding range (Lathrop et al. 2018). These and other results suggest that there is some degree of overlap in breeding range of the three rufa DUs (USFWS 2014a). However, despite this, the genetic separation among the DUs indicates that they somehow remain largely or entirely reproductively isolated (Baker et al. 2012a,b). More information is needed on this aspect of knot breeding and migration.

Following breeding, large numbers of rufa knots pass southwards through the southwest coast of Hudson Bay (Manitoba and Ontario) and western and southern coasts of James Bay (Ontario), during July and August (Hope and Shortt 1944; Manning 1952; Ross et al. 2003), including birds from the Tierra del Fuego / Patagonia wintering population (DU3) banded in Argentina (Friis 2017). The most important areas appear to be in southwestern James Bay between Big Piskwamish Point and North Point, where up to 10,000 Red Knot have been observed during aerial surveys in August (Morrison, Ross, and Friis unpubl. data; Friis and Morrison 2018). Mark-recapture analyses indicated a total population passing through western James Bay of 9,200 in 2017 and 13,200 in 2018, accounting for turnover (MacDonald 2020).

In eastern Canada, the most important area for rufa Red Knot on southward migration is the Mingan Islands Archipelago on the north shore of the St. Lawrence estuary (Buidin et al. 2010; Allard et al. 2014), where over 9,000 knots have been estimated to stop (Lyons et al. 2017). Ouellet (1969) identified four Red Knot collected from a flock of 200 on Anticosti Island as belonging to the rufa subspecies. Large numbers of re-sightings of colour-marked individuals between Mingan and Argentina confirm that many of these birds belong to the Tierra del Fuego / Patagonia wintering population (DU3), although birds from the northeastern South America wintering population (DU4) and southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) also occur (Aubry pers. comm. 2019).

Red Knots from the Tierra del Fuego / Patagonia wintering population (DU3) also pass through the east coast of the United States in fall. Although some mixing with the other rufa DUs occurs there, the three groups differ in migration chronologies, length of stopover, weight gain, and moult patterns, as well as foods and feeding habitats (Harrington et al. 2007, 2010a,b; Niles et al. 2008, 2012a; Burger et al. 2012a, 2020; Lyons et al. 2018). Knots from the Tierra del Fuego / Patagonia wintering population (DU3) typically arrive and depart earlier and have a shorter stopover duration; in addition, they put on weight for the forthcoming long migration flight and do not undergo wing moult. These differences in phenology, moult patterns, and requirements for weight gain distinguish the DUs, despite their using some of the same stopover sites during migration.

Southbound Red Knot from the Tierra del Fuego / Patagonia wintering population (DU3) leave from the east coast of North America to fly south-southeast across the Atlantic Ocean to the northeastern coast of South America. Although Tierra del Fuego / Patagonia wintering knots (DU3) may pass through the northeastern coast of Brazil (used by the northeastern South America wintering population DU4 in winter) on migration, there are no records of such birds present during winter in Maranhão or Ceara (Baker et al. 2005a; Mobley pers. comm. 2019). Similarly, Tierra del Fuego / Patagonia wintering knots (DU3) are thought to migrate through French Guiana, although the few birds that winter there are probably from the northeastern South America wintering population DU4 (Niles et al. 2013a; de Pracontal 2017). Given that many thousands of birds have been marked in different wintering areas, these observations indicate that the wintering populations remain functionally separate, as supported by genetic studies. Tierra del Fuego / Patagonia wintering knots (DU3) continue southwards, arriving in Uruguay, southern Patagonia, and Tierra del Fuego in October and November (Baker et al. 2005b; Aldabe et al. 2015; Figure 7).

The small number of Red Knots wintering in Chiloé Island, Chile are thought to be mostly rufa birds from DU3 (Navedo and Gutiérrez 2019), although geolocator records indicate that a few roselaari (DU2) birds may also occur there (Newstead and LeBlanc 2018; Handmaker 2020).

Less is known about the distribution of over-summering one-year old knots south of the breeding grounds. Regular numbers are observed during the northern summer at Punta Rasa, Buenos Aires Province, Argentina (Martínez-Curci et al. 2015, 2020) (although not all birds were one-year-olds) and southern Brazil (Belton 1984; Scherer and Petry 2012).

DU4 - northeastern South America wintering population

The main wintering grounds of Red Knot from the northeastern South America wintering population (DU4) are thought to centre along the northeastern coast of Brazil, especially in the states of Maranhão (Morrison and Ross 1989; Wilson et al. 1998; Rodrigues 2000a; Rodrigues and Lopes 2000; Baker et al. 2005a) and Ceara (Carlos et al. 2010; Fedrizzi et al. 2016; Mobley pers. comm. 2019; Figure 8), with a few birds wintering in nearby French Guiana and Suriname. Birds from the northeastern South America wintering population (DU4) depart northwards by about March (Rodrigues 2000; Rodrigues and Lopes 2000; Fedrizzi 2016) and geolocator records indicate that most fly up the east coast of the United States (90% of geolocator birds stopped in Delaware Bay; Burger et al. 2020). Flagged birds from the northeastern South America wintering population (DU4) pass northwards through Virginia during northward migration, before moving to other areas, including Delaware Bay (Duerr et al. 2011; Watts and Truitt 2015). Marked birds from Brazil have not been recorded in Georgia (Smith et al. 2017). From the east coast of the United States, northeastern South America wintering population (DU4) birds move on to James Bay and Hudson Bay (95% of geolocator birds) en route to the breeding grounds (Burger et al. 2020; Porter pers. comm. 2020).

As with the Tierra del Fuego / Patagonia wintering population (DU3), there is uncertainty regarding which parts of the rufa breeding range are occupied by birds from the northeastern South America wintering population (DU4). Geolocator birds wintering in northeast Brazil have been tracked to Southampton Island and near Pelly Bay in the Canadian Arctic (Niles et al. 2010b).

On southward migration, knots from northeastern South America wintering population (DU4) pass through James Bay (sightings of flagged birds; Friis 2017; MacDonald 2020) and the Mingan Islands (Aubry pers. comm. 2019). One geolocator bird stopped at Mingan on both its northward (2009) and southward journeys (2009, 2010) after which it flew directly to northern Brazil (Burger et al. 2020). The northeastern South America wintering population (DU4) knots also pass through various other sites on the east coast of the United States, such as Georgia (Lyons et al. 2018) and Monomoy, Massachusetts (17% of geolocator birds from the northeastern South America wintering population (DU4); note no geolocator birds from the Tierra del Fuego / Patagonia wintering population (DU3) have been detected at Monomoy; Burger et al. 2020). Long-distance migrants from the Tierra del Fuego / Patagonia wintering population and the northeastern South America wintering population (DU3, DU4) generally have different migration strategies than the shorter distance migrants from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5), including migration chronologies (earlier), length of stopover (shorter), weight gain (greater), and moult patterns (no moult), as well as different foods and feeding habitats (Harrington et al. 2007, 2010a,b; Niles et al. 2008, 2012a; Burger et al. 2012a, 2020; Lyons et al. 2018).

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population

Red Knot from wintering areas on the Atlantic coast of Florida and Georgia, as well as parts of the Caribbean (part of the southeastern USA / Gulf of Mexico / Caribbean wintering population, DU5), migrate up the Atlantic coast of the United States in spring. Their flights are shorter than those of the long-distance migrants from the Tierra del Fuego / Patagonia wintering population and the northeastern South America wintering population (DU3, DU4) and may involve leap-frog movements: only about half are thought to stop in Delaware Bay (compared to approximately 90% of the Tierra del Fuego / Patagonia wintering population (DU3) and the northeastern South America wintering population (DU4; Burger et al. 2020)). In Delaware Bay, it is likely that the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) birds make greater use of coastal habitats and are less dependent on Horseshoe Crab eggs within Delaware Bay, because shorter-distance migrants are able to use hard-shelled bivalves in these habitats as they have not undergone as extensive a reduction in digestive organs as long-distance migrants (Niles et al. 2009, 2012a). Geolocator studies show that some birds fly directly from Florida or other southeastern states to Hudson Bay (Burger et al. 2020).

Knots in the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) wintering on the west coast of Florida, as well as Louisiana, Texas, and Caribbean islands, migrate up through central North America, some stopping in the Canadian Prairies (Saskatchewan), with others flying directly to the Nelson River area on the west coast of Hudson Bay (Newstead et al. 2013; Newstead pers. comm. 2018; Bianchini et al. 2020). Recent geolocator and nanotag results suggest that birds wintering in Louisiana and Texas may take different routes. Birds from Louisiana appear to move up the Mississippi Flyway directly to James Bay and Hudson Bay, while those from Texas move up the Central Flyway to use stopover sites in Saskatchewan en route to James Bay and Hudson Bay. Birds wintering on the Gulf coast of Florida likely fly directly to James Bay (Newstead pers. comm. 2018). Some of these birds may return south in fall via the east coast of the United States, as suggested by recent geolocator records (Niles et al. 2012a; Lyons et al. 2018; Bianchini et al. 2020).

The portions of the breeding range of rufa occupied by birds from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) are unclear. The central migration route of the Texas/Louisiana birds might suggest a destination in the west-central Arctic. One knot that wintered in coastal Maryland migrated northwards through Delaware Bay, then to Hudson Bay and on to a breeding site thought to be near Foxe Basin in the eastern part of the range; it returned south to the same wintering area via James Bay (Burger et al. 2020).

Interspecific interactions

Nest and adult predation

Long-tailed Jaeger (Stercorarius longicaudus) and Arctic Fox (Alopex lagopus) are common egg and chick predators of Red Knot on the Arctic breeding grounds, especially in years with low lemming populations (e.g., Birula in Pleske 1928; Nettleship 1974). High nest predation by Arctic Fox may also occur in years with late snowmelt, when predators have a smaller area of patchy open tundra to search (Tomkovich and Soloviev 1996). Other breeding ground predators include Parasitic (S. parasiticus) and Pomarine Jaeger (S. pomarinus), Gyrfalcon (F. rusticolus), and sometimes Herring (Larus argentatus) and Glaucous Gull (L. hyperboreus; Niles et al. 2008). Other potential undocumented predators include Common Raven (Corvus corax), Sandhill Crane (Antigone canadensis), and Ermine (Mustela erminea), especially in the lower latitudes of the breeding range (Smith pers. comm. 2020).

Away from the breeding grounds, most common predators are large falcons such as Peregrine Falcon (Falco peregrinus; Piersma et al. 1993), but others include harriers (Circus spp.), accipiters (Accipiter spp.), Merlin (F. columbarius), Short-eared Owl (Asio flammeus), and Great Black-backed Gull (L. marinus; Piersma et al. 1993; Niles et al. 2008). Large avian predators generally migrate southwards later than most shorebirds, so that early migrating shorebirds (e.g., female knots) are less prone to predation compared to later migrants (e.g., juvenile and some male knots) (Lank et al. 2003).

Other interspecific interactions

Red Knots usually form and fly in monospecific flocks, but will readily join with other species of shorebirds in flight on feeding areas, including Ruddy Turnstone (Arenaria interpres), dowitchers Limnodromus spp., Black-bellied Plover (Pluvialis squatarola), and larger shorebirds such as godwits (Limosa spp.).

On the breeding grounds, knots and turnstones may combine to defend their chicks against predators such as Long-tailed Jaeger, perhaps more effectively than if breeding separately (Parmelee and MacDonald 1960).

The Tierra del Fuego / Patagonia wintering population (DU3) is heavily dependent on the eggs of Horseshoe Crab as their main prey in Delaware Bay and other coastal areas of the Atlantic United States during spring migration (Tsipoura and Burger 1999; Haramis et al. 2007). Birds from the northeastern South America wintering population (DU4) and the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) passing through Delaware Bay also depend on this food resource, although likely to a lesser extent (Atkinson et al. 2007). Elsewhere in its wintering and migration ranges, Red Knot feeds mostly on bivalves (Alerstam et al. 1992; Piersma et al. 1993; González et al. 1996; Cohen et al. 2009), although a variety of invertebrates are eaten on migration in eastern Canada (Sahlin 2010, 2011). On its breeding grounds, Red Knot feeds on tundra invertebrates as well as vegetation (Parmelee and MacDonald 1960; Nettleship 1974; Baker et al. 2013).

Population sizes and trends

Sampling effort and methods

Aerial surveys

Counting Red Knot on the wintering grounds is generally considered the best method of assessing population size, as birds are often concentrated in relatively restricted stretches of suitable habitat, and little movement of birds is likely to occur among sites (Brown et al. 2001). Aerial surveys usually provide the most effective method of covering extensive areas of habitat, especially in remote areas that are difficult to access from the ground. If the entire wintering range can be surveyed within one season, the overall survey effectively becomes a census in which all the birds are counted. Any uncertainties in the total number of birds result from counting, identification, and detection errors, as there is no sampling or extrapolation involved. Detection issues may arise when coastal surveys need to be carried out at a specific tide height (usually high tide) and coverage of large areas may preclude ideal conditions throughout the survey (Morrison 2018; Morrison et al. 2020c; NJA 2020).

For C. c. islandica (DU1), aerial surveys have been used to determine numbers on migration in Iceland (Gudmundsson and Gardarsson 1993) but are not generally used on the wintering grounds in Europe where most information comes from ground counts.

For C. c. roselaari (DU2), aerial surveys provided early information on Red Knot distribution (Morrison and Ross 2009) on the wintering grounds of C. c. roselaari in Mexico. Aerial surveys have also been used extensively on Alaskan migration areas (Gill and Handel 1990; Alaska Shorebird Group 2018).

The Tierra del Fuego / Patagonia wintering population (DU3) has been extensively censused by aerial surveys. The entire Patagonian coast and suitable coastline of Tierra del Fuego were originally surveyed in the 1980s, when the main wintering sites were discovered (Morrison and Ross 1989). Surveys were resumed in 2000 and continued annually until 2019. In recent years, accuracy of counts has been assessed by comparing aerial counts with those from photographs, and for these and other air/ground comparisons, mean overall errors were within 5-10% of the photographic counts (Morrison 2018), with mean absolute errors averaging 8-10%. A notable feature of the Tierra del Fuego surveys is that all have been carried out by the same observers (R.I.G. Morrison, often with R.K. Ross), maximizing the consistency of counting. In addition, counts from Tierra del Fuego and estimates of the population size made through re-sighting studies during migration have been in close agreement (González et al. 2004).

Aerial surveys of wintering areas used by rufa birds in the northeastern South America wintering population (DU4) were originally carried out in the 1980s, and have been repeated in recent years (2008-2019; Morrison and Ross 1989; Baker et al. 2005a; Morrison et al. 2012, 2020c).

Aerial surveys have been used to count rufa Red Knot the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) in coastal Texas and Louisiana (Newstead pers. comm. 2018) and Florida (Niles et al. 2010c), albeit on a sporadic basis, and these do not cover all known wintering areas used by birds from this DU.

Aerial surveys have also been used to count Red Knot on migration in other areas where DU identification is uncertain or where birds from more than one DU may occur. For instance, aerial surveys have been conducted in Delaware Bay since 1982 and are ongoing, until recently using standard protocols and the same observers (Clark et al. 1993, 2001; Niles et al. 2010c). Red Knot from the Tierra del Fuego / Patagonia wintering population (DU3) mix with those from the northeastern South America wintering population (DU4) and the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) during migration through the bay, although most knots from the latter two DUs pass through this site earlier than those from the Tierra del Fuego / Patagonia wintering population (DU3; Atkinson et al. 2005). Aerial surveys have also been conducted during northward migration in coastal Virginia and Georgia (Watts and Truitt 2015; Smith et al. 2017). Aerial surveys of the James Bay coastline have confirmed that a significant number of rufa knots (>10,000 individuals) use this area during southward migration (Friis 2017; R.I.G. Morrison, R.K. Ross, and C. Friis unpubl. data), although it is unclear which DU(s) these birds are from.

Ground counts

Although numbers at migration areas may be affected by turnover rates (e.g., birds may move through a site at different times, or at different rates in different years) and by uncertainties regarding the proportion of the population using the site (Bart et al. 2007), they nevertheless provide valuable additional data on trends in a migratory population (Morrison et al. 1994; Morrison 2001). Maximum or mean counts have been used as indices of annual abundance, sometimes during a specific time window, e.g., to estimate adult numbers when their passage time differs from juveniles (Morrison 2004).

In Europe, information on wintering numbers of C. c. islandica (DU1) comes from an internationally coordinated program of ground counts (Wetlands International 2018).

In North America, various volunteer survey operations are coordinated through PRISM (Bart et al. 2002). Major components include the Atlantic Canada Shorebird Survey (ACSS, originally the Maritimes Shorebird Survey - MSS), the Ontario Shorebird Survey (OSS), and the International Shorebird Survey (ISS) covering areas in the United States and farther south. The MSS/ACSS and ISS were started in 1974, and typically involve volunteers who count shorebirds in a consistent manner at their study site at two-week or 10-day intervals throughout the period of southward migration (Morrison et al. 1994; Morrison 2001; Morrison and Hicklin 2001; Howe et al. 1989). Analyses of these data are conducted by Environment and Climate Change Canada scientists at the National Wildlife Research Centre.

Combined results from different regions (referred to as ISS results in the analyses below) are useful and relevant for examining trends in different DUs of Red Knot. These counts are conducted during southward migration (July to November) and the sampling regions are shown in Figure 10. ISS trends were estimated with a hierarchical Bayesian model using Markov Chain Monte Carlo sampling, assuming that counts follow an over-dispersed, Poisson distribution, for the periods indicated (ECCC 2019), except for Pacific and Intermountain Region, Texas Coastal Region, and Delaware Bay, for which linear regression of annual indices was used.

Figure 10. North American regions of the International Shorebird Survey (including the Atlantic Canada Shorebird Survey and Ontario Shorebird Survey) used in analysis of survey results on southward migration (July-August; Figure courtesy of P.A. Smith).

Counts from coastal sites in the Pacific and Intermountain region most likely refer to the roselaari population (DU2) migrating along the Pacific coast, although there is a possibility that some southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) rufa may also occur there. Counts from Atlantic Canada and the Northeast US Coast are likely to involve all three rufa DUs, but may nevertheless provide relevant perspective on declines of different DUs. It is likely that birds in Atlantic Canada may contain a higher proportion of birds from the Tierra del Fuego / Patagonia wintering population (DU3), whereas areas farther south on the east coast of the United States may contain a higher proportion of birds from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) (Harrington et al. 2010b; Lyons et al. 2018).

In Quebec, trends in numbers of Red Knot have been obtained from analysis of checklist data submitted to the Étude des populations d’oiseaux du Québec (ÉPOQ) for areas along the St. Lawrence River system from 1976-1998 (Aubry and Cotter 2001, 2007) and likely contain a high proportion of birds from the Tierra del Fuego / Patagonia wintering population (DU3). Counts reported via eBird will have a similar relevance to the different DUs on the geographical basis indicated for the ISS counts.

Migration counts from the southeast US Coast region may be relevant to the more easterly wintering portion of the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) (with some from the Tierra del Fuego / Patagonia wintering population (DU3) and the northeastern South America wintering population (DU4)); counts from the Texas coast region may be relevant to the portion of the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) that winters on the coast of Texas; and counts from the Midcontinental Region may be useful in assessing portions of the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) that winter in west Florida, the Louisiana Gulf coast, and Texas.

Christmas Bird Counts, organized by the National Audubon Society since 1900, provide information on numbers of birds wintering in the United States and Canada (National Audubon Society 2020). Counts are carried out within a 24.1 km diameter circle over a one-day period (24-hours) between 14 December and 5 January (Audubon Science-CBC 2014). Number of count-hours and observers are recorded in order to assess sampling effort. CBC trends are estimated using a log-linear hierarchical model with an effort function, as described by Link and Sauer (2007). Counts from the Pacific coast will refer to DU2 roselaari subspecies, in the more northerly parts of its wintering range, while counts from the Gulf of Mexico and southeastern United States will refer to wintering populations of DU5 rufa subspecies.

Trends in the Tierra del Fuego / Patagonia wintering population (DU3) have been estimated from counts at various sites in southern South America. At San Antonio Oeste, Rio Negro Province, on the coast of Patagonia in Argentina, a complete “local census” has provided approximately weekly counts during March and April. Counts have been conducted at Fracasso Beach, on the Valdes Peninsula, Chubut Province, Argentina. Finally, a series of counts spanning 1995-2003 is available from the National Park at Lagoa do Peixe, Rio Grande do Sul state, in southern Brazil, another major stopover area for Tierra del Fuego / Patagonia wintering population knots (DU3). These all showed declines in Red Knot numbers that are consistent with those observed at the core sites in Tierra del Fuego (COSEWIC 2007). Updated information is not available from these areas.

Arctic PRISM surveys provide the most comprehensive description of abundance and distribution on the breeding grounds (Bart and Johnston 2012, Rausch and Smith 2013, Lathrop et al. 2018). These surveys involve ground-based counts in 12-16 ha plots distributed in a stratified random fashion across the whole of the Canadian Arctic. More than 2700 plots were surveyed between 1994 and 2018. Additional plots were surveyed intensively over a 5-week period at 14 sites throughout the Arctic, to establish detection rates and allow for corrections in the larger sample. Although Arctic PRISM surveys will eventually provide population trends from the breeding grounds, full coverage of the Canadian Arctic was just recently achieved and trends are therefore not yet available. The only information on recent trends in rufa Red Knot numbers on the breeding grounds in the central Canadian Arctic comes from surveys conducted annually in a 9.2 km² study area on Southampton Island, between 2000 and 2005 (Niles et al. 2005). Changes in numbers of Red Knots of the roselaari subspecies (DU2) breeding on Wrangel Island, Russia, were reported by Tomkovitch and Dondua (2008).

Abundance

Arctic PRISM surveys provide regional estimates of abundance, but because Red Knot from DUs 3, 4 and 5 appear to mix on the breeding grounds, and the southern boundary separating DU 1 from DUs 3, 4 and 5 is not well-known, it is difficult to partition Arctic PRISM results into DU-specific population estimates. Across all of Arctic Canada, PRISM surveys yielded an preliminary Red Knot population estimate (±SE) of 667,633 ± 188,608 breeding (mature) individuals (Smith pers. comm. 2020). Density was higher in wetland habitats than in mesic and sparsely vegetated, dry habitats (0.80 birds/km², 0.26 birds/km², and 0.30 birds/km², respectively). However, owing to the much larger spatial extent of the latter habitat category, most Red Knot were estimated to occur in these dry, barren habitats (proportion: 0.17 in wetlands, 0.16 in mesic habitats, and 0.67 in dry habitats; Smith pers. comm. 2020).

Summing regional PRISM results from within the range of DUs 3, 4, and 5 yields a preliminary estimate for rufa of 81,530 ± 45,404 breeding indivuals. The imprecision reflects the rarity of sightings within the surveyed plots. This estimate is consistent with population estimates given below for these DUs from non-breeding grounds, especially when considering the confidence limits of the estimate, and that the surveys occurred over periods stretching back to 1994 (Smith pers. comm. 2020).

If it is assumed that all Red Knot nesting on Devon, Prince Patrick and Melville Islands, and areas further north, are islandica, PRISM surveys suggest a preliminary population estimate for islandica of 552,567 ± 165,164 mature individuals. In contrast to results for rufa, this estimate is substantially larger the previous population estimates. As described below for DU1, previous estimates rely on unverified assumptions about the proportion of the population occurring in Canada, and PRISM survey results suggest that the proportion is likely larger than previously believed (Smith pers. comm. 2020).

Age structure and number of mature individuals

COSEWIC considers species abundance in terms of the number of mature individuals, defined as “the number of individuals known, estimated or inferred to be capable of reproduction” (IUCN Standards and Petitions Subcommittee 2017). Most Red Knot counts, either aerial or ground, record the total number observed, with little information on the age categories present. Red Knot is generally considered to start breeding when two (or more) years old. A bird up to 1 year old is considered a juvenile, a bird 1-2 years old approaching its first breeding season is a sub-adult, and a bird older than 2 years is an adult. The proportion of each age class in the population depends on the annual survival of each age class and the fecundity of the birds and can be modelled in a population matrix. This modelling exercise, undertaken by S. Wilson and R.I.G. Morrison using parameter values considered to be the most realistic, is presented in Appendix 1.

Overall results suggest that a relatively stable population would contain about 25% juveniles, 15% subadults, and 60% adults (Appendix 1). For surveys on the wintering grounds, the proportion of mature individuals would be 60% of the counted population, because sub-adults are not yet considered mature individuals. This value has been used to convert wintering survey numbers to numbers of mature individuals. Uncertainties may arise where the three age classes have different geographical distributions, and in declining populations which may have age-specific differences in mortality. These proportions may not apply during migration, e.g., all birds counted during northward migration at North American stopover areas are presumably adults, and adults precede juveniles during southward migration.

DU1 - islandica subspecies

The global islandica population was previously considered to number about 270,000 individuals (then considered equivalent to 202,500 mature individuals using 75% adults plus sub-adults, currently 162,000 using 60% adults) (COSEWIC 2007). More recent estimates indicate population levels of 450,000 birds (equivalent to 270,000 mature individuals; Delaney et al. 2009), and 500,000-565,000 birds (up to 2016) (equivalent to 300,000-339,000 mature individuals; mean of about 320,000) based on counts and expert opinion (Wetlands International 2018). International Waterbird Census count totals in Europe fluctuated between 273,000 and 423,000 during the period of 2011-2015 (Wetlands International 2018) and increases may represent wider survey coverage, in part.

The Canadian breeding population of islandica Red Knot (DU1) is thought to hold at least 40% of the subspecies population, based on previous population estimates (Whitfield et al. 1996; Meltofte 1985; Morrison et al. 2006; COSEWIC 2007; Smith pers. comm. 2020). However, this proportion should be regarded as approximate, and recent Arctic PRISM survey estimates suggest it may be an underestimate (Smith pers. comm. 2020). Applying this proportion to a global estimate of about 320,000 mature individuals gives a Canadian breeding population estimate of islandica Red Knot of at least 128,000 mature individuals (Morrison et al. 2006; Andres et al. 2012).

DU2 - roselaari subspecies

Carmona et al. (2013) reviewed records of Red Knot on the Pacific coast of the Americas, showing that there were few sites there which held large numbers of birds, and concluding that the concentrations observed were compatible with the then current estimate of 17,000 individuals. More recent work using superpopulation modelling approaches by Lyons et al. (2016) has estimated the population of adult roselaari (DU2) using the Pacific coast at 21,770 (16,200-30,320), which is considered to be equivalent to the number of mature individuals in the Canadian population estimate in this report.

DU3 - Tierra del Fuego / Patagonia wintering population

Initial estimates of the size of the rufa population in the 1980s, derived from band re-sighting data and counts, suggested the population numbered between 100,000 and 150,000 individuals (B.A. Harrington unpubl. results, in Morrison and Harrington 1992), although this estimate included all three rufa DUs (Harrington et al. 1988; Morrison and Harrington 1992; Morrison et al. 2001). While these counts are considerably higher than current combined estimates (Morrison et al. 2020b) of the three rufa DUs, the general trajectory of abundance indices from the International Shorebird Surveys and Delaware Bay in particular (see Trends), suggests they may well be relatively accurate.

The first direct count for the Tierra del Fuego / Patagonia wintering population (DU3) was by Morrison and Ross (1989) who found some 67,500 knots during aerial surveys of the coastlines of Patagonia (14,314) and Tierra del Fuego (53,232), including approximately 40,500 mature individuals, in the 1980s. This population has since suffered a major decline (see Trends) and the latest survey in January 2020 resulted in total of 11,795 individuals on Tierra del Fuego (Morrison et al. 2020c). As estimates for the total number on the coast of Patagonia in 2003, 2004, and 2012 averaged approximately 670 birds, it is likely that the current total population of birds in the Tierra del Fuego / Patagonia wintering population (DU3) is 12,500 knots or less, representing approximately 7,500 mature individuals. It is thought likely that not all juvenile birds migrate to the southern parts of the wintering range (Baker et al. 2004, 2013, 2020), so that this estimate of the number of mature individuals may be a slight underestimate.

DU4 - northeastern South America wintering population

Counts of Red Knot on the northeastern coast of Brazil have increased in recent years, although this is thought to be almost entirely a result of better survey coverage. The original surveys in the 1980s produced a total of 8,150 knots in the Maranhão region (Morrison and Ross 1989). Subsequent aerial surveys in 2005 found a similar number of 7,575 birds (Baker et al. 2005a) but were conducted at variable tide heights. Smaller numbers of knots were found using ground or boat surveys during the winter, although as many as 7,000 have been recorded there during the migration period (Wilson et al. 1998; Rodrigues 2000; Rodrigues and Lopes 2000). Aerial surveys in 2011 (total knots 3,660) and 2013 (total knots 15,485) provided improved coverage of the Maranhão and northeastern Brazil coastline. However, experience gained during these surveys showed that detection of knots was extremely dependent on tide height during the survey, necessitating coverage of the main roosting areas on headlands, offshore islands and sandbars at or very close to high tide. The most recent survey in 2019, following this protocol, resulted in a count of 32,515 (estimated 19,500 mature individuals), centred mostly in Maranhão.. Numbers recorded in 2019 in areas covered in previous years at similar tide conditions were similar, so the additional coverage of offshore areas likely accounted for the higher total in 2019 (see further comments below in Trends; Morrison et al. 2020c).

The 2019 survey may be regarded as the most accurate estimate of the population to date (Morrison et al. 2020c; NJA 2020). The most recent survey confirms that the Cajuais Bank, farther east in Brazil in the State of Ceara, supports approximately 1000 knots in winter (>500, Fedrizzi et al. 2016; 900-1200, Mobley pers. comm. 2019).

Although Red Knot is not reported as wintering in Suriname (Spaans 1978), small numbers have been recorded on eBird (eBird 2019). In French Guiana, small (irregular) numbers have been recorded in winter (up to 480; de Practontal 2017; up to 105, eBird 2019). These records are likely referable to the northeastern South America wintering population (DU4).

The total wintering population size for Brazil and the Guianas is thus estimated as approximately 33,000 birds, including 19,800 mature individuals.

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population

Estimates of the number of Red Knot in Florida and southeastern Atlantic states (part of the southeastern USA / Gulf of Mexico / Caribbean wintering population DU5) over the past 30 years have ranged from 10,000 (Morrison and Harrington 1992) to 7,500 (Harrington pers. comm. 2005) to 4,500 total individuals (Sprandel et al. 1997; Niles et al. 2005). The latter estimate was based on aerial and ground surveys during the winter of 2005-2006 (Niles et al. 2006). However, more recent results from mark-recapture-resight studies of Red Knot in Georgia (Lyons et al. 2018) resulted in estimates of approximately 10,400 knots wintering in the southeastern United States, with another 5,100 wintering elsewhere in the northern wintering range, with most probably on islands in the Caribbean (a further 5,400 in Brazil are referable to the northeastern South America wintering population DU4). This gives an overall wintering estimate for DU5 of 15,500 individuals, and assuming that 60% of these birds are adults, the total number of mature individuals is approximately 9,300.

Fluctuations and trends

DU1 - islandica subspecies

Trend analyses of islandica Red Knot wintering in Europe are mixed, but indicate that whereas over the long term (1975-2015) there has been a statistically significant strong increase (annual rate 1.0138, SE 0.0043), in more recent years (2006-2015) the trend has been uncertain or fluctuating (annual rate 0.9923, SE 0.0314) (Figure 11; IWC 2020). Moderate decreases up to 2012 were followed by more recent increases (statistically significant long-term 1975-2015) or fluctuating estimates (Nagy et al. 2014; BirdLife International 2015; Wetlands International 2018); the population trend in recent years (2006-2016) is less certain and appears to be either stable or fluctuating slightly (IWC 2020; van Roomen pers. comm. 2020) (Figure 11). The trend is based on counts of wintering knot in ten countries, dominated by counts from the United Kingdom and Netherlands, where wintering numbers have decreased in Great Britain and Ireland, but increased in the Wadden Sea (Netherlands) and in northwest France. Analytical methods are described by Wetlands International (2017). Van Roomen et al. (2012) estimated the population trend of wintering Red Knot in the Wadden Sea at between +1 and +2% per year for the period 1991-2009. It is assumed that the population trends observed for Red Knot islandica birds wintering in western Europe are representative of the Canadian population.

Figure 11. Annual indices of abundance and estimated trend of C. c. islandica Red Knot wintering in Europe, 1976-2016, based on International Waterbird Census counts, including DU1 birds from Canada (Wetlands International 2018; IWC 2020; van Roomen pers. comm. 2020). Analytical methods are described in van Roomen et al. (2018): trends were detected and estimated using the program TrendSpotter, which produces trend lines (dark line) and 95% confidence intervals (light blue lines) (Visser 2004; Soldaat et al. 2007; Figure from van Roomen et al. 2018, courtesy of M. van Roomen).

DU2 - roselaari subspecies

There was a strong decline in numbers of Red Knot roselaari subspecies breeding on Wrangel Island, Russia, between 1974-1977 and 2007, with densities falling from an estimated 6.7 pairs/km² to a maximum of 2.5 pairs/km², a decrease of at least 63% over the 30-year period (Tomkovich and Dondua 2008).

The limited amount of information available to assess trends in the roselaari population (DU2) migrating along the Pacific coast also suggests large long-term decreases. Trends calculated from the International Shorebird Survey for the Pacific/Intermountain Region (Table 2; Figure 12) indicate dramatic decreases over the first 20 years of records (1974-1994), with ongoing but lower declines during the next 20-year period, when fewer counts were made in this region (Smith pers. comm. 2020; Figure 12). A logarithmic plot shows a significant relationship for the entire period (1974-2013) with an overall rate of decline of -8.45% per year, equivalent to a decrease of 96.8% over the entire period (not illustrated; Table 2). Over the 3-generation period (1992-2013; the latest for which data are available), there was a significant rate of decline of -4.73% per year, equivalent to a decrease of 63.9% over three generations (Figure 12; Table 2). It should be noted, however, that precision of this estimate is low owing to small sample sizes (5 out of 23 sites; Smith pers. comm. 2020).

Figure 12. Linear fit of annual indices of abundance of Red Knot, mostly birds from C. c. roselaari (DU2), based on fall surveys from the International Shorebird Survey Pacific and Intermountain Region for the 21-year period 1992-2013. The linear rate of decline was significant (-4.73%/year, r=-0.594, p=0.004), although precision of this estimate is relatively low.

Christmas Bird Counts conducted in California (BCR-32) and Washington (BCR-5), which would sample DU2 roselaari knots in the northern part of their wintering range (Carmona et al. 2013, Baker et al. 2020), also suggest substantial declines. Over the most recent 21 year period (1998-2019), trends were estimated as -2.33% per year (significant) and -3.47% per year, respectively, which would imply decreases of -38.7% in California and -51.7% in Washington over that period (Table 3). The longer-term (1970-2019) decrease was significant in both BCRs, at -2.32% and -3.93% per year implying decreases of -67.1% in California and -85.4% in Washington, respectively (Table 3).

Table 3. Trend analyses of Christmas Bird Count data for different Bird Conservation Regions (BCRs) used by wintering populations of Red Knot in DU 2 (Pacific coast wintering population of C.c. roselaari) and DU5 (southeastern USA/Caribbean/Gulf of Mexico wintering population of C. c. rufa). Trends are shown as % change/year over the period indicated: (a) long-term 1970-2019 (49 years), and (b) 1993-2019 (26 years) provided by National Audubon Society (T. Meehan pers. comm. 2020), with upper and lower 95% confidence limits. Significant declines, where the confidence limits do not include zero, are shown in bold. Estimated declines over indicated periods are calculated from the annual rate of change for the entire period (49 years) and most recent three-generation period (21 years, based on the 1993-2019, 26-year period estimate).

Counts from the large Alaskan estuaries (Copper River and Yukon-Kuskokwim deltas) used as stopover sites on northward migration are more complicated to interpret, but also suggest that substantial decreases have occurred. Analysis of a 31-year (1978-2008) series of spring counts from the Tutakoke River area on the Yukon-Kuskokwim delta showed no statistical evidence for a decrease in peak spring counts (McCaffery et al. 2009). However, several much larger counts were recorded in the 1970s, suggesting that larger numbers of knot occurred there then than in recent years. For instance, Kessel and Gibson (1978) reported a one-day count of 40,000 knots on the Copper River Delta on 11 May 1975, where estimates of up to 100,000 knots have been made (Islieb 1979; Islieb in Kessel 1989). However, Islieb’s (1979) observations appear to be based on extrapolation, which would not be appropriate for knots which occur in clumped distributions. A count of a possible 110,000 knots on the central Yukon-Kuskokwim Delta on 21 May 1980 (Gill and Handel 1990) may be anomalous, perhaps a result of late spring conditions (Kessel and Gibson 1978; Gill and Handel 1990). Given the unusual nature of this count, the data and original field observations were thoroughly reviewed for this report by Gill and Handel (Gill pers. comm. 2020), who concluded that a revised total of 90,000 was appropriate for that observation. Interestingly, and perhaps coincidentally, back-calculating from the recent estimate of 22,000 roselaari in 2009 (Lyons et al. 2017), using the 3-generation rate of decline of -4.73%, gives an estimated population of 86,725 birds in 1980. No clear reason has been established for the high count in 1980 (McCaffery et al. 2009), but such numbers may have been possible if unusual conditions brought together all knots that normally staged across the un-vegetated flats and coastal meadows of the large Yukon-Kuskokwim and Copper River deltas (Gill pers. comm. 2020). Reports of Red Knot passing through both deltas have generally involved several tens of thousands of birds (Kessel and Gibson 1978; Islieb 1979; Gill and Handel 1981, 1990), compared with current estimates of about 10,000 knots using these areas (Bishop et al. 2016). If most roselaari knots move through southern Alaska on spring migration, the total would be closer to 22,000 (Buchanan pers. comm 2020). Overall, it appears there have been substantial decreases in numbers of Red Knots using Alaskan estuaries during northward migration, despite some uncertainties surrounding earlier counts.

DU3 - Tierra del Fuego / Patagonia wintering population

The overall wintering population of Tierra del Fuego / Patagonia wintering population rufa Red Knot (DU3) was approximately 67,500 birds in 1982, of which 78.8% were reported in Tierra del Fuego and 21.2% on the coast of Patagonia (Morrison and Ross 1989). At core wintering areas in Tierra del Fuego, the population count fell from 51,255 birds when surveys were resumed in 2000 to a low of 9,840 in 2018, representing a decrease of 80.8% over 18 years, less than three generations (Morrison 2018) (Figure 13). The most recent count in January 2020 of 11,795 (Morrison et al. 2020a) indicates a three-generation decline of 77.0%. Although the steepest declines occurred in steps between 2000 and 2011, a logarithmic plot of counts from 2000-2020 shows a significant relationship, with an annual decrease of -6.3%, equivalent to a decline of 73.4% over 3 generations (21 years: 1999-2020; Figure 13). The reasons for this very substantial decline are discussed under DU3 in Dispersal and Migration above, showing that the declines in Tierra del Fuego are reflected in the decrease in annual survival recorded in Delaware Bay during this period (Baker et al. 2004).

Figure 13. Total counts of C. c. rufa Red Knots from the Tierra del Fuego / Patagonia wintering population (DU3) during aerial surveys in Tierra del Fuego, 1982-2020 (from: Morrison et al. 2020a,b; Morrison unpubl. data). There was a significant exponential decline across the period 2000-2020 (-6.3%/year, r=0.794, p=0.000).

Four surveys have been flown along the Patagonia coast since 2000 (in 2002, 2003, 2004, 2012) to determine whether declines in Tierra del Fuego may have resulted from redistribution to more northerly areas. They showed instead that declines had been steeper and more extensive in Patagonia (Morrison et al. 2004; Morrison unpubl. data). Whereas in 1982 about 21.2% of the southern population wintered at Patagonian sites, this proportion fell to 6.9%, 1.8%, 2.8%, and 4.0% in the four survey years, respectively, so that by 2012, >95% of the Tierra del Fuego / Patagonia wintering population (DU3) wintered in Tierra del Fuego.

Declines have been particularly severe at Rio Grande, Argentina on the Atlantic coast of Tierra del Fuego (Morrison 2018). Whereas some 3,500-5,000 wintered in this area up to 2008 (and in 1982), numbers fell rapidly to less than 200 by 2012. Logarithmic plots of counts show the annual overall decrease between 2000 and 2018 was -27.0% and between 2008 and 2018 was -33.0%. Note that the rapid declines at Rio Grande began after the major declines in Bahia Lomas, suggesting that different factors may have influenced numbers at this site (Escudero et al. 2012).

DU4 - northeastern South America wintering population

There is relatively little information available with which to assess trends for birds from the northeastern South America wintering population (DU4), centred in northeastern Brazil. Early surveys suggested that approximately 8,000 Red Knot wintered in the Maranhão region (Morrison and Ross 1989; Baker et al. 2005a), with a survey in 2013 increasing this total to 15,485, and the most recent aerial survey of this region in 2019 producing a total of 32,515 knots (Morrison et al. 2020c; NJA 2020). Experience gained during the surveys showed that numbers of knots encountered were very sensitive to tide height during the surveys, as roosting flocks are found almost entirely on sandy outer headlands and offshore sandy islands and sandbars, with the birds dispersing rapidly on the falling tide to feeding areas, where they are not detected. Differences in survey timing and coverage appear to account for the large difference between the 2013 and 2019 surveys. In 2019, all survey sectors were covered at or very close to high tide, including onshore outer headlands/beaches and offshore islands/sandbars. In 2013, only 72% of sectors were covered at high tide, and only one sandbar or island was covered. If the 2013 total (15,485) is adjusted by the difference in totals between the areas not covered at high tide in the two years (5,595) and the additional offshore sandbars/islands covered in 2019 (8,320), the adjusted total would be 29,400, a difference of about 5.3% lower than the 2019 total. The difference in totals between survey years thus appears to be a result of the more complete coverage in 2019 rather than an appreciable population increase. Conditions during aerial surveys prior to 2013 were also highly subject to variable timing at key roosting areas, as they were designed to assess numbers of all shorebird species and to cover long stretches of coastline under constraints of time and fuel availability. Thus, it is difficult to ascertain trends from the survey results over the years. Ground observations, however, suggest that the overall size of this population has been relatively stable (Mobley pers. comm. 2019).

It is important to note that there appears to be negligible interchange of Red Knot between DU3 and DU4, as discussed in Dispersal and Migration (above), so that changes in numbers in the two wintering areas cannot be accounted for by redistribution of the birds.

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population

Red Knot wintering on the Atlantic coast of the southeastern United States are likely to be surveyed at ISS sites there during migration. While some birds from the Tierra del Fuego / Patagonia wintering population (DU3) and the northeastern South America wintering population (DU4) may pass through the southeastern United States area, the bulk of these birds appear to be from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5; Lyons et al. 2018). Birds from wintering areas on the west coast of Florida, Gulf of Mexico and Texas are thought to take an interior route to and from the breeding grounds, so counts from the Texas and Midcontinent Regions of the ISS may also reflect population trends for these birds (southeastern USA / Gulf of Mexico / Caribbean wintering population DU5).

Trends of numbers of Red Knot in the ISS Southeast US Coast region, primarily from this DU, are shown in Figure 14. The population appears to have been relatively stable from 1974 to about 1985, then declined rapidly until about 1995, and has been relatively stable at a lower level or declining slightly since then. The rate of decline over the past 21 years (three generations) was -1.91% per year (-33.1% total), although the trend parameter was not significantly different from zero. Over the longer term 1974-2016, the annual rate of change was -4.61%, implying an 85.6% population decrease, which was statistically significant (Table 2).

Counts of Red Knot from the ISS Midcontinental Region, likely mostly from the southeastern USA / Gulf of Mexico / Caribbean wintering population, have shown dramatic decreases (Table 2), and the long-term rate of decline from 1974-2014 was -11.3%/year, which would be equivalent to an apparent (and somewhat unrealistic) decrease of -99.1% over 40 years. The rate of decline over a recent three-generation period (1995-2016) was -8.84 %/year, also significant, equivalent to a decrease of -84.4% over 3 generations (Figure 15). While this rate of decline is substantial, ISS survey coverage is modest in the Midcontinental Region, so these results must be interpreted with caution.

Fall ISS counts in the Texas Coastal Region include Red Knot wintering in Texas and in areas farther south, mostly from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5). A significant long-term decline occurred over the period 1974-2013 (Table 2), at a rate of -6.37% per year, equivalent to a decrease of 92.3% over 40 years. The rate of decline over a recent three-generation period (1993-2013) was
-2.73%/year (44.1% decrease), but was not significant (Table 2, Figure 16).

Figure 14. Annual index of abundance of C. c. rufa Red Knot, mostly birds from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5), based on fall surveys from the International Shorebird Survey in the Southeast US Coast Region of the United States, 1974-2016. While the overall regression is significant (dashed line, r=0.804, p=0.000), the points (solid lines) suggest relative stability from about 1974 to 1985 (r=0.210, p=0.512), followed by a period of significant decline from about 1984 to 1995 (r=-0.721, p=0.019), with more stable counts since about 1995 (r=-0.270, p=0.236).

Figure 15. Exponential fit of annual indices of abundance of C.c. rufa Red Knot, mostly birds from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5), based on fall surveys from the International Shorebird Survey Midcontinental Region for the 21-year period 1995-2016.

Figure 16. Exponential fit of annual indices of abundance of C.c. rufa Red Knot, mostly birds from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5), based on fall surveys from the International Shorebird Survey Texas Coastal Region for the 21-year period 1993-2013.

Trends derived from Christmas Bird Count data directly measure changes in some DU5 wintering populations, and CBC results are broadly similar to those from the ISS. In Florida (BCR-31, equivalent to the ISS Southeast Region), the decrease over three generations (1998-2019) was calculated as -58.8%, based on the statistically significant decline rate of -4.22%/year recorded for 1993-2019 (Table 3). The long-term (1970-2019) rate of decline was also significant at -3.63%/year (-83.1% decrease). For the Texas and northwest Gulf of Mexico region (BCR-37, equivalent to the Midcontinental and Texas Regions of the ISS), the decrease over three generations was also significant and calculated as -81.7%, using a 21-year rate of decline of -8.08%/year. The long-term (1970-2019) rate of decline was also significant at -9.09%/year (-98.8% decrease).

The ISS and CBC results are thus consistent in indicating that appreciable decreases in numbers of Red Knots wintering in the Gulf of Mexico/Texas region appear to be considerably greater than for those birds wintering in Florida.

In summary, these results suggest that Red Knot numbers in the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) have declined substantially over three generations, with decreases in the western part of the wintering range (northern Gulf Coast and Texas) (Figures 15, 16; Table 2) being higher than those in Florida (Figure 14, Table 2). Efforts to derive an overall rate of population decline for Red Knot in this DU are complicated by birds in different areas having different migration routes, and possibly belonging to different subgroups; e.g., the USFWS considers DU5 to consist of two different wintering populations (USFWS 2014a). Estimated decreases over three generations for the more westerly wintering regions were -84.4% (ISS Midcontinental), -44.1% (ISS Texas Coastal) and -81.7% (CBC; BCR-37), while decreases for Florida were estimated as
-33.1% (ISS Southeast US Coast) and -58.8% (CBC; BCR-31) (Tables 2, 3).

Trend estimates for populations of rufa on spring and fall migration in eastern North America (Tierra del Fuego / Patagonia wintering population DU3, northeastern South America wintering population DU4, and southeastern USA / Gulf of Mexico / Caribbean wintering population DU5)

Fall migration (ISS)

Although rufa Red Knot from all three DUs occur at most major migration sites in eastern North America on fall migration, the relative proportion of the different populations using those sites differs. Harrington et al. (2007) found that most knots passing southward through Massachusetts migrate to Patagonia and Tierra del Fuego (DU3), whereas most knots found in Georgia winter in the southeastern United States and are therefore from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5). Subsequent work in Georgia has supported this conclusion, based on re-sighting analysis of flagged birds supported by stable isotope analysis of birds from different populations (Lyons et al. 2018). Although it appears that increasing numbers of rufa Red Knot from the “northern” wintering groups (northeastern South America wintering population DU4, and southeastern USA / Gulf of Mexico / Caribbean wintering population DU5) have been using Massachusetts stopovers since about 2009, they use the area for different purposes (moult versus ongoing migration, with moulting birds staying longer and birds on migration gaining weight and leaving) and generally feed on different resources in different habitats (Harrington et al. 2010a,b). It appears likely that knots migrating south through Atlantic Canada and the northeast coast of the United States include a high proportion of birds from the Tierra del Fuego / Patagonia wintering population (DU3), and that declines in different ISS survey regions may reflect differences in rates of decline of the various DUs. As the most severe declines have been recorded for the Tierra del Fuego / Patagonia wintering population (DU3), higher rates of decline might be expected at more northerly migration areas on the east coast of North America. This appears to be the case (Table 2). Counts during the period 1974-2016 showed an annual rate of decline of -8.37%/ year in the Atlantic Canada region of the ISS,
-4.48%/year in the Northeast US Coast region, and -4.61%/year in the Southeast US Coast region: all were statistically significant. The same pattern was observed for the decline rates during the past three generations (21 years, 1995-2016): Atlantic Canada -5.79% (significant), Northeast US Coast -1.78% (significant) and Southeast US Coast -1.91% (not significant). The consistency of these patterns suggests that the declines are the result of reductions in numbers rather than changes in distribution, and that the large declines recorded on the wintering grounds of the Tierra del Fuego / Patagonia population (DU3) are reflected in the decline rates observed during southward migration at sites on the east coast of North America, especially in eastern Canada.

Spring migration (Delaware Bay)

Delaware Bay is the key refuelling stop for C. c. rufa from the Tierra del Fuego / Patagonia wintering population (DU3) during spring migration, before the final leg of their journey to the Arctic breeding grounds. Although knots from Florida and the southeastern United States (part of the southeastern USA / Gulf of Mexico / Caribbean wintering population DU5) and northeastern South America (DU4) wintering populations also pass through this site, they do so slightly earlier and may use different habitats (Atkinson et al. 2005). Up to 90% of the Tierra del Fuego / Patagonia wintering population (DU3) and the northeastern South America wintering population (DU4) may use Delaware Bay, compared to perhaps 50% of the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5; Bittel 2017; Burger et al. 2020), so that declines at this site are also likely to reflect the extensive decrease in numbers wintering in the far south. Comparison of modelled and aerial survey estimates of numbers in Delaware Bay suggests that Horseshoe Crab abundance influences length-of-stay of the Tierra del Fuego / Patagonia wintering population (DU3) and thus the peak numbers observed during the aerial surveys (Lyons 2017; Niles and Morrison unpubl. data).

Aerial survey totals in Delaware Bay before 1990 showed peaks of >90,000 knots, which have fallen to about 20,000 over the past 15 years (2003-2017; Figure 17). A logarithmic plot of the counts from 1982-2017 shows a significant decline of -4.84% per year equivalent to an overall decrease of -85.5% over 35 years, and over the most recent 21-year period a significant decline of -3.60% per year, equivalent to a decline of -53.7% over three generations (Table 2).

Figure 17. Total number of C. c. rufa Red Knot counted on aerial surveys (likely including birds from DUs 3, 4, and 5) during spring migration in Delaware Bay, 1982-2017 (L.J. Niles unpubl. data), showing linear (dashed line) and exponential (solid line) estimates of decline.

Trends on the breeding grounds

Surveys on Southampton Island showed that rufa Red Knot breeding densities fell from 1.16 nests/km² in 2000 to 0.33-0.55 nests/km² in 2003-2004 (Niles et al. 2005). The difference in mean density in 2000 compared to the last two years was significant (ANOVA, F_1,3 = 10.09, p = 0.0502) (Niles et al. 2007, 2010a). This work occurred at a time when the Tierra del Fuego / Patagonia wintering population (DU3) underwent particularly steep numerical declines, although the wintering area used by knots breeding in this area is currently not known.

Summary of trends

DU1 - islandica subspecies

Survey data from European wintering grounds suggest the population is stable or fluctuating over the past three generations.

DU2 - roselaari subspecies

Trend analyses of data from International Shorebird Survey (migration counts) and Christmas Bird Count (wintering counts) suggest major continuing declines. Estimates of decreases over the most recent three generations were -63.9% in the Pacific and Intermountain Region (ISS migration counts; 1992-2013), and -38.7% in California (BCR-32) and -51.7% in Washington (BCR-5) (CBC wintering counts; 1998-2019). This is consistent with counts of about 100,000 birds in Alaska in the 1970s compared to current estimates of 22,000 individuals. Data from the breeding grounds on Wrangel Island, Russia, also suggest decreases of about 63% between 1974-1977 and 2007.

DU3 - Tierra del Fuego / Patagonia wintering population

Winter counts in Tierra del Fuego show that the population has declined substantially since 2000, with an observed reduction of 77.0% over 20 years. There was an annual decrease of -6.3% in Tierra del Fuego, equivalent to a decline of 73.4% over a 21-year period (3 generations). As almost all birds now occur in Tierra del Fuego, it is presumed that the rate of decline was higher at other wintering sites in southern Patagonia.

DU4 - northeastern South America wintering population

Differences in estimates from aerial survey counts in 2013 and 2019 suggested an appreciable population increase, but this is believed to primarily reflect more complete survey coverage in 2019 rather than population change. Calculations to assess the effect of expanded coverage in 2019 suggest that actual population change was within about 5%, and overall numbers are thought to be relatively stable.

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population

Both International Shorebird Surveys (migration) and Christmas Bird Counts (wintering) indicate that substantial declines have taken place. Counts in major wintering areas show significant large decreases over three generations (1998-2019) in Florida (BCR-31) and the Northwest Gulf/Texas Region (BCR-37), of -58.8% and -81.7%, respectively. Smaller non-sigificant decreases were recorded in other areas of the Northeast Gulf/Southeastern US Region(-16.7%). ISS migration period trends also showed large and significant three-generation decreases in the Southeastern US Region (mainly Florida, comparable to BCR-31) of -33.1%, while decreases in Texas Coastal and Midcontinental Regions (comparable to BCR-37) were estimated at -44.1% and -84.4%, respectively. Although these results only present population trends for unknown but likely substantial portions of this population, the weight of evidence drawn from results of the ISS and CBC together indicates that the numbers have declined appreciably over the past three generations, with a high probability that the overall decline is in the range of 33-84%.

Rescue effect

DU1 - islandica subspecies

Studies show that adult male Red Knot tend to be very site-faithful on the breeding grounds (Tomkovich and Soloviev 1994; Morrison et al. 2005; Baker et al. 2013, 2020), but little is known about dispersal from natal areas of birds breeding for the first time. Whereas it is theoretically possible that C. c. islandica DU1 Red Knot from Greenland might potentially rescue populations in northern Canada, it is unknown whether this is likely to occur in practice.

DU2 - roselaari subspecies

C. c. roselaari breeds on Wrangel Island, Russia, and in Alaska, and occurs in Canada only as a relatively scarce migrant in British Columbia, so rescue considerations do not apply.

Tierra del Fuego / Patagonia wintering population (DU3), northeastern South America wintering population (DU4), southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5)

The three DUs within the C. c. rufa subspecies, all of which breed entirely within Canada, are by definition separate populations and are thus not candidates for rescuing one another.

Threats and limiting factors

Threats

The threats to the five designatable units of Red Knot reviewed below are categorized following the IUCN-CMP (International Union for Conservation of Nature - Conservation Measures Partnership) unified threats classification system, based on the standard lexicon for biodiversity conservation of Salafsky et al. (2008). This assessment addresses threats to the five Red Knot DUs in Canada, as well as those on migration and on the wintering grounds, based on perspectives provided by species experts captured in Appendices 2, 3, 4, 5, and 6.

The highest impact threats affecting all Red Knot DUs to varying degrees were human disturbance, ecosystem modifications and changes, and other problem species, while climate change was important for all DUs (Appendices 2, 3, 4, 5, and 6). The assigned overall threat impacts are: islandica subspecies (DU1): Low-Medium (Appendix 2), roselaari subspecies (DU2): Medium-High (Appendix 3), Tierra del Fuego / Patagonia wintering population (DU3): High-Very High (Appendix 4), northeastern South America wintering population (DU4): Medium-High (Appendix 5), southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5): Medium High (Appendix 6). The lowest overall threat impact score was for DU1, which winters in Europe, and the highest threat impact score was for the Tierra del Fuego / Patagonia wintering population (DU3), which undergoes the longest migration.

In order to facilitate useful comparison of commonalities and differences among threats across the five Red Knot DUs, and for easy cross-referencing to the threats calculator tables (Appendices 2, 3, 4, 5, and 6), the applicable threats are discussed below in numerical order by sub-category, rather than in decreasing order of severity of impact.

1. Residential and commercial development

1.1 Housing and urban areas;1.2 Commercial and industrial areas; 1.3 Tourism and recreation areas

Continuing human population growth, resulting in increasing industrial activity and expanding recreation and tourism, leads to pressure to develop coastal environments, creating conflicts with many waterbird species, including Red Knot. While threat impacts in this category for most DUs were generally considered Low, such threats are widespread both in Europe and many parts of the Americas.

DU1 - islandica subspecies. Negligible threat impact (1.1, 1.2, 1.3).

Increased pressure from housing demands and from commercial and industrial developments in coastal NE Europe are presumed to result in loss of winter habitat used by the islandica subspecies (DU1) of Red Knot. Increased development of tourist and recreation facilities at beaches in NE Europe is also likely affecting knots, for instance in the Wadden Sea in the Netherlands (Blew et al. 2017). An estimated 9% of the islandica population winters along the Atlantic coast of France (Bocher et al. 2012), where suitable roosting habitat may be limited by pressure from urban, commercial, and industrial development (Leyrer et al. 2014).

DU2 - roselaari subspecies. Low threat impact (1.1, 1.2), negligible threat impact (1.3).

For many years, increasing pressure from housing demands and from commercial and industrial developments has affected or limited areas and habitats used by roselaari subspecies (DU2) Red Knot in many areas of the Pacific coast of United States (e.g. Washington, San Francisco area) and Mexico (e.g., Baja California, Guerrero Negro) (USFWS 2014; Buchanan pers. comm. 2020). Development of coastal tourist facilities and beach access points also cause limited habitat loss in areas used on migration in the western United States (USFWS 2014a; Buchanan pers. comm. 2020), and in winter in Mexico (Carmona et al. 2019).

DU3 - Tierra del Fuego / Patagonia wintering population. Low threat impact (1.1, 1.2, 1.3).

In Río Gallegos, Argentina, reclamation of tidal flats and salt marshes for urban, commercial, and industrial development presents a threat to the Tierra del Fuego / Patagonia wintering population (DU3) of Red Knot, and development in Rio Grande, Tierra del Fuego, appears to have reduced knot numbers. Housing, tourism, and industrial developments are all thought to affect Red Knot at the important stopover area at San Antonio Oeste, Argentina. The development of coastal tourist facilities and beach access points, leading to disturbance and habitat loss, are affecting areas used by Red Knot on migration in the eastern United States, and on migration and in winter in Argentina and Tierra del Fuego (Ferrari et al. 2002; Escudero et al. 2012; USFWS 2014a; Morrison 2018; WHSRN 2020; Morrison unpubl. obs.). Human disturbance threatens Red Knot at southbound stopovers in Massachusetts and New Jersey, especially during public holidays, when long distance migrants are putting on weight prior to the arrival of raptors in early September (Niles unpubl. obs.).

DU4 - northeastern South America wintering population. Low threat impact (1.1), negligible threat impact (1.2, 1.3).

Many migration stopover areas in E and SE North America used by Red Knot from the northeastern South America wintering population (DU4) are being significantly affected by increased housing pressure, as well as by increased impacts from tourist facilities and beach access, and commercial and industrial development (USFWS 2014a). Urban, commercial, and industrial development may pose a risk to birds from this DU (Andreade et al. 2016).

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Low threat impact (1.1, 1.3), negligible threat impact (1.2).

Habitats used by Red Knot in E and SE United States (USFWS 2014a) and the Caribbean are affected and/or limited by increasing demands for housing and urban development, and by commercial and industrial development. Impacts of development of coastal tourist facilities and beach access points in areas used on migration and winter in the United States are also locally important.

2. Agriculture and aquaculture

2.1 Annual and perennial non-timber crops; 2.2 Wood and pulp plantations; 2.3 Livestock farming and ranching; 2.4 Marine and freshwater aquaculture

Threats in sub-categories 2.1 and 2.2 were not considered to be measureable for any of the five Red Knot DUs. Sub-category 2.3 was considered to have a potential effect on the Tierra del Fuego / Patagonia wintering population (DU3) in South America, whereas sub-category 2.4 was thought to have a considerable potential impact on the roselaari subspecies (DU2) and the three rufa populations (DUs 3, 4, and 5).

DU2 - roselaari subspecies. Low threat impact (2.4).

Threats to Red Knot roselaari subspecies (DU2) from aquaculture relate to shellfish aquaculture in Grays Harbor, Washington, and to extensive shrimp aquaculture in Upper Gulf of California and Marismas Nacionales, Mexico, which was considered to reduce quality of foraging habitats (Berlanga-Robles et al. 2011; Arreola-Lizárraga et al. 2014; FAO 2019), and thus potentially affect the population (Carmona et al. 2019, WHSRN 2020).

DU3 - Tierra del Fuego / Patagonia wintering population. Unknown threat impact (2.3), low threat impact (2.4).

Threats to Red Knot in the Tierra del Fuego / Patagonia wintering population (DU3) from agriculture and aquaculture are fairly widespread, although the impact is uncertain. In South America, cattle ranching occurs on lands adjacent to reserves at Río Gallegos, Argentina (Niles et al. 2008), and extensive cattle grazing impacts coastal habitats near Lagoa do Peixe on the southeast coast of Brazil (WHSRN 2020). Neighbouring upland coastal habitats near Lagoa do Peixe in Brazil and Río Gallegos in Argentina show signs of degradation from food farming (e.g., of onions, rice, corn) (USFWS 2014a; WHSRN 2020). Stopover sites in Brazil may be negatively impacted by adjacent farming practices, including shrimp farming (Carlos et al. 2010), that alter hydrology and increase siltation of important lagoon habitats (Niles et al. 2008; USFWS 2014a). In Canada, clam farming in Quebec impacts the quality of habitat for foraging rufa, involving birds from all three DUs (Sahlin 2010, 2011; Aubry pers. comm. 2020). New aquaculture initiatives (especially for oysters) in Delaware Bay may threaten essential habitats used by shorebirds, including Red Knot, during migration (Burger et al. 2015; Burger and Niles 2017), but a recent study indicates that intertidal oyster aquaculture and migrating shorebirds can effectively co‐utilize the resource-rich intertidal areas in which they both occur (Maslo et al. 2020). Seaweed farming and salmon aquaculture are potentially degrading the quality of Red Knot habitat in Argentina and on Chiloé Island, Chile (USFWS 2014a).

DU4 - northeastern South America wintering population. Low threat impact (2.4).

Red Knot from this DU pass through Quebec on migration, where foraging habitats may be affected by clam farming in the Gulf of St. Lawrence (Aubry pers. comm. 2020; Sahlin 2010, 2011). In Delaware Bay, new aquaculture initiatives may affect shorebird use of important habitats during migration (Burger and Niles 2017; Maslo et al. 2020). Shrimp farming and resultant habitat loss and degradation have likely greatly reduced available stopover and wintering coastal habitats for Red Knots and other migratory shorebirds in NE Brazil over the past 20-25 years (Carlos et al. 2010).

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Low threat impact (2.4).

Red Knot in the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) may be somewhat less affected by threats from agriculture and aquaculture than other rufa DUs, owing to their smaller migration range. Foraging habitats may be affected by clam farming in the Gulf of St. Lawrence (Sahlin 2010, 2011; Aubry pers. comm. 2020) and new aquaculture initiatives in Delaware Bay may affect shorebird use of important habitats during migration (Burger and Niles 2017; Maslo et al. 2020).

3. Energy production and mining

3.1 Oil and gas drilling; 3.2 Mining and quarrying; 3.3 Renewable energy

Threats in this category relate mostly to direct impact from exploration and infrastructure, rather than with resulting pollution or spills, which are considered under sub-category 9.2. Although the likely overall impact of threats in these sub-categories is considered low, the potential for local impacts is high, whether on Arctic breeding grounds, migration areas, or wintering grounds. Mining and associated infrastructure in the Canadian and Alaskan Arctic may have had past effects in reducing the quality of breeding habitat. Increased mining activities in the Canadian Arctic (e.g., for diamonds, iron ore, aggregate extraction) and associated infrastructure may pose a localized threat to breeding rufa Red Knot. Quarrying and mining also occur along watercourses that flow through stopover sites along the east (Quebec) and west (Ontario) coasts of James Bay, and exploration in this area is ongoing (ECCC 2017). Developments of new mines and quarries near coastal habitats in South America may affect habitat quality. Sand mining from eastern US beaches may reduce quality of migration habitat for rufa birds from three DUs (van Dusen et al. 2012), as may gravel mining in Tierra del Fuego for birds wintering there (DU3). Infrastructure, such as wind turbines, may have both direct (i.e., mortality owing to collisions) and indirect (e.g., habitat loss, avoidance behaviour) effects on birds (e.g., Stewart et al. 2007; Sansom et al. 2016).

DU1 - islandica subspecies. Negligible threat impact (3.1, 3.3).

Coastal oil and gas industry production and infrastructure may have local effects on European wintering habitats. Mining and associated infrastructure in the Canadian Arctic may have had past localized effects in reducing the quality of breeding habitat. A controversial proposal for coal extraction on Ellesmere Island put forward in 2012 is currently on hold (Latimer 2012; Braden 2014). Further assessment is needed of potential impacts on Red Knot and other waterbirds of existing and proposed infrastructure wind power installations near the Wadden Sea in the Netherlands (Blew et al. 2017). Wind turbines have had a significant disturbance effect on Golden Plover (Pluvialis apricaria) on breeding grounds in the United Kingdom (Sansom et al. 2016).

DU2 - roselaari subspecies. Negligible threat impact (3.1), unknown threat impact (3.3).

Development and infrastructure associated with the oil and gas industry may have significant impacts on coastal or breeding habitat in northern Alaska (Alaska Shorebird Group 2019). Mining and associated infrastructure in the Alaskan Arctic may have had past localized effects in reducing the quality of breeding habitat. New petroleum discoveries and a projected increase in oil production are expected onshore in the Arctic in Alaska (Resource Development Council 2015). The impacts of coastal wind turbines in the small area between Willapa Bay and Grays Harbor which Red Knot use in spring are unknown (Buchanan pers. comm. 2020).

DU3 - Tierra del Fuego / Patagonia wintering population. Negligible threat impact (3.1, 3.2), unknown threat impact (3.3).

The major wintering site for the Tierra del Fuego / Patagonia wintering population (DU3) Red Knot at Bahia Lomas, Chile, is the focus of extensive oil drilling and exploration: infrastructure per se may not directly affect wintering knot populations, although some of the drilling rigs are within the intertidal zone (RIGM pers. obs.). Quarrying of sand and gravel near Rio Grande, Tierra del Fuego, Argentina, is thought to have affected habitats and food resources of wintering knots (González pers. comm. 2019). Breeding grounds in the Arctic may be affected by increased mining (e.g., for diamonds, iron ore, aggregate extraction) and associated infrastructure may pose a local threat to Red Knot. Quarrying and mining along watercourses that flow into James Bay could affect important migration stopover sites along both coasts, where exploration is ongoing (Brownell et al. pers. comm. 2015 in ECCC 2017). Gold mining (largely uncontrolled) in northern South America may directly damage riverbeds and banks, causing siltation downstream, and releasing mercury into the environment that could reach the coast and affect migration habitats (Alvarez-Berríos and Aide 2015). Within the Canadian Arctic, the use of wind to power industry and communities is expected to increase (Lamont pers. comm. 2015, in ECCC 2017). Since 2009, wind power has rapidly increased as a source of power in Brazil, extensive wind farm development has already occurred near the coast in northern Brazil (Lucena and Lucena 2019; Morrison unpubl. obs.), and there is growing interest in developing offshore sites (Lucena and Lucena 2019). Environmental impacts of a coastal wind farm in the northeastern state of Ceará include removal of large quantities of sand that was replaced by quarry sand and clay, effects on sediment transport, burial of inter-dunal lakes, and compaction of soil and sand (Meireles et al. 2013). Such developments would affect migration areas used by the Tierra del Fuego / Patagonia wintering population (DU3), and it is presently unclear how these and future wind developments would affect Red Knot.

DU4 - northeastern South America wintering population. Negligible threat impact (3.1, 3.2), unknown threat impact (3.3).

New oil drilling and exploration is taking place in Para and Maranhão on the northeastern coast of Brazil (Pellegrini and Ribeiro 2019), potentially affecting birds from this DU. A massive oil spill occurred in this area in 2019 (Handmaker 2019). Sand mining from eastern US beaches may reduce quality of migration habitat (van Dusen et al. 2012). Increased use of wind power in the Canadian Arctic could potentially affect breeding DU4 Red Knot (Lamont pers. comm. 2015, in ECCC 2017). Extensive development of coastal wind farms has occurred in northern Brazil since 2009, with effects on habitats described for the Tierra del Fuego / Patagonia wintering population (DU3), where there is growing interest in developing offshore sites (Lucena and Lucena 2019; Morrison unpubl. obs.). However, the overall impact of these and future wind developments on the northeastern South America wintering population (DU4) Red Knot is unclear.

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Negligible threat impact (3.1, 3.2), unknown threat impact (3.3).

Breeding Red Knot from this DU are likely affected by threats from oil and gas drilling, and from mining and quarrying, as described above for the Tierra del Fuego / Patagonia wintering population (DU3) and for the northeastern South America wintering population (DU4), as well as for portions of the population migrating through James Bay. Sand mining from eastern US beaches may reduce quality of migration and wintering habitats (van Dusen et al. 2012). Wind development is also increasing within the Canadian (e.g., southwestern Ontario and Lake Ontario shoreline) and United States migration range of Red Knot, and onshore wind farms are already established (Burger et al. 2011), which may affect migrating and wintering birds from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5). A proposal for wind farm development near migration stopover areas at Chaplin Lake, Saskatchewan, was denied a permit (Lusney 2016), but has since re-located to a site 5 km southwest of Reed Lake IBA, also an important stopover site for Red Knot (McKellar pers comm. 2020). Wind energy development is projected to increase (Zimmerling et al. 2013) in an effort to reduce carbon pollution (Executive Office of the President 2013).

4. Transportation and service corridors

4.1 Roads and railroads; 4.2 Utility and service lines; 4.3 Shipping lanes; 4.4 Flight paths

Factors occurring in this category were not considered overall to be measurable threats for any Red Knot DUs. Impacts of oil spills from shipping are considered in 9.2. Industrial and military effluents.

5. Biological resource use

5.1 Hunting and collecting terrestrial animals; 5.2 Gathering terrestrial plants; 5.3 Logging and wood harvesting; 5.4 Fishing and harvesting aquatic resources

Threats in sub-categories 5.2, 5.3, and 5.4 were not considered to be measurable for any Red Knot DUs. Impacts of Horseshoe Crab harvest in Delaware Bay and of the Grunion (Pejerrey; Leuresthes sardina) fishery in northwest Mexico on migrating Red Knot are considered in 7.3 Other ecosystem modifications.

5.1 Hunting and collecting terrestrial animals

Although shorebirds are widely protected in North America and much of Europe, both subsistence and recreational hunting of Red Knot may still occur in some areas, including the Caribbean islands, the Guianas, and other parts of the northeast coast of South America (Bourget and Laporte 1983; Baker et al. 2013, 2020; Wege et al. 2014; Watts and Turrin 2016), as well as France (Bocher et al. 2012). Increasing awareness of the potential effects on Red Knot and other shorebird populations in the Caribbean has led to the Red Knot recently being added to the no-hunting list for French Guiana (2014), Guadeloupe (2012), and Martinique (2013) (Sorenson and Douglas 2013; Andres 2017). Hunting in these areas would affect birds from all three rufa DUs that occur in these areas during migration or after weather events. Red Knot is still a game species in France (Bocher et al. 2012; Duncan pers. comm. 2015), although it may soon be removed from the list of hunted species (Sorensen and Douglas 2013; Duncan pers. comm. 2015).

DU1 - islandica subspecies. Negligible threat impact.

Hunting of shorebirds still occurs in some countries in Europe, including France (Bocher et al. 2012). The specific threat to islandica Red Knot is uncertain, although likely small, as the population occurring in France comprises an estimated 9% of the European wintering population of islandica subspecies (DU1) (Bocher et al. 2012). Most key wintering sites for knots in that country (5 of 6) are all or partly in reserves where hunting is not allowed (Bocher et al. 2012).

DU2 - roselaari subspecies. Negligible threat impact.

Shorebirds are legally protected throughout their range in North America, and it would appear that threats from hunting are limited for roselaari subspecies (DU2). Red Knot is not on the list of species available for subsistence hunting in northwest Alaska (Alaska Department of Fish and Game 2019; Buchanan pers. comm. 2020).

DU3 - Tierra del Fuego / Patagonia wintering population. Unknown threat impact.

Red Knot from the Tierra del Fuego / Patagonia wintering population (DU3) may be affected by shorebird hunting while on migration through northern South America, which is legal in several countries (see Introduction to 5.1 above and DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population).

DU4 - northeastern South America wintering population. Unknown threat impact.

Red Knot from the northeastern South America wintering population (DU4) may be affected by hunting for food which occurs in parts of the Guianas and northeastern Brazil, although harvest levels are not well understood (Andres 2017) (see Introduction to 5.1 above).

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Negligible threat impact.

Red Knot from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) are most likely to be affected by shorebird hunting that occurs in the Caribbean, where these birds spend the winter. Although subsistence and recreational hunting, both legal and illegal, is still common in parts of the region, Red Knot is now protected in Guadeloupe (2012) and Martinique (2013), as well as French Guiana (Sorenson and Douglas 2013; Andres 2017). Harvest levels are not well documented but are likely low.

6. Human intrusions and disturbance

6.1 Recreational activities; 6.2 War, civil unrest and military exercises; 6.3 Work and other activities

Threats in sub-category 6.2 were not considered to be measurable for any Red Knot DUs.

Numerous studies have shown that repeated human-related disturbance (e.g., walkers, fishers/collectors, dogs, off-highway vehicles (OHVs), boats, kite surfers) can negatively affect shorebirds, disrupting behaviour patterns and affecting energy balance (e.g., Davidson and Rothwell 1993a,b; West et al. 2002). All Red Knot DUs experience disturbance at some point in their annual cycle, and the effects may be significant in some areas.

Surveys, banding, and research activities are designed to minimize impacts, but may disturb Red Knot at migration or wintering sites, although population-level effects are likely insignificant, and in the context of providing information needed for conservation, acceptable. The Mexican Grunion fishery can result in disturbance and disruption to knots feeding on Grunion eggs (Carmona et al. 2017).

DU1 - islandica subspecies. Negligible threat impact (6.1, 6.3).

The effects of disturbance on European estuaries on shorebirds, including islandica subspecies (DU1) Red Knot, have been documented for many years (Cayford 1993; Davidson and Rothwell 1993a,b), and pressure from disturbance has increased as human populations have grown. In open estuarine areas, disturbance is likely to be much more significant for roosting congregations than to dispersed feeding flocks (Collop et al. 2016). Increasing disturbance by recreationists may affect the quality of roosting areas in NE Europe, and Blew et al. (2017) noted that recreation in the Wadden Sea already impacting many high tide roost sites may expand, as more people visit the area, expanding their stay into spring and autumn. Ongoing banding activities on some UK and European estuaries may cause periodic disturbance.

DU2 - roselaari subspecies. Low threat impact (6.1), negligible threat impact (6.3).

Increasing disturbance by recreationists likely has a significant effect on quality of foraging and roosting areas used by Red Knot roselaari subspecies (DU2) along Pacific coasts of the United States (especially near urban areas such as San Francisco Bay and San Diego), Mexico (e.g., Santa Clara, upper Gulf of California; Carmona et al. 2017, 2019) and Central America. Less disturbance may occur in stopover areas such as Willapa Bay, Washington, and in Alaska (Donaldson pers. comm. 2015; Buchanan pers. comm. 2020). Disturbance from humans and dogs occurs on sandy beaches (McCrary and Pierson 2002), and many shorebird areas on the coast of British Columbia are thought to be disturbed by human activities (Drever et al. 2016). Banding studies and aerial surveys may cause occasional disturbance. Recreationists and those involved in the shoreline Grunion fishery in the Upper Gulf of California, Mexico may periodically disturb foraging or roosting birds in late winter and spring (Carmona et al. 2017).

DU3 - Tierra del Fuego / Patagonia wintering population. Medium-low threat impact (6.1), negligible threat impact (6.3).

Human disturbance from recreationists is common in migration and wintering areas for the Tierra del Fuego / Patagonia wintering population (DU3) of Red Knot. Disturbance on southward migration in the Magdalen Islands, from recreational clam-digging, kite buggying, wildlife viewing, and off-road vehicle use in intertidal areas, is a concern for rufa birds, many of which are from the Tierra del Fuego / Patagonia wintering population (DU3; ECCC-CWS Quebec region unpubl. data). Although disturbance was once a significant problem for shorebirds in Delaware Bay in spring (Burger et al. 1995), since 2003, closure of major sections of the New Jersey shore to human use during peak migration has successfully reduced disturbance (Burger et al. 2004; Niles et al. 2005), although there are no restrictions on use on the Delaware side of the bay. Disturbance is still a significant factor elsewhere on the east coast of the United States, causing shorebirds to abandon prime foraging or roosting habitats (USFWS 2014a; Mengak and Dayer 2020). Disturbance of roosting and foraging flocks by humans and dogs has been reported in Florida, Georgia, North Carolina, South Carolina, Virginia, Massachusetts, and Panama (Buehler 2002; Niles et al. 2005) and represents an important threat. Disturbance also affects beaches in southern Brazil used on migration (Soniak 2015). On the wintering grounds in Tierra del Fuego, roosting flocks at Rio Grande are frequently disturbed by walkers, runners, fishers, dogs, OHVs, and motor cycles (Niles et al. 2005; Morrison pers. obs.) and this disturbance is considered to be one cause of the extensive decline of rufa knots using Rio Grande (Escudero et al. 2012). In Argentina, similar disturbance to knots during migration, including kite-surfers, has been reported in Río Gallegos, Peninsula Valdes, San Antonio Oeste, Estuario de Bahía Blanca, and Bahía Samborombon (Niles et al. 2005; Martínez-Curci et al. 2015; ICFC 2018; Rare 2018; González pers. comm. 2019). Aerial surveys for determining population status occur in most years in Delaware Bay and on the wintering areas in Tierra del Fuego, although population-level effects are likely negligible.

DU4 - northeastern South America wintering population. Low threat impact (6.1), negligible threat impact (6.3).

Many of the issues related to disturbance from recreationists in eastern North America noted for Red Knot from the Tierra del Fuego / Patagonia wintering population (DU3) also apply to birds from the northeastern South America wintering population (DU4), which pass through the same areas on migration. Shorebird disturbance caused by tourism has been reported in wintering areas of northeast Brazil (Cardoso and Nascimento 2007; Andrade et al. 2016). Aerial surveys for determining population status occur in Delaware Bay and on the wintering areas on the north coast of South America, although population-level effects are likely insignificant.

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Medium-low threat impact (6.1), negligible threat impact (6.3).

Many of the issues related to disturbance from recreationists in eastern North America noted for Red Knot from the Tierra del Fuego / Patagonia wintering population (DU3) also apply to birds from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5), which pass through the same areas on migration to its wintering areas in the southeastern United States, Gulf of Mexico, and the Caribbean Sea (Mengak and Dayer 2020). However, the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) knots are exposed to disturbance threats for a longer period than other DUs each year because they winter in an area of high recreational activity. Aerial surveys for determining population status occur in Delaware Bay and occasionally in Florida, although population-level effects are likely negligible.

7. Natural system modifications

7.1 Fire and fire suppression, 7.2 Dams and water management/use, 7.3 Other ecosystem modifications

Threats in sub-category 7.1 were not considered to be measurable for any Red Knot DUs.

7.2 Dams and water management/use

Altered river flows into estuaries, lagoons and deltas, including management of water levels of inland wetlands, can have a great impact on physical and biological properties of coastal estuaries (Gillanders and Kingsford 2002). Altered flow patterns can reduce food and habitat availability and quality of coastal areas, including stopover and wintering areas used by shorebirds. Such phenomena are widespread (Roseberg et al. 1995, 1997) and likely affect all Red Knot DUs, although effects of much of this management may have taken place in the past.

DU1 - islandica subspecies. Negligible.

Altered flow into estuaries and deltas has reduced habitat quality of coastal wintering areas in Europe in the past, but altered river flow is likely having little effect currently on wintering islandica subspecies (DU1) Red Knots.

DU2 - roselaari subspecies. Unknown threat impact.

Many rivers in Mexico have been dammed, mainly for hydroelectric power generation (Rhoda and Burton 2010), resulting in altered river flows in coastal habitats, including the important area at the mouth of the Colorado estuary, upper Gulf of California, used by roselaari subspecies (DU2) Red Knots, where fresh water input has almost ceased (Gillanders and Kingsford 2002; All 2006; Carmona et al. 2017). These effects may reduce habitat quality of stopover and wintering areas; while some effects may have taken place in the past, many may be ongoing.

DU3 - Tierra del Fuego / Patagonia wintering population. Low threat impact.

Some Red Knot in this DU may be affected by the conditions described below for interior migration routes of the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) birds. The important staging area identified near the mouth of the Nelson River on the coast of Hudson Bay (McKellar et al. 2015) has likely been affected by dams on the Nelson River (Rosenberg et al. 1995, 1997). Although many of the changes have already taken place, there are ongoing plans for new proposals (Lunn 2013). Hydroelectric dams in Quebec are thought to have affected coastal habitats in southern James Bay (Drinkwater and Frank 1994; Rosenberg et al. 1995, 1997; Environment Canada 2013), altering the coastal ecology and likely affecting shorebirds including Red Knot.

DU4 - northeastern South America wintering population. Low threat impact.

Red Knot from the northeastern South America wintering population (DU4) are likely subject to the same effects of dams and water management and use as those for the Tierra del Fuego / Patagonia wintering population (DU3) described above.

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Low threat impact.

An estimated 50% of Red Knot in the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5), primarily those that winter in the Gulf of Mexico, migrate northwards through the interior of North America (Burger et al. 2020). Many important wetlands used by migrating shorebirds are intensively managed in the Canadian prairies (Gratto-Trevor pers. comm. 2015, in ECCC 2017), which may have a negative effect on food supplies and suitable roosting habitat of migrating shorebirds. Water management (i.e., drawdown or re-flooding within a wetland complex) may benefit shorebirds in some areas if the timing and duration of management is appropriate (Skagen and Thompson 2013). Unregulated and unlicensed drainage of wetlands has been identified as a threat to shorebird habitat at Quill Lakes, Saskatchewan (WHSRN 2020), and infilling is documented as a threat to ephemeral and temporary inland wetlands important for shorebirds (Skagen and Thompson 2013). In the Gulf of Mexico, altered freshwater inflow may be one of the most common stressors on estuaries, lagoons, and deltas (Sklar and Browder 1998), potentially affecting nutrient levels, salinity, sedimentation, topography, dissolved oxygen levels, and other ecosystem components. The ecosystem response to altered freshwater flow is complex and often unpredictable (Sklar and Browder 1998). Knot from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) concentrate at the important staging area near the mouth of the Nelson River on the coast of Hudson Bay (McKellar et al. 2015) during spring migration, which has likely been affected by dams on the Nelson River (Rosenberg et al. 1995, 1997). Although many of the changes have already taken place, there are ongoing plans for new proposals (Lunn 2013). Habitats in southern James Bay have also likely been affected by hydroelectric developments (Drinkwater and Frank 1994; Environment Canada 2013).

7.3 Other ecosystem modifications

Harvesting of marine and intertidal resources used by Red Knots for food has a major impact on their populations, particularly the three rufa DUs which migrate through Delaware Bay in spring. Harvesting of Grunion in northwest Mexico is likely affecting populations of roselaari subspecies (DU2) on the Pacific coast of North America during spring migration (Carmona et al. 2017, 2019); harvesting of intertidal resources in Europe has also affected knot islandica subspecies populations (DU1) (Piersma et al. 2001; Blew et al. 2017).

Efforts to stabilize shorelines, using hard structures such as seawalls and soft ones such as sandbags and beach nourishment of eroding coastlines may reduce quality of some migration stopover and wintering sites (USFWS 2014a). Beach management activities in the Delaware Bay area to maintain habitat for Red Knot and Horseshoe Crabs are important for the three rufa DUs and may have a net benefit.

DU1 - islandica subspecies. Low threat impact.

Until recently, there was an extensive harvest of Common Cockles (Cerastoderma edule) and other invertebrates in the Dutch Wadden Sea (Piersma et al. 2001), which was thought to have caused declines in numbers of islandica subspecies (DU1) Red Knot and other shorebirds using the area, although this harvest has now been restricted (Nehls et al. 2009; Blew et al. 2017). The carrying capacity of the Wadden Sea decreased for Red Knot as the result of this overexploitation of benthic resources (Kraan et al. 2009). In France, some islandica Red Knot may be impacted by professional clam or cockle harvesters at estuarine bays during winter (Bocher et al. 2012).

DU2 - roselaari subspecies. Medium-low threat impact.

It is likely that the harvest of Grunion in northern Baja California in northwest Mexico is affecting Red Knot on northward migration (Carmona et al. 2019). Grunion eggs are a major food resource taken by Red Knot roselaari subspecies (DU2) before departure on northward migration. Grunions come to the edge of the shore to lay their eggs, in a manner comparable to Horseshoe Crabs in Delaware Bay (Hernández-Alvares et al. 2013), and extensive human intervention in harvesting the fish has resulted in the resource being compromised for roselaari Red Knots (Carmona et al. 2019).

Shoreline stabilization may be a threat to subspecies roselaari (DU2) throughout its range in the continental United States (USFWS 2011), especially in the San Francisco Bay and San Diego areas (Buchanan pers. comm. 2020).

DU3 - Tierra del Fuego / Patagonia wintering population. High-low threat impact.

In eastern Canada, seaweed harvesting occurs at fall stopover sites in Cacouna, Quebec, with uncertain implications for rufa stopover habitat (Aubry pers. comm. 2015, in ECCC 2017). Harvest of Horseshoe Crabs, and the concomitant reduction in availability of their eggs, which are a major food resource for knots migrating through Delaware Bay in the spring (Morrison and Harrington 1992; Castro and Myers 1993; Clark et al. 1993; Botton et al. 1994; Tsipoura and Burger 1999; Karpanty et al. 2006; Baker et al. 2013; Haramis et al. 2007), has been a major factor in the decline of the three Red Knot rufapopulations since about 2000 (Baker et al. 2004; González et al. 2006; Morrison 2018; Morrison et al. 2020b). This once-superabundant food supply was greatly reduced by over-harvesting of adult Horseshoe Crabs (USFWS 2014a). Reduced egg densities were too low to enable knots to meet their energetic requirements (Baker et al. 2004; Hernández 2005), leading to inadequate departure masses and subsequent reduced survival, reflected in the observed decline in the wintering population in Tierra del Fuego (Baker et al. 2004; González et al. 2006; Morrison 2018; Morrison et al. 2020a,b). The southern Tierra del Fuego / Patagonia wintering population (DU3) is thought to have been particularly impacted, because of the additional physical demands and constraints related to their long-distance migration (Niles et al. 2010a). Horseshoe Crab harvest is now adaptively managed in Delaware Bay in accordance with a collaborative management plan approved in 1998, with addenda added up to 2006 (Kreamer and Michels 2009; Niles et al. 2010a). The restricted harvest has resulted in apparent stability of the crab population, although not recovery (Atlantic States Marine Fisheries Commission 2015; Dey et al. 2020), so it is not known to what extent knot populations will be able to recover.

Much of the developed coastline of the United States within the migration range of all three rufa DUs, and wintering grounds of some knots from the southeastern USA / Gulf of Mexico / Caribbean wintering populations (DU5), has undergone some form of shoreline stabilization, e.g., hard structures such as groins, seawalls, and breakwaters; soft structures such as geotubes, coir matting, sand bags, and beach nourishment through the addition of sand to eroding shorelines (USFWS 2014a). Shoreline stabilization measures impact some coastal sites in Canada as well (Lemmen et al. 2016). Loss of beach and intertidal habitats required by Red Knot is accelerated when shoreline stabilization projects are implemented that block natural shoreline landward migration and alter beach morphology, sediment quality, and water dynamics (e.g., Najjar et al. 2000).

Severe storms (Lathrop et al. 2013) and shoreline stabilization with hard structures (Myers 1986; Jackson et al. 2010) may degrade habitat required for spawning Horseshoe Crabs. After Hurricane Sandy destroyed many beaches used by nesting Horseshoe Crabs in Delaware Bay in 2012 (Niles et al. 2012b), massive efforts to replenish the beaches restored these habitats in time for Horseshoe Crabs to breed and for the Red Knot migration (Niles et al. 2013b; Wetlands Institute 2018). However, beach nourishment may have negative impacts on shorebirds, as it must be repeated to maintain beaches and may disturb shorebirds if work is undertaken while birds are present. Nourishment can cause temporary or permanent alteration of shorebirds’ invertebrate prey base (Schlacher et al. 2012; Peterson et al. 2014; USFWS 2014a), but can also enhance, restore, or create suitable habitat for invertebrates at degraded sites. Such restoration efforts are underway in Delaware Bay to maintain habitat for both Horseshoe Crabs and shorebirds that depend on their eggs to fuel northward migration (Siok and Wilson 2011; Niles et al. 2013b; USFWS 2014a).

DU4 - northeastern South America wintering population. Medium-low threat impact.

Red Knot from the northeastern South America wintering population (DU4) pass through Delaware Bay on northward migration and have been substantially affected by the reduction in their main food source, Horseshoe Crab eggs, as described for the Tierra del Fuego / Patagonia wintering population (DU3). Northeastern South America wintering population (DU4) knots may also be affected on southward migration by seaweed harvesting at fall stopover sites in Cacouna, Quebec, with uncertain implications for rufa stopover habitat (Aubry pers. comm. 2015).

Shoreline stabilization threats described for the Tierra del Fuego / Patagonia wintering population (DU3) also apply to the northeastern South America wintering population (DU4) of Red Knot while migrating through eastern North America.

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Medium-low threat impact.

Some 50% of Red Knots from this DU pass northwards through Delaware Bay on northward migration (Burger et al. 2020), compared to approximately 90% of Red Knots from the Tierra del Fuego / Patagonia (DU3) and the northeastern South America wintering populations (DU4; Burger et al. 2020), and were also likely substantially affected by the reduction in Horseshoe Crab eggs described above. However, these shorter-distance migrants may more readily use alternate hard-shelled prey, as they are not thought to undergo the physiological changes shown by longer-distance migrants (Niles et al. 2010a).

Shoreline stabilization threats described for the Tierra del Fuego / Patagonia wintering population (DU3) also apply to populations of southeastern USA / Gulf of Mexico / Caribbean (DU5) Red Knot, both on migration through the United States and during the wintering period in southeastern North America.

8. Invasive and other problematic species and genes

8.1 Invasive non-native species/diseases, 8.2 Problematic native species/diseases, 8.3 Introduced genetic material, 8.4 Problematic species/diseases of unknown origin, 8.5 Viral/prion-induced diseases, 8.6 Diseases of unknown cause

Threats in sub-categories 8.3, 8.4, 8.5, and 8.6 were not considered to be measurable for any Red Knot DUs. Potential alterations to habitat through changing vegetation structure are considered under sub-category 11.1 Habitat shifting and alteration.

8.1 Invasive non-native species/diseases

DU2 - roselaari subspecies. Negligible threat impact.

Important intertidal mudflat habitats used by Red Knot roselaari subspecies (DU2) in Willapa Bay and Grays Harbor, Washington, were largely over-run by the invasion of non-native Smooth Cordgrass Spartina alterniflora, native to the Atlantic coast, and converted to higher-level saltmarsh habitat (WDA 2017). Cordgrass has been largely removed but is likely to return if management is not continued (WDA 2017; WHSRN 2020; Buchanan pers. comm. 2020).

Migration areas used by birds of this DU in Willapa Bay and Grays Harbor, Washington, may be affected by the European Green Crab (Carcinus maenas) and other invasive species, which have the potential to significantly alter benthic prey communities (Buchanan pers. comm. 2020).

8.2 Problematic native species/diseases

Threats under this sub-category come under two main sources, firstly, an increase in risk from native predator populations, either from increases in predator numbers or from increased predation pressure resulting from habitat alteration caused by hyperabundant geese, and secondly, die-offs from diseases caused by toxic algal blooms.

Shorebirds enjoyed what Butler et al. (2003) termed a “predator vacuum” for several decades in the late twentieth century, as a result of greatly reduced populations of birds of prey (especially falcons) caused by human persecution and pesticide poisoning. Peregrine Falcon populations have increased in much of their range and are no longer considered at risk: the anatum/tundrius subspecies was delisted in Canada under the Species at Risk Act (SARA) in 2017 (COSEWIC 2017b). Impacts of falcons on knots and other shorebirds include disturbance, reducing foraging bouts, restricting access to prime foraging sites, modified migration behaviour, and even changes in physiology and mortality (e.g., Ydenberg et al. 2004, 2007; Stillman et al. 2005; Pomeroy et al. 2006; Niles et al. 2008, Niles 2010; van den Hout 2010). Although Peregrine Falcon populations may have simply returned to historically “normal” levels, many Red Knot populations are now considerably reduced, reflecting the “conservation conflict” situation that may appear under such circumstances (Watts 2009a; Watts and Truitt 2021). In some cases, Peregrine Falcon were introduced to areas in which the species did not breed historically, and nesting towers in some areas have been removed and birds relocated to historical areas to reduce the “conflict” (Watts 2009a,b; Watts et al. 2015, 2018; Wurst 2018).

On the Arctic breeding grounds, the combined effects of hyperabundant goose-induced changes in habitat and predator-prey interactions with shorebirds may be contributing to local or regional declines in Arctic-nesting shorebird populations (Flemming et al. 2016, 2019a,b,c). Overgrazing by Snow Geese (Chen caerulescens) has altered many coastal habitats used by rufa Red Knots on migration in Hudson Bay and James Bay, although how this may affect shorebirds on migration is not well known (Abraham and Jefferies 1997).

Harmful algal blooms caused by a variety of organisms are widespread throughout the range of Red Knot (USFWS 2014a; USNOHAB 2020). These include Amnesic Shellfish Poisoning (ASP; occurring in Atlantic Canada, caused by Pseudo-nitzchia spp.); Neurotoxic Shellfish Poisoning (NSP, also called “red tide”; occurring on the US coast from Texas to North Carolina, caused by Karenia brevis and other species); and Paralytic Shellfish Poisoning (PSP; occurring in Atlantic Canada, the US coast in New England, Argentina, and Tierra del Fuego, caused by Alexandrium spp. and others; FAO 2004; USNOHAB 2020). The highest levels of PSP toxins have been recorded in shellfish from Tierra del Fuego (IAEA 2004, in USFWS 2014a), and high levels can persist in molluscs for months following a PSP bloom (FAO 2004).

DU1 - islandica subspecies. Unknown threat impact.

Peregrine Falcon has increased greatly on wintering grounds of the islandica subspecies (DU1) in the Dutch Wadden Sea (van den Hout 2009) and, in addition to causing direct mortality (which may be low), has a significant effect on the distribution and physiology of the knots (van den Hout 2009, 2010; Blew et al. 2017).

Harmful algal blooms have occurred in many parts of the European seaboard used by knots from this DU, increasing in number and distribution between 1970 and 2015 (USNOHAB 2020).

DU2 - roselaari subspecies. Low threat impact.

Peregrine Falcon populations appear to have increased along the Pacific coast of North America. This species is a known predator of Red Knot on wintering grounds in Mexico (Enderson et al. 1991; White et al. 2002; COSEWIC 2017c), which are likely to be affected by this threat in a manner similar to other DUs.

Harmful algal blooms occur on the Pacific coast and have increased in number and distribution between 1970 and 2015 (USNOHAB 2020). Agricultural runoff has led to the development of blooms on the northwest coast of Mexico (Berman et al. 2005).

DU3 - Tierra del Fuego / Patagonia wintering population. Medium threat impact.

Recovering peregrine populations are believed to have altered stopover behaviour of shorebirds in the Bay of Fundy (Dekker et al. 2011) during the fall migration period. In this and other parts of the east coast, predation threat is considered important, with southbound migrants attempting to depart before the arrival of migrating raptors (Lank et al. 2003; Niles pers. comm. 2018). Watts and co-workers (Watts 2009a; Watts and Truitt 2021; Watts et al. 2015) showed that falcon presence reduced the shorebird carrying capacity of coastal Virginia by 30% during spring migration. Other impacts of falcons on knots may include disturbance, reducing foraging bouts, restricting access to prime foraging sites, modified migration behaviour, and changes in physiology (e.g., Stillman et al. 2005; Pomeroy et al. 2006; Ydenberg et al. 2007; Niles et al. 2008, Niles 2010; van den Hout 2010).

Increasing Peregrine Falcon numbers have been noted in South America, including Suriname (Ottema et al. 2009), French Guiana (USFWS 2014a) and by implication northern Brazil, where Tierra del Fuego / Patagonia wintering birds (DU3) occur on migration. Many Red Knot freshly killed by Peregrine Falcons were reported by Baker et al. (1998) on northward migration at Lagoa do Peixe in southern Brazil in early April 1997. At the important northward stopover area at San Antonio Oeste, Argentina, higher numbers of falcons, including Peregrines, have caused knots to move to lower quality habitats and changed timing of migration (González pers. comm. 2020). Shorebirds are known to be amongst prey taken by Peregrine Falcons in Patagonia and Tierra del Fuego (Ellis et al. 2002). Peregrine and Aplomado Falcons (Falco femoralis) are known to hunt shorebirds on the main wintering area in Bahia Lomas, Chile (Matus pers. comm. 2020).

Some breeding areas in the central Canadian Arctic used by the Tierra del Fuego / Patagonia wintering population (DU3) have likely been negatively affected by overabundant geese (Flemming et al. 2016, 2019a,b,c). Overgrazing by geese has also altered many coastal habitats at migration stopover areas in Hudson and James Bays, although how this may affect shorebirds on migration is not known (Abraham and Jefferies 1997).

Harmful algal blooms are widespread in the migration and wintering range of knots from this DU (USFWS 2014a; USNOHAB 2020). Various types of shellfish poisoning occur in Atlantic Canada (caused by Pseudo-nitzchia spp.), on the east coast of the United States (red tides caused by K. brevis and other species), and in New England, Argentina, and Tierra del Fuego (caused by Alexandrium spp. and others; FAO 2004; USNOHAB 2020). The highest levels of PSP toxins have been recorded in shellfish from Tierra del Fuego (IAEA 2004, in USFWS 2014a), and high levels can persist in molluscs for months following a PSP bloom (FAO 2004). Mortality events have been documented for rufa knots from the Tierra del Fuego / Patagonia wintering population (DU3) in Uruguay in 2007 (over 300 knots found dead, Aldabe 2007; Aldabe et al. 2015; Aspiroz et al. 2018), and in southern Brazil in 1997 and 2000 (Baker et al. 1998; Buehler et al. 2010; Aspiroz et al. 2018). In Tierra del Fuego, mortality of clams eaten by Red Knot, possibly from accumulation of algal toxins or parasites, was recorded by Escudero et al. (2012; USFWS 2014a). “Red tides” regularly occur in Tierra del Fuego (Almandoz et al. 2011). The wider geographical spread of threat from harmful algal blooms suggests that the Tierra del Fuego / Patagonia wintering population (DU3) may be more at risk from this threat than other DUs.

DU4 - northeastern South America wintering population. Medium-low threat impact.

The northeastern South America wintering population (DU4) Red Knots are subject to the threats from falcons described for the Tierra del Fuego / Patagonia wintering population (DU3) during migration through eastern North America, and on their wintering grounds in northern South America.

Some breeding areas in the central Canadian Arctic, and migration areas in Hudson and James Bays used by the northeastern South America wintering population (DU4) of Red Knots have likely been negatively affected by overabundant geese, although effects are not clearly known (Abraham and Jefferies 1997; Flemming et al. 2016, 2019a,b,c).

Red Knot from the northeastern South America wintering population (DU4) are subject to the same risks from harmful algal blooms as other rufa DUs while on migration in North America, as they pass through broadly the same areas. Risk on the wintering areas in northeastern Brazil would appear to be lower than that on wintering areas used by the other rufa DUs (USNOHAB 2020), although little information is available from that region.

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Medium-low threat impact.

Populations of southeastern USA / Gulf of Mexico / Caribbean (DU5) Red Knot are subject to the threats from falcons described for the Tierra del Fuego / Patagonia wintering population (DU3) on southbound migration through eastern North America, on northbound migration through central North America, and on wintering areas in the Gulf of Mexico and Caribbean (COSEWIC 2017c). Peregrine Falcons frequently occur along beaches in Texas where Red Knots forage along the narrow beachfront (Niles et al. 2009), and peregrine predation on Red Knots has been observed in Florida (A. Schwarzer in USFWS 2014a). Some migrating knots from this DU are affected by Peregrine Falcons known to hunt shorebirds at migration stopover sites in Virginia and Delaware Bay (Niles et al. 2008; Niles 2010).

Some breeding areas in the central Canadian Arctic, and migration areas in Hudson and James bays used by Red Knots from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) have likely been negatively affected by overabundant geese, although effects are not clearly known (Abraham and Jefferies 1997; Flemming et al. 2016, 2019a,b,c).

Harmful algal blooms are thought to affect birds from this DU, especially on wintering areas in Florida and the Gulf of Mexico coast (Woodward et al. 1977; Corcoran et al. 2013; USFWS 2014a). Harmful algal blooms can be caused by a variety of organisms, with red tides produced by the dinoflagellate K. brevis being particularly common in the Gulf of Mexico, including areas in Florida and Texas used by Red Knot (Niles et al. 2008; Corcoran et al. 2013; Florida Fish and Wildlife Conservation Commission 2020). The dinoflagellate produces highly potent neurotoxins (brevetoxins), which accumulate in benthic invertebrates including those consumed by knots (Bricelj et al. 2012) and can be highly toxic to birds and other organisms. There is some evidence of Red Knots being directly affected by red tides in Florida (USFWS 2014a).

9. Pollution

9.1 Domestic and urban waste water, 9.2 Industrial and military effluents, 9.3 Agricultural and forestry effluents, 9.4 Garbage and solid waste, 9.5 Air-borne pollutants, 9.6 Excess energy

Threats in sub-categories 9.4 and 9.6 were not considered to be measurable for any Red Knot DUs.

All Red Knot DUs are likely to be affected by pollution during their annual cycles. Untreated sewage in NW Mexico, Brazil, Argentina and other coastal migration stopover and wintering sites may have undetermined toxic effects on Red Knot. Risk of oil spills from shipping and petroleum exploration and extraction in coastal areas used by Red Knot on migration or in winter have potential for serious impacts on birds and their habitats. Human-related sources of such pollution include spills from shipping vessels; leaks or spills from offshore oil rigs or undersea pipelines; leaks, spills, or effluent from onshore facilities such as petroleum refineries and petrochemical plants; beach-stranded barrels and containers that fall from cargo ships or offshore rigs; discharges of ballast water from oil tankers; oil/water separators on production platforms; and terrestrial sources such as effluent from sewage treatment plants and runoff from roads and parking lots (Blackburn et al. 2014; USFWS 2014a). Several key Red Knot wintering or stopover areas contain large-scale operations for petroleum extraction, transportation, or both (USFWS 2014a). Red Knot and its prey may be exposed to toxic agricultural effluents in many parts of its range (Mateo-Sagasta et al. 2017; FAO 2018), including northwest Mexico, northern South America and other regions, on migration or in winter. Most Red Knot are likely exposed to airborne pollutants at some point in their life cycle, but it is unclear whether these may affect the species.

9.1 Domestic and urban waste water

DU1 - islandica subspecies. Unknown threat impact.

Proximity of some wintering sites to urban areas may expose birds to impacts of sewage and wastewater. In the Dutch Wadden Sea, eutrophication has resulted from elevated levels of phosphorus, nitrogen and phosphates entering from rivers (van Beusekom et al. 2017).

DU2 - roselaari subspecies. Unknown threat impact.

Proximity of some stopover and wintering sites to urban areas, such as Willapa Bay and Grays Harbor, Washington, and northwest Mexico, may expose knots to impacts of sewage and wastewater (Donaldson pers. comm. 2015). Contaminant issues at the Salton Sea spring stopover may affect roselaari Red Knots on northward migration (Buchanan pers. comm. 2020). Important wetlands in northwest Mexico are affected by eutrophication resulting from sewage and agrochemicals (WHSRN 2020).

DU3 - Tierra del Fuego / Patagonia wintering population. Unknown threat impact.

Red Knots from the Tierra del Fuego / Patagonia wintering population (DU3) may be affected by sewage discharges into coastal waters in eastern North America during migration. On wintering areas, untreated sewage was discharged in Red Knot habitat in Río Gallegos, Argentina, until 2012 (USFWS 2014a; WHSRN 2020), and the short- and long-term impacts of previously dumped sewage are unknown. Untreated sewage has also been discharged into coastal habitats at Rio Grande (Atkinson et al. 2005; WHSRN 2020), although a sewage treatment plant was scheduled to be constructed by 2019 (BNamericas 2017).

DU4 - northeastern South America wintering population. Unknown threat impact.

Red Knot from the northeastern South America wintering population (DU4) may be affected by sewage discharges into coastal waters in eastern North America during migration. Sewage discharge is likely to be relatively low in the more remote parts of the wintering areas in northeastern Brazil.

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Unknown threat impact.

Red Knot from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) may be affected by sewage discharges into coastal waters in eastern North America during migration, and in wintering areas in the southeastern United States and Gulf of Mexico regions.

9.2 Industrial and military effluents

DU1 - islandica subspecies. Low threat impact.

Risk of oil spills in coastal areas of NE Europe used by islandica Red Knot on migration or in winter have potential for periodic serious impacts on birds and their habitats, although the incidence of oil spills in the North Sea area has decreased over the past several decades (Schultz et al. 2017). A 1978 spill off the coast of France caused mass mortality of clams (Blackburn et al. 2014), and ingestion of contaminated prey may be a source of toxicity for shorebirds (Peterson et al. 2003).

DU2 - roselaari subspecies. Low threat impact.

Risk of oil spills in areas of the Pacific coast of the United States and Mexico used by roselaari Red Knot on migration or in winter have potential for periodic serious impacts on birds and their habitats. Threats from oil spills and toxic contaminants are present on the Copper River Delta, Alaska (WHSRN 2020). Knot are at risk from both catastrophic spills, such as the Exxon Valdez in Alaska in 1989, and chronic low levels of pollution (Peterson et al. 2003). Spills in Willapa Bay or Grays Harbor, Washington, or in Alaska, could have population-level impacts on Red Knot roselaari subspecies (DU2) during migration periods (Buchanan pers. comm. 2020).

DU3 - Tierra del Fuego / Patagonia wintering population. Low threat impact.

Shipping to re-supply communities during the ice-free season occurs along the coasts of James and Hudson bays (Andrews 2017) and throughout the Canadian Arctic, and activity is projected to grow as the northern ice-free period increases (Smith and Stephenson 2013; Pizzolato et al. 2014). Response times to major spills in these remote areas may be inadequate (DFO 2012). Important estuarine areas for Red Knot such as Delaware Bay, the coasts of James Bay, and the Gulf of St. Lawrence are at risk from effluents and shipping accidents. Both birds (e.g., Leighton 1991; Peterson et al. 2003; Henkel et al. 2012) and their marine invertebrate prey (Blackburn et al. 2014) could be exposed to petroleum in contaminated intertidal habitats. Foraging areas near the Mingan Islands, in the Gulf of St. Lawrence, are at risk of contaminant exposure from large ships carrying titanium and iron that transit the archipelago throughout the year (Aubry pers. comm. 2015). A ship-sourced oil spill in March 1999 resulted in oil reaching the shore in the Mingan area (Roberge and Chapdelaine 2000; Niles et al. 2008).

Oil and natural gas exploration have intensified along the northeastern and northern coasts of Brazil (Paschoa 2013) and is ongoing in Suriname and Guyana (Morrison et al. 2012). In northern and northeast Brazil, an enormous oil spill covering 4,000 km of coast came ashore in August 2019, including areas used extensively by shorebirds, including Red Knots (Handmaker 2019; Schulte and Stirling 2019; BirdLife International 2020). Extensive onshore and offshore oil developments near major wintering areas of the Tierra del Fuego / Patagonia population (DU3) in both Chilean and Argentinian sectors of Tierra del Fuego represent a considerable threat (WHSRN 2020; Morrison and Ross unpubl. data). Two oil spills from shipping have been recorded near the Strait of Magellan First Narrows (Niles et al. 2005), and small amounts of oil have been noted on Red Knot captured during banding operations in Bahía Lomas (Dey and Niles unpubl. data). Harrington and Morrison (1980) noted 15% of knots seen near Commodoro Rivadavia on the coast of Argentina in December 1979 were visibly oiled. The important migration stopover area at San Antonio Oeste, Argentina, also faces potential pollution by calcium chloride from a soda ash factory and from port activities (González pers. comm. 2019).

DU4 - northeastern South America wintering population. Low threat impact.

Red Knot from this DU face risks from oil spills very similar to those described for the Tierra del Fuego / Patagonia wintering population (DU3) in the Arctic, in James and Hudson bays, and in eastern North America on migration. Petroleum exploration and iron ore and gold mining can result in oil and mercury pollution and habitat loss. These activities are important threats on the northcentral coast of Brazil for Red Knots in the northeastern South America wintering population (Niles et al. 2005). An enormous oil spill covering 4,000 km of coast came ashore in northeastern Brazil in August 2019, affecting areas used extensively by the northeastern South America wintering population (DU4) of Red Knots (Handmaker 2019; Schulte and Stirling 2019; BirdLife International 2020).

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Low threat impact.

Red Knot from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) face risks from oil spills similar to those described for the Tierra del Fuego / Patagonia wintering population (DU3) in the Arctic, in James and Hudson Bays, and in eastern North America on migration, as well as on the southeast coast of the United States on the wintering grounds. Large amounts of oil have been released into the Gulf of Mexico from shipping and drilling operations, including the catastrophic Deepwater Horizon spill in 2010 (Blackburn et al. 2014; USFWS 2014a). While direct observations of oiled Red Knots were sparse, their habitats were compromised, and it is highly likely the birds themselves were negatively affected (USFWS 2014a).

9.3 Agricultural and forestry effluents

Red Knot and their prey may be exposed to toxic agricultural effluents in many parts of their range (Mateo-Sagasta et al. 2017; FAO 2018), including northwest Mexico, northern South America and other regions, on migration or in winter.

DU1 - islandica subspecies. Unknown threat impact.

Agricultural runoff likely contributes to eutrophication in the Dutch Wadden Sea, an important wintering area for islandica subspecies (DU1) Red Knot (van Beusekom et al. 2017), and herbicides have been reported to affect estuaries in western France (Niquil et al. 2006).

DU2 - roselaari subspecies. Unknown threat impact.

Red Knot roselaari subspecies (DU2) overwintering at the mouth of the Colorado River may be particularly negatively affected by agricultural effluent in the United States and Mexico (Donaldson pers. comm. 2015; WHSRN 2020). Farther south in Sonora Province, Mexico, agricultural runoff has led to large blooms of phytoplankton in coastal waters (Berman et al. 2005).

DU3 - Tierra del Fuego / Patagonia wintering population. Unknown threat impact.

In Canada, small numbers of the Tierra del Fuego / Patagonia wintering population (DU3) Red Knot may be exposed to herbicides and pesticides originating from farming activities upstream of the Bay of Fundy (WHSRN 2020). Red Knot and their prey may be exposed to toxic agricultural effluent associated with the management of rice fields in Trinidad, Uruguay, Argentina, and French Guiana (Blanco et al. 2006; Niles 2012; USFWS 2014a). Although few Red Knot were recorded in rice field surveys in Brazil, Uruguay and Argentina, larger numbers (e.g., 1,700 birds) have been observed in rice fields in French Guiana (Niles 2012b), and Red Knots have been reported from rice fields in Trinidad (eBird 2019).

DU4 - northeastern South America wintering population. Unknown threat impact.

In Canada, small numbers of the northeastern South America wintering population (DU4) Red Knot may be exposed to herbicides and pesticides in the Bay of Fundy (WHSRN 2020). Red Knot and their prey may be exposed to toxic agricultural effluent associated with the management of rice fields in Trinidad, Uruguay, Argentina, and French Guiana (Blanco et al. 2006; Niles 2012; USFWS 2014a). In Suriname, shorebirds are known to use rice fields, which are regularly sprayed with pesticides, adjacent to coastal areas, although knots were not amongst the species recorded (Vermeer et al. 1974; Hicklin and Spaans 1993). While the chemicals previously used were toxic to wildlife, most currently used are not harmful to birds (WHSRN 2020). There have been unverified concerns, however, of disposal of residual chemicals on the mudflats, which would degrade the quality of the mudflats as foraging habitat (WHSRN 2020).

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Unknown threat impact.

In Canada, small numbers of the southeastern USA / Gulf of Mexico / Caribbean wintering population of Red Knot (DU5) may be exposed to herbicides and pesticides in the Bay of Fundy (WHSRN 2020), and to agricultural effluents during northbound migration in midcontinent agricultural fields (McKellar pers comm. 2020). Red Knot, and their prey, may be exposed to toxic agricultural effluent associated with the management of rice fields in Trinidad (Blanco et al. 2006; Niles 2012; USFWS 2014a). Agricultural effluents are not listed as a threat for WHSRN sites bordering the Gulf of Mexico (WHSRN 2020).

9.5 Air-borne pollutants

All DUs

Unknown threat impact.

Most Red Knot are likely exposed to air-borne pollutants at some point in their life cycle, but there is no information as to whether these pollutants may affect the species, or how such effects might differ among the five Red Knot DUs.

10. Geological events

10.1 Volcanoes, 10.2 Earthquakes/tsunamis, 10.3 Avalanches/landslides

Threats in sub-categories 10.1, 10.2, and 10.3 were not considered to be measureable for any of the five Red Knot DUs.

11. Climate change and severe weather

11.1 Habitat shifting and alteration, 11.2 Droughts, 11.3 Temperature extremes, 11.4 Storms and flooding, 11.5 Other impacts

Threats in sub-category 11.3 and 11.5 were not considered to be measureable for any Red Knot DUs. Ecosystem-level changes related to rising temperatures are considered in sub-category 11.1 Habitat Shifting and Alteration.

Climate change and severe weather are anticipated to affect many aspects of the Red Knot life cycle. Climatic changes in Arctic breeding areas present cumulative risks to Red Knot through reductions in breeding habitat quality (Meltofte et al. 2007), such as the invasion of shrubby vegetation into tundra habitat (Myers-Smith et al. 2011), and increased predation due to disruption of predator-rodent cycles. Drying of habitats and uncoupling of food availability from breeding requirements may be regionally important (Kwon et al. 2020). Rising sea levels will reduce coastal habitat availability in areas used in migration and winter, and ocean acidification may reduce availability of bivalve prey. More frequent severe weather, such as storms and hurricanes, may affect migration performance or survival. Many climate-related effects may primarily occur beyond the 3-generation time period, and some may be positive. Rapid irreversible ecosystem change may occur if climatic changes exceed a threshold, with negative effects in many regions (USCCSP 2009a,b; USFWS 2014a).

11.1 Habitat shifting and alteration

Responses of Red Knot and their prey to climate change are difficult to predict, as changes may have positive, neutral, or negative effects which may change over time or with the degree of environmental change. Galbraith et al. (2014) indicated that climate change increased risk and vulnerability scores for most shorebird species, including Red Knot. The Arctic has warmed more than any other region over the past 30 years (NSID 2015) and is most likely to be affected by climate change (ACIA 2004). Lathrop et al. (2016) and Wauchope et al. (2016) indicated negative effects from habitat shifts resulting from climate change. Meltofte et al. (2007) reviewed potential effects of climate change in the Arctic on shorebirds, among which long-term reductions in High Arctic habitat quality and uncoupling of phenology of food resources and breeding events (e.g., chicks no longer hatching during period of peak food availability) were potentially important. Such effects have already been noted for Red Knot breeding in the Russian Arctic, where reduced chick growth rates led to increased mortality on wintering grounds (van Gils et al. 2016), and for Hudsonian Godwit (Limosa haemastica) breeding in the North American Arctic (Senner 2012). Effects may differ across the Arctic (Kwon et al. 2020) and may affect different populations to varying extents (Senner et al. 2017; Smith et al. 2020). Disruption of predator-rodent cycles linked to climate change is already occurring, and may lead to increased predation of breeding adult Red Knots, their eggs and chicks (Meltofte et al. 2007; Kausrud et al. 2008; Niles et al. 2008; Fraser et al. 2013; Bulla et al. 2019, Kubelka et al. 2018, 2019).

On migration and wintering areas, ocean acidification may lead to a decline in calcium-dependent prey such as bivalves (Byrne and Przeslawski 2013; Parker et al. 2013), and may also result in increased disease in the marine environment, with negative impacts on Red Knot and its prey (Burge et al. 2014). Potential loss of intertidal habitats owing to sea level rise were projected to range between 20 and 70% during the next century, at five major stopover sites in the United States, including Delaware Bay (60% loss of habitat; Galbraith et al. 2002). Habitat loss due to sea level rise is projected in Tierra del Fuego (USFWS 2014a) and at other key sites. While detailed effects are difficult to predict (IPCC 2001; CCSP 2009; USFWS 2014a), substantial changes to shorelines are expected over the next 100 years, which may reduce the capacity of sites to support shorebirds, with increased future stress on Red Knot populations (Iwamura et al. 2013). Iwamura et al. (2013) found that predicted reductions in population in migratory networks far exceeded the proportion of habitat lost from sea level rise.

Red Knot in the three rufa DUs may benefit from projected short-term warmer temperatures, if climate warming results in fewer cold-induced spawning delays of Horseshoe Crabs in Delaware Bay (Smith and Michels 2006), although warmer waters may lead to earlier crab spawning and possible mismatch of timing with Red Knot migration. On the Arctic breeding grounds, climate change may result in earlier snowmelt but also heavier snow cover (Meltofte et al. 2007). Rakhimberdiev et al. (2015) found that Bar-tailed Godwit (Limosa lapponica taymyrensis) could partly compensate for changing insect phenology in the Arctic by decreasing refuelling times at the last northward stopover. This enabled birds to reach the breeding grounds earlier, but at a cost of decreased survival.

DU1- islandica subspecies. Medium-low threat impact.

Anticipated impacts on the Arctic breeding grounds of islandica subspecies (DU1) Red Knot are similar to those described above. Climate change induced sea-level rises are expected to affect wintering habitats in the Dutch Wadden Sea, although with uncertain results (Oost et al. 2017), and most will likely take effect in the future beyond the 10 year or 3-generation (21 years) time frame.

DU2 - roselaari subspecies. Medium-low threat impact.

Impacts on the Arctic breeding grounds of Red Knot roselaari subspecies (DU2) in Alaska and Russia are likely similar to those described above. Galbraith et al. (2005) found that predicted sea level rise would have a major effect on estuaries on the Pacific coast of North America, including Willapa Bay and San Francisco Bay, reducing the size and carrying capacity of these key shorebird stopover sites to only fractions of their current importance. The need to seek alternate food resources could reduce fitness of Red Knots (Buchanan pers. comm. 2020).

DU3 - Tierra del Fuego / Patagonia wintering population. Medium-low threat impact.

Anticipated impacts on the Arctic breeding grounds of the Tierra del Fuego / Patagonia wintering population (DU3) rufa Red Knot are as described above. Sea-level rise is expected to have a negative impact on quality and extent of migration habitats on the east coast of North America, including the critically important spring migration stopover in Delaware Bay (Galbraith et al. 2005), as well as important migration and wintering areas in South America (USFWS 2014a).

DU4 - northeastern South America wintering population. Medium-low threat impact.

Anticipated impacts on the Arctic breeding grounds of the northeastern South America wintering population (DU4) Red Knot are as described above. Sea-level rise is expected to have a negative impact on quality and extent of migration habitats on the east coast of North America, including the critically important spring migration stopover in Delaware Bay (Galbraith et al. 2005).

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Medium-low threat impact.

Anticipated impacts on the Arctic breeding grounds of the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) Red Knot are as described above. Sea-level rise is expected to have a negative impact on quality and extent of migration habitats on the east coast of North America, including the critically important spring migration stopover in Delaware Bay (Galbraith et al. 2005), used by about 50% of the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) population (Burger et al. 2020).

11.2 Droughts

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Unknown threat impact.

Few direct threats are anticipated from droughts, except in the Prairie provinces and states, where drying out of potholes and seasonal sloughs may affect habitat and food availability for the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) of Red Knot at spring migration stopover sites in interior North America. Ecosystem-level changes related to drying conditions are considered in sub-category 11.1 Habitat Shifting and Alteration.

11.4 Storms and flooding

There has been a significant increase in the number and strength of hurricanes globally (1970-2004), including those in areas of the North Atlantic used by Red Knot (Webster et al. 2005; Bender et al. 2010; R.I.G. Morrison unpubl. results). Geolocator tracking data have shown that Red Knot can modify its flight patterns to avoid weather systems, which increases energy expenditure and may influence survivorship (Niles et al. 2010b). Hurricanes may also destroy or disrupt habitats used by Red Knots (Niles et al. 2012b). The extent to which Red Knot is actually affected, either directly through increased mortality or indirectly through effects of storms reducing prey at foraging sites, is unknown. However, the increasing severity of weather events, including precipitation events (Fischer and Knutti 2015), represents a risk which is likely to increase with changing climates and rising ocean temperatures.

DU1 - islandica subspecies. Unknown threat impact.

Increased frequency and intensity of storms may periodically cause significant mortality of islandica subspecies (DU1) Red Knot on migration and wintering areas, and in the Arctic could result in loss of nests and chicks (Meltofte et al. 2007).

DU2 - roselaari subspecies. Unknown threat impact.

Hurricanes rarely strike the Pacific coast of the Americas (Thompson 2009) and are thus less likely to affect Red Knot roselaari subspecies (DU2) than birds of other DUs, although increased frequency and intensity of storms in the Arctic could result in loss of nests and chicks (Meltofte et al. 2007).

DU3 - Tierra del Fuego / Patagonia wintering population. Medium-low threat impact.

Red Knots from the Tierra del Fuego / Patagonia wintering population (DU3) will likely be impacted by changing weather and storms on the Arctic breeding grounds, as well as increasing hurricanes and severe weather on migration and in wintering areas, particularly early fall hurricanes that may strike southeastern North America during their trans-oceanic migration (Webster et al. 2005; Meltofte et al. 2007; Bender et al. 2010). An extremely rare hurricane in the South Atlantic Ocean came ashore in southern Brazil, impacting areas used by Red Knot north of Lagoa do Peixe (NASA Earth Observatory 2004).

DU4 - northeastern South America wintering population. Medium-low threat impact.

Red Knots in the northeastern South America wintering population (DU4) will likely be impacted by changing weather and storms on the Arctic breeding grounds, and increasing hurricanes and severe weather on migration and wintering areas, particularly early fall hurricanes that may strike southeastern North America during their trans-oceanic migration (Webster et al. 2005; Meltofte et al. 2007).

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population. Medium-low threat impact.

Red Knots from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) will likely be impacted by changing weather and storms on the Arctic breeding grounds, and the increasing incidence of severe hurricanes that may strike the southeastern United States, Gulf of Mexico, and Caribbean Sea during fall migration or early winter (Webster et al. 2005; Meltofte et al. 2007).

Limiting factors

Factors limiting the productivity and survival of Red Knot are the same for all five DUs, and most are related to its long-distance migration strategy, and the associated physiological changes it undergoes to maximize its flying efficiency during migration (Morrison et al. 2007). This relatively inflexible adaptation to long distance migration makes Red Knot particularly sensitive to the effects of human interventions and changing climates and habitat conditions. For instance, reduction of food resources at key migration or wintering areas may prevent knots from attaining or maintaining optimal condition, with a consequent lowering of annual survival (Baker et al. 2004). The short season available for nesting and raising young on Arctic breeding grounds, together with a maximum clutch size of four eggs, limits potential reproductive output and restricts the knots’ ability to respond to adverse weather and changing climate (Meltofte et al. 2007). Many of the above threats may negatively affect the knots’ ability to undertake long-distance migratory flights between widely separated stopover sites, and subsequently breed successfully. Adult annual survival is generally high (Mendez et al. 2018), so factors that affect survival, such as reduced foraging effectiveness on migration, or disturbance at roosting and foraging sites, may contribute to population declines or prevent population recovery.

Number of locations

For all DUs that nest at many widely dispersed sites across the Arctic in Canada (islandica subspecies - DU1, Tierra del Fuego / Patagonia wintering population - DU3, northeastern South America wintering population - DU4, southeastern USA / Gulf of Mexico / Caribbean wintering population - DU5) or in Alaska and Russia (roselaari subspecies - DU2), the number of locations calculated during the breeding season is likely much greater than 10, as these geographically distinct nesting areas are likely exposed to differing risks from key threats, such as ecosystem modifications and climate change-related habitat shifting and alteration. However, for most DUs, fewer locations are used during migration or when overwintering, as described below.

DU1 - islandica subspecies

Threats with the highest impact for this DU likely occur on the wintering grounds. Red Knot from the islandica subspecies (DU1) concentrate in coastal areas on the wintering grounds in Europe, occurring there at more than 10 discrete locations, as wintering areas across many European coastal states are exposed to differing risks from key threats such as human disturbance, coastal habitat modification and coastline stabilization, industrial development, and industrial effluents. The number of locations used on migration is difficult to determine, but likely well exceeds 10.

DU2 - roselaari subspecies

The number of breeding locations in Canada is not applicable for roselaari subspecies (DU2), as the numbers recorded in Canada are very small and variable (likely <1% of the estimated global population of roselaari) on spring migration and occasionally in winter on the Pacific coast of British Columbia (Campbell et al. 1998; eBird 2019; Johnson pers. comm. 2020), although most birds in this DU likely travel through Canadian airpace on migration without landing in Canada. Widely scattered records of small numbers of Red Knots have been recorded along the central and northern coasts of British Columbia during northward migration (Buchanan pers. comm. 2020; Johnson pers. comm. 2020). C. c. roselaari is thought to concentrate at a relatively small number of key sites on migration between the wintering areas and breeding grounds (Carmona et al. 2013; USFWS 2014a). For instance, a substantial proportion of the C. c. roselaari population stops at Grays Harbor and adjacent Willapa Bay, Washington each spring (Buchanan et al. 2012; Lyons et al. 2016), and telemetry studies by Bishop et al. (2016) confirm that sizable numbers using those sites also stop at both the Copper River and Yukon-Kuskokwim River Deltas in Alaska. However, telemetry studies also show that many other sites in the coastal United States are also used by smaller numbers of birds on migration (Buchanan pers. comm. 2020; Johnson pers. comm. 2020). The relevant threats to birds of the roselaari subspecies (DU2) that could rapidly impact portions of the population on migration include coastal development, aquaculture, shoreline stabilization, and over-fishing of Grunion in north-coastal Mexico. As these likely occur with different impacts and intensities at the many coastal sites used by Red Knot on migration, the number of locations used is likely well above 10.

DU3 - Tierra del Fuego / Patagonia wintering population.

The number of occurrences for the southern rufa Tierra del Fuego / Patagonia wintering population of Red Knot (DU3) is given by NatureServe (2017) as 1-5 on the basis of the number of sites used on migration, as most of the population migrates through Delaware Bay (Niles et al. 2007). Over 90% of birds from this DU are thought to stop on the coast of Hudson Bay near the mouth of the Nelson River during northward migration (Burger et al. 2020). The key threats in Delaware Bay are impacts of the Horseshoe Crab fishery on food for migrating knots. Over 95% of the Tierra del Fuego / Patagonia wintering population (DU3) spends the boreal winter at a single site, Bahia Lomas in Tierra del Fuego (Morrison et al. 2004, 2020a,b), with smaller numbers at a small number of nearby sites and in southern Patagonia (Figure 7) where the main threats likely relate to severe weather conditions and oil developments and spills. These threats are likely to affect most birds of the population at once. The total number of locations for the Tierra del Fuego / Patagonia wintering population (DU3) in winter is therefore likely to be between 5 and 10.

DU4 - northeastern South America wintering population

Most of the northeastern South America wintering population of Red Knot (DU4) over-winter in the northeastern Brazilian state of Maranhão, with fewer birds in the state of Ceara, and a few birds in nearby French Guiana and Suriname. They are distributed at many sites along the coast, each with different degrees of risk from human disturbance, effluents, etc., which suggests that the number of wintering locations is likely greater than 10. Some 90% of northbound migrants are thought to stop over in the Nelson River area of the coast of Hudson Bay (Burger et al. 2020). However, in the absence of a plausible threat that could rapidly affect all individuals present there, the concept of locations likely does not apply in Hudson Bay. Many knots from this DU (recently estimated as 90%; Burger et al. 2020) pass through Delaware Bay on northward migration, although they also use many other Atlantic coast sites, which are exposed to different combinations of threats, including effects of Horseshoe Crab harvesting. About 21% of birds from the northeastern South America wintering population (DU4) used stopovers in Georgia, North Carolina and South Carolina (Burger et al. 2020), and it is likely that the number of locations used during spring migration well exceeds 10.

DU5 - southeastern USA / Gulf of Mexico / Caribbean wintering population

Red Knot from the southeastern USA / Gulf of Mexico / Caribbean wintering population (DU5) over-winter at various locations on both coasts of Florida, in Louisiana and Texas, and on islands in the Caribbean, and as these areas are subject to different risks from threatening events, such as human intrusion and disturbance, recreation and ecological modification, the number of locations in winter is likely appreciably greater than 10. Populations from west Florida, the Gulf coasts and Caribbean likely migrate northwards through the interior of the United States and Canada and are found at a relatively small number of locations in Saskatchewan and northern US interior states, as well as on the Hudson Bay coast near the Nelson River, where an estimated 100% of geolocator-marked birds from this DU occurred (Burger et al. 2020). The apparent high dependence on the Hudson Bay stopover identified by McKellar et al. (2015) suggests the number of sites used there may be <10. However, in the absence of a plausible threat that could rapidly affect all individuals present there, the concept of locations likely does not apply in Hudson Bay. Populations from the southeastern United States likely pass northwards through Delaware Bay (about 50%; Burger et al. 2020) and other Atlantic coast sites which are exposed to different combinations of threats, including effects of Horseshoe Crab harvesting, so in total, it is likely that the number of locations on migration likely well exceeds10.

Protection, status and ranks

Legal protection and status

In Canada, Red Knot is protected under the Migratory Birds Convention Act 1994 (Government of Canada 2017). C. c. rufa is listed as Endangered, C. c. roselaari as Threatened, and C. c. islandica as a species of Special Concern on Schedule 1 of the federal Species at Risk Act (Government of Canada 2019), following assessment by COSEWIC in 2007 (ECCC 2017). Ontario, New Brunswick, Nova Scotia, and Newfoundland and Labrador have listed C. c. rufa under their endangered species acts (ECCC 2017). In Quebec, C. c. rufa is listed on the Liste des espèces susceptibles d’être désignées menacées ou vulnérables (list of wildlife species likely to be designated threatened or vulnerable). This list is produced according to the Loi sur les espèces menacées ou vulnérables (RLRQ, c E-12.01), (Act respecting threatened or vulnerable species) (CQLR, c E-12.01). C. c. islandica and C. c. roselaari are not listed under provincial or territorial endangered species legislation.

In the United States (Table 4), Red Knot is protected under the Migratory Bird Treaty Act (USFWS 2017), and C. c. rufa was listed as Threatened under the U.S. Endangered Species Act in 2014 (USFWS 2014b). At the state level, C. c. rufa is listed as Threatened in New Jersey and as a species of Special Concern in Georgia (Niles et al. 2005); other state ranks are shown in Table 4.

Internationally, C. c. rufa was added to Appendix 1 of the Convention on Migratory Species in 2005 (Leyrer et al. 2014) concerning migratory species threatened with extinction. Red Knot was listed as Critically Endangered on the Brazilian Ministry of the Environment Red List in 2014 (Portaria Ministerio do Meio Ambiente (MMA) no. 444 on 17 Dec 2014). It was categorized as Endangered in Argentina (López-Lanús et al. 2008, Resolución 348 / 2010 Secretaría de Ambiente y Desarrollo Sustentable) and in Chile by the Ministerio de la Secretaría General de la Presidencia de Chile in 2008. In Uruguay, Red Knot is also categorized as Endangered (Azpiroz et al. 2012) and as a priority species for conservation by the Dirección Nacional de Medio Ambiente (Aldabe et al. 2015). France declared the species to be protected in French Guiana in 2014 (Journal Officiel n. 0235, p 16464, Arrete 1 Oct 2014), and other French territories including Guadeloupe and Martinique (30 juin 2012. Interdiction de la chasse au Bécasseau maubèche. Arrêté n°2012-746 PREF/DEAL-RN relatif à la saison de chasse dans le département de la Guadeloupe; 31 juillet 2013. Arrêté NOR : DEVL1312811A relatif à la protection du bécasseau maubèche dans le département de la Guadeloupe et de la Martinique. Ministère de l’écologie, du développement durable et de l’énergie).

C. c. roselaari has been designated as Endangered in Mexico (Diario Oficial de la Federacion 2010). In addition to being listed as Threatened in Canada, C. c. roselaari is considered a species of management concern in the United States (Alaska Department of Fish and Game 2015), and continentally as a Species of Greatest Concern (Shorebird Conservation Plan Partnership 2017; WDFW 2015).

Non-legal status and ranks

Table 5 provides conservation status ranks for Red Knot in Canada, as designated by NatureServe (2017) and CESCC (2016). The global status of C. c. rufa is listed as G4T2, or imperilled at the subspecies level, and nationally as N1B, indicating the breeding population is critically imperilled. C. c. roselaari (G4TNR) is unranked, and C. c. islandica is now considered G4T4 or apparently secure. Red Knot conservation status ranks for the United States are shown in Table 4.

The International Union for the Conservation of Nature (IUCN) up-listed Red Knot globally from Least Concern in 2012 to Near Threatened in 2015 (BirdLife International 2017).

The Canadian Shorebird Conservation Plan (Donaldson et al. 2000) lists Red Knot as a Species of High Concern, and the US Shorebird Conservation Plan (Brown et al. 2001) lists C. c. rufa as a (sub-)Species of High Concern, and C. c. islandica and C. c. roselaari as (sub-)Species of Moderate Concern. In 2004, C. c. rufa was listed as Highly Imperilled in an update to the list of shorebirds considered of High Priority in the U.S. Shorebird Conservation Plan (US Shorebird Conservation Plan 2004; US Shorebird Conservation Plan Partnership 2017). Red Knot is categorized as Highly Imperilled in Canada by Hope et al. (2020).

In Alaska, the Alaska Center for Conservation Science (2019) ranked the Red Knot (C. c. roselaari) in its highest category (Red) of conservation concern and in Alaska and Washington it is a Species of Greatest Conservation Need (Alaska Department of Fish and Game 2015; Alaska Shorebird Group 2019; WDFW 2020).

In Canada, a Species at Risk Act recovery strategy and management plan for Red Knot has been published by Environment and Climate Change Canada (ECCC 2017). The Western Hemisphere Shorebird Reserve Network has published a Red Knot Conservation Plan for the Western Hemisphere (Niles et al. 2010a), and Red Knot was included in a proposal for concerted action by CMS (Convention on Migratory Species) in 2014 (Leyrer et al. 2014).

Habitat protection and ownership

Most of the important Red Knot habitats used on migration and in winter have been recognized by various conservation and habitat protection programs and initiatives, providing a variable degree of formal and informal protection. The Western Hemisphere Shorebird Reserve Network (WHSRN) is a non-government organization that identifies and seeks protection for important shorebird sites. The WHSRN system currently covers 107 sites in 17 countries, from Alaska to Tierra del Fuego (WHSRN 2020). Although designation as a WHSRN site itself carries no formal legal protection, it increases the conservation status of the site significantly. The Ramsar Convention is a worldwide intergovernmental treaty that provides the framework for national action and international cooperation for the conservation and wise use of wetlands identified under the Convention. Several shorebird areas of importance to Red Knot are designated as both Ramsar and WHSRN sites (e.g., Quill Lakes, Saskatchewan). The Important Bird Areas (IBA) program of BirdLife International identifies and promotes conservation of important areas for birds. Nearly all sites designated by WHSRN are also identified as IBAs for shorebirds.

Protection for shorebird sites is also provided by various other designations, often at a national, state, or regional level, such as Wildlife Management Areas, Wildlife Refuges, Provincial Parks, and National Parks (e.g., Table 6). These initiatives raise the profile of important areas and may provide some level of legal protection for key habitats. Critical habitats for Red Knots in Canada (ECCC 2017) are listed in Table 6 (and see McKellar et al. 2020 for the most recent listing of potential WHSRN sites in Canada), and key international sites are listed in Table 7.

Acknowledgements and authorities contacted

Funding for the preparation of this status report was provided by Environment and Climate Change Canada (ECCC).

A special thanks goes to the following for supplying unpublished information, reports, or data on Red Knot: Jennie Rausch (ECCC-CWS, Northern Region), Scott Wilson (ECCC, Wildlife and Landscape Science Directorate), Yves Aubry (ECCC-CWS, Quebec Region), Amie MacDonald (Trent University, Peterborough), Christian Friis (ECCC-CWS, Ontario Region), Ron Porter (Delaware Bay Project), Julie McKnight (ECCC-CWS, Atlantic Region), David Newstead (Coastal Bend Bays and Estuaries Program, Texas), Mary Anne Bishop (Prince William Sound Science Center, Alaska), Jim Johnson (US Fish and Wildlife Service, Alaska), Joe Buchanan (Department of Fish and Wildlife, Washington), Jason Mobley (Aquasis, Brazil), Oliver Haddrath and Erica Sendra (Royal Ontario Museum, Toronto), Jim Wilson (International Wader Study Group, Norway), Theunis Piersma (NIOZ, University of Groningen, Netherlands), Yvonne Verkuil (University of Groningen, Netherlands). Thanks to Peter Taylor, Rudolph Koes, and Cal Cuthbert for information on knots in Manitoba. Major thanks to Andrea Clouston, Neil Jones, and Sonia Schnobb of the COSEWIC Secretariat for their assistance. A special thanks to Rosie Nobre Soares and Sydney Allen at the COSEWIC Secretariat for assistance with mapping. Very special thanks to Richard Elliot, Co-Chair of the COSEWIC Birds Specialist Subcommittee (SSC), for extensive help in completion of this report and the Red Knot Designatable Unit report. Thanks also to Paul A. Smith, member of the Birds SSC, for his considerable contributions of unpublished information and data analysis, and for reviewing earlier drafts of this report, along with Louise Blight, Marcel Gahbauer, and Elsie Krebs. Special thanks to Larry J. Niles, who reviewed an early draft of this report, and has provided a wealth of information on the status of Red Knot, and their breeding, migration and wintering ecology in many conversations over the years. Thanks also to the writers of the 2007 COSEWIC status report on Red Knot: R.I. Guy Morrison, Allan J. Baker, Larry J. Niles, Patricia M. González, and R. Ken Ross.

Authorities contacted

Artuso, Christian. Former Manitoba Program Manager, Bird Studies Canada, Winnipeg, Manitoba.

Aubry, Yves. Biologist-Migratory Birds, Canadian Wildlife Service Quebec Region, Environment and Climate Change Canada, Quebec, Quebec.

Basterfield, Mark. Director of Wildlife Management, Nunavik Marine Region Wildlife Board, Inukjuak, Quebec.

Bennet, Bruce. Coordinator, Yukon Conservation Data Centre, Whitehorse, Yukon Territory.

Bennett, Ron. Manager, Conservation Planning and Stewardship, Canadian Wildlife Service Prairie Region, Environment and Climate Change Canada, Edmonton, Alberta.

Benville, Andrea. Data Manager, Saskatchewan Conservation Data Centre, Regina, Saskatchewan.

Bijleveld, Allert. Coastal Systems Scientist, NIOZ (Royal Netherlands Insttitute for Sea Research), 't Horntje, Texel, The Netherlands.

Blaney, Sean. Executive Director/Senior Scientist, Atlantic Canada Conservation Data Centre, Sackville, New Brunswick.

Boyne, Andrew. Head, Conservation Planning, Canadian Wildlife Service Atlantic Region. Environment and Climate Change Canada. Dartmouth, Nova Scotia.

Brunelle, Josée. Analyst, Hunting, Fishing and Trapping Coordinating Committee, James Bay and Northern Quebec Agreement and the Northeastern Quebec Agreement, Montréal, Quebec.

Buchanan, Joe. Wildlife Biologist/Natural Resource Scientist, Wildlife Diversity Division, Washington Department of Fish and Wildlife, Olympia, Washington.

Cannings, Syd. Species at Risk Biologist, Canadian Wildlife Service Northern Region, Environment and Climate Change Canada, Whitehorse, Yukon.

Carmona, Roberto. Biologist, Bird Laboratory, Academic Department of Marine and Coastal Sciences, Universidad Autónoma de Baja California Sur, La Paz, Baja California Sur, Mexico.

Carriere, Suzanne. Biologist, Wildlife Division, Department of Environment and Natural Resources, Government of the Northwest Territories, Yellowknife, Northwest Territories.

Conklin, Jesse. Researcher, Royal Netherlands Institute for Sea Research (NIOZ), Den Burg, Texel, Netherlands.

De Smet, Ken. Species at Risk Specialist, Manitoba Department of Conservation and Water Stewardship, Winnipeg, Manitoba.

Dey, Amanda. Principal Zoologist, Endangered and Nongame Species Program, Division of Fish and Wildlife, New Jersey Department of Environmental Protection, Millville, New Jersey.

Drever, Mark. Research Biologist, Canadian Wildlife Service Pacific Region, Environment and Climate Change Canada, Delta, British Columbia.

Durocher, Adam. Data Manager, Atlantic Canada Conservation Data Centre, Newfoundland and Labrador Wildlife Division, Endangered Species and Biodiversity Section, Corner Brook, Newfoundland and Labrador.

Friesen, Chris. Coordinator, Manitoba Conservation Data Centre, Winnipeg, Manitoba.

Friis, Christian. Wildlife Biologist, Canadian Wildlife Service Ontario Region, Environment and Climate Change Canada, Toronto, Ontario.

Gauthier, Isabelle. Biologiste, Coordonnatrice provinciale des espèces fauniques menacées ou vulnerables, Direction générale de la gestion de la faune et des hábitats, Ministère des Forêts, de la Faune et des Parcs, Québec, Québec.

Gill, R.E. Research Wildlife Biologist (Emeritus), United States Geological Survey, Alaska Science Center, Anchorage, Alaska.

González, Patricia M. Researcher, Fundación Inalafquen, San Antonio Oeste, Rio Negro Province, Argentina.

Harrington, Brian A. Independent Shorebird Researcher, Plymouth, Massachusetts.

Humber, Jessica. Ecosystem Management Ecologist, Endangered Species and Biodiversity Section, Department of Environment and Conservation, Government of Newfoundland and Labrador, Corner Brook, Newfoundland and Labrador.

Jean-Gagnon, Frankie. Wildlife Biologist, Nunavik Marine Region Wildlife Board, Inukjuak, Quebec.

Johnson, Jim. Shorebird Biologist, US Fish and Wildlife Service, Anchorage, Alaska.

Johnston, Vicky. Manager, Northern Region, Canadian Wildlife Service Northern Region, Environment and Climate Change Canada, Yellowknife, Northwest Territories.

Jung, Thomas. Senior Wildlife Biologist, Fish and Wildlife Branch, Environment Yukon, Government of Yukon, Whitehorse, Yukon.

Klymko, John. Zoologist, Atlantic Canada Conservation Data Centre, Sackville, New Brunswick.

MacDonald, Amie. Ph.D. student, Department of Biology, Trent University, Peterborough, Ontario.

McDonald, Rachel. Senior Environmental Advisor, National Defence (ADM(IE)/ DGESM/ DESM), Ottawa, Ontario.

McKellar, Ann. Wildlife Biologist, Canadian Wildlife Service Prairie Region, Environment and Climate Change Canada, Saskatoon, Saskatchewan.

McKnight. Julie. Conservation Biologist, Canadian Wildlife Service Atlantic Region. Environment and Climate Change Canada, Dartmouth, Nova Scotia.

Meijer, Marge. Staff, Alberta Conservation Information Management System, Parks Division, Environment and Parks, Edmonton, Alberta.

Milliken, Rhonda. Manager, Canadian Wildlife Service Pacific Region, Environment and Climate Change Canada, Delta, British Columbia.

Niles, Larry. Independent Shorebird Researcher, Wildlife Restoration Partnerships, Greenwich, New Jersey.

Paquet, Julie. Shorebird Biologist. Canadian Wildlife Service Atlantic Region. Environment and Climate Change Canada, Sackville, New Brunswick.

Picard, Karine. Chief Conservation Planning, Canadian Wildlife Service Quebec Region, Environment and Climate Change Canada, Quebec, Quebec.

Porter, Ron. Independent Researcher, Ambler, Pennsylvania, United States.

Powell, Todd. Manager, Biodiversity Programs, Fish and Wildlife Branch, Environment Yukon, Whitehorse, Yukon.

Rausch, Jennie. Shorebird Biologist, Canadian Wildlife Service Northern Region, Environment and Climate Change Canada, Yellowknife, Northwest Territories.

Ritchie, Kyle. Wildlife Management Biologist, Habitat and Species at Risk, Nunavut Wildlife Management Board, Iqaluit, Nunavut.

Robertson, Myra. Head, Wildlife and Habitat Assessment, Canadian Wildlife Service Northern Region, Environment and Climate Change Canada, Yellowknife, Northwest Territories.

Sabine, Mary. Biologist, Species at Risk Program, Department of Natural Resources, Hugh John Flemming Forestry Centre, Fredericton, New Brunswick.

Shepherd, Pippa. Ecosystem Scientist, Parks Canada, Vancouver, British Columbia.

Sinclair, Pam. Bird Conservation Biologist, Canadian Wildlife Service - Northern Region, Environment and Climate Change Canada, Whitehorse, Yukon.

Smith, Paul. Research Scientist, National Wildlife Research Centre, Environment and Climate Change Canada, Ottawa, Ontario.

Song, Samantha. Manager, Canadian Wildlife Service - Prairie Region, Environment and Climate Change Canada, Edmonton, Alberta.

Stipec, Katrina. B.C. Staff, Conservation Data Centre, Ecosystems Branch, British Columbia Ministry of Environment, Victoria, British Columbia.

Sutherland, Donald A. Zoologist, Ontario Ministry of Natural Resources and Forestry, Peterborough, Ontario.

van Roomen, Marc. Senior Project Manager-Monitoring, Sovon (Dutch Centre for Field Ornithology), Nijmegen, The Netherlands.

Verkuil, Yvonne. Researcher, NIOZ (Royal Netherlands Institute for Sea Research), Den Burg, Texel, Netherlands.

Walsh, Wendy. Senior Fish and Wildlife Biologist, New Jersey Field Office, United States Fish and Wildlife Service, Galloway, New Jersey.

Watkins, William. Zoologist, Water Stewardship and Biodiversity Division, Wildlife and Fisheries Branch, Manitoba Department of Conservation, Winnipeg, Manitoba.

Wilson, Greg. A/Head, Conservation Planning Unit, Canadian Wildlife Service Prairie Region, Environment and Climate Change Canada, Edmonton, Alberta.

Wilson, Scott. Research Scientist, National Wildlife Research Centre, Environment and Climate Change Canada, Ottawa, Ontario.

Zakharov, Yuri. Ecologist Team Leader, Parks Canada, Ucluelet, British Columbia.

Information sources

Abraham, K.F., and R.L. Jefferies. 1997. High goose populations: causes, impacts and implications. Pp. 7-72 In Batt, B.D. [ed.] Arctic Ecosystems in Peril: Report of the Arctic Goose Habitat Working Group. Arctic Goose Joint Venture Special Publication. U.S. Fish and Wildlife Service, Washington, D.C. and Canadian Wildlife Service, Ottawa, Ontario.

ACIA (Arctic Climate Impact Assessment). 2004. Impacts of a warming Arctic. Cambridge University Press, Cambridge, United Kingdom. Website: http://www.amap.no/arctic-climate-impact-assessment-acia. [accessed May 2019].

Alaska Center for Conservation Science. 2019. Alaska Species Ranking System - Red Knot. University of Alaska Anchorage-Alaska Center for Conservation Science (UAA-ACCS), Anchorage, Alaska. Website: https://accs.uaa.alaska.edu/wildlife/alaska-species-ranking-system/ [accessed March 2020].

Alaska Department of Fish and Game. 2015. Alaska wildlife action plan. Alaska Department of Fish and Game, Juneau, Alaska. Website: http://www.adfg.alaska.gov/static/species/wildlife_action_plan/2015_alaska_wildlife_action_plan.pdf. [accessed March 2020].

Alaska Department of Fish and Game. 2019. Alaska 2019 - 2020 Migratory Game Bird Hunting Regulations. 40. Alaska Department of Fish and Game, Juneau, Alaska. Website: https://www.adfg.alaska.gov/static/applications/web/nocache/regulations/wildliferegulations/pdfs/waterfowl.pdfFC9C13662B55D4475653F8BF70E4F632/waterfowl.pdf. [accessed March 2020].

Alaska Shorebird Group. 2019. Alaska Shorebird Conservation Plan. Version III. Alaska Shorebird Group, Anchorage, Alaska. Website: https://pacificbirds.org/wp-content/uploads/2019/06/alaska_shorebird_conservation_plan_2019.pdf [accessed March 2020].

Aldabe, J. 2007. Registro de Calidris canutus. 1-2. Aves Uruguay, BirdLife, Montevideo, Uruguay. Unpublished Report.

Aldabe, J., P.I. Rocca, P.M. González, D. Caballero-Sadi, and A.J. Baker. 2015. Migration of endangered Red Knots Calidris canutus rufa in Uruguay: important sites, phenology, migratory connectivity and a mass mortality. Wader Study 122:221-235.

Alerstam, T., G.A. Gudmundsson, and K. Johannesson. 1992. Resources for long distance migration: intertidal exploitation of Littorina and Mytilus by Red Knots Calidris canutus in Iceland. Oikos 65:179-189.

All, J.D. 2006. Environmental assessment. Colorado River floods, droughts, and shrimp Fishing in the Upper Gulf of California, Mexico. Environmental Management 37:111-125.

Allard, K., A. Hanson, and M. Mahoney. 2014. Important marine habitat areas for Migratory birds in eastern Canada. Technical Report Series No. 530. Canadian Wildlife Service, Sackville, New Brunswick.

Almandoz, G.O., M.P. Hernando, G.A. Ferreyra, I.R. Schloss, and M.E. Ferrario. 2011. Seasonal phytoplankton dynamics in extreme southern South America (Beagle Channel, Argentina). Journal of Sea Research 66:47-57.

Álvarez-Berríos, N.L. and T.M. Aide. 2015. Global demand for gold is another threat for tropical forests. Environmental Research Letters 10: 014006. http://iopscience.iop.org/1748-9326/10/1/014006/article.

Andrade, L.P., H.M.L. Silva-Andrade, R.M. Lyra-Neves, L.P. Albuquerque, and W.R. Telina-Junior. 2016. Do artisanal fishers perceive declining migratory shorebird populations? Journal of Ethnobiology and Ethnomedicine 12:16, 1-11.

Andres, B. A. 2017. Current harvest policies and management actions and recent changes for the Caribbean, North America and northern South America, 2012-2017. Unpublished report, U.S. Fish and Wildlife Service, Falls Church, Virginia.

Andres, B.A., P.A. Smith, R.I.G. Morrison, C.L. Gratto-Trevor, S.C. Brown, and C.A. Friis. 2012. Population estimates of North American shorebirds, 2012. Wader Study Group Bulletin 119:178-194.

Andrews, J. 2017. Climate change and sea ice: shipping in Hudson Bay, James Bay, Hudson Strait, and Foxe Basin. M. Env. Winnipeg, M. Env. Thesis. 115 pp. Department of Environment and Geography, University of Manitoba, Winnipeg, Manitoba.

Arreola-Lizárraga, J.A., R. Barraza-Guardado, R. Casillas-Hernández, F. Magallón-Barajas and M.A. López-Torres. 2014. The ecosystem approach to shrimp farming: an analysis on the NW Mexico. World Aquaculture Society, Sorrento, Louisiana. Website: https://www.was.org/Meetings/ShowAbstract.aspx?Id=32077 [accessed March 2020].

Aspiroz, A.B., N. Martínez-Curci, and M. Alfaro. 2018. Playero Rojizo Calidris canutus rufa. Pp. 143-153 In Aspiroz, Jiménez and Alfaro [eds.]. Libro Rojo de las Aves del Uruguay. Biología y conservación de las aves en peligro de extinción a nivel nacional. Categorías "Extinto a Nivel Regional". Edición digital (versión 1.1). Dinamarca y Dinamarca, Montevideo.

Atkinson, P.W., A.J. Baker, R.M. Bevan, N.A. Clark, K.B. Cole, P.M. González, J. Newton, L.J. Niles, and R.A. Robinson. 2005. Unravelling the migration and moult strategies of a long-distance migrant using stable isotopes: Red Knot Calidris canutus movements in the Americas. Ibis 147:738-749.

Atkinson, P.W., A.J. Baker, K.A. Bennett, N.A. Clark, J.A. Clark, K.B. Cole, A. Dekinga, A. Dey, S. Gillings, P.M. González, K. Kalasz, C.D.T. Minton, L.J. Niles, R.A. Robinson, and H.P. Sitters. 2007. Rates of mass gain and energy deposition in red knot on their final spring staging site is both time- and condition-dependent. Journal of Applied Ecology 44:885-895.

Atlantic States Marine Fisheries Commission. 2015. Horseshoe Crab. Web publication: www.asmfc.org/species/horseshoe-crab. [accessed May 2019].

Aubry, Y., pers. comm. 2015. Cited in: ECCC (Environment and Climate Change Canada) 2017. Wildlife Biologist, Canadian Wildlife Service, Environment and Climate Change Canada, Quebec City, Quebec.

Aubry, Y., pers. comm. 2019. Email correspondence with R.I.G. Morrison. November 2019. Biologist, Canadian Wildlife Service, Environment and Climate Change Canada, Quebec.

Aubry, Y., pers. comm. 2020. Email correspondence with R.I.G. Morrison. March 2020. Biologist, Canadian Wildlife Service, Environment and Climate Change Canada, Quebec.

Aubry, Y., and R. Cotter. 2001. Using trend information to develop the Quebec Shorebird Conservation Plan. Bird Trends 8:21-24.

Aubry, Y., and R. Cotter. 2007. Quebec Shorebird Conservation Plan. Environment Canada, Canadian Wildlife Service - Quebec Region, Sainte-Foy, Quebec.

Audubon Science-CBC. 2014. Audubon Christmas Bird Count Compiler's Manual. 1-11. Audubon Science-CBC. Willow Grove, Pennsylvania. Website: http://docs.audubon.org/sites/default/files/documents/compilers_manual_oct_2014_0.pdf [accessed January 2020].

Azpiroz, A. and A. Rodríguez -Ferraro. 2006. Banded Red Knots Calidris canutus sighted in Venezuela and Uruguay. Cotinga 25:82-83.

Azpiroz, A.B., R.A. Dias, A.S. Di Giacomo, CS. Fontana, and C.M. Palarea. 2012. Ecology and conservation of grassland birds in southeastern South America: a review. Journal of Field Ornithology 83:217-246.

Baker, A.J., P.M. González, T. Piersma, C.D.T. Minton, J.R. Wilson, H. Sitters, D. Graham, R. Jessop, P. Collins, P. de Goeij, M.K. Peck, R. Lini, L. Bala, G. Pagnoni, A. Vila, E. Bremer, R. Bastida, E. Ieno, D. Blanco, I.d.L.S. Nascimento, S.S. Scherer, M.P. Schneider, A. Silva, and A.A.F. Rodrigues. 1998. Northbound migration of Red Knots Calidris canutus rufa in Argentina and Brazil: Report on results obtained by an international expedition in March-April 1997. Wader Study Group Bulletin 88:64-75.

Baker, A.J., T. Piersma, and A. Greenslade. 1999. Molecular vs. phenotypic sexing in Red Knots. Condor 101:887-893.

Baker, A.J., P.M. González, T. Piersma, L.J. Niles, I.d.L.S. Nascimento, P.W. Atkinson, N.A. Clark, C.D.T. Minton, M. Peck, and G. Aarts. 2004. Rapid population decline in red knots: fitness consequences of decreased refuelling rates and late arrival in Delaware Bay. Proceedings of the Royal Society B 271:875-882.

Baker, A.J., P.M. González, I.L. Serrano, W.R.T. Júnior, M. Efe, S. Rice, V.L. D'Amico, M. Rocha, and M.A. Echave. 2005a. Assessment of the wintering area of red knots in Maranhão, northern Brazil, in February 2005. Wader Study Group Bulletin 107:10-18.

Baker, A.J., P.M. González, L. Benegas, S. Rice, V.L. D'Amico, M. Abril, A. Farmer, and M. Peck. 2005b. Annual international expeditions to study the Red Knot population in Rio Grande, Tierra del Fuego, 2000-2004. Wader Study Group Bulletin 107:19-23.

Baker, A.J., E. Tavares, K. Choffe, and O. Haddrath. 2012a. Genetic differentiation among the three major wintering populations of the Red Knot (Calidris canutus rufa). Unpublished report. Royal Ontario Museum, Toronto, Ontario.

Baker, A., E. Tavares, P. González, O. Haddrath, K. Choffe, and L. Niles. 2012b. Genetic differentiation among the three major wintering populations of the Red Knot Calidris canutus rufa. Wader Study Group Bulletin 119:214.

Baker, A.J., P. González, R.I.G. Morrison, and B.A. Harrington. 2013. Red Knot (Calidris canutus), version 2.0. The Birds of North America. Cornell Lab of Ornithology, Ithaca, New York.

Baker, A., P. González, R.I.G. Morrison and B.A. Harrington. 2020. Red Knot (Calidris canutus), version 1.0. In Birds of the World. Ed. by Billerman,S.M. Cornell Lab of Ornithology, Ithaca, New York. https://doi.org/10.2173/bow.redkno.01

Bart, J., and V.H. Johnston. 2012. Arctic Shorebirds in North America. A Decade of Monitoring. Studies in Avian Biology 44:1-320.

Bart, J., B. Andres, S. Brown, G. Donaldson, B. Harrington, H. Johnson, V. Johnston, S. Jones, R.I.G. Morrison, M. Sallaberry, S. Skagen, and N. Warnock. 2002. Program for Regional and International Shorebird Monitoring (PRISM). Project Report, USGS, Boise, Idaho.

Bart, J., S. Brown, B. Harrington, and R.I.G. Morrison. 2007. Survey trends of North American shorebirds: population declines or shifting distributions? Journal of Avian Biology 38:73-82.

Belton, W. 1984. Birds of Rio Grande do Sul, Brazil. Part 1. Rehidae through Furnariidae. Bulletin of the American Museum of Natural History 178:369-636.

Bender, M.A., T.R. Knutson, R.E. Tuleya, J.A. Sirutis, G.A. Vecchi, S.T. Garner, and I.M. Held. 2010. Modeled impact of anthropogenic warming on the frequency of intense Atlantic hurricanes. Science 327:454-458.

Berlanga-Robles, C.A., A. Ruiz-Luna, and R. Hernández-Guzman. 2011. Impact of shrimp farming on mangrove forest and other coastal wetlands: the case of Mexico. In Sladonja, B. (Ed.). Aquaculture and the Environment. A Shared Destiny. InTech, Rijeka, Croatia. https://books.google.ca/books?hl=en&lr=&id=UdCPDwAAQBAJ&oi=fnd&pg=PA17&dq=coastal+aquaculture+mangrovedeforestation+mexico&ots=7o0j1XAM2K&sig=yWAxkRiAoxfygf9dHRdxgSqPwTc#v=onepage&q=coastal%20aquaculture%20mangrovedeforestation%20mexico&f=false. [accessed March 2020].

Berman, M., K. Amigo, and P. Matson. 2005. Agricultural runoff fuels large phytoplankton blooms in vulnerable areas of the ocean. Nature 434:211-214.

Beyersbergen, G.W., and D.C. Duncan. 2007. Shorebird abundance and migration chronology at Chaplin Lake, Old Wives Lake and Reed Lake, Saskatchewan: 1993 and 1994. Canadian Wildlife Service Technical Report Series No. 484. Prairie and Northern Region. Edmonton, Alberta. vi + 46 pp.

Bianchini, K.M., J.E. Howell, A.E. McKellar, D.J. Newstead, and C.A. Morrissey. 2020. Motus automated telemetry reveals Sanderling and Red Knot migration patterns in the North American Midcontinental Flyway. North American Ornithological Conference, Virtual Conference, 10-15 August 2020. Abstract Book, pp 200-201. https://amornithmeeting.files.wordpress.com/2020/08/naoc2020_abstractbook_v4.pdf. [accesssed August 2020]

Bird, J., M. Martin, H.R. Akçakaya, J. Gilroy, I.J. Burfield, S. Garnett, A. Symes, J. Taylor, C. Sekercioglu, and S.H.M. Butchart. 2020. Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology. Website: https://doi.org/10.1111/cobi.13486 [accessed February 2020].

BirdLife International. 2018. Calidris canutus. The IUCN Red List of Threatened Species 2018: e.T22693363A132285482. https://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T22693363A132285482.en. [accessed August 2020.]

Bishop, M.A., J.B. Buchanan, B.J. McCaffery, and J.A. Johnson. 2016. Spring stopover sites used by the Red Knot Calidris canutus roselaari in Alaska, USA: connectivity between the Copper River Delta and the Yukon-Kuskoswim River Delta. Wader Study 123:143-152.

Bittel, J. 2017. This tiny seabird's colossal migration is in danger from all sides on Earth. National Resource Defense Council, New York. Website: https://www.nrdc.org/onearth/tiny-seabirds-colossal-migration-danger-all-sides [accessed May 2018].

Blackburn, M., C.A.S. Mazzacano, C. Fallon, and S. Hoffman Black. 2014. Oil in our oceans: a review of the impacts of oil spills on marine invertebrates. The Xerces Society for Invertebrate Conservation, Portland, Oregon.

Blanco, D.E., B. López-Lanús, R.A. Dias, A. Azpiroz, and F. Rilla. 2006. Use of rice fields by migratory shorebirds in southern South America. Implications for conservation and management. Wetlands International, Buenos Aires, Argentina.

Blew, J., K. Gunther, B. Halterlein, R. Kleefstra, K. Laursen, J. Ludwig, and G. Scheiffarth. 2017. Migratory birds. In Kloepper S. et al. (eds.). Wadden Sea Quality Status Report 2017. Common Wadden Sea Secretariat, Wilhelmshaven, Germany. qsr.waddensea-worldheritage.org/reports/migratory-birds. [accessed March 2020].

BNamericas. 2017. Argentina's Tierra del Fuego to get new wastewater treatment plant. BNamericas, Santiago, Chile. Website: https://www.bnamericas.com/en/news/argentinas-tierra-del-fuego-to-get-new-wastewater-treatment-plant/ [accessed March 2020].

Bocher, P., G. Quaintenne, P. Delaporte, C. Goulevant, B. Deceuninck, and E. Caillot. 2012. Distribution, phenology and long-term trend of Red Knots Calidris canutus in France. Wader Study Group Bulletin 119:17-25.

Botton, M.L., R.E. Loveland, and R. Jacobsen. 1994. Site selection by migratory shorebirds in Delaware Bay, and its relationship to beach characteristics and abundance of horseshoe crab (Limulus polyphemus) eggs. Auk 111:605-616.

Bourget, A., and P. Laporte. 1983. Évaluation del problèmes concernant les oiseaux migrateurs dans les départements français en amérique latine. 1-48. Unpublished Report. Service canadien de la faune, Sainte-Foy, Québec.

Boyd, H., and T. Piersma. 2001. Changing balance between survival and recruitment explains population trends in Red Knots Calidris canutus islandica wintering in Britain, 1969-1995. Ardea 89:301-317.

Bricelj, V.M., A.G. Haubois, M.R. Sengco, R. Pierce, J. Cutler, and D.M. Anderson. 2012. Trophic transfer of brevetoxins to the benthic macrofaunal community during a bloom of the harmful dinoflagellate Karenia brevis in Sarasota Bay, Florida. Harmful Algae 16:27-34.

Brown, S., C. Hickey, B. Harrington, and R. Gill. 2001. United States Shorebird Conservation Plan, Second Edition. Manomet Center for Conservation Sciences, Manomet, Massachusetts.

Brownell, V., J. Fitzsimmons, C. Risley, A. Tamachi, A. Wheeldon, R. Donley, pers. comm. 2015. Cited in: ECCC (Environment and Climate Change Canada) 2017. Wildlife Biologists, Ontario Ministry of Natural Resources and Forestry, Ontario.

Braden, B. 2014. New resources emerging because of diminishing Arctic ice pack. Canadian Mining Journal, January 1, 2014. Website: https://www.canadianminingjournal.com/features/new-resoursces-emerging-because-of-diminishing-arctic-ice-pac/#:~:text=Coal%20Nunvut%E2%80%99s%20longest%20of%20its%20long-shot%20projects%20might,it%20has%20barely%20two%20months%20of%20open%20water. [accessed August 2020.]

Buchanan, J.B., pers. comm. 2020. Email correspondence with R.D. Elliot. February 2020. Wildlife Biologist/Natural Resource Scientist, Washington Department of Fish and Wildlife, Olympia, Washington.

Buchanan, J.B., L.J. Salzer, G.E. Hayes, G. Schirato, and G.J. Wiles. 2010. Red Knot Calidris canutus migration at Grays Harbor and Willapa Bay, Washington: spring 2009. Wader Study Group Bulletin 117:41-45.

Buchanan, J.B., J.E. Lyons, L.J. Salzer, R. Carmona, N. Arce, G.J. Wiles, K. Brady, G. E. Hayes, S.M. Desimone, G. Schirato, and W. Michaelis. 2012. Among-year site fidelity of Red Knots during migration in Washington. Journal of Field Ornithology 83:282-289.

Buchanan, J.B., L.J. Salzer, and V. Loverti. 2018. Between-year variation in the timing of peak passage of spring migrant Red Knots at Grays Harbor, Washington, USA. Wader Study 124:238-240.

Buehler, D.M. 2002. Shorebird counts in Panama during 2002 emphasize the need to monitor and protect the Upper Panama Bay. Wader Study Group Bulletin 99:41-44.

Buehler, D.M., and A.J. Baker. 2005. Population divergence times and historical demography in Red Knots and Dunlins. Condor 107:497-513.

Buehler, D.M., A.J. Baker, and T. Piersma. 2006. Reconstructing palaeo-flyways of the late Pleistocene and early Holocene Red Knot Calidris canutus. Ardea 94:485-498.

Buehler, D.M., and T. Piersma. 2008. Travelling on a budget: predictions and ecological evidence for bottlenecks in the annual cycle of long-distance migrants. Philosophical Transactions of the Royal Society B 363:247-266.

Buehler, D.M., G.M. Bugoni, P.M. Dorrestein, P.M. González, P. Pereira-Jr., L. Proenca, I. de Lima Serrano, A.J. Baker, and T. Piersma. 2010. Local mortality events in migrating sandpipers (Calidris) at a staging site in southern Brazil. Wader Study Group Bulletin 117:150-156.

Buidin, C., Y. Rochepault, and Y. Aubry. 2010. L'archipel de Mingan: une halte migratoire primordiale pour les oiseaux de rivage. le naturaliste canadian 134:73-81.

Bulla, M., J. Reneerkens, E.L. Weiser, A. Sokolov, A.R. Taylor, B. Sittler, B.J. McCaffery, D.R. Ruthrauff, D.H. Catlin, D.C. Payer, D.H. Ward, D.V. Solovyeva, E.S.A. Santos, E. Rakhimberdiev, E. Nol, E. Kwon, G.S. Brown, G.D. Hevia, H.R. Gates, J.A. Johnson, J.A. van Gils, J. Hansen, J.-F. Lamarre, J. Rausch, J.R. Conklin, J. Liebezeit, J. Bêty, J. Lang, J.A. Alves, J. Fernández-Elipe, K.-M. Exo, L. Bollache, M. Bertellotti, M.-A. Giroux, M. van de Pol, M. Johnson, M.L. Boldenow, M. Valcu, M. Soloviev, N. Sokolova, N.R. Senner, N. Lecomte, N. Meyer, N.M. Schmidt, O. Gilg, P.A. Smith, P. Machín, R.L. McGuire, R.A.S. Cerboncini, R. Ottvall, R.S.A. van Bemmelen, R.J. Swift, S.T. Saalfeld, S.E. Jamieson, S. Brown, T. Piersma, T. Albrecht, V. D’Amico, R.B. Lanctot, and B. Kempenaers. 2019. Comment on “Global pattern of nest predation is disrupted by climate change in shorebirds.” Science 364(6445). https://doi.org/10.1126/science.aaw8529

Burge, C.A., C.M. Eakin, C.S. Friedman, B. Froelich, P.K. Hershberger, E.E. Hofmann, L.E. Petes, K.C. Prager, E. Weil, B.L. Willis, S.E. Ford, and C.D. Harvell. 2014. Climate change influences on marine infectious diseases: implications for management and society. Annual Review of Marine Science 6:249-277. Website: http://www.annualreviews.org/doi/abs/10.1146/annurev-marine-010213-135029. [accessed May 2019].

Burger, J., G. Caleb, L. Lawrence, J. Newman, G.M. Forcey, and L. Vlietsrta. 2011. Risk evaluation for federally listed (Roseate Tern, Piping Plover) or candidate (Red Knot) bird species in offshore waters: A first step for managing the potential impacts of wind facility development on the Atlantic outer continental shelf. Renewable Energy 36:338-351.

Burger, J., M. Gochfield, and L. Niles. 1995. Habitat choice, disturbance, and management of foraging shorebirds and gulls at a migratory stopover. Environmental Conservation 22:56-65.

Burger, J., C. Jeitner, K. Clark and L. Niles. 2004. The effect of human activities on migrant shorebirds: successful adaptive management. New Jersey Division of Fish and Game, Trenton, New Jersey.

Burger, J., and L. Niles. 2017. Shorebirds, stakeholders, and competing claims to the beach and intertidal habitat in Delaware Bay, New Jersey, USA. Natural Science 9:181-205.

Burger, J., L.J. Niles, R.R. Porter, A.D. Dey, S. Koch, and C. Gordon. 2012a. Migration and over-wintering of Red Knots (Calidris canutus rufa) along the Atlantic coast of the United States. Condor 114:302-313.

Burger, J., L.J. Niles, R.R. Porter, and A.D. Dey. 2012b. Using geolocator data to reveal incubation periods and breeding biology in Red Knots Calidris canutus rufa. Wader Study Group Bulletin 119:26-36.

Burger, J., L.J. Niles, A.D. Dey, T. Dillingham, A.S. Gates, and J. Smith. 2015. An experiment to examine how Red Knots Calidris canutus rufa and other shorebirds respond to oyster culture at Reed's Beach, Delaware Bay, New Jersey. Wader Study 122:89-98.

Burger, J., R. Porter, and L. Niles. 2020. On the importance of geolocators for long-term studies of Red Knots Calidris canutus rufa that use Delaware Bay. Wader Study in press.

Butler, R.W., R.C. Ydenberg, and D.B. Lank. 2003. Wader migration on the changing predator landscape. Wader Study Group Bulletin 100:130-133.

Byrne, M., and R. Przeslawski. 2013. Multistressor impacts of warming and Acidification of the ocean on marine invertebrates' life histories. Integrative and Comparative Biology 53:586-596.

Campbell, R.W., N.K. Dawe, I. McTaggart-Cowan, J.M. Cooper, G.W. Kaiser, and M.C.E. McNall. 1998. The Birds of British Columbia. Volume II. Non-passerines. Royal British Columbia Museum, Victoria, British Columbia.

Cardoso, T.A.L. and J.L.X. Nascimento. 2007. Avaliação de atividades turísticas prejudiciais à permanência de aves migratórias na Coroa do Avião, Pernambuco Brasil. Ornithologia 2:170-177.

Carmona, R., N. Arce, V. Ayala-Perez, A. Hernández-Alvarez, J.B. Buchanan, L.J. Salzer, P.S. Tomkovich, J.A. Johnson, R.E. Gill, B.J. McCaffery, J.E. Lyons, L.J. Niles, and D. Newstead. 2013. Red Knot Calidris canutus roselaari migration connectivity, abundance and non-breeding distribution along the Pacific coast of the Americas. Wader Study Group Bull.120: 168-180.

Carmona, R., G.D. Danemann, V. Ayala-Perez, A. Nallely-Arce, A. Hernández -Alvarez, L.F. Mendoza, and S. Vidal. 2019. Spatio-temporal importance of Northwest Mexico for Red Knot (Calidris canutus roselaari). Unpublished report presented at the Western Hemisphere Shorebird Group Conference, October 2019, Panama City, Panama.

Carmona, R., A. Hernández-Alvarez, B. Martínez-Reséndiz, G. Ruiz-Campos, J. de la Cruz Agüero, R. Saldiema, V.M. de la Cruz Agüero, M. Hernández-Rivas, and G. D. Danemann. 2017. Biología y conservación del pejerrey (Atherinopsidae, Leuresthes sardina). Ciencia Pesquera 25:53-69.

Carlos, C.J., C.E. Fedrizzi, A.A. Campos, H. Matthews-Cascon, C.X. Barroso, S.G. Rabay, L.E.A. Bezerra, C.A.O. Meirelles, A.J. Merieles, and P.R.L. Theirs. 2010. Migratory shorebirds conservation and shrimp farming in NE Brazil: final report. Part 1: Shorebirds and their Prey. Part 2: Shorebird Habitat Loss. 85 pp.. Aquasis, Caucaia, Ceará, Brazil.

Castro, G., and J.P. Myers. 1993. Shorebird predation on eggs of Horseshoe Crabs during spring stopover on Delaware Bay. Auk 110:927-930.

Cayford, J.T. 1993. Wader disturbance: a theoretical overview. Wader Study Group Bull. 68:3-5.

CCSP (United States Climate Change Science Program). 2009. Thresholds of climate change in ecosystems. U.S. Climate Change Science Program synthesis and assessment product 4.2. U.S. Geological Survey, Reston, Virginia.

CEC (Commission for Environmental Cooperation). 2017. Identification of important Semipalmated Sandpiper and Red Knot sites along the North American Atlantic and Pacific Flyways. Commission for Environmental Cooperation, Montreal, Quebec.

CESCC (Canadian Endangered Species Conservation Council). 2016. Wild Species 2015: The General Status of Species in Canada. National General Status Working Group. Website: http://www.wildspecies.ca [accessed May 2019].

Clark, K.E., L.J. Niles, and J. Burger. 1993. Abundance and distribution of migrant shorebirds in Delaware Bay. Condor 95:694-705.

Clark, K.E., L.J. Niles, and A. Doolittle. 2001. Fifteen years of spring shorebird surveys at Delaware Bay. Wader Study Group Bulletin 95:16-17.

Cohen, J.B., S.M. Karpanty, J.D. Fraser, and B.R. Truitt. 2009. The effect of benthic prey abundance and size on Red Knot (Calidris canutus) distribution at an alternative migratory stopover site on the US Atlantic coast. Journal of Ornithology 151:355-364.

Cohen, J.B., S.M. Karpanty, and J.D. Fraser. 2010. Habitat selection and behavior of Red Knots on the New Jersey Atlantic coast during spring stopover. Condor 112:655-662.

Collop, C., R.A. Stillman, A. Garbutt, M.G. Yates, E. Rispin, and T. Yates. 2016. Variability in the area, energy and time costs of wintering waders responding to disturbance. Ibis 158:711-725.

Conklin, J., pers. comm. 2020. Telephone correspondance with P.A. Smith. June 2020. Researcher, Royal Netherlands Institute for Sea Research (NIOZ), Den Burg, Texel, Netherlands.

Corcoran, A., M. Dornback, B. Kirkpatrick, and A. Jochens. 2013. A Primer on Gulf of Mexico Harmful Algal Blooms. Florida Fish and Wildlife Conservation Commission, Tallahassee, Florida.

COSEWIC (Committee on the Status of Endangered Wildlife in Canada). 2007. COSEWIC assessment and status report on the Red Knot Calidris canutus in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa, Ontario.

COSEWIC (Committee on the Status of Endangered Wildlife in Canada). 2017a. COSEWIC guidelines for recognizing designatable units (modified 2017). Website: http://cosewic.ca/index.php/en-ca/reports/preparing-status-reports/guidelines-recognizing-designatable-units [accessed May 2019].

COSEWIC (Committee on the Status of Endangered Wildlife in Canada). 2017b. COSEWIC wildlife species assessments (detailed version), November 2017. Website: https://www.canada.ca/en/environment-climate-change/services/committee-status-endangered-wildlife/assessments/detailed-version-november-2017.html [accessed November 2018].

COSEWIC (Committee on the Status of Endangered Wildlife in Canada). 2017c. COSEWIC assessment and status report on the Peregrine Falcon Falco peregrinus (pealei subspecies - Falco peregrinus pealei and anatum/tundrius - Falco peregrinus anatum/tundrius) in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa, Ontario. Website: http://www.registrelepsararegistry.gc.ca/default.asp?lang=en&n=24F7211B-1. [accessed March 2020].

COSEWIC (Committee on the Status of Endangered Wildlife in Canada). 2019. Guidelines for use of the Index of Area of Occupancy in COSEWIC Assessments. Website: http://cosewic.ca/index.php/en-ca/reports/preparing-status-reports/guidelines-index-area-occupancy. [accessed August 2020].

COSEWIC Birds Specialist Subcommittee. 2019. Identification of designatable units for Red Knot in Canada. COSEWIC Designatable Unit Report. Committee on the Status of Endangered Wildlife in Canada, Ottawa. 19 pp.

Cramer, D. 2015. The Narrow Edge. A Tiny Bird, An Ancient Crab and An Epic Journey. Yale University Press, New Haven, Connecticutt.

Cramp, S., and K.E.L. Simmons. 1983. The birds of the Western Palearctic, Vol. 3: waders to gulls. Oxford University Press, Oxford, United Kingdom.

CWS (Canadian Wildlife Service). 2009. Northwest Territories - Nunavut Bird Checklist Survey program data (unpublished). Canadian Wildlife Service - Prairie and Northern Region, Yellowknife, Northwest Territories. (Retrieved 16 January 2009 from Checklist database).

Dahl, T.E. 1990a. Wetlands losses in the United States 1780's to 1980's. U.S. Department of the Interior, Fish and Wildlife Service, Washington, D.C.

Dahl, T.E. 1990b. Wetland loss since the revolution. National Wetlands Newsletter November/December 1990:16-17.

Davidson, N.C. 2014. How much wetland has the world lost? Long-term and recent trends in global wetland area. Marine and Freshwater Research 65: 936-941 Website: http://dx.doi.org/10.1071/MF14173. [accessed May 2019].

Davidson, N.C., and J.R. Wilson. 1992. The migration system of European-wintering Knots Calidris canutus islandica. Wader Study Group Bulletin 64, Supplement: 39-51.

Davidson, N.C., and P.I. Rothwell. 1993a. Introduction. Wader Study Group Bull. 68, Supplement: 1-2.

Davidson, N.C., and P.I. Rothwell. 1993b. Disturbance to waterfowl on estuaries: the conservation and coastal management implications of current knowledge. Wader Study Group Bulletin 68:97-105.

Dekker, D., I. Dekker, D. Christie, and R. Ydenberg. 2011. Do staging Semipalmated Sandpipers spend the high-tide period in flight over the ocean to avoid falcon attacks along shore? Waterbirds 34:195-201.

Delaney, S., D. Scott, T. Dodman, and D. Stroud. 2009. An Atlas of Wader Populations in Africa and Western Eurasia. Wetlands International, Wageningen, The Netherlands.

de Pracontal, N. 2017. Suivi de l'hivernage des limicoles sur 3 sites de Guyane. GEPOG and Environment and Climate Change Canada, Cayenne, French Guiana. Unpublished report.

Dey, A., L.J. Niles, J.A.M. Smith, H.P. Sitters and R.I.G. Morrison. 2020. Update to the status of the Red Knot (Calidris canutus rufa) in the Western Hemisphere, March 2020. 1-29. Unpublished Report, Trenton, New Jersey.

DFO (Department of Fisheries and Oceans). 2012. Technical review of Baffinland's Mary River Project draft environmental impact statement (EIS). Department of Fisheries and Oceans Canadian Science Advisor Secretariat. Science Advisor Report. 2011/065.

Diario Oficial de la Federación (DOF). 2010. Norma Oficial Mexicana NOM-059-ECOL-2010, Protección ambiental-especies nativas de México de flora y fauna silvestre categorías de riesgos y especificaciones para su inclusión, exclusión o cambio-lista de especies en riesgo. México, D.F. 78pp.

Dietz, M.W., B. Spaans, A. Dekinga, M. Klaassen, H. Korthals, C. van Leeuwen, and T. Piersma. 2010. Do Red Knots (Calidris canutus islandica) routinely skip Iceland during southward migration? Condor 112:48-55.

Donaldson, G., pers. comm. 2015 Cited in: ECCC (Environment and Climate Change Canada) 2017. Manager - Population Conservation, Canadian Wildlife Service, Environment and Climate Change Canada, Sackville, New Brunswick.

Donaldson, G.M., C. Hyslop, R.I.G. Morrison, H.L. Dickson, and I. Davidson. 2000. Canadian Shorebird Conservation Plan. Canadian Wildlife Service, Ottawa, Ontario.

Drever, M.C., B.A. Beasley, Y. Zharikov, M.J.F. Lemon, P.G. Levesque, M.D. Boyd, and A. Dorst. 2016. Monitoring migrating shorebirds at the Tofino mudflats in British Columbia, Canada: is disturbance a concern? Waterbirds 39:125-135.

Duerr, A.E., B.D. Watts, and F.M. Smith. 2011. Population dynamics of Red Knots stopping over in Virginia during spring migration. College of William and Mary and Virginia Commonwealth University, Williamsburg, Virginia.

Duijns, S., L.J. Niles, A. Dey, Y. Aubry, C. Friis, S. Koch, A.M. Anderson, and P.A. Smith. 2017. Body condition explains migratory performance of a long-distance migrant. Proceedings of the Royal Society B 284: 20171374.

Duncan, A., pers. comm. 2015. Cited in: ECCC (Environment and Climate Change Canada) 2017. Biologiste, Ligue pour la Protection des Oiseaux (LPO), France.

eBird. 2019. eBird: An online database of bird distribution and abundance. Red Knot. Website: https://ebird.org/species/redkno. [accessed May 2019].

ECCC (Environment and Climate Change Canada). 2017. Recovery strategy and management plan for the Red Knot (Calidris canutus) in Canada. Species at Risk Recovery Strategy Series. Environment and Climate Change Canada, Ottawa. Ontario.

ECCC (Environment and Climate Change Canada). 2019. Status of birds in Canada 2019. Background information. Analyses of shorebird migration monitoring data. Website: https://wildlife-species.canada.ca/bird-status/info-info-eng.aspx?sY=2019&sL=e&sM=c&sB=REKN&sT=70e0fa33-a4eb-46a5-b0ac-4aa58a2baa65&iid=d868046a-3325-4770-a995-6d852a3ca3f1&sDoc=1191&RS=7. [accessed August 2020.]

Ellis, D. H., B.A. Sabo, J.K. Fackler, and B.A. Millsap. 2002. Prey of the peregrine falcon (Falco peregrinus cassini) in southern Argentina and Chile. Journal of Raptor Research 36:315-319.

Enderson, J.H., C. Flatten, and J.P. Jenny. 1991. Peregrine Falcons and Merlins in Sinaloa, Mexico, in Winter. Journal of Raptor Research 25:123-126.

Engelmoer, M., and C.S. Roselaar. 1998. Geographical Variation in Waders. Kluwer Academic Publishers, Dordrecht, The Netherlands.

Escudero, G., J.G. Navedo, T. Piersma, P. de Goeij, and P. Edelaar. 2012. Foraging conditions ‘at the end of the world' in the context of long-distance migration and population declines in red knots. Austral Ecology 37:355-364.

Executive Office of the President. 2013. The President's Climate Action Plan. The White House, Washington, DC.

FAO (Food and Agriculture Organization of the United Nations). 2004. Marine biotoxins. FAO food and nutrition paper 80. Food and Agriculture Organization of the United Nations, Rome, Italy.

FAO (United Nations Food and Agriculture Organization). 2018. More people, more food, worse water? a global review of water pollution from agriculture. (Eds. Mateo-Sagasta, J., Zadeh, S. M., and Turral, H.). United Nations Food and Agriculture Organization, Rome, Italy.

FAO (Food and Agriculture Organization of the United Nations). 2019. Aquaculture growth potential in Mexico. Food and Agriculture Organization of the United Nations, Rome, Italy. Website: http://www.fao.org/3/ca7136en/ca7136en.pdf [accessed March 2020].

Fedrizzi, C.E., C.J. Carlos, and A.A. Campos. 2016. Annual patterns of abundance of Nearctic shorebirds and their prey at two estuarine sites in Ceará, NE Brazil, 2008-2009. Wader Study 123:122-135.

Ferrari, S., C. Albrieu, and P. Gandini. 2002. Importance of the Rio Gallegos estuary, Santa Cruz, Argentina, for migratory shorebirds. Wader Study Group Bulletin 99:35-40.

Fischer, E.M., and R. Knutti. 2015. Anthropogenic contribution to global occurrence of heavy-precipitation and high-temperature extremes. Nature Climate Change 5:550-564.

Flemming, S.A., A. Calvert, E. Nol, and P.A. Smith. 2016. Do hyperabundant Arctic-nesting geese pose a problem for sympatric species? Environmental Reviews 24:1-10 dx.doi.org/10.1139/er-2016-0007.

Flemming, S.A., E. Nol, L.V. Kennedy, A. Bédard, M.A. Giroux, and P.A. Smith. 2019a. Spatio-temporal responses of predators to hyperabundant geese affect risk of predation for sympatric-nesting species. PLOS One 14: e0221727. https://doi.org/10.1371/journal.pone.0221727.

Flemming, S.A., E. Nol, L.V. Kennedy, and P.A. Smith. 2019b. Hyperabundant herbivores limit habitat availability and influence nest site selection of Arctic-breeding birds. Journal of Applied Ecology 56:976-987. DOI: 10.1111/1365-2664.13336.

Flemming, S.A., P.A. Smith, J. Rausch, and E. Nol. 2019c. Broad-scale changes in tundra-nesting bird abundance in response to hyperabundant geese. Ecosphere 10:e02785. 10.1002/ecs2.2785.

Flint, V.E. 1972. The breeding of the knot on Vrangelya (Wrangel) Island, Siberia: comparative remarks. Proceedings of the Western Foundation of Vertebrate Zoology 2:27-29.

Florida Fish and Wildlife Conservation Commission. 2020. Red tide. Florida Fish and Wildlife Conservation Commission, Tallahassee, Florida. Website: https://myfwc.com/research/redtide/ [accessed March 2020].

Fraser, J.D., S.M. Karpanty, J.B. Cohen, and B.R. Truitt. 2013. The Red Knot (Calidris canutus rufa) decline in the western hemisphere: is there a lemming connection? Canadian Journal of Zoology 91:13-16.

Friis, C. 2017. James Bay Shorebird Project. 2016 Report. Environment and Climate Change Canada, Canadian Wildlife Service, Toronto, Ontario. (Unpublished Report).

Friis, C., and G. Morrison. 2018. Aerial Survey 2018. James Bay shorebird project. Website: https://www.jamesbayshorebirdproject.com/seasonsummaries/ [accessed November 2018].

Galbraith, H., R. Jones, R. Park, J. Clough, S. Herrod-Julius, B. Harrington, and G. Page. 2002. Global climate change and sea level rise: potential losses of intertidal habitat for shorebirds. Waterbirds 25:173-183.

Galbraith, H., R. Jones, R. Park, J. Clough, S. Herrod-Julius, B. Harrington, and G. Page. 2005. Global Climate Change and Sea Level Rise: Potential Losses of Intertidal Habitat for Shorebirds. USDA Forest Service Gen. Tech. Rep. PSW-GTR-191: 1119-1122.

Galbraith, H., D.W. DesRochers, S. Brown, and J.M. Reed. 2014. Predicting vulnerabilities of North American shorebirds to climate change. PLOS One 9:1-12.

Gaston, A.J. 2019. Birds of Mansel Island, Hudson Bay. Canadian Field-Naturalist 133:20-24.

Gill, R.E., and C.M. Handel. 1981. Shorebirds of the East Bering Sea. Pp. 719-738 in Hood and Calder (eds.). The Eastern Bering Sea Shelf: Oceanography and Resources. Vol. 1. University of Washington Press, Seattle, Washington.

Gill, R.E., and C.M. Handel. 1990. The importance of subarctic intertidal habitats to shorebirds: a study of the central Yukon-Kuskokwim Delta, Alaska. Condor 9:709-725.

Gill, R.E. pers.comm. 2020. Email correspondence with R.I.G. Morrison. April 2020. Research Wildlife Biologist (Emeritus), United States Geological Survey, Alaska Science Center, Anchorage, Alaska.

Gillanders, B.M. and M.J. Kingsford. 2002. Impact of changes in flow of freshwater on estuarine and open coastal habitats and the associated organisms. Oceanography and Marine Biology: an annual review 40 233-309.

Glick, P., J. Clough, and B. Nunley. 2007. Sea-level rise and coastal habitats in the Pacific Northwest. An analysis for Puget Sound, southwestern Washington, and northwestern Oregon. National Wildlife Federation, Seattle, Washington.

Godfrey, W.E. 1986. The Birds of Canada. Revised Edition. National Museum of Natural Sciences, Ottawa.

Godfrey, W.E. 1992. Subspecies of the Red Knot Calidris canutus in the extreme north-western Canadian arctic islands. Wader Study Group Bulletin, Supplement 64:24-25.

González, P.M., pers. comm. 2019. Conversation with R.I.G. Morrison. March 2019. Biologist, Fundacíon Inalafquen, San Antonio Oeste, Argentina.

González, P.M., pers. comm. 2020. Conversation with R.I.G. Morrison. February 2020. Biologist, Fundacíon Inalafquen, San Antonio Oeste, Argentina.

González, P.M., A.J. Baker, and M.E. Echave. 2006. Annual survival of Red Knots (Calidris canutus rufa) using the San Antonio Oeste stopover sites is reduced by domino effects involving late arrival and food depletion in Delaware Bay. El Hornero 21:109-117.

González, P.M., M. Carbajal, R.I.G. Morrison, and A.J. Baker. 2004. Tendencias poblacionales del playero rojizo (Calidris canutus rufa) en el sur de Sudamerica. Ornitologia Neotropical 15 (Suppl.):357-365.

González, P.M., T. Piersma, and Y. Verkuil. 1996. Food, feeding, and refuelling of Red Knots during northward migration at San Antonio Oeste, Rio Negro, Argentina. Journal of Field Ornithology 67:575-591.

González, P.M., D. Price, and G. Morrison. 2001. Migration of Knots through Bahia de San Antonio, Rio Negro, Argentina. Wader Study Group Bulletin 95:11.

Google Earth. 2019. Google Earth Pro. 2019 © Google LLC [accessed September 2020].

Government of Canada. 2017. Migratory Birds Convention Act, 1994. Website: https://laws-lois.justice.gc.ca/eng/acts/m-7.01/ [accessed January 2019].

Government of Canada. 2018. Arctic Program for Regional and International Shorebird Monitoring. Website: https://www.canada.ca/en/environment-climate-change/services/bird-surveys/shorebird/arctic-program-regional-international-monitoring.html [accessed May 2019].

Government of Canada. 2019. Species at Risk Act, 2002. Website: https://laws-lois.justice.gc.ca/eng/acts/s-15.3/ [accessed January 2019].

Gratto-Trevor, C.L., pers. comm. 2015. Research Scientist, Wildlife and Landscape Science Directorate, Environment and Climate Change Canada, Saskatoon, Saskatchewan.

Gratto-Trevor, C.L., G.W. Beyersbergen, H.L. Dickson, P. Erickson, R. MacFarlane, M. Raillard, and T. Sadler. 2001. Prairie Canada shorebird conservation plan. Prairie Habitat Joint Venture and Canadian Wildlife Service, Edmonton, Alberta.

GRID-Arendal. 2010. Arctic Biodiversity Trends 2010. GRID-Arendal &amp. Conservation of Arctic Flora and Fauna. Website: www.grida.no/resources/6241 [accessed November 2018].

Griffith, G.E., J.M. Omernik, and S.H. Azevedo 2019. Ecoregions of Central and South America. US Geological Survey and US Environmental Protection Agency. Website: http://ecologicalregions.info/htm/sa_eco.htm [accessed September 2019].

Gudmundsson, G.A., and A. Gardarsson. 1993. Numbers, geographic distribution and habitat utilization of waders (Charadrii) in spring on the shores of Iceland. Ecography 16:82-93.

Handmaker, M. 2019. Oil spill on Brazil Coast spans almost 2,500 Miles. Western Hemisphere Shorebird Reserve Network, Manomet, MA. Website: https://whsrn.org/oil-spill-on-brazil-coast-spans-almost-2500-miles/ [accessed March 2019].

Handmaker, M. 2020. Uncovering the mysteries of Red Knot movements on the Gulf Coast. Western Hemisphere Shorebird Reserve Network, Manomet, MA. Website: https://whsrn.org/uncovering-the-mysteries-of-red-knot-movements-on-the-gulf-coast/ [accessed March 2020].

Haramis, G.M., W.A. Link, P.C. Osenton, D.B. Carter, R.G. Weber, N.A. Clark, M.A. Teece, and D.S. Mizrahi. 2007. Stable isotope and penfeeding trial studies confirm value of horseshoe crab eggs to spring migrant shorebirds in Delaware Bay. Journal of Avian Biology 38:367-376.

Harrington, B.A., pers. comm. 2005. Correspondence with R.I.G. Morrison. September 2005. Biologist, Manomet Bird Observatory, Manomet, Massachusetts.

Harrington, B., and C. Flowers. 1996. The flight of the Red Knot. W.W. Norton and Company, New York and London.

Harrington, B.A., J.M. Hagan, and L.E. Leddy. 1988. Site fidelity and survival differences between two groups of New World Red Knots Calidris canutus. Auk 105:439-445.

Harrington, B.A., N.P. Hill, and B. Nikula. 2010a. Changing use of migration staging areas by Red Knots: an historical perspective from Massachusetts. Waterbirds 33:188-192.

Harrington, B.A., S. Koch, L.J. Niles, and K. Kalasz. 2010b. Red Knots with different winter destinations: differential use of an autumn stopover area. Waterbirds 33:357-363.

Harrington, B.A., and R.I.G. Morrison. 1980. Notes on the wintering areas of Red Knot Calidris canutus rufa in Argentina, South America. Wader Study Group Bulletin 28:40-42.

Harrington, B.A., B. Winn, and S.C. Brown. 2007. Molt and body mass of Red Knots in the eastern United States. Wilson Journal of Ornithology 119:35-42.

Hayman, P., J. Marchant, and T. Prater. 1986. Shorebirds. An identification guide to the waders of the world. Croom Helm Ltd., Beckenham, Kent, United Kingdom.

Henkel, J.R., B.J. Sigel, and C.M. Taylor. 2012. Large-scale impacts of the Deepwater Horizon oil spill: can local disturbance affect distant ecosystems through migratory shorebirds? BioScience 62:676-685.

Hernández, D. 2005. Foraging efficiency of migratory shorebirds relative to horseshoe crab egg availability. M.A. Thesis. Rutgers University, New Brunswick, New Jersey.

Hernández-Alvarez, A., R. Carmona, and N. Arce. 2020. Feeding ecology of Red Knots Calidris canutus roselaari at Golfo de Santa Clara, Sonora, Mexico. Wader Study Group Bulletin 120:194-201.

Hicklin, P.W., and A.L. Spaans. 1993. The birds of the SML rice fields in Suriname: species composition, numbers and toxichemical threats. Technical Report Series 174. Canadian Wildlife Service, Ottawa. 66 pp.

Hoose, P. 2012. Moonbird: A year on the wind with the great survivor B95. Farrar, Straus and Giroux, New York.

Hope, C.E. and T.M. Shortt. 1944. Southward migration of adult shorebirds on the west coast of James Bay, Ontario. Auk 61:572-576.

Hope, D. D., C. Pekarik, M.C. Drever, P.A. Smith, C. Gratto-Trevor, J. Paquet, Y. Aubry, G. Donaldson, C. Friis, K. Gurney, J. Rausch, A.E. McKellar, and B. Andres. 2020. Shorebirds of conservation concern in Canada - 2019. Wader Study 126:88-100.

Howe, M.A., H. Geissler, and B.A. Harrington. 1989. Population trends of North American shorebirds based on the International Shorebird Survey. Biological Conservation 49:185-199.

IAEA (International Atomic Energy Agency). 2004. The algae´s toxic brews. Quoted from USFWS 2014a. Website: http://www.iaea.org/newscenter/features/algalbloom/algae.html [accessed October 2012; no longer available]

IBA (Important Bird Areas) Canada. 2013. IBA Site Summary: Nelson River Estuary and Marsh Point, Hudson Bay Coast, Manitoba. Bird Studies Canada, Port Rowan, Ontario and Nature Canada, Ottawa, Ontario. Website: https://www.ibacanada.ca/site.jsp?siteID=MB008&lang=EN&frame=null&version=2013&range=A&seedet=Y. [accessed August 2020.]

ICFC (International Shorebird Conservation Fund of Canada). 2018. Shorebird conservation at Bahía de San Antonio, Argentina. Online publication. International Shorebird Conservation Fund of Canada, Chester, Nova Scotia. Website: http://icfcanada.org/our-projects/projects/san_antonio [accessed May 2019].

IPCC (Intergovernmental Panel on Climate Change). 2001. Climate Change 2001: Impacts, Adaptation and Vulnerability. Chapter 6. Coastal Zones and Marine Ecosystems. Online. IPCC Secretariat, World Meteorological Organization, Geneva, Switzerland. Website: http://www.grida.no/climate/ipcc_tar/wg2/index.htm. [accessed November 2018].

Islieb, M.E. 1979. Migratory shorebird populations on the Copper River Delta and eastern Prince William Sound, Alaska. Studies in Avian Biology 2:125-129.

IUCN Standards and Petitions Subcommittee. 2017. Guidelines for using the IUCN Red List Categories and Criteria. Version 13 (March 2017). Prepared by the Standards and Petitions Subcommittee. Website: http://www.iucnredlist.org/documents/RedListGuidelines.pdf. [accessed May 2019].

Iwamura, T., H.P. Possingham, I. Chades, C. Minton, N.J. Murray, D.I. Rogers, E.A. Treml, and R.A. Fuller. 2013. Migratory connectivity magnifies the consequences of habitat loss from sea-level rise for shorebird populations. Proceedings of the Royal Society B 280:20130: 1-8. Website: http://dx.doi.org/10.1098/rspb.2013.0325 [accessed May 2019].

IWC (International Waterbird Census). 2020. Flyway trend analyses based on data from the African-Eurasian Waterbird Census from the period of 1967-2015. Calidris canutus (Red Knot) - islandica, NE Canada and Greenland/Western Europe. Online publication. Wetlands International, Wageningen, The Netherlands. Website: http://iwc.wetlands.org/index.php/aewatrends [Accessed September 2020].

Jackson, N.L., K.F. Nordstrom, and DR. Smith. 2010. Armoring of estuarine shorelines and implications for horseshoe crabs on developed shorelines in Delaware Bay. Pp. 195-202 in Shipman, Dethier, Gelfenbaum, Fresh and Dinicola (eds.). Puget Sound Shorelines and the Impacts of Armoring-Proceedings of a State of the Science Workshop, May 2009. United States Geological Survey Scientific Investigations Report 2010-5254, Reston, Virginia.

Johnson, J.A. 2018. Breeding ecology of red knot (Calidris canutus roselaari). Pages 48-49 in Kennedy, L. Annual summary compilation: new or ongoing studies of Alaska shorebirds, December 2018. Alaska Shorebird Group, Anchorage, Alaska.

Johnson, J.A., pers. comm. 2020. Email correspondence with R.I.G. Morrison. March 2020. Shorebird Biologist, US Fish and Wildlife Service, Anchorage, Alaska.

Johnston, V.H., pers. comm. 2015. Cited in: ECCC (Environment and Climate Change Canada) 2017. Wildlife Biologist, Canadian Wildlife Service, Environment and Climate Change Canada, Yellowknife, Northwest Territories.

Johnston, V.H., C.L. Gratto-Trevor, and S.T. Pepper. 2000. Assessment of bird populations in the Rasmussen Lowlands, Nunavut. Canadian Wildlife Service Occasional Paper No. 101: 1-56. Canadian Wildlife Service, Ottawa.

Karnicki, J. 2016. Scarlet experiment. Birds and humans in America. University of Nebraska Press, Lincoln, Nebraska.

Karpanty, S.M., J.D. Fraser, J. Berkson, L.J. Niles, A. Dey, and E.P. Smith. 2006. Horseshoe crab eggs determine Red Knot distribution in Delaware Bay. Journal of Wildlife Management 70:1704-1710.

Kausrud, K.L., A. Mysterud, H. Steen, L.O. Vik, E. Ostbye, B. Cazelles, E. Framstad, A. M. Eikeset, I. Mysterud, T. Solhoy, and N.C. Stenseth. 2008. Linking climate change to lemming cycles. Nature 456:93-98.

Kessel, B., and D.D. Gibson. 1978. Status and distribution of Alaska Birds. Studies in Avian Biology 1:1-100.

Kessel, B. 1989. Birds of the Seward Peninsula, Alaska; their Biogeography, Seasonality and Natural History. University of Alaska Press, Fairbanks, Alaska

Kraan, C., J.A. van Gils, B. Spaans, A. Dekinga, and A.I. Bijleveld. 2009. Landscape-scale experiment demonstrates that Wadden Sea intertidal flats are used to capacity by molluscivore migrant shorebirds. Journal of Animal Ecology 78:1259-1268.

Kreamer, G., and S. Michels. 2009. History of horseshoe crab harvest on Delaware Bay. 299-313 In J.T. Tanacredi et al.(eds.). Biology and Conservation of Horseshoe Crabs. Springer Science and Business Media, Heidelberg, Germany.

Kubelka, V., M. Salek, P. Tomkovitch, Z. Vegvari, R.P. Freckleton, and T. Szekely. 2018. Global pattern of nest predation is disrupted by climate change in shorebirds. Science 362:680-683.

Kubelka, V., M. Salek, P. Tomkovitch, Z. Vegvari, R.P. Freckleton, and T. Szekely. 2019. Response to Comment on "Global pattern of nest predation is disrupted by climate change in shorebirds". Science 364 (6445):eaaw9893.

Kwon, E., E.L. Weiser, R.B. Lanctot, S.C. Brown, H.R. Gates, G. Gilchrist, S.J. Kendall, J.R. Liebezeit, L. McKinnon, E. Nol, D.C. Payer, J. Rausch, D.J. Rinella, S.T. Saalfield, N.R. Senner, P.A. Smith, D. Ward, R.W. Wisseman, and B.K. Sandercock. 2020. Geographic variation in the intensity of warming and phenological mismatch between Arctic shorebirds and invertebrates. Ecological Monographs 89 (Article e01383):1-20.

Lamont, M., pers. comm. 2015. Cited in: ECCC (Environment and Climate Change Canada) 2017. Wildlife Technician, Department of Environment, Government of Nunavut, Kugluktuk, Northwest Territories.

Lank, D.B., R.W. Butler, J. Ireland, and R.C. Ydenberg. 2003. Effects of predation danger on migration strategies of sandpipers. Oikos 103:303-319.

Lathrop, R.G., L. Niles, D. Merchant, T. Farrel, and C. Licitra. 2013. Mapping the critical horseshoe crab spawning habitats of Delaware Bay. Rutgers Center for Remote Sensing and Spatial Analysis, New Brunswick, New Jersey.

Lathrop, R.G., L. Niles, M. Peck, A. Dey, P. Smith, R. Sacatelli, and J. Bognar. 2018. Mapping and modeling the breeding habitat of the western Atlantic Red Knot, Calidris canutus rufa, at local and regional scales. Condor 120:650-665.

Lathrop, R.G., R. Sacatelli, L. Niles, D. Mizrahi, J. Smith, and A. Dey. 2016. Arctic Shorebird Habitat Climate Change Resilience Analysis for the Arctic Migratory Birds Initiative (AMBI) - the Americas Flyway Action Plan. v.1.0, October 2016. Commission for Environmental Cooperation, Montreal, Quebec.

Latimer, C. 2012. Proposed arctic coal mine draws fire. Australian Mining, 11 July 2012. https://www.australianmining.com.au/news/proposed-arctic-coal-mine-draws-fire/. [accessed August 2020]

Leighton, F.A. 1991. The toxicity of petroleum oils to birds. Pp. 43-57 in White, J. and L. Frink (eds.). The effects of oil on wildlife: research, rehabilitation, and general concerns. The Oil Symposium, 16-18 October 1990. Sheridan Press, Hanover, Pennsylvania.

Lemmen, D.S., F.J. Warren, T.S. James and C.S.L. Mercer Clarke (eds). 2016. Canada's Marine Coasts in a Changing Climate. 247pp. Government of Canada, Ottawa, Ontario.

Leyrer, J., N. van Nieuwenhove, N. Crockford, and S. Delaney. 2014. Proposals for Concerted and Cooperative Action for Consideration by CMS COP 11, November 2014. BirdLife International and International Wader Study Group.

Li, X., R. Bellerby, C. Craft, and S. E. Widney. 2018. Coastal wetland loss, consequences, and challenges for restoration. Anthropocene Coasts 1:1-15. Website: https://doi.org/10.1139/anc-2017-0001. [accessed May 2019].

Link, W. A., and J. R. Sauer. 2007. Seasonal components of avian population change: Joint analysis of two large-scale monitoring programs. Ecology 88: 49-55.

Loktionov E.Y., P.S. Tomkovich, and R.R. Porter. 2015. Study of incubation, chick rearing and breeding phenology of Red Knots Calidris canutus rogersi in sub-Arctic Far Eastern Russia aided by geolocators. Wader Study 122:142-152.

López-Lanús, B., P. Grilli, E. Coconier, A. Di Giacomo, and R. Branchs. 2008. Categorización de las aves de la Argentina según su estado de conservación. 2008:64. Informe de Aves Argentinas/AOP y Secretaría de Ambiente y Desarrollo Sustentable, Buenos Aires, Argentina.

Lucena, J.d.A.Y., and K.A.A. Lucena. 2019. Wind energy in Brazil: an overview and perspectives under the triple bottom line. Clean Energy zkz001. Website: https://doi.org/10.1093/ce/zkz001 [accessed May 2019].

Lunn, L. 2013. Hydro power plans leap to new highs. Renewable Energy Focus 14:10-11.

Lusney, T. 2016. Power Market Analysis, Procurement Initiatives: Saskatchewan denies permit for Chaplin Wind and issues new guidelines for wind projects. Power Advisory LLC, 22 September 2016. Website: https://poweradvisoryllc.com/saskatchewan-denies-permit-for-chaplin-wind-and-issues-new-guidelines-for-wind-projects/. [accessed August 2020]

Lyons, J. 2017. Red Knot stopover population estimate for 2017. Unpublished Report. Patuxent Wildlife Research Center, Laurel, Maryland.

Lyons, J.E., A.J. Baker, P.M. González, Y. Aubry, C. Buidin, and Y. Rochepault. 2017. Migration ecology and stopover population size of Red Knots Calidris canutus rufa at Mingan Archipelago after exiting the breeding grounds. Wader Study 124:197-205.

Lyons, J.E., W. J. Kendall, J.A. Royle, S.J. Converse, B.A. Andres, and J.B. Buchanan. 2016. Population size and stopover duration estimation using mark-resight data and Bayesian analysis of a superpopulation model. Biometrics 72: 262-271.

Lyons, J.E., B. Winn, T. Keyes, and K.S. Kalasz. 2018. Post-breeding migration and connectivity of Red Knots in the Western Atlantic. Journal of Wildlife Management 82:383-396.

MacDonald, A. J. 2020. Passage population size, demography, and timing of migration of Red Knots (Calidris canutus rufa) staging in southwestern James Bay. M.Sc. Thesis. 168 pp. Trent University, Peterborough, Ontario.

MacDonald, S.D. 1953. Report on biological investigations at Alert, N.W.T. National Museum of Canada Bulletin 128:241-256.

Manning, T.H. 1952. Birds of the west James Bay and southern Hudson Bay coasts. National Museum of Canada Bulletin 125:1-114.

Manning, T.H., E.O. Hohn, and A.H. Macpherson. 1956. The birds of Banks Island. National Museum of Canada Bulletin 143:1-144.

Manning, T.H., and A.H. Macpherson. 1961. A biological investigation of Prince of Wales Island, N.W.T. Transactions of the Royal Canadian Institute 33:116-239.

Martínez-Curci, N. S, E. Bremer, A.B. Azpiroz, G.E. Battaglia, J.C. Salerno, J.P. Isacch, P.M. González, G.J. Castresana, and P. Rojas. 2015. Annual occurrence of Red Knot Calidris canutus rufa at Punta Rasa, Samborombon Bay, Argentina over a 30-year period (1985-2014). Wader Study 122:236-242.

Martínez-Curci, N., J. P. Isacch, V. L. D'Amico, P. Rojas, and G. J. Castresana. 2020. To migrate or not: drivers of over-summering in a long-distance migratory shorebird. Journal of Avian Biology in press. doi: [10.1111/jav.02401].

Maslo B., J.C. Burkhalter, D. Bushek, T. Yuhas, B. Schumm, J. Burger, J.L. Lockwood. 2020. Assessing conservation conflict: Does intertidal oyster aquaculture inhibit foraging behavior of migratory shorebirds? Ecosphere 11(5):e03097. 10.1002/ecs2.3097.

Mateo-Sagasta, J., S.M. Zadeh and H. Turral. 2017. Water pollution from agriculture: a global review. Executive Summary. United Nations Food and Agriculture Organization, Rome, Italy.

Matus, R., pers. comm. 2020. Email correspondence with R.I.G. Morrison. March 2020. Biologist, Centro de Rehabilitación de Aves Leñadura, Punta Arenas, Chile.

McCrary, M.D., and M.O. Pierson. 2002. Influence of human activity on shorebird beach use in Ventura County, California. In Proceedings of the fifth California Islands symposium, pages 424-427. (Eds. Browne, D. R., Mitchell, K. L., and Chaney, H. W.). Santa Barbara Museum of Natural History, Santa Barbara, California.

McGowan, C.P., J.E. Hines, J.D. Nichols, J.E. Lyons, D.R. Smith, K.S. Kalasz, L.J. Niles, A.D. Dey, N.A. Clark, P.W. Atkinson, C.D.T. Minton, and W. Kendall. 2011. Demographic consequences of migratory stopover: linking red knot survival to horseshoe crab spawning abundance. Ecosphere 2: art69, 1-22. doi:10.1890/ES11-00106.1.

McKellar, A.E., pers. comm. 2020. Email correspondence with Richard Elliot. November 2020. Shorebird Biologist, Canadian Wildlife Service, Environment and Climate Change Canada, Saskatoon, SK.

McKellar, A.E., R.K. Ross, R.I.G. Morrison, L.J. Niles, R.R. Porter, J. Burger, D.J. Newstead, A.D. Dey, and P.A. Smith. 2015. Shorebird use of western Hudson Bay near the Nelson River during migration, with a focus on the Red Knot. Wader Study 122:201-211.

McKellar, A.E., Y. Aubry, M.C. Drever, C.A. Friis, C.L. Gratto-Trevor, J. Paquet, C. Pekarik and P.A. Smith. 2020. Potential Western Hemisphere Shorebird Reserve Network sites in Canada: 2020 update. Wader Study 127:102-112.

Meehan, T., pers. comm. 2020. Email correspondence with Scott Wilson. September 2020. Quantitative Ecologist, National Audubon Society, Boulder, Colorado.

Meireles, A.J.A., A. Gorayeb, D.R.F. Silva, and G.S. Lima. 2013. Socio-environmental impacts of wind farms on the traditional communities of the western coast of Ceará, in the Brazilian Northeast. Journal of Coastal Research Special Issue No. 65:81-86.

Meltofte, H. 1985. Populations and breeding schedules of waders, Charadrii, in high Arctic Greenland. Meddeleser om Grönland 16:43 pp.

Meltofte, H., T. Piersma, H. Boyd, B.J. McCaffery, B. Ganter, V.V. Golovnyuk, K. Graham, C.L. Gratto-Trevor, R.I.G. Morrison, E. Nol, H.-U. Rösner, D. Schamel, H. Schekkerman, M.Y. Soloviev, P.S. Tomkovich, D.M. Tracy, I. Tulp, and L. Wennerberg. 2007. Effects of climate variation on the breeding ecology of Arctic shorebirds. Meddeleser om Grönland (Bioscience) 59:1-48.

Mendez, V., J.A. Alves, J.A. Gill, and T.G. Gunnarsson. 2018. Patterns and processes in shorebird survival rates: a global review. Ibis 160 (4):723-741. Website: https://onlinelibrary.wiley.com/toc/1474919x/2018/160/4 [accessed May 2019].

Mengak, L. and A.A. Dayer. 2020. Defining human disturbance to shorebirds using manager and scientist input. Environmental Management 65:62-73.

Mobley, J.A., pers. comm. 2019. Conversation with R.I.G. Morrison. February 2020. Biologist, AQUASIS (Associação de Pesquisa e Preservação de Ecossistemas Aquáticos), Iparana, Caucaia, Ceará, Brasil.

Morrison, R.I.G. 1975. Migration and morphometrics of European Knot and Turnstone on Ellesmere Island, Canada. Bird-Banding 46:290-301.

Morrison, R.I.G. 1992. Avifauna of the Ellesmere Island National Park Reserve. Canadian Wildlife Service Technical Report Series 158:1-110. Canadian Wildlife Service, Ottawa.

Morrison, R.I.G. 2001. Shorebird population trends and issues in Canada - an overview. Bird Trends 8:1-5.

Morrison, R.I.G. 2004. Using migration counts from eastern Canada to assess productivity of Arctic-breeding shorebirds in relation to climate. The ACIA International Scientific Symposium on Climate Change in the Arctic. AMAP Report No. 2004 (4). Extended Abstract, Poster Session A2. Arctic Monitoring and Assessment Programme, Oslo, Norway.

Morrison, R.I.G. 2006. Body transformations, condition, and survival in Red Knots Calidris canutus travelling to breed at Alert, Ellesmere Island, Canada. Ardea 94:607-618.

Morrison, R.I.G. 2018. Aerial surveys of Red Knots (Calidris canutus rufa) in Tierra del Fuego, January 2018. Unpublished Report for Manomet, Inc., Ottawa, Canada.

Morrison, R.I.G., R.W. Butler, G.W. Beyersbergen, H.L. Dickson, A. Bourget, P.W. Hicklin, J.P. Goosen, R.K. Ross and C.L. Trevor-Gratto. 1995. Potential Western Hemisphere Shorebird Reserve Network sites for shorebirds in Canada: Second edition 1995. Canadian Wildlife Service Technical Report Series 227, Ottawa.

Morrison, R.I.G., R.W. Butler, F.S. Delgado, and R.K. Ross. 1998. Atlas of Nearctic shorebirds and other waterbirds on the coast of Panama. Canadian Wildlife Service Special Publication, Ottawa. 112 pp.

Morrison, R.I.G., N.C. Davidson, and T. Piersma. 2005. Transformations at high latitudes: why do Red Knots bring body stores to the breeding grounds? Condor 107:449-457.

Morrison, R.I.G., N.C. Davidson, and J.R. Wilson. 2007. Survival of the fattest: body stores on migration and survival in red knots Calidris canutus islandica. Journal of Avian Biology 38:479-487.

Morrison, R.I.G., C. Downes, and B. Collins. 1994. Population trends of shorebirds on fall migration in eastern Canada 1974-1991. Wilson Bulletin 106:431-447.

Morrison, R. I. G., C. Espoz, and R. Matus. 2020a. Aerial Surveys of Red Knots (Calidris canutus rufa) in Tierra del Fuego, January 2020. Report (English version). 1-33 pp. Manomet Inc., Manomet, Massacheusetts.

Morrison, R.I.G., R.E. Gill, Jr., B.A. Harrington, S. Skagen, G.W. Page, C.L. Gratto-Trevor, and S.M. Haig. 2001. Estimates of shorebird populations in North America. Canadian Wildlife Service Occasional Paper No.104 1-64. Canadian Wildlife Service, Ottawa.

Morrison, R.I.G., and B.A. Harrington. 1979. Critical shorebird resources in James Bay and eastern North America. Transactions of the North American Wildlife Natural Resources Conference 44:498-507.

Morrison, R.I.G., and B.A. Harrington. 1992. The migration system of the Red Knot Calidris canutus rufa in the New World. Wader Study Group Bulletin 64, Supplement:71-84.

Morrison, R.I.G., and P. Hicklin. 2001. Recent trends in shorebird populations in the Atlantic Provinces. Bird Trends 8:16-19.

Morrison, R.I.G., and K.A. Hobson. 2004. Use of body stores in shorebirds after arrival on High-Arctic breeding grounds. Auk 121:333-344.

Morrison, R.I.G., B.J. McCaffery, R.E. Gill, S.K. Skagen, S.L. Jones, G.W. Page, C.L. Gratto-Trevor, and B.A. Andres. 2006. Population estimates of North American shorebirds, 2006. Wader Study Group Bulletin 111:67-85.

Morrison, R.I.G., D.S. Mizrahi, R.K. Ross, O.H. Ottema, N. de Pracontal, and A. Narine. 2012. Dramatic declines of Semipalmated Sandpipers on their major wintering areas in the Guianas, northern South America. Waterbirds 35:120-134.

Morrison, R.I.G., L.J. Niles, D.S. Mizrahi, K. Ross, C. Espoz, T. Barreto, R. Matus, P.T. Z. Antas, and P. Petracci. 2020b. Status and trends of Red Knot populations wintering in Tierra del Fuego, northern Brazil, and Florida. Wader Study in press.

Morrison, R.I.G., and R.K. Ross. 1989. Atlas of Nearctic shorebirds on the coast of South America. Canadian Wildlife Service Special Publication, Ottawa.

Morrison, R.I.G., and R.K. Ross. 2009. Atlas of Nearctic shorebirds on the coast of Mexico. Canadian Wildlife Service Special Publication. Environment Canada, Ottawa, Ontario.

Morrison, R.I.G., R.K. Ross, and L.J. Niles. 2004. Declines in wintering populations of Red Knots in southern South America. Condor 106:60-70.

Morrison, R.I.G., R.K. Ross, D.S. Mizrahi, J. Mobley, and D. Santos. 2020c. A reassessment of numbers of Red Knots Calidris canutus rufa wintering on the north coast of South America. Manuscript Report for New Jersey Audubon, Ottawa, Ontario.

Motus. 2018. Motus Wildlife Tracking System. Online. Bird Studies Canada, Port Rowan, ON. Website: https://motus.org/ [accessed November 2018].

Myers, J.P. 1986. Sex and gluttony on Delaware Bay. Natural History 95: 68-77.

Myers, J.P., R.I.G. Morrison, P.Z. Antas, B.A. Harrington, T.E. Lovejoy, M. Sallaberry, S.E. Senner, and A. Tarak. 1987. Conservation strategy for migratory species. American Scientist 75:19-26.

Myers-Smith, I.H., B.C. Forbes, M. Wilmking, M. Hallinger, T. Lantz, D. Blok, K.D. Tape, M. Macias-Fauria, U. Sass-Klassen, E. Lévesque, and S. Boudreau. 2011. Shrub expansion in tundra ecosystems: dynamics, impacts and research priorities. Environmental Research Letters 6: 045509.

Nagy, S., S. Flink, and T. Langendoen. 2014. Waterbird Trends1988-2012: Results of trend analyses of data from the International Waterbird Census in the African-Eurasian Flyway. Wetlands International, Ede, The Netherlands.

Najjar, R.G., H.A. Walker, P.J. Anderson, E.J. Barron, R.J. Bord, J.R. Gibson, V.S. Kennedy, C.G. Knight, J.P. Megonigal, and R.E. O'Connor. 2000. The potential impacts of climate change on the mid-Atlantic coastal region. Climate Research 14:219-233.

NASA Earth Observatory. 2004. "Hurricane" Catarina hits Brazil. NASA, Washington, DC. Website: https://earthobservatory.nasa.gov/images/4369/hurricane-catarina-hits-brazil [accessed March 2020].

National Audubon Society. 2020. Audubon Christmas Bird Count. New York, New York. Website: https://www.audubon.org/conservation/science/christmas-bird-count [accessed September 2020].

NatureServe. 2017. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. Online. NatureServe, Arlington, Virginia. Website: http://explorer.natureserve.org. [accessed May 2019].

Navedo, J.G. and J.S. Gutiérrez. 2019. Migratory connectivity and local site fidelity in red knots on the southern Pacific coast of South America. Aquatic Conservation: Marine and Freshwater Ecosystems 29: 670-675.

Nehls, G., S. Witte, N. Dankers, J. de Vlas, F. Quirijns, and P.S. Kristensen. 2009. Quality Status Report 2009. Wadden Sea Ecosystem No. 25. Common Wadden Sea Secretariat, Trilateral Monitoring and Assessment Sea Ecosystem No. 25, 2009. Fishery Thematic Report No. 3.3. In: Quality Status Report 2009 (Marencic and de Vlas [eds.], Ed.). Common Wadden Sea Secretariat, Trilateral Monitoring and Assessment Group, Wilhelmshaven, Germany.

Nettleship, D.N. 1968. The incubation period of the Knot. Auk 85:687.

Nettleship, D. N. 1974. The breeding of the Knot Calidris canutus at Hazen Camp, Ellesmere Island, N.W.T. Polarforschung 44:8-26.

Nettleship, D.N., and W.J. Maher. 1973. The avifauna of Hazen Camp, Ellesmere Island, N.W.T. Polarforschung 43:66-74.

Newstead, D., pers. comm. 2018. Email correspondence with R.I.G. Morrison. March 2018. Director, Coastal Bird Program, Coastal Bend Bays and Estuaries Program, Corpus Christi, Texas.

Newstead, D. and D. LeBlanc. 2018. Use of geolocators to define migratory pathways of Red Knots in Louisiana. Unpubl. report, U.S. Fish and Wildlife Service, Louisiana Ecological Services Field Office, Lafayette, Louisiana.

Newstead, D.J., L.J. Niles, R.R. Porter, A.D. Dey, J. Burger, S.P. Flemming, and O.N. Fitzsimmons. 2013. Geolocation reveals mid-continent migratory routes and Texas wintering areas of Red Knots Calidris canutus rufa. Wader Study Group Bulletin 120:53-59.

Niles, L.J. 2010. A rube with a view: Delaware Bay update 5/28/10-The importance of good habitat. Greenwich, New Jersey. Website: http://arubewithaview.com/2010/05/29/delaware-bay-update-52810-the-importance-of-good-habitat/ [accessed December 2019].

Niles, L.J. 2012. A rube with a view: The challenge of the rice fields of Mana. Online. Greenwich, New Jersey. Website: www.arubewithaview.com/2012/08/26/the-challege-of-the-rice-fields-of-mana/ [accessed May 2019].

Niles, L., Y. Aubry, S. Gates, A. Dey, N. de Pracontal, and A. Levesque. 2013a. Status of Migratory Shorebirds in French Guiana and Guadeloupe With Emphasis On Red Knots And Ruddy Turnstones. 1-30. Environment Canada and Groupe d'Étude et de Protection des Oiseaux en Guyane. Unpublished Report, Laval, Québec.

Niles, L., A. Dey, D. Mizrahi, L. Tedesco, and K. Sellers. 2012b. Second Report: Damage from superstorm Sandy to horseshoe crab breeding and shorebird stopover habitat on Delaware Bay. Report to New Jersey Natural Lands Trust, December 7, 2012, New Jersey.

Niles, L., H. Sitters, A. Dey, A. Baker, R.I.G. Morrison, D. Hernández, K.E. Clark, B. Harrington, M. Peck, P. González, K. Bennett, P. Atkinson, N. Clark, and C. Minton. 2005. Status of the Red Knot (Calidris canutus rufa) in the Western Hemisphere. New Jersey Department of Environmental Protection, Division of Fish and Wildlife, Endangered and Nongame Species Program, Trenton, New Jersey.

Niles, L.J., J. Bart, H.P. Sitters, A.D. Dey, K.E. Clark, P.W. Atkinson, A.J. Baker, K.A. Bennett, K.S. Kalasz, N.A. Clark, J. Clark, S. Gillings, A.S. Gates, P.M. González, D.E. Hernández, C.D.T. Minton, R.IG. Morrison, R. R. Porter, R.K. Ross, and C.R. Veitch. 2009. Effects of horseshoe crab harvest in Delaware Bay on Red Knots: Are harvest restrictions working? BioScience 59:153-164.

Niles, L.J., J. Burger, R.R. Porter, A.D. Dey, S. Koch, B. Harrington, K. Iaquinto, and M. Boarman. 2012a. Migration pathways, migration speeds and non-breeding areas used by northern hemisphere wintering Red Knots Calidris canutus of the subspecies rufa. Wader Study Group Bulletin 119:195-203.

Niles, L.J., J. Burger, R.R. Porter, A.D. Dey, C.D.T. Minton, P.M. González, A.J. Baker, J.W. Fox, and C. Gordon. 2010b. First results using light level geolocators to track Red Knots in the Western Hemisphere show rapid and long intercontinental flights and new details of migration pathways. Wader Study Group Bulletin 117:123-130.

Niles, L.J., A.D. Dey, N.J. Douglass, J.A. Clark, A.S. Gates, B.A. Harrington, M.K. Peck, and H.P. Sitters. 2006. Red Knots wintering in Florida: 2005/6 expedition. Wader Study Group Bulletin 111:86-99.

Niles, L.J., H.P. Sitters, A.D. Dey, N. Arce, P.W. Atkinson, V. Ayala-Perez, A.J. Baker, J.B. Buchanan, R. Carmona, N.A. Clark, C. Espoz, J.D. Fraser, P.M. González, B.A. Harrington, D.E. Hernández, K.S. Kalasz, R. Matus, B.J. McCaffery, C.D.T. Minton, R.I.G. Morrison, M.K. Peck, W. Pitts, I.L. Serrano, and B.D. Watts. 2010c. Update to the status of the Red Knot Calidris canutus in the Western Hemisphere, April 2010. Unpublished report, Manomet, New Jersey.

Niles, L.J., H.P. Sitters, A.D. Dey, P.W. Atkinson, A.J. Baker, K.A. Bennett, R. Carmona, K.E. Clark, N.A. Clark, C. Espoz, P.M. González, B.A. Harrington, D.E. Hernández, K.S. Kalasz, R.G. Lathrop, R. Matus, C.D.T. Minton, R.I.G. Morrison, M.. Peck, W. Pitts, R.A. Robinson, and I.L. Serrano. 2008. Status of the Red Knot (Calidris canutus rufa) in the Western Hemisphere. Studies in Avian Biology 36:xviii + 1-185.

Niles, L.J., H.P. Sitters, A.D. Dey, P.W. Atkinson, A.J. Baker, K.A. Bennett, K.E. Clark, N.A. Clark, C. Espoz, P.M. González, B.A. Harrington, D.E. Hernández, K.S. Kalasz, R. Matus, C.D.T. Minton, R.I.G. Morrison, M.K. Peck, and I.L. Serrano. 2007. Status of the Red Knot (Calidris canutus rufa) in the Western Hemisphere. New Jersey Department of Environmental Protection, Division of Fish and Wildlife, Endangered and Nongame Species Program, Trenton, New Jersey.

Niles, L.J., H. Sitters, A. Dey, P.W. Atkinson, A.J. Baker, K.A. Bennett, K.E. Clark, N.A. Clark, C. Espoz, P.M. González, B.A. Harrington, D.E. Hernández, K.S. Kalasz, R. Matus, C.D.T. Minton, R.I.G. Morrison, M.K. Peck, and I.L. Serrano. 2010a. Red Knot Conservation Plan for the Western Hemisphere (Calidris canutus), Version 1.1. Manomet Center for Conservation Sciences, Manomet, Massachusetts.

Niles, L.J., J.A.M. Smith, D.F. Daly, W. Dillingham, W. Shadel, A.D. Dey, M.S. Danihel, S. Hafner, and D. Wheeler. 2013b. Restoration of horseshoe crab and migratory shorebird habitat on five Delaware Bay beaches damaged by Superstorm Sandy. Website: http://arubewithaview.com/wordpress/wp-content/uploads/2012/12/RestorationReport_112213.pdf [accessed May 2019].

Niquil, N., G. Kerleguer, G. Leguerrier, P. Richard, H. Legrand, C. Dupuy, P.-Y. Pascal, and C. Bachet. 2006. How would the loss of production due to an herbicide have repercussions in the food web of an intertidal mudflat? Sensitivity analysis of an inverse model for Brouage mudflat, Marennes-Oléron Bay, France. Cahiers de Biologie Marine 47:63-71.

NJA (New Jersey Audubon). 2020. Aerial Surveys for Shorebirds Wintering on Brazil's Northern South American Coast with an emphasis on Semipalmated Sandpipers and Red Knots - Phase 2. Unpublsihed Report for National Fish and Wildlife Foundation. 20pp. NJA, Center for Research and Eduction, Cape May Court House, New Jersey.

NSID (National Snow and Ice Data Center). 2015. Climate change in the Arctic. Boulder, Colorado. Website: https://nsidc.org/cryosphere/arctic-meteorology/climate_change.html. [accessed May 2019].

Oost P., J. Hofstede, R. Weisse, F. Baart, G. Janssen, and R. Zijlstra. 2017. Climate change. In: Wadden Sea Quality Status Report 2017. Eds.: Kloepper S. et al., Common Wadden Sea Secretariat, Wilhelmshaven, Germany. Last updated 21.12.2017. Website: qsr.waddensea-worldheritage.org/reports/climate-change [accessed March 2020].

Ouellet, H. 1969. Les oiseaux de l'île Anticosti, province de Québec, Canada. Musée national des sciences naturelles, Ottawa, Ontario.

Ottema, O.H., J.H. J.M. Ribot, and A.L. Spaans. 2009. Annotated Checklist of the Birds of Suriname. World Wildlife Fund Guianas, Paramaribo, Suriname.

Parker, L.M., P.M. Ross, W.A. O'Connor, H.O. Portner, E. Scanes, and J.M. Wright. 2013. Predicting the response of molluscs to the impact of ocean acidification. Biology 2:651-692.

Parmelee, D.F., and S.D. MacDonald. 1960. The birds of west-central Ellesmere Island and adjacent areas. National Museum of Canada Bulletin 169:1-103.

Parmelee, D.F., H.A. Stephens, and R.H. Schmidt. 1967. The birds of southeastern Victoria Island and adjacent small islands. National Museum of Canada Bulletin 222:1-229.

Paschoa, C. 2013. North Brazil oil - deepwater oil off the State of Pará. Marine Technology News. Website: www.marinetechnologynews.com/blogs/north-brazil-oil-e28093-deepwater-oil-off-the-state-of-para-700381 [accessed May 2019].

Pellegrini, B.d.S. and H.J.P.S. Ribeiro. 2019. Exploratory plays of Pará-Maranhão and Barreirinhas basins in deep and ultra-deep waters, Brazilian Equatorial Margin. Brazilian Journal of Geology 48:485-502.

Peters, K.A., and D.L. Otis. 2006. Shorebird roost-site selection at two temporal scales: is human disturbance a factor? Journal of Applied Ecology 44:196-209.

Peterson, C.H., M.J. Bishop, L.M. D'Anna, and G.A. Johnson. 2014. Multi-year persistence of beach habitat degradation from nourishment using coarse shelly sediment. Science of the Total Environment 487:481-492.

Peterson, C.H., S.D. Rice, J.W. Short, D. Esler, J.L. Bodkin, B.E. Ballachey, and D.B. Irons. 2003. Long-term ecosystem response to the Exxon Valdez oil spill. Science 302:2082-2086.

Petracci, P., pers. comm. 2019. Email correspondence with R.I.G. Morrison. June 2019. Biologist and Tutor, National University of La Plata, La Plata, Argentina.

Piersma, T. 1998. Phenotypic flexibility during migration: optimization of organ size contingent on the risks and rewards of fueling and flight? Journal of Avian Biology 29:511-520.

Piersma, T., and A.J. Baker. 2000. Life history characteristics and the conservation of migratory shorebirds. In: Behaviour and conservation (Gosling and Sutherland [eds.], Ed.). Cambridge University Press, Cambridge, United Kingdom.

Piersma, T., and N. Davidson. 1992. The migration of Knots. Wader Study Group Bulletin 64, Supplement:209 pp.

Piersma, T., G.A. Gudmundsson, and K. Lilliendahl. 1999. Rapid changes in the size of different functional organ and muscle groups during refueling in a long-distance migrating shorebird. Physiological and Biochemical Zoology 72:405-415.

Piersma, T., A. Hoekstra, A. Dekinga, A. Koolhaas, and P. Wolf. 1993. Scale and intensity of intertidal habitat use by knots Calidris canutus in the Western Wadden Sea in relation to food, friends and foes. Netherlands Journal of Sea Research 31:331-357.

Piersma, T., A. Koolhaas, A. Dekinga, J.J. Beukema, R. Dekker, and K. Essink. 2001. Long-term indirect effects of mechanical cockle-dredging on intertidal bivalve stocks in the Wadden Sea. Journal of Animal Ecology 38:976-990.

Piersma, T., and B. Spaans. 2004. Inzicht uit vergelijkingen: ecologisch onderzoek aan wadvogels wereldwijd. Limosa 77:43-54.

Piersma, T., I. Tulp, Y. Verkuil, P. Wiersma, G.A. Gudmundsson, and Å. Lindstrom. 1991. Arctic sounds on temperate shores: the occurrence of song and ground display in Knots Calidris canutus at spring staging sites. Ornis Scandinavica 22:404-407.

Pizzolato, L., S.E.L. Howell, C. Derksen, J. Dawson, and L. Copland. 2014. Changing sea ice conditions and marine transportation activity in Canadian Arctic waters between 1990 and 2012. Climatic Change 123:161-173.

Pleske, T. 1928. Birds of the Eurasian tundra. Memoirs of the Boston Society for Natural History 6:111-485.

Pomeroy, A.C., R.W. Butler, and R.C. Ydenberg. 2006. Experimental evidence that migrants adjust usage at a stopover site to trade off food and danger. Behavioral Ecology 17:1041-1045.

Portenko, L.A. 1981. Birds of the Chukchi Peninsula and Wrangel Island. Vol. 1. New Delhi: Translation of Russian text by Amerind Publishing Co. Pvt. Ltd.

Porter, R., pers. comm. 2020. Email correspondence with R.I.G. Morrison. April 2020. Independent Researcher, Ambler, Pennsylvania.

Porter, R., and P.A. Smith. 2013. Techniques to improve the accuracy of location estimation using light-level geolocation to track shorebirds. Wader Study Group Bulletin 120:147-158.

Prater, A.J., J.H. Marchant, and J. Vuirinen. 1977. Guide to the identification and aging of Holarctic waders. British Trust for Ornithology, Tring, United Kingdom.

Rakhimberdiev, E., P.J. van den Hout, M. Brugge, B. Spaans, and T. Piersma. 2015. Seasonal mortality and sequential density dependence in a migratory bird. Journal of Avian Biology 46:1-10. doi: 10.1111/jav.00701.

Rare. 2018. Protecting the winter habitat of the famed Red Knot. Program Brochure. Rare, Arlington, Virginia.

Rausch, J., and P.A. Smith. 2013. Notes on critical habitat for Red Knot. Unpublished Report. Environment Canada, Ottawa.

Resource Development Council. 2015. Alaska's oil and gas industry. Website: www.akrdc.org/oil-and-gas#background [accessed May 2019]

Rhoda, R., and T. Burton. 2010. Geo-Mexico: the geography and dynamics of modern Mexico. Sombrero Books, Ladysmith, British Columbia.

Ridgely, R.S., T.F. Allnutt, T. Brooks, D.K. McNicol, D.W. Mehlman, B.E. Young, and J.R. Zook. 2007. Digital Distribution Maps of the Birds of the Western Hemisphere, version 3.0. NatureServe, Arlington, Virginia.

Roberge, B., and G. Chapdelaine. 2000. Suivi des impacts du déversement de pétrole du Gordon C. Leitch sur les populations d'oiseaux nicheurs de la réserve de parc national de l'Archipel-de-Mingan (QC), Canada. Série des rapports techniques 359. xi+21p-Service canadien de la faune, région du Québec, Environnement Canada, Sainte-Foy, Québec. https://www.pc.gc.ca/fr/pn-np/qc/mingan/decouvrir-discover/Naturel/6-recherche-research/b-result/6 [accessed August 2020].

Rodrigues, A.A.F. 2000. Seasonal abundance of Nearctic shorebirds in the Gulf of Maranhao, Brazil. Journal of Field Ornithology 71:665-675.

Rodrigues, A.A.F., and A.T.L. Lopes. 2000. The occurrence of Red Knots Calidris canutus on the north-central coast of Brazil. Bulletin of the British Ornithologists' Club 120:251-259.

Rogers, D.I., T. Piersma, and C. Hassell. 2006. Roost availability may constrain shorebird distribution: Exploring the energetic costs of roosting and disturbance around a tropical bay. Biological Conservation 133:225-235.

Roselaar, C.S. 1983. Subspecies recognition in knot Calidris canutus and occurrence of races in western Europe. Beaufortia 33:97-109.

Rosenberg, D.M., F. Berkes, R.A. Bodaly, R.E. Hecky, C.K. Kelly, and J.W.M. Rudd. 1997. Large-scale impacts of hydroelectric development. Environmental Reviews 5:27-54.

Rosenberg, D.M., R.A. Bodaly, and P.J. Usher. 1995. Environmental and social impacts of large scale hydroelectric development: who is listening? Global Environmental Change 5:127-148.

Ross, R.K., K. Abraham, R. Clay, B. Collins, J. Iron, R. James, and D.W.R. McLachlin. 2003. Ontario Shorebird Conservation Plan. Environment Canada, Downsview, Ontario.

Sahlin, J. 2010. Utilisation des habitats des Îles-de-la-Madeleine par le Bécasseau Maubèche (Calidris canutus rufa) et les autres limicoles. Canadian Wildlife Service unpublished report. Sainte-Foy, Québec. 67pp.

Sahlin, J. 2011. Habitats et alimentation du Bécasseau maubèche (Calidris canutus rufa) sur la plaine intertidale de Fatima, Îles-de-la-Madeleine (Québec) et impact potentiel d'un nouveau site maricole. Canadian Wildlife Service unpublished report. Sainte-Foy, Québec. 77pp.

Salafsky, N., D. Salzer, A.J. Stattersfield, C. Hilton-Taylor, R. Neugarten, S.H.M. Butchart, B. Collen, N. Cox, L.L. Master, S. O'Connor, and D. Wilkie. 2008. A standard lexicon for biodiversity conservation: unified classifications of threats and actions. Conservation Biology 22:897-911.

Salomonsen, F. 1950. Grönland Fugle. The Birds of Greenland. Munksgaard, Kobenhavn, Denmark.

Salomonsen, F. 1967. Fuglene pa Grönland. Rhodos, Kobenhavn, Denmark.

Sansom, A., J.W. Pearce-Higgins, and D.J.T. Douglas. 2016. Negative impact of wind energy development on a breeding shorebird assessed with a BACI study design. Ibis 158:541-555.

Scherer, A.L. and M.V. Petry. 2012. Seasonal variation in shorebird abundance in the state of Rio Grande do Sul, southern Brazil. Wilson Journal of Ornithology 124:40-50.

Schlacher, T.A., R. Noriega, A. Jones, and T. Dye. 2012. The effects of beach nourishment on benthic invertebrates in eastern Australia: impacts and variable recovery. Science of the Total Environment 435-436:411-417.

Schneider, D.C., and B.A. Harrington. 1981. Timing of shorebird migration in relation to prey depletion. Auk 98:801-811.

Schulte, S., and A. Sterling. 2019. Oiled coasts mean oiled shorebirds: Brazil oil spill impacts shorebirds. Manomet, Inc., Manomet, Massachusetts. Website: https://www.manomet.org/publication/oiled-coasts-mean-oiled-shorebirds/ [accessed March 2020].

Schultz M., D.M. Fleet, K.C.J. Camphuysen, M. Schulze-Dieckhoff, and K. Laursen. 2017. Oil pollution and seabirds. In: Wadden Sea Quality Status Report 2017. Eds.: Kloepper S. et al., Common Wadden Sea Secretariat, Wilhelmshaven, Germany. Last updated 01.03.2018. qsr.waddenseaworldheritage.org/reports/oil-pollution-and-seabirds [accessed March 2020].

Senner, N.R. 2012. One species but two patterns: populations of the Hudsonian Godwit (Limosa haemastica) differ in spring migration timing. Auk 129:670-682.

Senner, N. R., M. Stager, and B. K. Sandercock. 2017. Ecological mismatches are moderated by local conditions for two populations of a long-distance migratory bird. Oikos 126: 61-72. First published online 2016: doi: 10.1111/oik.03325.

Sinclair, Pam, pers. comm. 2019. Email correspondence with R.D. Elliot. November 2019. Bird Conservation Biologist, Canadian Wildlife Service - Northern Region, Environment and Climate Change Canada, Whitehorse, Yukon.

Siok, D., and B. Wilson. 2011. Using dredge spoils to restore critical American horseshoe crab (Limulus polyphemus) spawning habitat at the Mispillion Inlet. Delaware Coastal Program, Dover, Delaware.

Skagen, S.K., and G. Thompson. 2013. Northern Plains/Prairie Potholes Regional Shorebird Conservation Plan. United States Shorebird Conservation Plan, Lakewood, Colorado.

Sklar, F.H., and J.A. Browder. 1998. Coastal environmental impacts brought about by alterations to freshwater flow in the Gulf of Mexico. Environmental Management 22:547-562.

Smith, D.R., and S.F. Michels. 2006. Seeing the elephant: importance of spatial and temporal coverage in a large-scale volunteer-based program to monitor horseshoe crabs. Fisheries 31:485-491.

Smith, F.M., B.D. Watts, J.E. Lyons, T.S. Keyes, and B. Winn. 2017. Investigating Red Knot Migration Ecology along the Georgia Coast: Fall 2015 Season and 2013, 2015-16 Spring Season Summaries. Center for Conservation Biology Technical Report Series: CCBTR-17-04. College of William and Mary/Virginia Commonwealth University, Williamsburg, Virginia.

Smith, L.C., and S.R. Stephenson. 2013. New trans-Arctic shipping routes navigable by mid-century. Proceedings of the National Academy of Science USA 110: 4871-4872. doi: 10.1073/pnas.1214212110.

Smith, P.A., pers. comm. 2019. Email correspondence with R.I.G. Morrison and R.D. Elliot. November 2019. Member, COSEWIC Birds Specialist Sub-committee; Research Scientist, Wildlife and Landscape Science Directorate, Environment and Climate Change Canada, Ottawa, Ontario.

Smith, P.A., pers. comm. 2020. Comments on Draft Status Report for Red Knot. March and December 2020. Member, COSEWIC Birds Specialist Sub-committee; Research Scientist, Wildlife and Landscape Science Directorate, Environment and Climate Change Canada, Ottawa, Ontario.

Smith, P.A., L. McKinnon, H. Meltofte, R.B. Lanctot, A.D. Fox, J.O. Leafloor, M. Soloviev, A. Franke, K. Falk, M. Golovatin, V. Sokolov, A. Sokolov, and A.C. Smith. 2020. Status and trends of tundra birds across the circumpolar Arctic. Ambio 49: 732-748. https://doi.org/10.1007/s13280-019-01308-5.

Soldaat L., Visser H., M. van Roomen, and A. van Strien. 2007. Smoothing and trend detection in waterbird monitoring data using structual time-series analysis and the Kalman filter. Journal of Ornithology 148: 351-357.

Soniak, M. 2015. Saving São Paulo's shorebirds. Hakai Magazine, 16 June 2015. Tula Foundation, Victoria, British Columbia.

Sorensen, L., and L. Douglas. 2013. She did not die in vain. Website: www.scscb.org/news/machi-she-did-not-die-in-vain.htm. [accessed November 2018].

Soto-Montoya, E., R. Carmona, M. Gómez, V. Ayala-Pérez, N. Arce, and G.D. Danemann. 2009. Oversummering and migrant Red Knots at Golfo de Santa Clara, Gulf of California, Mexico. Wader Study Group Bulletin 116:191-194.

Sprandel, G.L., J.A. Gore, and D.T. Cobb. 1997. Winter Shorebird Survey. Final performance report. Florida Game and Fresh Water Fish Commission, Tallahassee, Florida.

Stewart, G.B., A.S. Pullin, and C.F. Coles. 2007. Poor evidence-base for assessment of windfarm impacts on birds. Environmental Conservation 34:1-11. doi:10.1017/S0376892907003554.

Stillman, R.A., A.D. West, J.D. Goss-Custard, S. McGrorty, N.J. Frost, D.J. Morrisey, A.J. Kenny, and A.L. Drewitt. 2005. Predicting site quality for shorebird communities: a case study on the Humber Estuary, United Kingdom. Marine Ecology Progress Series 305:203-217.

Taylor, P.D., T.L. Crewe, S.A. Mackenzie, D. Lepage, Y. Aubry, Z. Crysler, G. Finney, C.M. Francis, C.G. Gugliemo, D.J. Hamilton, R.L. Holberton, P.H. Loring, G.W. Mitchell, D. Norris, J. Paquet, R.A. Ronconi, J. Smetzer, P.A. Smith, L.J. Welch, and B.K. Woodworth. 2017. The Motus Wildlife Tracking System: a collaborative research network to enhance the understanding of wildlife movement. Avian Conservation and Ecology 12:8. https://doi.org/10.5751/ACE-00953-120108.

Thompson, A. 2009. Why Pacific hurricanes hit the Americas so rarely. Live Science 1 September 2009. Live Science, Future US, New York, New York. Website: https://www.livescience.com/7866-pacific-hurricanes-hit-americas-rarely.html [accessed March 2020].

Toews, D.P.L., pers. comm. 2019. Email correspondence with R.D. Elliot. September 2019. Member, COSEWIC Birds Specialist Sub-committee; Assistant Professor, Department of Biology, Pennsylvania State University, State College, Pennsylvania.

Tomkovich, P.S. 1992. An analysis of the geographical variability in knots Calidris canutus based on museum skins. Wader Study Group Bulletin 64, Supplement:17-23.

Tomkovich, P.S. 2001. A new subspecies of Red Knot Calidris canutus from the New Siberian Islands. Bulletin of the British Ornithologists' Club 121:257-263.

Tomkovich, P.S. and A.G. Dondua. 2008. Red Knots on Wrangel Island: results of observations and catching in summer 2007. Wader Study Group Bulletin 115:102-109.

Tomkovich, P.S. and M. Soloviev. 1994. Site fidelity in high arctic breeding waders. Ostrich 65:174-180.

Tomkovich, P.S., and M.Y. Soloviev. 1996. Distribution, migrations and biometrics of knots Calidris canutus canutus on Taimyr, Siberia. Ardea 84:85-98.

Tsipoura, N. and J. Burger. 1999. Shorebird diet during spring migration stopover on Delaware Bay. Condor 101635-644.

U.S. Shorebird Conservation Plan. 2004. High priority shorebirds - 2004. Unpublished Report. U. S. Fish and Wildlife Service, Arlington, Virginia.

U.S. Shorebird Conservation Plan Partnership. 2017. U.S. shorebirds of conservation concern - 2016. Website: https://www.shorebirdplan.org/science/assessment-conservation-status-shorebirds/ [accessed May 2019].

U.S. Shorebird Conservation Plan Partnership. 2018. Program for regional and international shorebird monitoring (PRISM). Website: https://www.shorebirdplan.org/science/program-for-regional-and-international-shorebird-monitoring/ [accessed November 2018].

USCCSP (U.S. Climate Change Science Program) 2009a. Thresholds of climate change in ecosystems. U.S. Climate Change Science Program synthesis and assessment product 4.2. U.S. Geological Survey, Reston, Virginia.

USCCSP (U.S. Climate Change Science Program) 2009b. Coastal sensitivity to sea-level rise: A focus on the Mid-Atlantic Region. U.S. Climate Change Science Program synthesis and assessment product 4.1. U.S. Geological Survey, Reston, Virginia.

USFWS (United States Fish and Wildlife Service). 2011. Endangered and Threatened wildlife and plants; 90-day finding on a petition to list the Red Knot subspecies Calidris canutus roselaari as Endangered. Federal Register 76, No. 2: Website: www.federalregister.gov/articles/2011-01/04/2010-33187/endangered-and-threatened-wildlife-and-plants-90-day-finding-on-a-petition-to-list-the-red-knot [accessed November 2018].

USFWS (United States Fish and Wildlife Service). 2014a. Rufa Red Knot Background Information and Threats Assessment. Supplement to Endangered and Threatened Wildlife and Plants; Final Threatened Status for the Rufa Red Knot (Calidris canutus rufa). [Docket No. FWS-R5-ES-2013-0097; RIN AY17]. U.S. Fish and Wildlife Service, Northeast Region, New Jersey Field Office, Pleasantville, New Jersey.

USFWS (United States Fish and Wildlife Service). 2014b. Endangered and Threatened Wildlife and Plants; Threatened Species. Status for the Rufa Red Knot; Final Rule. USA Federal Register 79, No. 238:73706-73748.

USFWS (United States Fish and Wildlife Service). 2015. Status of Species - Red Knot (Calidris canutus rufa). Unpublished Report. 1-48. United States Fish and Wildlife Service, Washington.

USFWS (United States Fish and Wildlife Service). 2017. Migratory Bird Treaty Act of 1918. Website: https://www.fws.gov/laws/lawsdigest/MIGTREA.HTML [accessed January 2019].

USFWS (United States Fish and Wildlife Service). 2019. Recovery document for the rufa Red Knot (Calidris canutus rufa) March 2019. Website: 2019fws.gov/docs/recovery_plan/20190409%20Red%20Knot%20Recovery%20Outline%20final%20signed.pdf [accessed September 2019].

USNOHAB (U.S. National Office for Harmful Algal Blooms). 2020. Harmful Algae. U.S. National Office for Harmful Algal Blooms, Woods Hole, Massachusetts. Website: https://www.whoi.edu/website/redtide/home/ [accessed March 2020].

van Beusekom J.E.E., P. Bot, J. Carstensen, A. Grage, K. Kolbe, H.-J. Lenhart, J. Pätsch, T. Petenati, and J. Rick. 2017. Eutrophication. In: Wadden Sea Quality Status Report 2017. Eds.: Kloepper S. et al., Common Wadden Sea Secretariat, Wilhelmshaven, Germany. Last updated 05.11.2018. qsr.waddensea-worldheritage.org/reports/eutrophication [accessed March 2020].

van den Hout, P.J. 2009. Mortality is the tip of an iceberg of fear: Peregrines Falco peregrinus and shorebirds in the Wadden Sea. Limosa 82:122-133. (Original article in Dutch: Mortaliteit is het topje van een ijsberg van angst Over lechtvalken en steltlopers in de Waddenzee.)

van den Hout, P.J. 2010. Struggle for safety: Adaptive responses of wintering waders to their avian predators. Ph.D. Thesis. University of Groningen, Groningen, The Netherlands.

van Dusen, B. M., S.R. Fegley, and C.H. Peterson. 2012. Prey distribution, physical habitat features, and guild traits interact to produce contrasting shorebird assemblages among foraging patches. PLOS One 7: e52694. https://doi.org/10.1371/journal.pone.0052694.

van Gils, J.A., S. Lisovski, T. Lok, W. Meissner, A. Ozarowska, J. de Fouvw, E. Rakhimberdiev, M.Y. Soloviev, T. Piersma, and M. Klaassen. 2016. Body shrinkage due to Arctic warming reduces red knot fitness in tropical wintering range. Science 352:819-821.

van Roomen, M.K. Laursen, C. van Turnhout, E. van Winden, J. Blew, K. Eskildsen, K. Gunther, B. Halterlein, R. Kleefstra, P. Potel, S. Schrader, G. Luerssen, and B.J. Ens. 2012. Signals from the Wadden sea: Population declines dominate among waterbirds depending on intertidal mudflats. Ocean and Coastal Management 68:79-88.

Van Roomen, M.K., pers. comm. 2020. Email correspondence with R.I.G. Morrison. August 2020. Senior Project Manager, Monitoring, Sovon (Dutch Centre for Field Ornithology), Nijmegen, The Netherlands.

Verkuil, Y., pers. comm. 2019. Conversation with R.I.G. Morrison. September 2019. Researcher, University of Groningen, The Netherlands.

Verkuil, Y., J.R. Conklin, and T. Piersma. 2017. Genetic evidence for two populations of roselaari Red Knots migrating along the Pacific coast of the Americas. Abstract Book 7th meeting of the Western Hemisphere Shorebird Group, p. 84. Western Hemisphere Shorebird Group and Corbidi, Lima, Peru.

Vermeer, K., R.W. Risenbrough, A.L. Spaans, and L.M. Reynolds. 1974. Pesticide effects on fishes and birds in rice fields of Suriname, South America. Environmental Pollution 7: 217-236.

Visser H. 2004. Estimation and detection of flexible trends. Atmospheric Environment 38: 4135-4145.

Watts, B. D. 2009a. Conservation in conflict: peregrines vs red knots. The Center for Conservation Biology, College of William and Mary and Virginia Commonwealth University, Williamsburg, Virginia. Website: https://ccbbirds.org/2009/09/01/conservation-in-conflict-peregrines-vs-red-knots/#:~:text=A%20red%20knot%20band%20recovered%20from%20peregrine%20falcon,location%20when%20both%20are%20of%20high%20conservation%20concern [accessed August 2020].

Watts, B.D. 2009b. End of an era: Metompkin peregrine tower removed after 25 years. The Center for Conservation Biology, College of William and Mary and Virginia Commonwealth University, Williamsburg, Virginia. Website: https://ccbbirds.org/2009/09/09/end-of-an-era-metompkin-peregrine-tower-removed-after-25-years/. [accessed August 2020.]

Watts, B. D., M.A. Byrd, E.K. Mojica, S.M. Padgett, S.R. Harding, and C.A. Koppie 2018. Recovery of Peregrine Falcons in Virginia. Ornis Hungarica 26:104-113. DOI: 10.1515/ orhu-2018-0018.

Watts, B.D., K.E. Clark, C.A. Koppie, G.D. Therres, M.A. Byrd, and K.A. Bennett. 2015. Establishment and growth of the Peregrine Falcon breeding population within the mid-Atlantic coastal plain. Journal of Raptor Research 49:359-366.

Watts, B., and B. Truitt. 2021. Conservation in conflict: The impact of nesting Peregrine Falcons on the distribution of migrant Red Knots along the Virginia barrier islands. In Abstracts, 33rd Annual Meeting - Waterbird Society. Waterbird Society, Cape May, New Jersey. PLoS ONE 16(1).

Watts, B., and B. Truitt. 2015. Spring migration of Red Knots along the Virginia Barrier Islands. Journal of Wildlife Management 79:288-295.

Watts, B.D., and C. Turrin. 2016. Assessing hunting policies for migratory shorebirds throughout the Western Hemisphere. Wader Study 123:6-15.

Wauchope, H.S., J.D. Shaw, O. Varpe, E.G. Lappo, D. Boertmann, R B. Lanctot, and R.A. Fuller. 2016. Rapid climate-driven loss of breeding habitat for Arctic migratory birds. Global Change Biology doi: 10.1111/geb.13404:

WDA (Washington Department of Agriculture). 2017. Spartina eradication program 2017 Progress Report. Washington Department of Agriculture. Olympia, Washington. Website: https://cms.agr.wa.gov/WSDAKentico/Documents/PP/PestProgram/505-FinalSpartinaReport2017.pdf [accessed April 2020].

WDFW (Washington Department of Fish and Wildlife). 2015. State Wildlife Action Plan. Washington Department of Fish and Wildlife, Olympia, Washington. Website: http://wdfw.wa.gov/publications/01742/wdfw01742.pdf [accessed November 2018].

WDFW (Washington Department of Fish and Wildlife). 2020. State Wildlife Action Plan. Washington Department of Fish and Wildlife, Olympia, Washington. Website: https://wdfw.wa.gov/species-habitats/at-risk/swap [accessed March 2020].

Webster, P.J., G.J. Holland, J.A. Curry, and H.-R. Chang. 2005. Changes in tropical cyclone number, duration, and intensity in a warming environment. Science 309:1844-1846.

Wege, D.C., W. Burke, and E.T. Reed 2014. Migratory shorebirds in Barbados: hunting, management and conservation. BirdLife International, Cambridge, UK. Website: https://www.cms.int/sites/default/files/document/Shorebird%20Conservation%20Trust.pdf [accessed August 2020].

West, A.D., J.D. Goss-Custard, R.A. Stillman, R.W.G. Caldow, S.E.A. le V. dit Durrell, and S. McGrorty. 2002. Predicting the impacts of disturbance on shorebird mortality using a behavior-based model. Biological Conservation 106:319-328.

Wetlands Institute. 2018. Restoring Shorebird Foraging and Horseshoe Crabs Spawning Habitat to Delaware Bay Beaches: Reeds, Cooks, Kimble's and Pierces Point, NJ. Online publication. Wetlands Institute, Stone Harbor, NJ. Website: https://wetlandsinstitute.org/conservation/horseshoe-crab-conservation/post-sandy-emergency-restoration/ [accessed November 2018].

Wetlands International. 2017. Flyway trend analyses based on data from the African Eurasian Waterbird Census from the period of 1967-2015. Online publication. Wetlands International, Wageningen, The Netherlands. Website: http://iwc.wetlands.org/static/files/0-IWC-trendanalysis-report-2017-final.pdf[accessed November 2018].

Wetlands International. 2018. Waterbird population estimates. Website: http://wpe.wetlands.org [accessed May 2019].

White, C.M., N.J. Clum, T.J. Cade, and G. Hunt. 2002. Peregrine Falcon (Falco peregrinus), version 2.0. In The Birds of North America. Poole, A.F. and F. B. Gill [eds.]. Cornell Laboratory of Ornithology, Ithaca, New York. https://doi.org/10.2173/bna.660 [accessed March 2020].

Whitfield, D.P. and J.J. Brade. 1991. The breeding behaviour of the knot Calidris canutus. Ibis 133:246-255.

Whitfield, D.P., J.J. Brade, R.W. Burton, and K.W. Hankinson. 1996. The abundance of breeding Knot Calidris canutus islandica. Bird Study 43:290-299.

WHSRN (Western Hemisphere Shorebird Reserve Network). 2020. Site profiles. Map of sites. Online publication. Western Hemisphere Shorebird Network, Manomet, Massachusetts. Website: https://whsrn.org/whsrn-sites/map-of-sites/ [accessed March 2020].

Wilson, J., Y. Aubry, C. Buidin, Y. Rochepault, and A.J. Baker. 2010. Three records of Red Knots Calidris canutus possibly changing flyways. Wader Study Group Bulletin 117:5-6.

Wilson, J., O. Benediktsson, R. Croger, W. Dick, K. Hooper, G. Morrison, P. Potts, B. Swinfen, and R. Swinfen. 2011. Red Knots marked in N Norway switch spring staging area to Iceland. Wader Study Group Bulletin 118:175-180.

Wilson, J., W. Dick, R. Leah, A. Pienkowski, M. Pienkowski, B.J. Swinfen, R.C. Swinfen, M. Thomas, J. van de Kam, and C. Werney. 2014. The status of Red Knots on spring migration in Varangerfjord, North Norway. Wader Study Group Bulletin 121:193-198.

Wilson, J.R., A.A.F. Rodrigues, and D.M. Graham. 1998. Red Knots Calidris canutus rufa and other shorebirds on the north-central coast of Brazil in April and May 1997. Wader Study Group Bulletin 85:41-45.

Wilson, S., pers. comm. 2018. Email correspondence with R.I.G. Morrison. August 2018. Member, COSEWIC Birds Specialist Sub-committee; Research Scientist, Wildlife and Landscape Science Directorate, Environment and Climate Change Canada, Ottawa, Ontario.

Woodward, J.C., D.J. Forrester, F.H. White, J.M. Gaskin, and N.P. Thompson. 1977. An epizootic among knots (Calidris canutus) in Florida. I. Disease syndrome, histology and transmission studies. Veterinary Pathology 14:338-350.

Working Group on General Status of NWT Species. 2016. NWT Species 2016-2020 - General status ranks of wild species in the Northwest Territories. Department of Environment and Natural Resources, Government of the Northwest Territories, Yellowknife, Northwest Territories. Website: http://www.nwtspeciesatrisk.ca/mwg-internal/de5fs23hu73ds/progress?id=BklfyQ079VdAUpZ6bMCiUYvhOUsmlIhVFFEC9ZJdSTw [acessed November 2018].

Wurst, B. 2018. Nests on towers and buildings maintain stability in the state population. Conserve Wildlife Blog. Conserve Wildlife Foundation of New Jersey. 3 January 2018. Website: http://www.conservewildlifenj.org/blog/2018/01/03/new-jersey-falcons-remain-stable-in-2017/ [accessed August 2020].

Ydenberg, R.C., R.W. Butler, D.B. Lank, B.D. Smith, and J. Ireland. 2004. Western sandpipers have altered migration tactics as peregrine falcon populations have recovered. Proceedings of the Royal Society B 271:1263-1269.

Ydenberg, R.C., R.W. Butler, and D.B. Lank. 2007. Effects of predator landscapes on the evolutionary ecology of routing, timing and molt by long-distance migrants. Journal of Avian Biology 38:523-529.

Zimmerling, J.R., A.C. Pomeroy, M.V. d'Entremont, and C.M. Francis. 2013. Canadian estimate of bird mortality due to collisions and direct habitat loss associated with wind turbine developments. Avian Conservation and Ecology 8:10. www.ace-eco.org/vol8/iss2/art10/.

Biographical summary of report writer

Dr. R.I. Guy Morrison retired in 2012 from his position as Research Scientist, Shorebirds, after a 38-year career with the Canadian Wildlife Service and Wildlife and Landscape Science Directorate of Environment Canada. He remains active as a Scientist Emeritus with Environment and Climate Change Canada and maintains active involvement in research and survey work throughout North and South America. Dr. Morrison completed his undergraduate studies at the University of St. Andrews, Scotland, and his PhD at Cambridge University, England. While at Cambridge, Dr. Morrison organized a series of expeditions to Iceland to study Red Knot migration, and after completing his PhD, took up a position as a Research Scientist with the Canadian Wildlife Service. From 1973 to 2012, his work on the distribution and ecology of shorebirds took him from the Canadian High Arctic to southern South America. This work led to the concept and development of the Western Hemisphere Shorebird Reserve Network, the most important non-government shorebird conservation organization in the Western Hemisphere, with over 100 reserves protecting shorebird habitat from Alaska to Tierra del Fuego. His work at Alert, Ellesmere Island, was instrumental in understanding the role of body stores in Red Knot during migration and breeding. With Ken Ross, his South American Shorebird Atlas surveys led to the discovery of wintering areas of rufa Red Knot in Tierra del Fuego and Patagonia in the 1980s, and Morrison and Ross have since conducted repeated surveys documenting the rapid decline in knots on their wintering grounds since 2000. Dr. Morrison was appointed to the Order of Canada in 2016 for his services in the conservation of Arctic shorebirds.

Collections examined

No collections were examined during the preparation of this report.

Appendix 1. Proportions of juvenile, sub-adult and adult birds in populations of Red Knot.

S. Wilson and R.I.G. Morrison. October 2018

Many counts of Red Knot are undertaken in non-breeding seasons, often in winter, and usually include birds of all age groups. However, as COSEWIC assessments require that abundance be given as the number of mature individuals, the proportion of these counts that represent mature individuals must be determined. Knots are generally considered to start breeding when two years old (Baker et al. 2013, 2020). Birds up to 1 year old are considered juveniles, those between 1 and 2 years old (approaching the first breeding season) as sub-adults, and birds 2 years and older as adults. The number of mature individuals in the population may thus be taken as the number of adults. The proportion of each age class in the population depends on the annual survival of each class and can be modelled in a population matrix.

A series of 11 scenarios is presented in which the annual survival of the three age groups is varied within likely limits (Appendix Table 1). In the most likely scenario (row 1), adult survival (S3) is taken as 0.80 (Mendez et al. 2018), juvenile survival (S1) from hatch to the wintering grounds as 0.2 (one quarter of adult survival, Boyd and Piersma 2011), and sub-adult survival (S2), from age 6 months to 18 months, as 0.65, intermediate between juvenile and adult. Annual population growth in this scenario of 0.979 is slightly negative, and the approximate proportions of juveniles, sub-adults and adults in the population are 22%, 14%, and 64%, respectively. The number of chicks produced per breeding pair was varied in the model between 1.5 and 2.0. Note that if productivity were 2.0 chicks/pair and juvenile survival half that of adults (and sub-adults) the population would increase rapidly (scenario 11). Considering the most likely scenario (row 1) and the mean of the scenarios presented, we suggest that the approximate proportions of each age group may be taken as juvenile 25%, sub-adult 15% and adult 60%, resulting in an estimate of the number of mature individuals for COSEWIC purposes as 60% of the total population.

Chicks/pair Mean number of chicks hatched per pair

S1 6 month survival probability from hatch to wintering grounds

S2 Annual survival probability from 6 to 18 months

S3 Annual survival probability beyond 18 months

Lambda Annual population growth

N1 Proportion 6 month old juveniles in January

N2 Proportion 18 month old subadults in January

N3 Proportion adults 30 months or older in January

Appendix 2. Threats calculator table for Red Knot, islandica subspecies (DU1).

Threats assessment worksheet

Species or ecosystem scientific name

Red Knot, islandica subspecies (DU1)

Date:

2020-02-12

Assessor(s):

Guy Morrison (writer), Richard Elliot (Birds SSC co-chair), David Fraser (facilitator), Marie-France Noel (COSEWIC Secretariat), Rosanna Nobre Soares (COSEWIC Secretariat), Yves Aubry (CWS), Louise Blight (SSC member), Mike Burrell (SSC member), Amanda Dey (New Jersey), Scott Flemming (CWS), Marcel Gahbauer (SSC co-chair), Patricia González (Argentina), Andy Horn (SSC member), Jessica Humber (Newfoundland and Labrador), Kevin Kalasz (USFWS), Amie MacDonald (Trent University), Ann McKellar (CWS), David Newstead (USA), Larry Niles (USA), Hayley Roberts (CWS), Paul Smith (SSC member), Don Sutherland (Ontario NHIC), Wendy Walsh (USFWS), Greg Wilson (British Columbia), Paul Woodard (CWS)

References:

Draft Red Knot update status report (27 January 2020), Draft Red Knot threats calculator (21 January 2020), Recovery strategy and management plan for the Red Knot (Calidris canutus) in Canada (ECCC 2017)

Overall threat impact calculation help:

Level 1 Threat Impact Counts

Overall threat comments

This is one of five designatable units of Red Knot assessed together on 11-12 February 2020. Generation time was assumed to be approximately 7 years.

Appendix 3. Threats calculator table for Red Knot, roselaari subspecies (DU2).

Threats assessment worksheet

Species or ecosystem scientific name

Red Knot, roselaari subspecies (DU2)

Date:

2020-02-12

Assessor(s):

Guy Morrison (writer), Richard Elliot (Birds SSC co-chair), David Fraser (facilitator), Marie-France Noel (COSEWIC Secretariat), Rosanna Nobre Soares (COSEWIC Secretariat), Yves Aubry (CWS), Louise Blight (SSC member), Mike Burrell (SSC member), Amanda Dey (New Jersey), Scott Flemming (CWS), Marcel Gahbauer (SSC co-chair), Patricia González (Argentina), Andy Horn (SSC member), Jessica Humber (Newfoundland and Labrador), Kevin Kalasz (USFWS), Amie MacDonald (Trent University), Ann McKellar (CWS), David Newstead (USA), Larry Niles (USA), Hayley Roberts (CWS), Paul Smith (SSC member), Don Sutherland (Ontario NHIC), Wendy Walsh (USFWS), Greg Wilson (British Columbia), Paul Woodard (CWS)

References:

Draft Red Knot update status report (27 January 2020), Draft Red Knot threats calculator (21 January 2020), Recovery strategy and management plan for the Red Knot (Calidris canutus) in Canada (ECCC 2017)

Overall threat impact calculation help:

Level 1 Threat Impact Counts

Overall threat comments

This is one of five designatable units of Red Knot assessed together on 11-12 February 2020. Generation time was assumed to be approximately 7 years.

Appendix 4. Threats calculator table for Red Knot, rufa subspecies, Tierra del Fuego / Patagonia wintering population (DU3)

Threats assessment worksheet

Species or ecosystem scientific name

Red Knot, rufa subspecies, Tierra del Fuego / Patagonia wintering population (DU3)

Date:

2020-02-12

Assessor(s):

Guy Morrison (writer), Richard Elliot (Birds SSC co-chair), David Fraser (facilitator), Marie-France Noel (COSEWIC Secretariat), Rosanna Nobre Soares (COSEWIC Secretariat), Yves Aubry (CWS), Louise Blight (SSC member), Mike Burrell (SSC member), Amanda Dey (New Jersey), Scott Flemming (CWS), Marcel Gahbauer (SSC co-chair), Patricia González (Argentina), Andy Horn (SSC member), Jessica Humber (Newfoundland and Labrador), Kevin Kalasz (USFWS), Amie MacDonald (Trent University), Ann McKellar (CWS), David Newstead (USA), Larry Niles (USA), Hayley Roberts (CWS), Paul Smith (SSC member), Don Sutherland (Ontario NHIC), Wendy Walsh (USFWS), Greg Wilson (British Columbia), Paul Woodard (CWS)

References:

Draft Red Knot update status report (27 January 2020), Draft Red Knot threats calculator (21 January 2020), Recovery strategy and management plan for the Red Knot (Calidris canutus) in Canada (ECCC 2017)

Overall threat impact calculation help:

Level 1 Threat Impact Counts

Overall threat comments

This is one of five designatable units of Red Knot assessed together on 11-12 February 2020. Generation time was assumed to be approximately 7 years.

Appendix 5. Threats calculator table for Red Knot, rufa subspecies, northeastern South America wintering population (DU4)

Threats assessment worksheet

Species or ecosystem scientific name

Red Knot, rufa subspecies, northeastern South America wintering population (DU4)

Date:

2020-02-12

Assessor(s):

Guy Morrison (writer), Richard Elliot (Birds SSC co-chair), David Fraser (facilitator), Marie-France Noel (COSEWIC Secretariat), Rosanna Nobre Soares (COSEWIC Secretariat), Yves Aubry (CWS), Louise Blight (SSC member), Mike Burrell (SSC member), Amanda Dey (New Jersey), Scott Flemming (CWS), Marcel Gahbauer (SSC co-chair), Patricia González (Argentina), Andy Horn (SSC member), Jessica Humber (Newfoundland and Labrador), Kevin Kalasz (USFWS), Amie MacDonald (Trent University), Ann McKellar (CWS), David Newstead (USA), Larry Niles (USA), Hayley Roberts (CWS), Paul Smith (SSC member), Don Sutherland (Ontario NHIC), Wendy Walsh (USFWS), Greg Wilson (British Columbia), Paul Woodard (CWS)

References:

Draft Red Knot update status report (27 January 2020), Draft Red Knot threats calculator (21 January 2020), Recovery strategy and management plan for the Red Knot (Calidris canutus) in Canada (ECCC 2017)

Overall threat impact calculation help:

Level 1 Threat Impact Counts