Gray-headed Chickadee (Poecile cinctus): COSEWIC assessment and status report 2024

Official title: COSEWIC assessment and status report on the Gray-headed Chickadee (Poecile cinctus) in Canada

Committee on the status of Endangered Wildlife in Canada (COSEWIC)

Endangered

2024

COSEWIC assessment summary

Assessment summary – May 2024

Common name: Gray-headed Chickadee

Scientific name: Poecile cinctus

Status: Endangered

Reason for designation: This small passerine bird has a Holarctic distribution from northern Europe across Asia, and into extreme northwestern North America. Historical Canadian range included Northwest Territories but more recently it has only been seen in Yukon, where there have been only two observations in Canada since 2000 despite extensive surveys in 2019. Although little is known about this species in Canada, it is considered at risk due to its very small population, and an inferred and projected decline in numbers. Key threats are likely climate change and severe weather, and related changes in natural processes such as freeze-thaw cycles and wildfire. These in turn affect the quality of habitats used for nesting, roosting, foraging, and food storage.

Occurrence: Yukon, Northwest Territories

Status history: Designated Endangered in May 2024.

COSEWIC executive summary

Gray-headed Chickadee

Poecile cinctus

Wildlife species description and significance

Gray-headed Chickadee (Poecile cinctus) is a brown-capped chickadee similar in appearance to Boreal Chickadee, but distinguished by its white cheeks and neck, lighter flanks and white-edged wing feathers. Both sexes have similar plumage. Gray-headed Chickadee vocalizations can be reliably distinguished from those of other chickadees by a distinct vocalization, the El call, characterized by a spectrogram that resembles the capital letter “L”. The subspecies resident in Canada, P. c. lathami, is endemic to North America. Gray-headed Chickadee is one of the least understood bird species in North America, due to limited scientific monitoring and research, and its remote, sparsely populated, largely inaccessible range. It has apparently suffered declines despite living year-round in remote, intact wilderness.

Aboriginal (Indigenous) knowledge

All species are significant and are interconnected and interrelated. Aboriginal Traditional Knowledge (ATK) has been included under relevant headings of the report.

Distribution

Gray-headed Chickadee has a Holarctic distribution from northern Europe across Asia and into extreme northwestern North America. Its historical Canadian range included the Northwest Territories, but recent data suggest a northward contraction of its historical North American range to the British–Richardson Mountains and Old Crow Basin ecoregions of northern Yukon and the Brooks Range of northern Alaska. There are only two records in Canada since 2000, with no birds detected during extensive surveys (historical revisits and design-based samples using autonomous recording units) and data processing (automated and manual processing of recordings) in Yukon in 2019.

Habitat

Gray-headed Chickadee is a year-round resident thought to occur in similar habitat throughout the year. It generally uses mixed conifer-deciduous forests in the Arctic-Boreal region near the northern and western edge of the treeline, in the Taiga Cordillera ecozone. Breeding habitat is dominated by spruce and willow (for example, riparian areas and tall shrublands) and stands of Balsam Poplar. Gray-headed Chickadee is an obligate cavity nester, excavating new cavities or renovating natural cavities or woodpecker holes. Shifts in land cover and forest types and tree composition in the Arctic-Boreal region within the last 20 to 30 years coincide with the northward range contraction of Gray-headed Chickadee.

Biology

Gray-headed Chickadee is a monogamous breeder, likely breeding at one year of age and producing one brood per year. Pairs nest singly and birds winter in small flocks. Nest building begins in early May, clutch size is typically 6 to 10 eggs, incubation period is 14 to 15 days and nestling period is 19 days. Females brood the newly hatched young, and both parents feed fledglings for approximately 10 days, after which the young begin to disperse. Generation length is estimated to be 2.2 years. Key limiting factors for Gray-headed Chickadee are not well known. The species may be susceptible to abrupt population declines, because it is non-migratory, occupies a range with a harsh northern climate, and has a small population size, distribution and year-round range. Additional limiting factors may include competition with Boreal Chickadee, dependence on cached food during non-breeding periods, and dependence on the availability of suitable nest and roost trees.

Population sizes and trends

Survey data are insufficient to estimate the size of the Gray-headed Chickadee breeding population in Canada. In 2019, surveys in northern Yukon at 24 targeted sites where the species historically occurred and at 62 design-based survey sites from the Boreal Bird Monitoring Program failed to detect the species. Bayesian analysis based on assumed detection ranges and simulations of various abundances of Gray-headed Chickadee indicates that this result of no detections occurs in 50% of simulations with a population of 159 individuals (that is, a 50% probability that there are fewer than 159 mature individuals in Canada). These simulations also suggest a 99% probability of fewer than 1,000 mature individuals and a 68% probability of fewer than 250 mature individuals in Canada. The survey data are insufficient to quantify population trends in Canada. However, a continuing decline is inferred based on the substantial contraction of the extent of occurrence in recent decades in both Canada and Alaska, and the scarcity of recent records from sites that previously provided regular sightings.

Threats

The key threats to Gray-headed Chickadee are thought to be climate change and severe weather, and natural system modifications (wildfire). Continuing and interacting climate-induced changes in natural disturbance regimes, natural processes and forest conditions cause ongoing shifts likely to reduce the area, spatial location and temporal distribution of mature forest containing suitable dead, dying or damaged trees for roosting and nesting, and live trees for foraging. Climate-induced changes in temperature, humidity, the number of freeze-thaw events and the presence/absence of deep-freeze events may influence the quality and integrity of cached food during the non-breeding period. Hybridization with Boreal Chickadee may pose an additional threat, as preliminary evidence of hybridization between the two species has been found in northern Alaska. The overall threat impact is Medium–Low.

Protection, status, and recovery activities

Gray-headed Chickadee is afforded protection in Canada under the Migratory Birds Convention Act, 1994. NatureServe (2024) ranks Gray-headed Chickadee as Vulnerable to Apparently Secure (G3G4) globally, Critically Imperilled (N1) in Canada, Critically Imperilled (S1) in Yukon, and Critically Imperilled to Imperilled (S1S2) in Alaska. It is considered Unrankable (SU) in the Northwest Territories. The species is designated II Red (very high conservation concern) under the Alaska Species Ranking System.

Technical summary

Poecile cinctus

Gray-headed Chickadee

Mésange lapone

Range of occurrence in Canada: Yukon, Northwest Territories

Demographic information

Generation time (usually average age of parents in the population)

Approximately 2.2 years

Based on Bird et al. (2020)

Is there an [observed, inferred, or projected] continuing decline in number of mature individuals?

Yes, inferred and projected

Based on targeted and random surveys, declining frequency of opportunistic observations and calculated threat impact

[Observed, estimated, or projected] percent of continuing decline in total number of mature individuals within 3 years [or 1 generation; whichever is longer up to a maximum of 100 years]

Unknown

Data are too sparse to estimate.

Estimated percent of continuing decline in total number of mature individuals within 5 years [or 2 generations, whichever is longer up to a maximum of 100 years]

Unknown

Data are too sparse to estimate.

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last [10 years, or 3 generations, whichever is longer up to a maximum of 100 years].

Unknown

Data are too sparse to estimate.

[Projected, inferred or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations, whichever is longer up to a maximum of 100 years].

Projected reduction of 0 to 30% over next 10 years

Based on calculated threat impact. Considered likely that the steepest decline has already occurred in the past, given the species’ disappearance from large portions of its historical range in Canada and Alaska. However, climate change impacts are ongoing.

[Observed, estimated, inferred, projected, or suspected] percent [reduction or increase] in total number of mature individuals over any period [10 years, or 3 generations, whichever is longer up to a maximum of 100 years], including both the past and the future.

Unknown

Past % decline is unknown.

Are the causes of the decline clearly reversible?

No

Threats associated with climate change unlikely to be mitigated. Climate refugia (areas buffered against effects of climate change) require identification of suitable habitat.

Are the causes of the decline clearly understood?

No

Contributing threats (primarily climate change and severe weather, and natural system modifications) are suspected or inferred, but specific causes not fully understood. Limiting factors on populations likely include competition, dependence on cached food and dependence on nest/roost trees.

Have the causes of the decline ceased?

No

Threats have not ceased and limiting factors remain. Limiting factors may become threats when a population is small.

Are there extreme fluctuations in number of mature individuals?

No

Population trends are insufficiently documented, but extreme fluctuations unlikely in most bird species.

Extent and occupancy information

Estimated extent of occurrence (EOO)

Not calculated

Only two documented occurrences in Canada from 2008 to 2019 (see Table 1), so EOO cannot be calculated

Index of area of occupancy (IAO), reported as 2x2 km grid value.

Estimated as 8 km²

Based on Canadian records in 2000 to 2023 (n = 2), IAO is estimated at 8 km². Actual IAO certainly < 500 km² threshold, as IAO based on historical occurrences was estimated at 60 km².

Is the population “severely fragmented” that is, is >50% of its total area of occupancy in habitat patches that are (a) smaller than would be required to support a viable population, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?

1. Unknown
2. Unknown

Number of “locations” (use plausible range to reflect uncertainty if appropriate)

Unknown

Not enough information to apply the concept of “locations”

Is there an [observed, inferred, or projected] continuing decline in extent of occurrence?

Yes, inferred and projected

Southern limit of range has shifted northward and may continue to do so due to effects of climate change. Historical Canadian EOO (pre-2000; see Figure 4) of 133,727 km² has been reduced such that it can no longer be calculated (only two recent occurrence records in Canada). As a proxy, current (2000 to 2023) North American EOO of 347,912 km² is less than 50% of the historical value (pre-2000; 845,276 km²), and historical Alaskan EOO was 681,126 km², while the current value is 320,104 km², meaning that the Alaskan EOO has declined by 53% relative to its historical value.

Is there an [observed, inferred, or projected] continuing decline in area of occupancy?

Yes, inferred and projected

Given inferred decline in number of individuals

Is there an [observed, inferred, or projected] continuing decline in number of subpopulations?

No

Only one subpopulation

Is there an [observed, inferred, or projected] continuing decline in number of “locations”*?

Unknown

Available information inadequate to apply concept of “locations”

Is there an [observed, inferred, or projected] continuing decline in [area, extent and/or quality of] habitat?

Yes, inferred and projected decline in habitat extent and quality

Analysis of recent land-cover changes in Arctic-Boreal region of North America (1984 to 2014) shows major shifts indicative of various adverse climate-induced changes to habitat.

Are there extreme fluctuations in number of subpopulations?

No

Only one subpopulation

Are there extreme fluctuations in number of “locations”

No

Concept of “locations” not applied

Are there extreme fluctuations in extent of occurrence?

No

Are there extreme fluctuations in index of area of occupancy?

No

Number of mature individuals (in each subpopulation)

Subpopulations

N Mature Individuals

(give plausible ranges)

Notes on individual estimates

Total

No population estimate, although Canadian population is inferred to be <250 mature individuals

Only Canadian detections since 2000 are family group of 4 in 2008, and one mature individual observed in 2014; no birds detected at 82 survey sites in northern Yukon in 2019. Bayesian analysis indicates there is a 99% probability that the number of mature individuals is < 1,000; a 68% probability that the number of mature individuals is < 250, and a 50% probability that the number of mature individuals is < 159 in Canada.

Quantitative analysis

Is the probability of extinction in the wild at least [20% within 20 years or 5 generations whichever is longer up to a maximum of 100 years, or 10% within 100 years]?

Unknown

No data to conduct analysis

Threats and limiting factors

Was a threats calculator completed for this species?

Yes, undertaken on 18 Jan 2024

Overall threat impact:

Medium–Low

Key threats were identified as:

1. Natural System Modifications – Fire and Fire Suppression (IUCN 7.1) – Medium–Low impact
2. Climate Change and Severe Weather – Habitat Shifting and Alteration (IUCN 11.1) – Medium–Low impact
3. Climate Change and Severe Weather – Temperature Extremes (IUCN 11.3) – Medium–Low impact
4. Invasive and Other Problematic Species, Genes and Diseases – Problematic Native Species/Diseases (IUCN 8.2) – Unknown impact
5. Invasive and Other Problematic Species, Genes and Diseases – Introduced Genetic Material (IUCN 8.3) – Unknown impact
6. Pollution – Air-Borne Pollutants (IUCN 9.5) – Unknown impact
7. Climate Change and Severe Weather – Droughts (IUCN 11.2) – Unknown impact
8. Climate Change and Severe Weather – Storms and Flooding (IUCN 11.4) – Unknown impact

What additional limiting factors are relevant?

This resident species has a small population size, distribution and year-round range. Life history characteristics that may also be limiting factors include potential competition with Boreal Chickadee, dependence on cached food, and dependence on the availability and suitability of nest/roost trees.

Rescue effect (natural immigration from outside Canada)

Status of outside population(s) most likely to provide immigrants to Canada.

Range contraction and population decline in Alaska, where it is ranked S1S2 by NatureServe

A stable population does not exist elsewhere in North America.

Is immigration known or possible?

Possible

Would immigrants be adapted to survive in Canada?

Yes

Is there sufficient habitat for immigrants in Canada?

Unknown

Habitat quality in Canada is likely declining.

Are conditions deteriorating in Canada?

Yes

Recent climate-induced shifts in land cover, forest type and forest tree composition are likely reducing the amount, spatial location, temporal distribution and quality of habitat.

Are conditions for the source (that is, outside) population deteriorating?

Yes

Analysis of recent land-cover changes in the Arctic-Boreal region of North America (1984 to 2014) shows major shifts indicative of various adverse climate-induced changes to habitat. Deteriorating conditions also inferred from range contraction and population size reduction in AK.

Is the Canadian population considered to be a sink?

Unknown

Is rescue from outside populations likely, such that it could lead to a change in status?

Unlikely

Potential source population in AK apparently declining; immigrants would be subject to reduced amount and quality of habitat in Canada.

Occurrence data sensitivity

Are occurrence data of this species sensitive?

No

Status history

COSEWIC

Designated Endangered in May 2024

Status and reasons for designation

Status: Endangered

Alpha-numeric codes: C2a(ii)

Reason for change of status: Not applicable

Reasons for designation: This small passerine bird has a Holarctic distribution from northern Europe across Asia, and into extreme northwestern North America. Historical Canadian range included the Northwest Territories, but more recently it has only been seen in Yukon, where there have been only two observations in Canada since 2000 despite extensive surveys in 2019. Although little is known about this species in Canada, it is considered at risk due to its very small population and an inferred and projected decline in numbers. Key threats are likely climate change and severe weather, and related changes in natural processes such as freeze-thaw cycles and wildfire. These in turn affect the quality of habitats used for nesting, roosting, foraging and food storage.

Applicability of criteria

A: Decline in total number of mature individuals

Not applicable. There is insufficient information available to estimate the rate of decline in the number of mature individuals in Canada.

B: Small distribution range and decline or fluctuation

Not applicable. While the estimated IAO is below the threshold of 500 km², and a continuing decline has been inferred and projected in (i) EOO; (ii) IAO; (iii) extent and quality of habitat; and (iv) number of mature individuals, there is not enough information to apply locations, and there are no extreme fluctuations.

C: Small and declining number of mature individuals

Meets Endangered, C2a(ii). Total number of mature individuals is estimated to be < 2,500; there is an inferred and projected continuing decline; and one subpopulation contains 95 to 100% of mature individuals.

D: Very small or restricted population

Meets Threatened, D1. The number of mature individuals is uncertain. The species/population likely exceeds the threshold for Endangered, but is below the threshold for Threatened.

E: Quantitative analysis

Not applicable. Analysis not conducted.

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 (2024)

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

Current classification:

Class: Aves

Order: Passeriformes

Family: Paridae

Genus and species: Poecile cinctus (Boddaert, 1783)

Subspecies in Canada:

There are four recognized subspecies of Gray-headed Chickadee (Hailman and Haftorn 2020). Only P. c. lathami occurs in the Nearctic, where it is endemic to Alaska and northwestern Canada (northern Yukon and the Northwest Territories). Three other subspecies occur in the Palearctic: P. c. lapponicus in Fennoscandia east to north-central Russia; P. c. cinctus in central Russia east to the Russian Far East; and P. c. sayanus in the Altai and Sayan mountains to northwestern Mongolia. The taxonomic distinctiveness of Gray-headed Chickadee is based on genetic evidence (Gill et al. 2005; Johansson et al. 2013), morphological evidence (when compared with P. c. cinctus, P. c. lathami has three distinct plumage differences and three distinct structural differences relating to bill size; DeCicco et al. 2017) and behavioural evidence (the species has distinct vocalizations that include the chick-a-dee and El calls; Hailman and Haftorn 2020). There is no evidence of historical or recent movements of Gray-headed Chickadee between Russia and Alaska via the Bering Strait (see Population Structure under Distribution).

Common names:

English: Gray-headed Chickadee (North America); Siberian Tit (Eurasia)

French: Mésange lapone

Other: Alaska Chickadee, Siberian Chickadee

Synonyms and notes:

Poecile cincta, Parus cinctus, Penthestes cinctus. Gray-headed Chickadee (Poecile cinctus) is found in clade B of the phylogeny of 67 parid taxa. Clade B parid species are distinguished from clade A species by the ability to excavate their own nests and to cache food (seeds and insects; Johansson et al. 2013). Gray-headed Chickadee is placed within the “brown-capped chickadee” clade of North American chickadees along with Boreal Chickadee (Poecile hudsonicus) and Chestnut-backed Chickadee (Poecile rufescens; Gill et al. 2005; Johansson et al. 2013).

Hybridization between Gray-headed Chickadee and Willow Tit (P. montanus) has occurred in Finnish Lapland, where both species are sparsely distributed (Hildén and Ketola 1985; Järvinen et al. 1985; Järvinen 1987, 1989). Hybridization between the more distantly related Black-capped Chickadee (P. atricapillus) and Boreal Chickadee has occurred in North America (Lait et al. 2012). Hybridization between Boreal Chickadee and Mountain Chickadee (Poecile gambeli) has been documented on two occasions in Yukon (Society of Yukon Bird Observatories 2006, 2008). These findings suggest that hybridization between the closely related Gray-headed and Boreal chickadees may occur. A research team investigating the rate of hybridization and gene flow between sympatric Gray-headed Chickadee and Boreal Chickadee in Alaska and Yukon, using museum specimens and blood samples from captured wild birds, has found preliminary and probable evidence of hybridization in northern Alaska (Johnson pers. comm. 2023).

Description of wildlife species

Gray-headed Chickadee is the largest chickadee in North America (body length: 13.5 to 14 cm, body mass: 11.3 to 13 g; Hailman and Haftorn 2020). Breeding adults have a distinctive grey-brown cap, white cheeks and neck, small dark bib, light cinnamon flanks, white-edged wings, and a long, white-edged tail. The back is grey-brown, with mottled white, grey and black wings. The breast and belly are primarily white. The bill is black and the legs are light grey. It is distinguished from the morphologically similar Boreal Chickadee by its white cheeks and neck, lighter flanks and white-edged tail feathers. Juveniles are similar to adults but have a dull brown-black cap, dull grey-brown back, pale creamy-white or buff-tinged cheeks, and a larger and slightly pale brown bib (Hailman and Haftorn 2020). In a comparison of Nearctic and Eastern Palearctic Gray-headed Chickadees, P. c. lathami is noted to have a darker mantle and flanks, redder edges of the flight feathers, and a larger bill size (length, width and depth) than P. c. cinctus (DeCicco et al. 2017).

Gray-headed Chickadee has a similar vocal repertoire to other Poecile species, consisting of 11 or 12 common vocalizations or call types (trill, gargle, chick-a-dee, alarm zee, flag, club, crackle, sexual see, broken dee, hiss and squawk), and no known song. This aligns them with Boreal Chickadee and Chestnut-backed Chickadee in North America (Mahon 2006; Dahlsten et al. 2020; Ficken et al. 2020). Gray-headed Chickadee vocalizations (with the exception of the alarm zee in the above list) can be reliably distinguished from those of other chickadee species by a number of unique tonal elements, which can be detected using both auditory and visual (spectrogram) traits. For example, the chick-a-dee call of Gray-headed Chickadee is typically shorter, lower pitched and more emphatic (chick-a-chew-chew) than that of the hoarse-sounding Boreal Chickadee. The one described call unique to Gray-headed Chickadee, the El call, is characterized as a modified dee note of the chick-a-dee complex and can be distinguished by its spectrogram, which resembles the capital letter “L” (Hailman and Haftorn 2020).

Although the identification of Gray-headed Chickadee using morphology and vocalizations may be challenging, the intense interest in this species by North American ecologists, birdwatching enthusiasts and citizen scientists suggests that it is unlikely to be consistently overlooked or incorrectly identified by observers within its range.

Designatable units

Only one subspecies of Gray-headed Chickadee is recognized in North America (P. c. lathami; see Name and classification; Hailman and Haftorn 2020). A designatable unit is a discrete and evolutionarily significant unit of biodiversity, where discrete means that there is currently no or very little transmission of heritable (cultural or genetic) information from other units and evolutionarily significant means that the unit harbours heritable adaptive traits or an evolutionary history not found elsewhere in Canada (COSEWIC 2020). As there is no evidence that breeding assemblages in Canada are sufficiently discrete or evolutionarily significant to warrant consideration as separate designatable units, Gray-headed Chickadee in Canada is considered here as one designatable unit.

Special significance

Gray-headed Chickadee is one of the least understood bird species in North America, due to limited scientific monitoring and research and its remote, sparsely populated and largely inaccessible range. Northern communities within the range of the Gray-headed Chickadee include Old Crow, Yukon (300 residents), Aklavik, N.W.T. (640 residents), Fort McPherson, N.W.T. (740 residents), Tuktoyaktuk, N.W.T. (960 residents) and Inuvik, N.W.T. (3,200 residents).

Aboriginal (Indigenous) knowledge

Aboriginal Traditional Knowledge (ATK) is relationship-based. It involves information on ecological relationships between humans and their environment, including characteristics of species, habitats and locations. Laws and protocols for human relationships with the environment are passed on through teachings and stories, and Indigenous languages, and can be based on long-term observations. Place names provide information about harvesting areas, ecological processes, spiritual significance or the products of harvest. ATK can identify life history characteristics of a species or distinct differences between similar species.

Cultural significance to Indigenous peoples

This species is culturally significant to Indigenous Peoples, who hold detailed knowledge on the evolving, dynamic nature of the species. ATK has been included under relevant headings of the report; sources of information are indicated. The species is known to residents of Old Crow, Yukon (Vuntut Gwitchin Government 2015). Publicly available Gwitchin science and knowledge on Gray-headed Chickadee can be found in the Dinehtl’èe Bird Book (Birds of the Van Tat Gwich’in Traditional Territory) (Vuntut Gwitchin Government 2015), a published reference to local birds in the Traditional Territory of the Vuntut Gwitchin, with modern Gwitchin transcriptions. The section on Gray-headed Chickadee (no Gwitchin name listed) includes the following text: “The rare Gray-headed Chickadee is very similar to the Boreal Chickadee, but has a larger white face patch and duller buffy flanks. It is known historically from the Old Crow River, but there are few observations in recent years. Its call is a peevish de-deer” (Vuntut Gwitchin Government 2015).

Distribution

Global range

Gray-headed Chickadee has a Holarctic distribution, ranging from northern Europe, across Asia and into northwestern North America (Figure 1). The year-round range of the endemic North American subspecies (P. c. lathami) takes in portions of interior and northern Alaska, Yukon and the western Northwest Territories. Its historical range (1864 to 1999) included interior and northern Alaska, extending broadly from the north slopes of the Brooks Range south to the Alaska Range; Yukon, where individuals were detected in the British–Richardson Mountains, Old Crow Basin, Old Crow Flats, North Ogilvie Mountains and Eagle Plains ecoregions; and in the Northwest Territories, where individuals were detected in the Aklavik Range and the Mackenzie River delta, and near the Anderson and Horton Rivers (Figure 2). Historical and current occurrence records of Gray-headed Chickadee in North America, based on outreach to avian ecologists, museum databases, eBird records, published and unpublished literature and citizen science programs, were collated and assessed for accuracy (Booms et al. 2020; this report).

The current North American range (2000 to 2023) of the species appears to be almost entirely limited to the Brooks Range of Alaska, extending into the British–Richardson Mountains and Old Crow Basin ecoregions of Yukon. North American range maps based on historical detections (prior to 2000; Figure 2) and current detections (2000 to 2010 and 2011 to 2023; Figure 3), following Booms et al. (2020), highlight the northward contraction of Gray-headed Chickadees in Alaska and Yukon.

Figure 1. Global distribution showing year-round range of Gray-headed Chickadee (Poecile cinctus; from BirdLife International 2020, with permission).

Figure 2. Historical North American range (Yukon and Northwest Territories, Canada and Alaska, United States) of Gray-headed Chickadee (Poecile cinctus): occurrence records of Gray-headed Chickadee prior to 2000 are shown with yellow dots (from Booms et al. 2020).

Figure 3. Current North American range (Yukon, Canada and Alaska, United States) of Gray-headed Chickadee (Poecile cinctus). Occurrence records of Gray-headed Chickadee in 2000 to 2010 are shown with red dots and, in 2011 to 2023, with blue-green dots. Site 1 is the confluence of the Kelly and Noatak rivers in Alaska; site 2, the Arctic National Wildlife Refuge (ANWR), Alaska; site 3, Ivvavik National Park, Yukon; and site 4, Old Crow, Yukon. Site A has 24 years of multi-year records (1989 to 2013; no dots), and site B has 18 years of multi-year records (1997 to 2015; no dots).

Canadian range

Canada comprises approximately 15% of the species’ historical North American range. This range extended across Yukon from the Alaska border into the western part of the Northwest Territories. It covered diverse ecoregions (for example, Old Crow Flats, Old Crow Basin, British–Richardson Mountains, Eagle Plains, Peel River Plateau and Fort MacPherson Plain) within the Taiga Cordillera and Taiga Plains ecozones. The current Canadian range extends from the Alaska border east to Ivvavik National Park and Old Crow in Yukon (Figure 3). Current areas of importance in Canada, such as areas with suitable habitats, specialized habitats or microhabitats or with high abundance/density, have not been identified.

Search effort and sampling methods for Gray-headed Chickadee in Yukon (2019) and Alaska (2010 to 2017) are described in detail in Population Sizes and Trends.

Population structure

There is no evidence of population structuring in the North American population, and it is not known whether the current North American distribution is contiguous or disjunct (see Distribution). Evidence of historical or recent movements of Gray-headed Chickadee between Russia and Alaska via the Bering Strait is also lacking.

Gray-headed Chickadee is considered to be a year-round resident in Canada. No significant barriers to post-breeding dispersal and movement (for example, seasonal or short-distance migration, nomadism and irruptions) have been identified for Gray-headed Chickadee, although physical barriers (mountains, large water bodies and geographical distance) are known to restrict dispersal and gene flow of Boreal Chickadee in North America, including the Alaska and Brooks mountain ranges (Lait and Burg 2013). There are no known morphological, behavioural or demographic variations in the North American population, although differences between Nearctic and Eastern Palearctic Gray-headed Chickadees have been noted (DeCicco et al. 2017).

Extent of occurrence and area of occupancy

The Gray-headed Chickadee’s historical (pre-2000) extent of occurrence (EOO) of 133,727 km² in Canada has declined to the extent that it can no longer be calculated for the present day (only two occurrence records in Canada since 2000; see Figure 4). As a proxy, the current (2000 to 2023) North American EOO of 347,912 km² is less than 50% of the historical value (845,276 km²; Figure 4). The historical EOO in Alaska was 681,126 km², while the current value is 320,104 km², representing a decline of 53%.

The index of area of occupancy (IAO) was calculated using historical data (prior to 2000) and current data (2000 to 2023). The historical value of the IAO in Canada based on documented occurrences prior to 2000 (n = 34) is estimated to be 60 km², and the current IAO based on records in 2000 to 2023 (n = 2), 8 km², calculated by assigning each known record to a different 2 km x 2 km grid square (COSEWIC 2021). Given the value of the estimated historical IAO, the current value is very likely below the 500 km² threshold for Endangered.

Figure 4. Historical (pre-2000) and current (2000 to 2023) extent of occurrence (EOO) for Gray-headed Chickadee (Poecile cinctus) in North America and Canada. The current Canadian EOO cannot be mapped, as there are only two documented records from 2000 to 2023.

Fluctuations and trends in distribution

Changes in EOO and IAO are described in the preceding section.

Biology and habitat use

Although Gray-headed Chickadee is rare and poorly studied in North America, the general biology of the species is well known from extensive research in Europe, primarily in Norway (Dale and Andreassen 2016; Hailman and Haftorn 2020), Finland (Järvinen 1978, 1982; Virkkala 1990a,b; Virkkala and Leihu 1990; Saari et al. 1994), and Russia (Hailman and Haftorn 2020). The information below draws on information from The Birds of the World species account (Hailman and Haftorn 2020) and Booms et al. (2020). The latter summarizes the current knowledge on and status of the species in North America.

Life cycle and reproduction

Gray-headed Chickadee is a monogamous breeder that forms lifelong pair bonds. Mean age of first breeding is unknown (Hailman and Haftorn 2020), but most Poecile species first breed at one year of age and produce one brood per year (Ficken et al. 2020). As is typical of Poecile species, the birds nest in single breeding pairs and winter in flocks (for example, one or two mated pairs plus juveniles).

Gray-headed Chickadee is an obligate cavity nester, using excavated or natural cavities, woodpecker holes or nest boxes (in Eurasia). In North America, nest trees include spruce (Picea) and poplar (Populus), although nest records are limited in number (Booms et al. 2020). In Europe, there are local variations in the selection of pine, spruce and birch (Betula) as nest tree species (Hailman and Haftorn 2020). This aligns with empirical evidence for Chestnut-backed Chickadee in northwestern Canada, where the type of nest tree selected appeared to shift depending on the species present and the condition (for example, live or dead, shape of tree stem and crown, condition of wood, presence of health agents like disease and insects, and physical defects) and size of the available trees (Mahon et al. 2007). In Eurasia, nest trees may include pine (Pinus), spruce, birch and aspen (Populus; Saari et al. 1994), with nest height averaging 1.8 to 4.6 m above the ground (Hailman and Haftorn 2020). Most brown-capped chickadee species excavate cavities in areas of decaying wood in dead or dying trees (for example, from wood-boring insects; branch, trunk and root diseases; scars; breakage; forks; frost cracks and dead tops; Mahon and Martin 2006; Mahon et al. 2007; Dahlsten et al. 2020; Ficken et al. 2020). Female Gray-headed Chickadees excavate or renovate nest cavities, including creating a three-layer nest with decayed wood and moss, with lagomorph or rodent fur lining the nest cup (Järvinen 1982; Hailman and Haftorn 2020). The degree of nest reuse and competition for nest sites is unknown. Males roost near the nest cavity and females, inside the nest cavity.

The size of breeding territories averages 16 to 17 ha in Europe, but is unknown in North America. Reported breeding density in Europe ranges from 0.05 pairs to 6.7 pairs/km² (Hailman and Haftorn 2020), with the most recent estimate, 0.05 to 0.17 pairs/km² in undisturbed mature forest in southern Norway (292.5-km line transect surveys at 51 sites in 2011 to 2012; Dale and Andreassen 2016). In Europe, nest building begins in early May, with copulation and egg laying occurring once the nest is completed or near completion. Date of first egg is approximately 10 to 24 June in Alaska and 1 to 30 June in Canada (Hailman and Haftorn 2020). One egg is laid per day until the clutch is complete. Clutch size (range: 4 to 11) may vary with habitat, laying date and year (Järvinen 1982), but is typically 6 to 10 in both North America and Europe (Hailman and Haftorn 2020). Incubation period in Europe is 13.7 to 16 days. The female broods the newly hatched young, and both parents feed nestlings a variety of invertebrates during the nestling period of approximately 19 days. Fledglings remain in the territory for roughly two weeks, and are fed by the adults for around 10 days before the young disperse (Hailman and Haftorn 2020).

Data on Gray-headed Chickadee survival rates are limited, with one estimate of annual adult mortality of 49%, and a maximum observed adult age of 7 years (Virkkala 1990a). Generation time (average age of adults in the population) is estimated to be 2.2 years, based on modelling of age of first reproduction (F), maximum longevity (L) and annual adult survival (S) (for example, as a function of phylogeny, body mass, migratory status, broad habitat, diet, breeding range centroid latitude and mean clutch size) and derived estimates of generation time (Bird et al. 2020). Data on annual reproductive success are limited, but estimates in Europe suggest a mean range of 4.8 to 7.7 fledglings/nest. Lifetime annual reproductive success is unknown because mean adult lifespan and age-specific reproductive success are unknown (Hailman and Haftorn 2020).

Key factors affecting the productivity and survival of Gray-headed Chickadee in North America are unknown, but may include the effects of climate change, both direct (exposure of eggs, nestlings and adults) and indirect (food and prey limitation, predator shifts, cache integrity, vegetation and habitat shifts and altered natural disturbance patterns). Cold temperatures appear to affect nestling survival during the breeding season (Järvinen 1983) and adult survival in winter in Finland (Järvinen 1982). Food limitation appears to influence nestling survival in Scandinavia (Järvinen 1982, 1983, 1990). Storage of seeds and invertebrates as a source of food is important for Gray-headed Chickadees throughout the year (Hailman and Haftorn 2020), and changes in the integrity of cached food during non-breeding periods may influence demographic rates in the species (see Diet under Interspecific interactions; Physiological, Behavioural, and Other Adaptations; Limiting factors; and Threats).

Habitat requirements

Breeding habitat

The characteristics of typical Gray-headed Chickadee breeding habitat are generally unknown in North America, due to a lack of studies on breeding ecology and habitat selection (Booms et al. 2020; Hailman and Haftorn 2020). In Yukon and Alaska, Gray-headed Chickadee uses habitats dominated by spruce and willow (Salix spp.) adjacent to rivers and surrounded by open tundra (Murie 1928; Spindler et al. 1980; Sinclair et al. 2003). In northwest Alaska, the species is found in low willow and spruce shrubland (< 6 m in height; Hines 1963). In the foothills of the Brooks Range in northeast Alaska, it also occurs in isolated Balsam Poplar (Populus balsamifera) stands (Booms et al. 2020). In Europe, the species occurs in a variety of northern forest types including thinned, low productivity pine forests in Norway, mature mixed forests (pine, spruce and birch) with standing dead trees in Finland (Virkkala and Liehu 1990; Saari et al. 1994), pure coniferous forests (spruce and pine) in Russia, and Upland Larch (Larix cajanderi) forests in Siberia (Hailman and Haftorn 2020). The degree of habitat and niche specialization is unknown, although forest stands with suitable structural attributes are required to provide nest and roost trees (standing decayed and dead conifer and deciduous trees; see Life cycle and reproduction) and forage trees (mature and old conifer and deciduous trees, deciduous shrubs; see Diet under Interspecific interactions). Gray-headed Chickadee is likely a specialist species of the northern boreal forest due to its dependence on mature or old, structurally complex forest types containing specific structural attributes needed for nesting, roosting and foraging.

Migration habitat

Gray-headed Chickadee is considered a permanent resident in Canada, with no evidence of movements to different habitats outside the breeding season. Young birds may wander south of the breeding range, especially in winter (Hailman and Haftorn 2020).

Winter habitat

Gray-headed Chickadee occurs in similar habitat throughout the year in Europe (Hailman and Haftorn 2020), and is thought to do the same in North America.

Movements, Migration, and Dispersal

Gray-headed Chickadee movements such as dispersal, short-distance or seasonal migration (movement between breeding and non-breeding areas), nomadism (irregular movements associated with fluctuating resources and opportunistic breeding) and irruptions (irregular movements associated with fluctuating food resources) are undocumented in North America. In Europe, sporadic nomadic movements may occur (Hailman and Haftorn 2020). Dispersal distance of juveniles is unknown.

Interspecific interactions

Diet

Adult Gray-headed Chickadees typically forage on small invertebrates, including insects (bug, butterfly and moth larvae and pupae; caddisflies; flies; sawflies; bees; wasps; ants; beetles; and adult weevils) and spiders (cocoons and adults), and also eat seeds (spruce, pine, larch, birch, juniper and rose) and carrion (Hailman and Haftorn 2020). Foraging habitat is variable but includes the needles/leaves, trunks, branches and twigs of, and lichens on, conifer (pine, spruce and larch) and deciduous trees (birch) and shrubs. Gray-headed Chickadee caches invertebrates and seeds in epiphytic lichens, bark crevices and on the underside of branches to provide a source of stored food throughout the year (Hailman and Haftorn 2020). No detailed studies of winter foraging and food caching in Gray-headed Chickadee have been conducted in North America.

Predators and competitors

Common predators of chickadees in Europe include squirrels, weasels, hawks, owls, shrikes and possibly jays. Known predators of Boreal Chickadee in North America, which include Red Squirrel (Tamiasciurus hudsonicus) and Black Bear (Euarctos americanus; Ficken et al. 2020), and of Chestnut-backed Chickadee, which include Red Squirrel, Northern Flying Squirrel (Glaucomys sabrinus) and American Marten (Martes americana; Mahon and Martin 2006), are also likely predators of Gray-headed Chickadee. As with most cavity-nesting bird species, the predation of eggs, nestlings, newly fledged young or adults is generally not likely to limit populations, although no relevant data are available (Hailman and Haftorn 2020). No detailed breeding or demographic studies of Gray-headed Chickadee have been conducted in North America, including identification of predators and measurements of predator-caused mortality during each breeding stage.

In North America, little is known about interspecific interactions between Gray-headed, Boreal and Black-capped chickadees either in, or outside of, the breeding season. In Europe, breeding season interactions may include competition for food and prey items or foraging, storage and nest sites (Hailman and Haftorn 2020).

Physiological, behavioural, and other adaptations

As a resident of northern boreal regions, Gray-headed Chickadees must survive extended periods of low temperatures and darkness during fall, winter and spring. A high degree of insulation (for example, large feather mass relative to body size) and a relatively low body temperature (range 34.6 to 39.8 °C), compared to other species of Paridae, crossbills (Loxia spp.) and creepers (Certhia spp.; typically > 41 °C), may reduce heat losses in Gray-headed Chickadee (Hailman and Haftorn 2020). The types of roost sites used during non-breeding periods are not known.

Although Gray-headed Chickadee is well adapted to surviving extended periods of very low temperatures and darkness, little is known about the tolerance of this species to anticipated changes in climate and habitat (Hailman and Haftorn 2020). Climate change is accelerating in northern regions of North America. Northern Canada is experiencing warming at almost three times the global average, with an increase of 2.3°C in the national average annual temperature between 1948 and 2016 (Bush and Lemmen 2019). For Gray-headed Chickadee, climate change can result in both direct effects (exposure of eggs, nestlings and adults) and indirect effects (food and prey limitation, predator shifts, cache integrity, vegetation and habitat shifts, and changes in natural processes and natural disturbance regimes) on the population (see Threats and Historical, Long-term, and Continuing Habitat trends). Owing to an absence of studies on demographics, nest site and habitat selection and food caching in Gray-headed Chickadee, no empirical data are available to develop integrated population models that include population and life history data (for example, demographic parameters), stressor effects (for example, climate-induced stressors) and environmental effects (Mahon and Pelech 2021) or to quantify clear links between greenhouse gas emissions, the environmental attributes affecting the population (for example, freeze-thaw events that limit the integrity of cached fall and winter food) and the species’ demographic parameters (for example, winter survival and spring fecundity; Amstrup and Blitz 2023). How Gray-headed Chickadee will adapt to the direct and indirect effects of climate change in northern Canada is currently unknown.

Limiting factors

Key limiting factors on Gray-headed Chickadees in North America are poorly known. The species may be prone to abrupt population declines, as it is a non-migratory species in a harsh northern climate with a small population size and patchy distribution. Life history characteristics that may be limiting factors (environmental or intrinsic factors that play an important role in restricting the size of the population) include: (i) competition with Boreal Chickadee; (ii) dependence on cached food during non-breeding periods; and (iii) dependence on the availability of suitable nesting and roosting trees. Limiting factors can become threats when a population is small; these limiting factors (or potential limiting factors) may act individually or in interaction with other factors to limit or reduce the population of Gray-headed Chickadee.

Competition may occur between sympatric Gray-headed and Boreal chickadees. Typically, sympatric chickadee species exhibit ecological segregation, whereby they occupy different habitats or microhabitats. In northwestern British Columbia, where the ranges of Black-capped, Chestnut-backed and Boreal chickadees overlap, Black-capped Chickadees occupy low-elevation deciduous forests; Chestnut-backed Chickadees, middle-elevation conifer and mixed forests; and Boreal Chickadees, high-elevation conifer forests (Mahon pers. obs.). Although historical records and observations suggest that Gray-headed Chickadee and Boreal Chickadee occupied different habitats in areas where their ranges overlap (Murie 1928), the absence of systematic historical and recent survey data from the northern regions of Yukon, Northwest Territories and Alaska limits our ability to assess changes or shifts in distribution, or habitat and microhabitat use within their respective ranges. Ecological segregation could break down in the Arctic-Boreal region, where multiple, climate-induced changes (for example, increased spring and summer temperatures, decreased water availability, decreased plant productivity, increased fire frequency and vegetation and land-cover changes) could alter the availability of key habitat attributes such as suitable nest and roost trees and foraging areas, leading to increased competition for these life requirements.

Dependence on cached food, particularly under the harsh conditions found during the non-breeding period, may limit Gray-headed Chickadee populations, and climate-induced changes may reduce the quality and integrity of cached food (see Physiological, Behavioural, and Other Adaptations and Threats). The importance of food storage and food integrity to the survival of adult and hatch-year Gray-headed Chickadees in winter, the body condition and reproductive fitness of breeding female Gray-headed Chickadees in late winter and early spring, and the fecundity of breeding pairs in spring is not known in North America or Eurasia.

The availability of suitable nest and roost trees could be critical to maintaining reproductive performance (for example, clutch size, nest success, brood size and nestling condition) and the winter survival of adults and juveniles (see Life cycle and reproduction; Physiological, Behavioural, and Other Adaptations; Threats; and Historical, Long-term, and Continuing Habitat trends). The dependence of Gray-headed Chickadee populations in Canada on suitable nest and roost trees and the effects of the loss of these trees are unknown. Recent research suggests that large-scale fire regime changes (Hanes et al. 2019) and habitat shifts (Wang et al. 2020) in the Arctic-Boreal region may have altered the amount, geographic location, temporal distribution and quality of dead or dying trees for cavities and live trees for foraging (see Physiological, Behavioural, and Other Adaptations; Threats; and Habitat trends).

Population sizes and trends

Data sources, methodologies, and uncertainties

In documenting specimens and observations of Gray-headed Chickadee in North America, Booms et al. (2020) compiled records from multiple sources (n = 156 records). These records were obtained from: (i) outreach to regional biologists (n = 60); (ii) online museum database searches (n = 58); (iii) eBird (n = 15; Sullivan et al. 2009); (iv) published literature and unpublished reports (n = 17); (v) citizen science programs (n = 4); and (vi) USGS Bird Banding Lab (n = 2), and are summarized here in Table 1. All records were assessed for accuracy, and unreliable or suspect records were omitted. Six additional records recovered during the writing of this status report are also included in Table 1, for a total of 36 occurrence records (specimens and observations) of Gray-headed Chickadee in Canada. Unconfirmed records also exist for Yukon and the Northwest Territories (for example, Godfrey 1966 in Frisch 1982; Frisch 1982; Bennett pers. comm. 2024), but are not detailed here.

^a S = specimen; O = observation

The regularity of occurrence and population persistence of Gray-headed Chickadee in Canada were considered using a weight-of-evidence approach. The limited number of records reflects in part the species’ range in remote areas of northern Canada where there are only small, dispersed human settlements (Figures 2 and 3; see Special significance), and no long-term avian monitoring programs. This species has been recorded in Canada for over 150 years (1864 to 2014), and in every decade from the 1910s to the 2010s, except for two. It has been reported at multiple sites in Yukon (n = 19) and the Northwest Territories (n = 12), during both the breeding (June) and post-breeding (July–September) life stages (Table 1). These records suggest the presence of small, persistent subpopulations rather than sporadic movements by the species (short-distance migration, nomadism or irruptions; see Movement, Dispersal, and Migration). Records include repeated detections (for example, 6 detections of 1 to 4 individuals over 6 days in August 1989), and multi-year detections (for example, 1987, 1989, 1990) at the same site (Reindeer Station) in the Northwest Territories (Table 1). Multi-year detections were also documented at two sites in Alaska near the Canada–U.S. border: (i) a trapper cabin roughly 16 km from the Canada–U.S. border, with annual detections between 1989 and 2013 (24 years) in winter (Figure 3, site A); and (ii) a site visited by a birdwatching tour company approximately 200 km from the Canada–U.S. border in the Arctic National Wildlife Refuge (ANWR) with annual detections in 1997 to 2015 (18 years) in summer, including evidence of nesting (Figure 3, site B; see also Fluctuations and trends, below). Finally, Indigenous science and knowledge provide both undocumented and published evidence of historically persistent occurrences of Gray-headed Chickadee in the Traditional Territory of the Vuntut Gwitchin First Nation in northern Yukon (see Cultural Significance to Indigenous Peoples).

Occurrence records prior to 2000

In the past, Gray-headed Chickadee was considered to be sparsely distributed from the Noatak and Kobuk River drainages in northwest Alaska to the northern foothills of the Brooks Range in northeast Alaska and Yukon, to the Old Crow Flats and Old Crow Basin ecoregions in northern Yukon (Booms et al. 2020). Between 1864 and 2000, there were at least 108 occurrence records in North America (Alaska, Yukon and the Northwest Territories), with records in every decade from the 1910s, except for the 1930s and the 1960s (Sinclair et al. 2003; Booms et al. 2020; Table 1). Detections in interior and central Alaska near Fairbanks were primarily during fall and winter (Gibson 2011). Olaus Murie, a wildlife biologist with the U.S. Biological Survey, made extensive observations and collections of Gray-headed Chickadee in summer and winter in Alaska and Yukon in the 1920s (Murie 1957). During an extended boat trip on the Old Crow River in Yukon in June–August 1926, Murie (1928) observed several family groups of Gray-headed Chickadee with “the broods of young evidently just out of the nests,” and collected 13 specimens of these birds (Table 1). Murie (1928) also described the species as “very common” in Old Crow, and notes that the individual collected in 1864 (at Anderson River, N.W.T.) was found with a nest and eggs.

Occurrence records since 2000

There were 48 occurrence records of Gray-headed Chickadee in North America from 2000 to 2020 (Booms et al. 2020), including 32 repeat detections from two localities in the ANWR in northeast Alaska near the Canada–U.S. border (see Distribution). No verifiable records in the species’ historical range in southwest and central Alaska have been obtained since 2000, although the species is still infrequently detected (1 to 3 records/year) at two sites in the Brooks Range in northern Alaska. The first of these sites is in northwest Alaska in the Noatak National Preserve, near the confluence of the Kelly and Noatak rivers (Figure 3, Site 1), where birdwatchers regularly attempt to detect the species. Although a cluster of detections occurred in 2016, there were none between 2017 and 2020 (Booms et al. 2020); nor have any been recorded subsequent to 2020 in the eBird database (Sullivan et al. 2009). The second site is in northeast Alaska approximately 200 km from the Canada–U.S. border in the ANWR (Figure 3, site 2), where recent breeding season records (for example, 2015) have been obtained, from sources that include a birdwatching tour company, recreational birdwatchers and Alaska Department of Fish and Game biologists conducting Gray-headed Chickadee surveys, the latter providing three detections (Booms et al. 2020).

Only two reliable occurrence records are known in Canada since 2000, both in northern Yukon. The first is of four birds (likely a family group; Bennett pers. comm. 2023) in July 2008 near the Firth River (Sheep Creek Base Camp) in Ivvavik National Park (Figure 3, site 3); the second is of a single individual in June 2014 near Old Crow, relatively close to the site where O. Murie reported the species in 1926 (Murie 1928; Figure 3, site 4). Both records were from biologists residing in Yukon (Table 1).

Intensive field surveys across the species’ historical range in Alaska detected only three individuals between 2010 and 2017, with no evidence of nesting (Booms et al. 2020). Parks Canada has no verifiable records of Gray-headed Chickadee in Ivvavik National Park, despite ongoing bird monitoring efforts since 2009 and annual visits to Sheep Creek by the park biologist for two to three weeks between spring and fall since 2015 (Frandsen pers. comm. 2024). Two students stationed at Sheep Creek over four summers (2009 to 2012) established 29 breeding bird survey plots within a 5-km radius. A 10-minute recording was made at each site in early June and again in mid-June, and local bird observations were undertaken daily. In 2015, the survey was modified to include Margaret Lake, a site closer to Old Crow. Since 2018, ten autonomous recording units (ARUs; five at Sheep Creek and five at Margaret Lake) have been deployed at these sites from early May to late October, with the recordings taken during optimal conditions and manually subsampled and transcribed (Frandsen pers. comm. 2024). Gray-headed Chickadee has not been detected through these efforts; one potential sighting of a group could not be confirmed (Straka pers. comm. 2024).

Extensive Gray-headed Chickadee field surveys in 2019 across the historical range in Yukon included 24 targeted sites with historical records, and 62 design-based survey sites in the Eagle Plains, Old Crow Basin, Old Crow Flats, British–Richardson Mountains and North Ogilvie Mountains ecoregions, as part of the Boreal Bird Monitoring Program in Yukon (Van Wilgenburg et al. 2020). Design-based survey sites were randomly selected using a hierarchical sampling design that incorporated cost constraints, habitat stratification, spatial balance and optimization to obtain a cost-effective sampling scheme to monitor changes in distribution and population size and support modelling of species-habitat relationships (Figure 5; Van Wilgenburg et al. 2020). There was no evidence of habitat change due to wildfire activity at any of the 24 targeted sites with historical Gray-headed Chickadee records or any of the 62 design-based survey sites.

Threats

Historical, long-term, and continuing habitat trends

Wang et al. (2020) used 30 years (1984 to 2014) of medium-resolution (30 m) Landsat satellite imagery, and climate, topographic and permafrost information from Alaska and northwestern Canada to map and characterize land-cover changes in the Arctic-Boreal region. Their results suggest that 13.6 ± 1.3% of the region changed over the last three decades due to: (i) simultaneous disturbance-driven (wildfire) decreases in conifer forest area (-14.7 ± 3.0% relative to 1984) and increases in deciduous forest area (+14.8 ± 5.2% relative to 1984) in the boreal biome; and (ii) climate-driven expansion of shrub and herb vegetation (+7.4 ± 2.0%) in the Arctic biome (Wang et al. 2020). This mapping effort encompassed the historical and current year-round North American range of Gray-headed Chickadee and captured all potential drivers of environmental change (for example, wildfire, timber harvesting, insect outbreaks, permafrost thaw and resource exploration). Specific drivers of vegetation change, particularly those that are rare or difficult to study (for example, permafrost thaw, insect outbreaks and shifts in surface water), require further investigation to assess temporal patterns, spatial location and magnitude. Habitat change can be characterized by shifts in land-cover and forest types (for example, biome shifts) and associated changes in tree species composition, canopy cover, tree mortality (see Helbig et al. 2016; Coop et al. 2020; Wang et al. 2020), vegetation regeneration (Whitman et al. 2019) and shrub and herb expansion (Myers-Smith et al. 2011, 2019; Wang et al. 2020). These changes are projected to have substantial impacts on bird species in northern regions. The modelling of future shifts in the distribution of 604 North American bird species reveals that two thirds of species are moderately or highly vulnerable to climate change (Bateman et al. 2020). The greatest changes in bird community composition are expected to occur in northern latitudes, including the Arctic and boreal regions. The recent shifts in land cover and forest types noted above (for example, 1984 to 2014; Wang et al. 2020) coincide with the apparent northward range contraction of Gray-headed Chickadee since 2000 in Yukon and Alaska, which could indicate a climate-induced distribution shift for this species. In southern Norway, climate-related threats (cache integrity), increased forestry activity in mature and old growth forests over the past 30 years and overlap in the habitat selected by Gray-headed Chickadee and three other tit species (Paridae) coincide with range contraction and population decline in Gray-headed Chickadee (Siberian Tit; Dale and Andreassen 2016).

Current and projected future threats

Gray-headed Chickadee is vulnerable to the cumulative effects of various threats, especially climate change and severe weather, and natural system modifications (wildfires). Invasive and other problematic species and genes, and pollution, pose threats of unknown impact. The nature, scope and severity of these threats are described in Appendix 1, following the IUCN-CMP (International Union for the Conservation of Nature–Conservation Measures Partnership) unified threats classification system (see Salafsky et al. 2008 for definitions and Master et al. 2012 for guidelines). The threat assessment process consists of assessing impacts for each of 11 main categories of threats and their subcategories, based on the scope (proportion of population exposed to the threat over the next 10-year period), severity (predicted population decline within the scope during the next 10 years or 3 generations, whichever is longer, up to ~ 100 years), and timing of each threat. The overall threat impact is calculated by taking into account the separate impacts of all threat categories and can be adjusted by the species experts participating in the threats evaluation.

The overall threat impact for Gray-headed Chickadee is Medium–Low, corresponding to an anticipated further decline of between 0% and 30% over the next ten years. These values must be interpreted with caution, as they may be based on subjective information such as expert opinion, although efforts have been made to corroborate the scores with available studies and quantitative data.

The sources of direct threats (for example, impacts on population) and indirect threats (for example, changes to food, predator dynamics and habitat) to Gray-headed Chickadee are relatively few in number. Minimal human disturbance, from human settlements and resource exploration and extraction, occurs in northern Yukon and the Northwest Territories. Most of the region can be accessed only by plane or helicopter; the exception is the Dempster Highway (that is, Highway 5 in Yukon and Highway 8 in the Northwest Territories), which connects Dawson City, Yukon, to Inuvik and Tuktoyaktuk, N.W.T. Furthermore, most northern towns and villages are small (the largest is Inuvik, with a population of fewer than 4,000 people). Evidence of climate change and severe weather, and natural system modifications (wildfires), which are the primary threats to the species, comes from long-term satellite data, including the observed and derived products of multiple sensors (optical imagery, thermal/surface temperatures, microwave and radar), collected over the past 30 to 40 years in the Arctic-Boreal region of North America (Duncan et al. 2019). New advances in sensor technology and processing techniques have resulted in substantial progress in understanding the surface temperature (a key driver of change) and properties of the Arctic Ocean and Arctic-Boreal land biosphere (land ice, seasonal snow cover, permafrost, tundra vegetation, boreal vegetation, fire regimes and wetlands), as well as the atmosphere. In particular, data from commercial very high resolution sensors can provide insights into the distribution of plant functional types, disturbances, productivity and land-atmosphere interactions, as well as changes in these phenomena over time (Duncan et al. 2019).

IUCN 7, Natural system modifications (medium–low threat impact)

IUCN 7.1, Fire and fire suppression (medium–low threat impact)

Weather and climate conditions affect wildfire characteristics at multiple temporal and spatial scales, with warmer, drier and windier conditions all increasing the likelihood that wildfires will ignite, spread and intensify (Moritz et al. 2005). Wildfire plays a significant role in shaping landscape and habitat diversity in northern boreal forests. This increasing wildfire risk poses indirect threats to Gray-headed Chickadee populations in the next 10 years. Evidence of the extent of past fire activity in the Arctic-Boreal region can be found in cumulative fire maps (area burned 1986 to 2022) compiled by the Canada Natural Fire Database (Natural Resources Canada 2024; Figure 6). In addition, recent evidence from wildfire regime changes in Canada, tracked for the periods 1959 to 2015 and 1980 to 2015, shows that the area burned and number of large fires and lightning-caused fires are increasing in most of western and northern Canada (Hanes et al. 2019). A significant increase in area burned has also been reported in the boreal region of northern Canada (Kasischke and Turetsky 2006). While wildfire is unlikely to kill adult chickadees, which are able to fly away from the affected area, regional increases in fire activity may reduce and modify the overall availability (for example, amount or area, spatial location and temporal distribution) of suitable habitat (for example, mature and old forest types containing standing decaying and dead conifer and deciduous trees large enough for excavating nest and roost cavities, and healthy live trees for foraging).

Evidence of ongoing and future changes in wildfire behaviour and activity comes from the examination of past fire data, as described above (Hanes et al. 2019; Natural Resources Canada 2024), as well as observations of recent fire behaviour and projections from climate and wildfire modelling for northern Canada. By the year 2100, the projected warmer and drier conditions are expected to increase the area burned annually by large fires (> 200 ha) in northern Yukon and Northwest Territories by 2 to 4% annually under the Representative Concentration Pathway (RCP) 2.6 (low emissions) and RCP 8.5 (high emissions) scenarios, as well as increasing the number of large fires in northern Yukon and Northwest Territories under the RCP 2.6 and RCP 8.5 scenarios by 0.1 to 0.2 fires per 100,000 ha/year) and 0.2 to 0.4 fires per 100,000 ha/year, respectively, relative to the 1981 to 2010 reference period (Natural Resources Canada 2021). Trends in the area burned, number of fires, fire size and fire seasonality appear to correspond to climate-induced changes—for example, increased temperatures (Gillett et al. 2004; Skinner et al. 2006) and associated moisture stress (Flannigan et al. 2016)—that have taken place over recent decades and that are projected to increase across Canada in the upcoming century (Wotton and Flannigan 1993; Girardin et al. 2009; Jain et al. 2017). In 2023, unprecedented extreme fire weather conditions occurred in most of northern and southern Canada, caused by record high temperatures and persistent and widespread drought (Barnes et al. 2023; Tracking and Monitoring of the Risks of Forest Fires (Canada) 2023). These conditions fuelled intense and extensive wildfires that burned about 18.4 million hectares (Mha) of forest in northern and southern Canada in 2023, nearly seven times the 10-year average, and equivalent to about 5% of Canada’s forest area (Natural Resources Canada 2022, 2023). In 2023, nearly 224,000 ha in Yukon and more than 4.1 Mha in the Northwest Territories were burned (Public Safety Canada 2023; Yukon Wildland Fire Management 2023; Government of Northwest Territories 2024). Short-term effects of wildfire include shifts in habitat type from mature and old forest to herb and shrub-herb habitats (for example, post-disturbance habitats), while long-term effects include fire-induced tree mortality and post-fire vegetation patterns, which influence the probability of tree regeneration, growth and survival, in turn affecting future fire probability (Coop et al. 2020).

Figure 6 National Burned Area Composite for Canada (NBAC), 1986 to 2022 (Natural Resources Canada 2024). Data sourced from (i) Natural Resources Canada (red polygons); and (ii) provincial, territorial and Parks Canada agencies (orange polygons). The NBAC is a GIS database and system that calculates the area of forest burned on a national scale for each year since 1986. It provides the only composite wildfire data for the Arctic-Boreal region in northern Canada.

Climate change and severe weather (IUCN 11; medium–low threat impact)

The threat posed by climate change to Gray-headed Chickadee in the next 10 years is primarily due to the impacts of current and projected annual increases in temperature in northern Canada. Between 1948 and 2016, the increase in mean annual temperatures was 1.7 °C for Canada and 2.3 °C for northern Canada, roughly three times the global rate. The greatest recent increases in mean annual temperature were in northwest Canada, with an increase of more than 3 °C during that period. Both Yukon and the Northwest Territories experienced significant winter warming, with temperature increases ranging from 4 °C to 6 °C during the 1948 to 2016 period (Bush and Lemmen 2019). For Gray-headed Chickadee, climate change can result in both direct effects (exposure of eggs, nestlings and adults) and indirect ones (food and prey limitation, predator shifts, cache integrity, vegetation and habitat shifts, changes to natural processes and natural disturbances).

IUCN 11.1, habitat shifting and alteration (medium–low threat impact)

Habitat shifts and alterations that decrease the amount, spatial location, temporal distribution and quality of suitable breeding and winter habitat (for example, nest and roost trees and foraging habitat) for Gray-headed Chickadee can occur as a result of (i) changes in plant hardiness zones and climate suitability zones that shift areas where trees and shrubs can grow and survive (for example, reduction of spruce in northern Yukon; Natural Resources Canada 2021); (ii) drier conditions and drought resulting in increased tree mortality from physiological stress or interactions with wildfire and insects (reflected in the climate moisture index; Allen et al. 2010; Bush and Lemmen 2019); and (iii) changes in permafrost conditions (temperature and thickness) that cause shifts in forest composition and structure (for example, decreases in tree cover in poorly drained areas and increases in tree cover in well-drained areas; Helbig et al. 2016; Bush and Lemmen 2019). Evidence to support such past and ongoing habitat shifts comes from an examination of land-cover changes in the Arctic-Boreal region from 1984 to 2014 using satellite imagery and climate, topographic and permafrost data (Wang et al. 2020; see Historical, Long-term, and Continuing Habitat trends, above). These land-cover changes result in changes in forest type (for example, biome shifts; see Historical, Long-term, and Continuing Habitat trends). The future predictions align with the current evidence for land-cover changes in recent decades (using satellite imagery and sensor data) in the Arctic-Boreal region (Wang et al. 2020) and the boreal forest region in North America and Europe (Berner and Goetz 2022). Evidence to support future shifts or decreases in suitable habitat for Gray-headed Chickadee or similar bird species comes from habitat suitability (density and distribution) projections to the end of the century, based on three global climate models and species distribution models for 46 species of terrestrial birds occupying ecoregions in northwestern Canada (Yukon and Northwest Territories) and Alaska (Van Oordt La Hoz et al. in prep.). For resident Boreal Chickadee and other conifer-associated landbirds, the amount of suitable habitat is predicted to decrease in future decades (Van Oordt La Hoz et al. in prep.). Impacts relevant to Gray-headed Chickadee include ongoing and future changes in forest stand types that alter the availability (for example, amount or area, spatial location and temporal distribution) of suitable habitat containing the required structural attributes (for example, standing decayed or dead conifer and deciduous trees for nest and roost trees and live mature or old conifer and deciduous trees for forage trees). Gray-headed Chickadee—like the weak cavity nesters Boreal Chickadee, Red-breasted Nuthatch (Sitta canadensis) and Brown Creeper (Certhia americana)—is likely a specialist species occupying uncommon, atypical and specialized habitats in northern portions of the boreal forest, due to its dependence on mature/old, structurally complex habitat types containing specific structural attributes needed for nesting, roosting and foraging (Mahon et al. 2016).

IUCN 11.2, droughts (unknown threat impact)

Droughts are climate dependent and are expected to increase along with the annual increases in temperature projected to occur in northern Canada. Evidence for past and ongoing droughts comes from an examination of observed and derived satellite data products for the Arctic-Boreal region during the 1982 to 2011 period. Earlier springs and associated warm and dry conditions late in the growing season may be decreasing peak summer ecosystem productivity, as well as increased tree mortality and fire activity (Buermann et al. 2013). Early spring warming and longer non-frozen periods are associated with decreases in both summer greenness and moisture (Parida and Buermann 2014). The impacts of increased droughts on Gray-headed Chickadee are unknown. While greater tree mortality may increase the availability of suitable nest and roost trees, other effects such as decreased productivity and higher fire activity may reduce the overall amount, area, spatial location or temporal distribution of suitable habitat (for example, mature and old forest types containing decaying and dead trees large enough for excavating nest and roost cavities, and healthy live trees for foraging).

IUCN 11.3, temperature extremes (medium–low threat impact) and IUCN 11.4, storms and flooding (unknown threat impact)

Direct climate effects include seasonal shifts or variability in temperature and precipitation that result in extreme weather events that may cause exposure-related mortality (for example, hailstorms causing fledgling mortality). The evidence supporting past, ongoing and future climate-induced effects is varied and may include empirical studies of closely related species (for example, other brown-capped chickadees) or species found in the same ecosystem with similar requirements. Changes or extremes in specific metrics such as temperature, humidity, number of freeze-thaw events and the presence/absence of deep-freeze events may influence the quality and integrity of cached food for species such as Gray-headed Chickadee that rely on fall and winter storage of perishable food items like seeds and nuts (Sutton et al. 2016, 2019). In Canada Jay (Perisoreus canadensis), another resident boreal species that depends on cached food, the number of autumn freeze-thaw events was found to influence late-winter fecundity (number of young produced per capita in a given breeding season) over a 38-year period in southern Ontario; late-winter fecundity is the primary vital rate affecting population growth in the species (Sutton et al. 2021). Warmer and more variable fall conditions accelerated the degradation of perishable cached food (arthropods, mushrooms, berries and vertebrate flesh, including carrion and prey; Sutton et al. 2019) required for successful reproduction and population stability (Sutton et al. 2021; see also Waite and Strickland 2006).

Severe events causing forest disturbance are also becoming more common as a result of climate change. At the stand level or higher, the greater incidence and severity of storms may result in increased windthrow, reducing habitat features such as the standing dead trees and mature and old decaying trees required by Gray-headed Chickadee. No stand-level data are available on the amount and location of windthrow created after storm events in northern boreal forests in the Arctic-Boreal region, although a new satellite-imagery-based system can map damaged areas in forests (Wegmueller and Townsend 2021). Therefore, the scope, severity and timing of this threat for Gray-headed Chickadee remain unknown.

IUCN 8, invasive and other problematic species, genes and diseases (unknown threat impact)

IUCN 8.2, problematic native species/diseases (unknown threat impact)

There is observational evidence of heavy predation by Northern Shrike (Lanius borealis) on Gray-headed Chickadee at one site in Alaska. Predation on juveniles occurred in multiple years in an area known to be occupied by one or more Gray-headed Chickadee breeding pairs. This included the predation of entire broods in some years, and the subsequent disappearance of this occurrence. It is unknown whether shrike predation was responsible for this disappearance (Booms pers. comm. 2023). It is uncertain whether this affects Gray-headed Chickadees in Canada, as there are no observations of shrike predation on the species in Canada. High predation rates combined with the species’ small clutch size, low number of fledglings, short lifespan and dispersed breeding subpopulations mean that consecutive years of high predation rates and low productivity could result in decreased population persistence for Gray-headed Chickadee (that is, the population cannot maintain sufficient density to persist over time)—an example of limiting factors becoming a threat in a small population.

IUCN 8.3, introduced genetic material (unknown threat impact)

Hybridization may limit populations by causing genetic swamping (where the rare form is replaced by hybrids) or demographic swamping (where population growth rates are reduced below replacement rates due to the production of maladaptive hybrids) (Todesco et al. 2016). This phenomenon may also threaten populations that have reduced ranges or population sizes due to other threats. Potential conditions that facilitate hybridization mechanisms are unknown but could involve climate patterns, chickadee distribution, life requisites (food or prey resources) and physical tolerances (Curry 2005). Preliminary evidence from ongoing hybridization and gene flow studies of Gray-headed and Boreal Chickadees in Alaska and Yukon has identified probable hybrids in northern Alaska (Johnson pers. comm. 2023). This research team is continuing their work to estimate the rate of hybridization between sympatric Gray-headed and Boreal Chickadees in Alaska and Yukon by estimating gene flow between the two species (using museum specimens and blood samples from captured wild birds), and by examining temporal changes in genetic diversity in Boreal Chickadees for samples collected before 1930, in 1931 to 1975, and in 2020 or later. The degree to which hybridization threatens Gray-headed Chickadee is currently unknown.

IUCN 9, pollution (unknown threat impact)

IUCN 9.5, air-borne pollutants (unknown threat impact)

Although empirical evidence of the negative effects of wildfire smoke on resident landbirds of the northern boreal forests of North America or Europe is limited, particulates from wildfire smoke could affect bird populations in northern Canada due to the recent increase in area burned and number of large fires. A recent review paper examining the effects of wildfire smoke on the health and behaviour of wildlife presents evidence for a number of acute and chronic health outcomes, which include carbon monoxide poisoning, respiratory distress, neurological impairment, respiratory and cardiovascular disease, oxidative stress (imbalance in free radicals) and immunosuppression (Sanderfoot et al. 2022). The impacts of wildfire smoke on Gray-headed Chickadee are unknown.

The atmospheric deposition of contaminants such as mercury is known to occur at high northern latitudes, although there are no empirical data on the negative effects of airborne mercury on resident landbirds of the northern boreal forests of North America or Europe. According to a review of knowledge gaps, most research to date has been conducted on waterbirds and associated trophic levels in marine and aquatic systems during reproductive periods, resulting in an incomplete assessment of the threat of atmospheric mercury to many bird taxa (Seewagen 2010). The impacts of airborne contaminants on Gray-headed Chickadee are thus unknown.

Number of threat locations

Key threats to Gray-headed Chickadee (climate change and severe weather, and related natural system modifications in the form of wildfire) are pervasive across the species’ year-round range in Canada. However, at present, specific climate-related impacts are poorly understood; consequently, there is not enough information to apply the concept of “locations” to Gray-headed Chickadee in Canada.

Protection and status

Legal protection and status

Because Gray-headed Chickadee is a resident species in Canada, it is afforded protection under the Migratory Birds Convention Act, 1994. It is not currently listed under the Species at Risk Act (2002). COSEWIC assessed this species as Endangered in May 2024.

Non-legal status and ranks

Gray-headed Chickadee is currently ranked by NatureServe (2024) as Vulnerable to Apparently Secure (G3G4) globally, Critically Imperilled (N1) in Canada, Unrankable in Northwest Territories (SU), and Critically Imperilled (S1) in Yukon. In the United States, it is considered Vulnerable (N3) nationally, while in Alaska it is ranked as Critically Imperilled to Imperilled (S1S2; rounded rank S1). Under the Alaska Species Ranking System, the species is designated II Red, that is, of very high conservation concern (Alaska Center for Conservation Science 2017).

Land tenure and ownership

Gray-headed Chickadee was detected in Ivvavik National Park in Yukon in 1993 and 2008, and in Vuntut National Park in 1999. Most of its range is on territorial public lands. Gray-headed Chickadee has been observed in the Inuvialuit Settlement Region in Yukon and the Northwest Territories, the Vuntut Gwitchin Traditional Territory in Yukon, and the Gwich’in Settlement Area in the Northwest Territories.

Information sources

Collections examined

No collections were examined for the preparation of this report.

Authorities contacted

• Booms, T. Wildlife Biologist – Threatened, Endangered, and Diversity Program. Alaska Department of Fish and Game. Fairbanks, Alaska, USA
• Cannings, S. Species-at-Risk Biologist. Canadian Wildlife Service – Northern Region, Environment and Climate Change Canada. Whitehorse, Yukon
• Iles, D. Biostatistician. Canadian Wildlife Service – National Capital Region, Environment and Climate Change Canada. Ottawa, Ontario
• Johnson, J. Supervisory Wildlife Biologist – Migratory Birds Management – Landbirds. U.S. Fish and Wildlife Service. Anchorage, Alaska, USA
• Sinclair, P. Bird Conservation Biologist. Canadian Wildlife Service – Northern Region, Environment and Climate Change Canada. Whitehorse, Yukon

Acknowledgements

Funding for the preparation of this report was provided by the Canadian Wildlife Service, Northern Region, Environment and Climate Change Canada. The report writers wish to extend thanks to SSC members Christian Artuso, Pete Davidson, Richard Elliott, Elsie Krebs and Dave Toews for their review comments, and to Amit Saini (COSEWIC Secretariat, ECCC) for generating Figure 4 and calculating EOO values. The authorities listed above provided valuable data and/or advice.

Biographical summary of report writer(s)

Dr. C. Lisa Mahon is Landbird Program Lead, Canadian Wildlife Service – Northern Region, Environment and Climate Change Canada, and an adjunct professor in the Department of Biological Sciences at the University of Alberta. She conducted post-doctoral work on modelling cumulative effects in boreal landbirds at the University of Alberta. Her graduate research included the breeding ecology of, and habitat selection in, Chestnut-backed Chickadee, and cavity nester response to partial cutting in northern British Columbia (Ph.D. at University of British Columbia); as well as habitat selection in Baird’s Sparrow in southern Alberta (M.Sc. at University of Alberta). Current areas of study include the conservation and management of terrestrial landbirds in northern boreal ecosystems, with a focus on monitoring and documenting the status of populations in boreal and high-elevation systems, assessing distribution shifts across elevational gradients, identifying shifts in seasonal phenology and habitat/resource use in high-elevation habitats during the breeding and post-breeding periods, assessing and quantifying climate change adaptation, identifying regional boreal refugia, designing and modelling regional cumulative effects assessments, and developing and applying acoustic tools to improve the reliability and accuracy of population metrics.

At time of writing, Logan McLeod was a Landbird Biologist with the Canadian Wildlife Service – Northern Region (Yukon Territory), Environment and Climate Change Canada. He has worked extensively on monitoring programs for terrestrial birds in boreal Canada. He earned a graduate degree (M.Sc., University of Alberta) for studies on the species distribution and population size of Yellow Rail in northern Alberta and the Northwest Territories.

Appendix A. Threats calculator for Gray-headed Chickadee (Poecile cinctus).

Threats assessment worksheet

Species or ecosystem scientific name

Gray-headed Chickadee, Poecile cinctus

Date: 18 Jan 24

Assessor(s): C. Lisa Mahon, Louise Blight, Dwayne Lepitzki (facilitator), Andrew Horn, Tom Jung, Alexandra Heathcote, Travis Booms, Bruce Bennett, Eve Lamontagne, Paul Leonard, Syd Cannings, Ryan Durack, Richard Elliot, Karen Timm (COSEWIC Secretariat)

References: Draft calculator accompanied draft 6-month COSEWIC report dated 26 June 2021, threats telecon occurred on 18 Jan 2024

Assigned overall threat impact:

CD = Medium–Low

Overall threat comments

As the generation length of Gray-headed Chickadee is estimated to be 2.2 years (Bird et al. 2020), threats are assessed over a 10-year period. Climate change impacts on Gray-headed Chickadee and its habitat are likely already underway, although poorly understood. Individuals may produce one brood each year, but can be long-lived due to resident status, obligate use of cavities for nesting and roosting, and adaptations for year-round survival (opportunistic foraging during breeding season, food caching in winter and survival during extreme cold temperatures and darkness). Immediate and short-term (annual, decadal) habitat shifts resulting from climate-induced changes to vegetation dynamics and to wildfire, permafrost and drought regimes are causing changes to land cover, forest types and tree structural attributes across the Arctic-Boreal region. As this species is a year-round resident, threats are only assessed in Canada. Number of mature individuals unknown, although not detected in historical range in targeted 2019 surveys. Modelling indicates that there may be < 1,000 or even < 250; insufficient data to quantity population trend. Contraction of historical range to Brooks Range and Old Crow Basin in northern Yukon (Figure 4). Limiting factors may include (i) potential competition with Boreal Chickadee; (ii) dependence on cached food during non-breeding periods; and (iii) dependence on the availability of suitable nesting and roosting trees. Limiting factors could become threats to species when population size is small.

Classification of Threats adopted from IUCN-CMP, Salafsky et al. (2008).

ARUs (n = 86 Song Meter SM4 recording units) were deployed from April to June 2019 at 24 targeted and 62 design-based survey sites, each separated by over 300 m. A total of 82 of 86 survey sites were in habitat considered suitable for breeding by Gray-headed Chickadee (land-cover types dominated by trees over 4 m). Each ARU had an effective detection radius of approximately 45.2 m (± 4.1 m) for detecting vocalizing Boreal or Gray-headed Chickadee (Matsuoka et al. 2012), corresponding to an area of 0.64 ha. A two-step process was used in the subsequent screening of 18,470 hours of recordings from the ARUs. First, the recordings were scanned with an automated vocalization recognizer developed by Logan McLeod to detect the Gray-headed Chickadee El call, and second, all potential Gray-headed and Boreal Chickadee vocalizations identified by the recognizer were examined manually (visual inspection of the spectrogram and aural review of the audio recording). No Gray-headed Chickadees were detected on the recordings from northern Yukon in 2019, although Boreal Chickadees were detected at 23 of 24 targeted survey sites, and at 10 of 62 randomly selected survey sites (Figure 5). Since 2019, no incidental observations of the species have been reported in Canada, nor have there been additional targeted surveys.

Abundance

The global population estimate for Gray-headed Chickadee is approximately 2 million mature individuals (Partners in Flight Science Committee 2013), and the North American population is estimated to be fewer than 5,000 mature individuals, based on expert opinion (Rosenberg et al. 2016), although neither estimate is backed up by empirical survey data. No systematic monitoring program undertaken in Alaska (for example, Christmas Bird Count, on-road North American Breeding Bird Survey, off-road Alaska Landbird Monitoring Survey and targeted surveys in the Brooks Range; Tibbitts et al. 2006; DeGroot and McMillan 2012) or Canada (Christmas Bird Count, on-road North American Breeding Bird Survey and off-road Boreal Bird Monitoring Program) has detected this species (Booms et al. 2020; Hailman and Haftorn 2020; Mahon et al. in prep.). Because Gray-headed Chickadees occur in low numbers in remote areas, comprehensive, off-road monitoring programs that are design-based, representative (in terms of spatial coverage and habitat types), and standardized (in terms of protocols and methods) are required to detect the species and estimate current distribution and abundance.

Although the survey data are insufficient to estimate the size of the Gray-headed Chickadee breeding population in Canada, the scarcity of the species in a rigorously designed survey provides some clues as to their maximum abundance. Surveys conducted in northern Yukon in 2019 at 24 targeted sites where the species historically occurred, as well as at 62 design-based survey sites from the Boreal Bird Monitoring Program, failed to detect the species. Bayesian analysis based on assumed detection ranges and simulations of various abundances of Gray-headed Chickadee indicate that a no-detection result occurs in 50% of simulations with a population of 159 individuals (that is, a 50% probability that there are fewer than 159 mature individuals in Canada). In addition, these simulations suggest a 99% probability that the number of mature individuals is less than 1,000 and a 68% probability that the number of mature individuals is less than 250.

These estimates are based on zero detections across the 82 ARU survey locations in suitable habitat (with habitat suitability determined from the locations of earlier records; see Table 1) in northern Yukon in 2019. The analysis assumed that, during the average of 225 hours that each ARU was active in Yukon in 2019, any male bird would be detected at least once if it had a territory overlapping the effective detection radius of each ARU. It was assumed that territory size was 0.17 km² (radius = 233 m; Hailman and Haftorn 2020) and that the ARU’s effective detection radius for Gray-headed Chickadee was 40 m (Matsuoka et al. 2012). The number of ARUs yielding positive detections (y=0) was modelled as a binomial random variable and tested using spatially explicit simulations to yield appropriate estimates at realistic population densities (Mahon et al. in prep.).

Fluctuations and trends

As Gray-headed Chickadee has not been detected in Canada using targeted or design-based monitoring programs, no empirical data are available to assess population fluctuations or trends.

Recent efforts (for example, 2010 to 2019) to detect Gray-headed Chickadee in its historical range in North America resulted in only three records in Alaska (Booms et al. 2020) and an incidental sighting in Yukon (Mahon et al. in prep.; Table 1; Figure 3). The detections in Alaska in 2011 and 2013 (Booms et al. 2020) and Canada in 2014 were in the northern part of the historical range, consistent with a northward shift or contraction in the distribution of Gray-headed Chickadee in North America (see Extent of Occurrence under Extent of occurrence and area of occupancy).

A comparison of the number of Gray-headed Chickadee detections in North America in recent decades can be used to consider whether numbers may be declining in Canada. There were 45 occurrence records in Alaska from 2000 to 2009, but only 3 records from 2010 to 2017, despite 862 survey hours in the northern part of the historical range during the second period. In addition, Gray-headed Chickadee has been monitored in two areas of northern Alaska for over 20 years (representing 32 of 48 records since 2000), but it has not been recorded in the northern portion of the ANWR since 2015, or in its eastern portion since 2013 (Booms et al. 2020). Only two incidental records of Gray-headed Chickadee have been obtained in Canada since 2000 (a group of four individuals in 2008 and one individual in 2014), and none from the extensive targeted and design-based surveys in 2019 in the Gray-headed Chickadee’s historical range in northern Yukon (see Population Sizes and Trends). This suggests that an ongoing decline may be occurring in Canada (as well as in Alaska), but the data are not sufficient to quantify the rate of decline over the last 10 years. No extreme fluctuations occur in the number of mature individuals of this species.

Severe fragmentation

A taxon can be considered severely fragmented if most (> 50%) individuals— or most (> 50%) of the total area occupied (as a proxy for a number of individuals)—is in habitat patches that are both (a) smaller than would be required to support a viable population; and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse. Details of Gray-headed Chickadee distribution in Canada are unknown, but severe fragmentation is unlikely to apply to this species, as its habitat is not highly patchy in nature and birds are able to disperse long distances.

Rescue effect

Gray-headed Chickadee could potentially immigrate from Alaska to Canada, although the availability of suitable breeding and non-breeding habitat in Canada is unknown. However, the small population size and likely range contraction and population decline in Alaska (Booms et al. 2020) and the potential decline in the amount, spatial location, temporal distribution and quality of habitat in Canada (Wang et al. 2020) suggest that rescue from the only North American source population in Alaska is unlikely.

Figure 5. Survey effort for Gray-headed Chickadee (Poecile cinctus) in Yukon in 2019, showing sites where autonomous recording unit (ARU) stations were deployed, including targeted historical Gray-headed Chickadee survey stations (dots; n = 24) and randomly selected Boreal Monitoring Strategy survey sites (crosses; n = 62). The presence of Boreal Chickadee (P. hudsonicus) records is shown by green fill, and the absence of chickadee species is indicated with no fill, for both survey types. Note that multiple ARU stations were used at each survey site.