Western Bumble Bee mckayi subspecies (Bombus occidentalis mckayi): management plan proposed 2026

Official title: Management Plan for the Western Bumble Bee mckayi subspecies (Bombus occidentalis mckayi) in Canada 2026 (proposed)

Species at Risk Act
Management Plan Series

Proposed
2026

Preface

The federal, provincial, and territorial government signatories under the Accord for the Protection of Species at Risk (1996)^{Footnote 2} agreed to establish complementary legislation and programs that provide for effective protection of species at risk throughout Canada^{Footnote 3}. Under the Species at Risk Act (S.C. 2002, c.29)^{Footnote 4} (SARA), the federal competent ministers are responsible for the preparation of management plans for listed species of special concern and are required to report on progress within five years after the publication of the final document on the Species at Risk Public Registry.

The Minister of the Environment, Climate Change and Nature and Minister responsible for Parks Canada is the competent minister under SARA for the Western Bumble Bee mckayi subspecies and has prepared this management plan, as per section 65 of SARA. To the extent possible, it has been prepared in cooperation with all relevant jurisdictions, wildlife management boards, indigenous organizations and others as per section 66(1) of SARA.

Success in the conservation of this species depends on the commitment and cooperation of many different constituencies that will be involved in implementing the directions set out in this plan and will not be achieved by Environment and Climate Change Canada and Parks Canada, or any other jurisdiction alone. All members of the public are invited to join in supporting and implementing this plan for the benefit of the species and society as a whole. Implementation of this management plan is subject to appropriations, priorities, and budgetary constraints of the participating jurisdictions and organizations.

Acknowledgments

This management plan was prepared by Syd Cannings (Environment and Climate Change Canada, Canadian Wildlife Service (CWS) Northern Region), with the able and necessary assistance of a technical team made up of Kirsten Wilcox (CWS Northern Region), Eric Gross (CWS Pacific Region), Cory Sheffield (Royal Saskatchewan Museum), Jennifer Heron (British Columbia Ministry of Water, Land and Resource Stewardship), Jessica Rykken (University of Alaska Fairbanks), Maria Leung (Consultant based in Whitehorse), and Anthony Colangelo (Pollinator Partnership Canada).

Thank you to the staff at the following people who provided edits and supported in the jurisdictional review process including, but not limited to, Diane Casimir and Elizabeth Vincer (Parks Canada), Erin Brotherston (British Columbia Ministry of Agriculture and Food), Lauren Hall (British Columbia Ministry of Environment and Climate Change Strategy), Sharilynn Wardrop (British Columbia Parks), Riley Waytes (British Columbia Ministry of Water, Land and Resource Stewardship), Joanna Wilson (Northwest Territories Environment and Climate Change), Tom Jung (Yukon Department of Environment), Alexandra Heathcote (Yukon Department of Environment), Brett Pagacz (Yukon Department of Environment), and Alice McCully (Tr’ondëk Hwëch’in Government). Acknowledgement and thanks are also given to all other parties that provided advice and input used to help inform the development of this management plan.

The document was largely based on the Management Plan for the Yellow-banded Bumble Bee; experts consulted on that document included Nigel Raine (University of Guelph), Leif Richardson (University of Vermont, Xerces Society), and Lincoln Best (Consultant, @beesofcanada).

Executive summary

In May 2014, the Western Bumble Bee mckayi subspecies (Bombus occidentalis mckayi) was assessed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) as Special Concern, owing to a large observed decline in abundance in its closely-related sibling, the Western Bumble Bee (Bombus occidentalis occidentalis), in southern Canada, and concern that the threats affecting that bee may soon cause declines in the northern form. It was added to Schedule 1 of the Species at Risk Act (SARA) in December 2023. The subspecies has recently been split from its southern sibling, and is now considered to be a full species, the McKay’s Bumble Bee (Bombus mckayi). This name will be used for the remainder of the document. It can be differentiated visually by a distinctive band of gold across abdominal segment 3, which occasionally is expanded into segment 2, and the tip of the abdomen, segment 5, is usually pale yellow-brown.

In Canada, this bee is restricted to the far northwest—from the northern Yukon east to the mountains of western Northwest Territories and south to northern British Columbia.

Because most of its range remains largely wilderness, the threats affecting its close relatives to the south are probably less severe in this region. In general, the three main threats impacting these bumble bees are: pathogen transmission and spillover from managed bumble bee populations in greenhouses; pollution (the use of insecticides, herbicides and fungicides in agriculture and silviculture); and climate change and severe weather (habitat shifting and alteration, and temperature extremes).

The McKay’s Bumble Bee also faces limiting factors. It requires a constant suite of floral resources to support colony growth: pollen and nectar need to be available throughout the growing season. Bumble bees have a type of sex determination that makes them susceptible to declines when population sizes are small.

The management objectives for the McKay’s Bumble Bee are to maintain its abundance throughout its Canadian range and to maintain the distribution of the species throughout its Canadian range. Broad strategies and conservation measures to achieve the management objectives for the species are presented in section 6.

1. COSEWIC* Species assessment information

Date of assessment: May 2014

Common name (population): Western Bumble Bee, mckayi subspecies

Scientific name: Bombus occidentalis mckayi

COSEWIC status: Special Concern

Reason for designation: This subspecies ranges in Canada from northern British Columbia (north of approximately 55-57ºN) through southern Yukon and westernmost Northwest Territories; at least 50% of its global range is in Canada. Recent surveys in northwestern Canada and Alaska suggest that it is still common. However, the southern subspecies of the Western Bumble Bee is experiencing a serious, apparently northward-moving decline, and because the causes of this decline are unknown, the northern subspecies faces an uncertain future. Recent studies in Alaska suggest that this subspecies has among the highest parasite loads (particularly the microsporidian Nosema bombi) of any bumble bee species in North America. Other potential threats include the unknown transmission of disease from exotic bumble bee species introduced for pollination in greenhouses (ongoing in the Yukon), pesticide use (including neonicotinoid compounds), and habitat change.

Canadian occurrence: Yukon, Northwest Territories, British Columbia

COSEWIC status history: Designated Special Concern in May 2014.

* COSEWIC (Committee on the Status of Endangered Wildlife in Canada)

2. Species status information

The Western Bumble Bee mckayi subspecies (Bombus occidentalis mckayi) was until recently considered the northern form of the Western Bumble Bee. It was assessed as that subspecies by COSEWIC (2014) and officially listed under that name as Special Concern under the federal Species at Risk Act (SARA) on 8 December 2023. However, the subspecies has recently been separated from the Western Bumble Bee and elevated to full species status as the McKay’s Bumble Bee, Bombus mckayi (Williams 2021, Rohde 2022). This latter name will be used for the remainder of the document.

The International Union for Conservation of Nature (IUCN) has designated the Western Bumble Bee (Bombus occidentalis) (including both B. occidentalis mckayi (= B. mckayi) and its southern sibling B. occidentalis occidentalis) as Vulnerable, based on rangewide declines assessed as greater than 30% (Hatfield et al. 2015); however there are no declines documented in the northern part of the range (i.e that of McKay’s Bumble Bee). The McKay’s Bumble Bee has not been assessed separately.

In the Northwest Territories, the Western Bumble Bee in the broad sense (although only the subspecies B. occidentalis mckayi [= B. mckayi] occurs in the territory) was assessed as Data Deficient under the Species at Risk (NWT) Act (Northwest Territories Species at Risk Committee 2019). In British Columbia it is on the provincial Blue List of species of conservation concern (British Columbia Conservation Data Centre 2024). The species has no formal status in the Yukon.

Table 1 summarizes the other, non-legal status designations assigned to the McKay’s Bumble Bee.

3. Species information

3.1. Species description

The McKay’s Bumble Bee is a medium-sized bumble bee, with queens, reproductive males, and a smaller worker caste. They have a short face and tongue length relative to most other bumble bees. The upperside of queens and workers is black, with a band of golden hair across the thorax in front of the wing bases, some gold between the wings, and a distinctive band of gold across abdominal segment 3, which occasionally is expanded into segment 2 (Figure 1, left). At the tip of the abdomen, segment 5 is usually pale yellow-brown.

The males are similar in colour to the females, although they usually have more yellow hairs on the face and elsewhere on the body (Figure 1, right). They are intermediate in size between queens and workers, and although their antennae have one more segment than the females, they are short relative to those of other male bumble bees (COSEWIC 2014).

The McKay’s Bumble Bee was formerly considered a subspecies of the Western Bumble Bee (Bombus occidentalis) but Williams (2021) and further research by Rhode (2022) found consistent genetic, distribution, and colour pattern differences which supports separating these into two distinct species. The McKay’s Bumblee Bee has more yellow on the third segment of the abdomen, a pale yellow-brown fitfth segment (instead of bright white), and is found predominantly above 55˚ latitude while the Western Bumble Bee is found south of 55˚ latitude (Rohde 2022).

Figure 1. McKay’s Bumble Bees. Left: Queen, Upper Liard, Yukon, 4 June 2022. Photo: Syd Cannings; used with permission. Right: Male, Thirtyseven Mile Cr., Yukon, 12 August 2023. Photo: Ryan Sealy; used with permission.

3.2. Species population and distribution

The McKay’s Bumble Bee occurs only in North America, from northern British Columbia (BC) (south to about 55°N in the east, about 57°N in the west), north into Yukon (YT), extreme western Northwest Territories (NT) and throughout most of Alaska (AK) (Figure 2).

Figure 2. Global range of McKay’s Bumble Bee by ecosystem polygons; these may exaggerate the actual range. Ecosystem-based automated range (EBAR) polygons are derived from: NatureServe Canada EBAR Range Mapping Dark purple: confirmed occurrence(s) in ecosystem polygons in the last 40 years by both specimen collection and obervations; magenta: presence expected; pink: presence historical. Hexagons represent locations where specimens have been collected in Canada (not necessarily centered on location).

In northern British Columbia, McKay’s Bumble Bee has been confirmed as far south as the Ningunsaw River (56.9° N) in the west, and Pine Pass (55.3° N) in the Rocky Mountains (iNaturalist 2024).

While the McKay’s Bumble Bee population is apparently stable in Canada, the population size is unknown (Rohdes 2022). Estimates of abundance have relied on relative abundance compared with other collected bumble bees from historic museum samples and localized studies, which may underestimate common species (Gotelli et al. 2021). The McKay’s Bumble Bee is still one of the most common bumble bees in the valleys and lowlands of northwestern Canada but concerns remain about its future abundance (COSEWIC 2014). The Western Bumble Bee, a close relative south of 55˚ has experienced serious declines of up to 85% in BC between 2002-2011 (COSEWIC 2014).

3.3. Needs of the species

The McKay’s Bumble Bee is a habitat generalist. It is found in a wide variety of open habitats, including meadows within coniferous, deciduous, and mixed-wood forests and woodlands; taiga; riparian zones; gardens, and agricultural areas; and along roadsides (COSEWIC 2014).

Little research has been published on the McKay’s Bumble Bee, but we can infer its needs from those known of its close relatives, the Western and Yellow-banded Bumble Bees (COSEWIC 2014, COSEWIC 2015). Like those bumble bees, the McKay’s Bumble Bee is a generalist pollen forager and visits the flowers of a wide variety of plant species, from willows to raspberries to clovers (see Appendix A). It is short-tongued, so requires relatively shallow flowers for pollen gathering, but can rob nectar from deeper flowers by chewing through the flower’s wall (Evans et al. 2008). Because it is a colonial species that is active throughout the growing season, its primary requirement is a series of pollen and nectar sources throughout the spring and summer (Goulson 2010). The active season is approximately May through early August (COSEWIC 2014). For Yellow-banded Bumble Bees in southern Ontario, a close relation of the McKay’s Bumblee Bee, the amount of foraging resources was consistently the most important variable in that species’ habitat selection (Liczner and Colla 2020). Many of the flowers used are considered invasive or exotic weeds in disturbed habitats (for example, White Sweet‑clover, Melilotus alba; Common Dandelion, Taraxacum officinale; White Clover, Trifolium repens). Gibson et al. (2019) found that in southern Ontario, Yellow-banded Bumble Bees, which likely have similar habitat requirements to McKay’s Bumble Bees, preferred to forage on invasive Tufted Vetch (Vicia cracca) and other exotic members of the pea family.

Geographic availability of floral resources within home range areas may vary both within and among years (for example, blueberries (Vaccinium spp.) may have abundant blooms one spring, but not the next). Given this variability, this species requires a variety of floral sources at a landscape scale.

Like other bumble bees, McKay’s Bumble Bee males and workers die at the onset of cold weather, as do the queens of the previous summer; thus the colonies are only active for one season (Williams et al. 2014, COSEWIC 2014). However, in the late summer and early autumn (late July and early August), new potential queens and males emerge from the nest and leave to find mates. After mating the new queens disperse to select an overwintering site, travelling an unknown distance to do so. The specific overwintering habitats of McKay’s Bumble Bee queens are unknown, but bumble bees typically burrow 2‑15 cm deep in loose soil or rotting logs (Macfarlane 1974; Benton 2006; Liczner and Colla 2019). Because the queens do not survive more than one winter, individuals do not use the same sites from year to year.

There is no specific research available on how McKay’s Bumblee Bees disperse; however for all bumble bees, dispersal likely occurs primarily in spring by queens while searching for suitable nest sites (Goulson 2010). There is evidence that bumble bees are able to disperse relatively long distances, at least between 2.6 and 10 km from the colony of origin (Stout and Goulson 2000, Kraus et al. 2008, Lepais et al. 2010). Natural expansions of some species, for example the rapid spread of B. bimaculatus into western Canada and the Maritime Provinces, indicates that the rate of dispersal can be higher than this (Sheffield and Palmier 2023).

McKay’s Bumble Bee nests have not been observed, but closely-related species nest underground (Laverty and Harder 1988), often in abandoned rodent burrows (Plath 1927; Hobbs 1968; Macfarlane 1974; Colla and Dumesh 2010).

3.4. Limiting factors

Bumble bees have a type of sex determination (haplodiploidy) that potentially makes them susceptible to declines when effective population sizes are very small (Zayed and Packer 2005). Put simply, as numbers decline, more and more females develop as sterile males instead, reducing the reproductive output of the population. However, it seems that bumble bees also have several strategies to reduce the impact of this sterile male production (Leung and Meulen 2022).

Rohde et al. (2024) found evidence that genetic diversity in McKay’s Bumble Bee populations has been decreasing since 2002.This may be the first evidence of a yet undetected decrease in population size. A decline in genetic resiliency may also mean this species is increasingly vulnerable to changing conditions or sudden disturbances such as forest fires, increased pesticide use, or pulses of disease (Rohde et al. 2024).

4. Threats

4.1. Threat assessment

The McKay’s Bumble Bee threat assessment (Table 2) is based on the IUCN-CMP (International Union for Conservation of Nature–Conservation Measures Partnership) unified threats classification system (Salafsky et al. 2008). The threats assessment was updated from that reported in COSEWIC (2015) in a meeting on 19 March 2024, attended by Syd Cannings, David Fraser (facilitator), Bruce Bennett, Eve Lamontagne, Maria Leung, Claire Singer, Jessica Rykken, David McCorquodale, Eric Gross, Piia Kukka, Aija White, Riley Waytes, Cory Sheffield, Jenny Heron, and Michael Stalberg. The calculated overall threat impact is Low.

Threats are defined as the proximate activities or processes that have caused, are causing, or may cause in the future the destruction, degradation, and/or impairment of the entity being assessed (population, species, community, or ecosystem) in the area of interest (global, national, or subnational). Limiting factors are not considered during this assessment process. For purposes of threat assessment, only present and future threats are considered. Historical threats, indirect or cumulative effects of the threats, or any other relevant information that would help understand the nature of the threats are presented in the Description of Threats section (4.2).

4.2. Description of threats

The McKay’s Bumble Bee is thought to be impacted by three main threats (Table 2 above): 1) invasive non-native/alien species (for example Common Eastern Bumble Bee outside of its native range and European Honey Bee) and problematic native species (for example pathogen spillover of native microsporidians from greenhouse bumble bees and from honey bees); 2) pollution (agricultural and silvicultural pesticides); and 3) climate change and severe weather (habitat shifting and alteration, temperature extremes). Habitat loss from cropland expansion and intensification is an additional negligible threat, but the geographic scope is limited. Threats are discussed in more detail below, ordered by the IUCN-CMP primary threat categories

Residential and commercial development (IUCN-CMP Threat 1) – Negligible Impact

Habitat loss as a result of urbanization can be a threat, but these threats occur primarily in a small portion of this species’ large range. Although some development (for example suburban landscaping) might include an increase in the amount of floral resources for bumble bees, other urban, industrial and agricultural development virtually eliminates these resources.

Annual and perennial non-timber crops (IUCN-CMP Threat 2) – Negligible Impact

Habitat loss as a result of agricultural expansion and intensification (that is, reduction of non-crop habitats in farmland) is a threat in small parts of the range of the McKay’s Bumble Bee. Like other bumble bees, this species requires large amounts of nectar and pollen over the entire flight season. Over the past few decades, the increasing practice of planting crops to edge of fields, with little or no adjacent hedgerow or meadow habitat, has resulted in decreased quality foraging habitat for bumble bees globally (for example, Kosior et al. 2007), and may have had a similar impact in Canada (Grant and Javorek 2011), including local areas of agriculture in the northwest.

Energy production and mining (IUCN-CMP Threat 3) and Transportation and service corridors (IUCN-CMP Threat 4) – Negligible Impact

Energy production, mining and transportation corridors could result in some long term and short-term loss of habitat but some development could also result in longer term increase in edge habitat and therefore increase in flowers (COSEWIC 2014). These threats are expected to have negligible impact on McKay’s Bumble bees.

Logging and wood harvesting (IUCN-CMP Threat 5.3) – Negligible Impact

Logging may have a short-term benefit in creating foraging habitat. However, dense second-growth forest is poor habitat and would result in a local decline. In British Columbia, new clearcuts are heavily managed (for example with herbicides, see Threat 9.3), meaning it is often hard for floral resources to thrive.

Natural systems modification (IUCN-CMP Threat 7) - Unknown or Negligible Impact

During the threats assessment (Table 2), concern was expressed about the effects of increasing frequency, size, and intensity of fires on bumble bees. Although large, intense fires would probably cause short-term declines and increased smoke may temporarily suppress colonies, the open habitat created would likely later allow bee populations to rebound (Johnson et al. 2023).

Dams and water management (Threat 7.2) is expected to have a negligible impact on McKay’s Bumble Bees. New hydro projects (for example Site C on the Peace River) flood valleys, and dams can eliminate natural seasonal fluctuations of water levels in floodplains, reducing riparian meadows, but these activites are restricted to small areas.

Invasive and other problematic species and genes (IUCN-CMP Threat 8.1 and 8.2) - Low Impact

The introduction and/or spread of pathogens from commercially raised bumble bees (used for pollination within and, in some cases, outside greenhouses) and European Honey Bees (Apis mellifera) ; and the release of non-native bumble bees are direct threats to the McKay’s Bumble Bee. The McKay’s Bumble Bee is a member of the subgenus Bombus, and in southern Canada, all the other members of this subgroup -Rusty-patched Bumble Bee, Western Bumble Bee, and Yellow-banded Bumble Bee—declined significantly following widespread outbreaks of these pathogens in the 1990s (COSEWIC 2010, 2014, 2015, 2022).

Parasites and pathogens of bumble bees

The prevalence of the microsporidian Varimorpha (=Nosema) bombi (a single-celled fungal parasite) in North American bumble bees increased dramatically from low frequency in the 1980s to significantly higher frequency in the mid- to late-1990s, corresponding to a period of reported massive infectious outbreak of V. bombi in commercial bumble bee rearing stocks in North America (Cameron et al. 2016). Although V. bombi is native to North America, it has been postulated that a novel strain was imported from Europe about this time; however genetic evidence to date does not support this (Cameron et al. 2016; Brown 2017). V. ceranae, a prevalent pathogen associated with managed European Honey Bees, has also been detected in bumble bees worldwide, though the impact of this pathogen on bumble bees remains unclear and requires further investigation (Goblirsch 2018).

Although its effects on McKay’s Bumble Bee have not been studied, Varimorpha bombi, a fungal parasite, is common in some populations of this species; Koch and Strange (2012) found the pathogen in 44% of sampled McKay’s Bumble Bees in east-central Alaska. However, the use of commercial bumble bees (that could cause an outbreak of Varimorpha) is limited within the range of McKay’s Bumble Bee as there is limited commercial agriculture, so this threat is only scored with a Low impact (Robinson 2010, Yukon Argicultrual Branch 2016). Neither the use of commercial bumble bees, nor their pathogen load is regulated within the range of McKay’s Bumble Bee.

Studies have shown the parasites Crithidia bombi, C. expeoki^{Footnote 5} and V. bombi can have a potentially devastating effect on bumble bee colonies (Brown et al. 2000, 2003; Otti and Schmid-Hempel 2007, 2008; van der Steen 2008). These parasites are found in a variety of bumble bee species (Macfarlane 1974; Macfarlane et al. 1995; Colla et al. 2006). However, V. bombi infection rates and infection intensities were significantly higher in the Western Bumble Bee (McKay’s closest relative), than they were in bumble bees with stable populations, such as the Common Eastern Bumble Bee (B. impatiens) and the Two-form Bumble Bee (B. bifarius [now considered to be B. vancouverensis] (Cameron et al. 2011). Similar trends were seen in species with known declines (Yellow-banded Bumble Bees and Rusty-patched Bumble Bees), but small sample sizes do not allow for statistical analyses (Cameron et al. 2011). High infection rates could have implications for the future decline of McKay’s Bumble Bees.

The rapid rise in V. bombi infection in commercial bumble bees, the coincident decline in the Yellow-banded Bumble Bee, and the fact that these pathogens are more prevalent in Yellow-banded Bumble Bees relative to healthy species have together caused pathogen spillover to be cited as one of the primary causes of the declines of the Yellow-banded Bumble Bee (Thorp and Shepherd 2005; Cameron et al. 2011; Szabo et al. 2012; Graystock et al. 2016; all cited in Colla 2017; Arbetman et al. 2017). Pathogen spillover occurs when managed populations of bees introduce pathogens to wild populations or amplify pathogens (spillback) that may have been naturally in lower abundances (Power and Mitchell 2004; Graystock et al. 2016). In Canada, the use of infected commercial bumble bees for greenhouse pollination is known to cause pathogen spillover into populations of wild bumble bees foraging near those greenhouse operations (Colla et al. 2006; Otterstatter and Thomson 2008).

Rohde (2022) discovered that the farther away that McKay’s Bumble Bee populations were from known V. bombi infections, the more gene flow they exhibited among themselves. The effect was statistically significant, indicating that infection may be influencing gene flow for this species, but the effect is perhaps moderated by the isolation of this species from other compounding stressors.

However, there is much to learn about the effects of pathogen spillover on wild bumble bee populations, and new pathogens are still being discovered (Palmier et al. 2020). See also section on Pollution (Threat 9, below) for apparent interactions between fungicides and pathogen prevalence.

Few commercial greenhouse operations exist within the range of McKay’s Bumble Bee, but some may import managed bumble bees for pollination. In addition, commercial bumble bees are used in other areas (for example southern British Columbia) outside greenhouses (J. Heron, pers. comm.). More information is needed on the scale of this threat in the region, and the reach of this threat beyond agricultural areas.

European Honey Bees as vectors of pathogens and viruses

European Honey Bees appear to be another vector for the transmission of pathogens to wild bumble bees. Graystock et al. (2014) showed that, in Great Britain, the prevalence of C. bombi was 18% greater in bumble bees near an apiary than in those farther away from it. There is also increasing evidence that a number of European Honey Bee pathogens are transferable to bumble bees (Plischuk et al. 2009; Meeus et al. 2011; Peng et al. 2011; Graystock et al. 2013). Under controlled conditions, V. ceranae, a common parasite of European Honey Bees, produced fewer spores in bumble bees than in European Honey Bees but exhibited greater virulence^{Footnote 6}, reducing survival by 48% and having sublethal effects on behaviour (Graystock et al. 2013).

European Honey Bees that are infected with Deformed wing virus through the Varroa Mite (Varroa destructor) during pupal stages develop into adults showing wing and other morphological deformities. Researchers in Germany and the United Kingdom have found this European Honey Bee virus in deformed individuals of Buff-tailed Bumble Bee (B. terrestris) and B. pascuorum (Genersch et al. 2005; Fürst et al. 2014), and recent studies in Vermont have found Deformed wing virus and Black queen cell virus in bumble bees collected near European Honey Bee apiaries (Alger et al. 2019). Because the Varroa Mite is widespread in Canada (Ontario Ministry of Agriculture, Food and Rural Affairs 2019, Canadian Association of Professional Apiculturalists 2020), Deformed wing virus may pose a serious potential threat to Canadian bumble bee populations.

Competition with European Honey Bees

European Honey Bees also compete directly with bumble bees when pollen and nectar resources are not abundant. Pollen can be a limiting resource; in the absence of European Honey Bees, native bees can remove 97-99% of the available pollen daily (Schlindwein et al. 2005, Larsson and Franzen 2007). One standard apiary of 40 European Honey Bee colonies can remove 400 kg of pollen during three summer months in wildlands (Winston 1987; Seeley 1995; Cane and Tepedino 2016). Cane and Tepedino (2016) point out that this amount of pollen would produce 4 million (range 3.7‑12 million) individuals of an average leafcutter bee (Megachile rotunda). Henry and Rodet (2018) found that high-density beekeeping (greater than 14 colonies/km²) triggers foraging competition that decreases both the occurrence (−55%) and nectar foraging success (−50%) of local wild bees. However, Mallinger et al. (2018) caution that more competition studies that include measures of wild bee reproductive success are needed to quantify ongoing effects.

European Honey Bees are kept throughout much of the range of McKay’s Bumble Bee, albeit more sparsely than they are in southern Canada. Beekeeping is apparently increasing in the north, but numbers and sizes of apiaries are not tracked, at least in the Yukon (M. Leung, pers. comm.). Some individuals are taking up the apiary hobby because they have heard (mistakenly) that honey bees are an essential part of the natural environment and are declining (Egerer and Kowarik 2020).

Competition with exotic bumble bees

The introduction and use of commercial bumble bees for pollination services may further impact the McKay’s Bumble Bee. None of the commercial bumble bees used in western Canada—the Common Eastern Bumble Bee, Yellow-faced Bumble Bee (B. vosnesenskii) and Hunt’s Bumble Bee (B. huntii) are native within the range of McKay’s Bumble Bee. If they become established outside greenhouses, they may compete with native bee species for nesting habitat or forage resources, and may serve as a source for pathogens or diseases. The recent establishment of wild, exotic populations of Common Eastern Bumble Bee in Atlantic Canada, southeastern Alberta, and southwestern British Columbia (Palmier and Sheffield 2019) has likely had a negative impact on native species, as has been documented in other parts of the world (Williams and Osborne 2009). In extreme southwestern British Columbia, Hunt’s Bumble Bee has also become established outside its natural range since 2019 (iNaturalist 2024). It is still used for pollination both within and outside of greenhouses in that region (J. Heron, pers. comm.), even though it previously did not range west of the dry, southern Interior.

Agricultural and forestry effluents (IUCN-CMP Threat 9.3) -Low Impact

It has long been known that pesticides can have negative impacts on bees (for example, Johansen and Mayer 1990; NRC 2007). Although the recent focus has largely been on neonicotinoid insecticides, other insecticides, herbicides and fungicides have also been tied to bumble bee declines. Although pesticide use is low throughout the vast majority of the range of McKay’s Bumble Bee, some queens and workers of McKay’s Bumble Bees will be exposed to pesticides while they forage, and while they burrow into the soil to expand nest sites. Agricultural and forestry are increasing in the north, and climate change will allow a more diverse array of crops and their associated pests, so pesticide use will probably increase as well. At this time, pesticide use is not tracked in the Yukon or BC within the agricultural sector and permitting is only required in specific circumstances, such as application to water bodies, in Alaska or for companies in the Northwest Territories (NWT). However, BC does require Pesticide Use Permits for application of pesticides on all public and private lands.

Neonicotinoid insecticides

Around the time when the declines of bumble bees in the subgenus Bombus were observed in North America, the neonicotinoid insecticide imidacloprid was registered for use in the United States and Canada (1994 and 1995 respectively: Cox 2001). Neonicotinoids can pose a particularly severe threat to bees because they can be harmful even at concentrations in the parts-per-billion (ppb) range (Marletto et al. 2003). These pesticides are systemic, travelling throughout plant tissues and integrating with pollen and nectar. They are routinely used on golf courses and agricultural lands (Sur and Stork 2003). They are also used prophylactically; that is, they are being applied even if there is no apparent insect outbreak needing attention (van der Sluijs et al. 2014). In Quebec, Labrie et al. (2020) found that preventative neonicotinoid seed treatments in field crops are useful in less than 5% of cases, and suggest that integrated pest management solutions would likely offer an effective alternative to these practices (Labrie et al. 2020).

Although neonicotinoids are applied extensively in southern Canada (Main et al. 2014; Ontario Ministry of Environment, Conservation and Parks 2018; Giroux 2019), there is no information on their use in the Yukon and other parts of the northwest (Leung et al. 2022).

The effects of imidacloprid are not lethal to individual bumble bees when used as directed (for example, Tasei et al. 2001), but colonial insects such as bumble bees can be negatively impacted by cumulative sub-lethal effects of this and other pesticides. In fact, recent studies have shown that chronic (that is 1-4 weeks) exposure to neonicotinoid pesticides can have significant effects on bumble bees at field-realistic exposure levels (that is levels similar to those that would be encountered in agricultural areas) (Pisa et al. 2014; van der Sluijs et al. 2014; Crall et al. 2018; Raine 2018): bees suffered impaired learning and short-term memory (Stanley et al. 2015a); decreased foraging performance (Feltham et al. 2014; Gill and Raine 2014; Stanley et al. 2015b; Stanley et al. 2016); reduced queen production (Whitehorn et al. 2012); and ultimately, colony failure (Bryden et al. 2013).

Other neonicotinoids such as thiamethoxam and clothianidin also have effects on bumble bees, although these effects are not identical. Moffat et al. (2016) found that both thiamethoxam and imidacloprid reduced “colony strength” (number of live bees), but clothianidin did not. However, although Arce et al. (2017) found only subtle, mixed effects by clothianidin on worker behaviour (for example foraging frequency, pollen load size), they did find reduced numbers of adult bees at colonies exposed to the insecticide.

Neonicotinoid exposure in concert with other threats can also have significant negative results. In a study on the Common Eastern Bumble Bee, imidacloprid exposure followed by an immune challenge significantly decreased survival probability relative to control bees (Czerwinski and Sadd 2017).

The effects of neonicotinoids on pollinators have been reviewed by Health Canada’s Pest Management Regulatory Agency and three re-evaluation decisions for thiamethoxam, clothianidin, and imidacloprid were released in April 2019 (Health Canada 2019a, 2019b, 2019c); the detailed regulation changes can be found in the cited documents. A summary is provided as well (Health Canada 2020). In general, application of these neonicotinoids have been cancelled or restricted for certain uses, especially those related to foliar or soil applications on fruits, nuts, ornamentals, and outdoor-grown fruiting vegetables; cereal and legume seed-treatment uses received additional label instructions only. Further regulation changes were made in re-evaluation decisions made in the spring of 2021 (Health Canada 2021a, 2021b, 2021c). The changes made in the 2021 re-evaluations took effect in the spring of 2023.

Other insecticides

Sulfoxamine-based insecticides are the most likely successors to neonicotinoids, but there are few studies into their sub-lethal effects on pollinators. A recent study, however, found that bumble bee colonies exposed to sulfoxaflor produced significantly fewer workers than unexposed controls, and ultimately produced fewer reproductive offspring (Siviter et al. 2018).

Chlorantraniliprole is another insecticide recently approved for use in Canada as a seed treatment of corn that will at least partially replace the use of neonicotinoid insecticides. Although Health Canada (2016) determined that as a seed coat it presented a “negliglible risk to … bees,” research has shown that low-level, chronic oral exposure via pollen lead to lethargic behaviour in bumble bee workers and drones (Smagghe et al. 2013).

Tebufenozide is an insect growth regulator insecticide used for Eastern Spruce Budworm (Choristoneura fumiferana) control in eastern Canada. A study on European Honey Bees found that those treated with field-realistic dosages of tebufenozide did not perform as well as untreated bees in learning experiments (Abramson et al. 2004). However, Smagghe et al. (2007) found no negative effects of tebufenozide on adult survival, nest reproduction, and larval growth in the Buff-tailed Bumble Bee.

As mentioned above, there is little agricultural insecticide use within the range of this species; more information is needed to properly assess this threat.

Herbicides

The use of glyphosate as a broad-spectrum, systemic herbicide has increased 15-fold in Canada since the mid-1990s, when genetically-engineered herbicide-tolerant crops were introduced (Benbrook 2016). Generally considered to have low toxicity to terrestrial insects, there are indications that glyphosate may have sub-lethal effects on bees (Helmer et al. 2014; Herbet et al. 2014; Balbuena et al. 2015; Vázquez 2018), impair brood thermoregulation (Weidenmüller et al. 2022) and increase susceptibility to infection by pathogens (Motta et al. 2018). The co-formulants of herbicides, the added ingredients used to enhance the products, may also harm bees by interfering with their breathing system when the herbicide directly contacts them (Straw et al. 2021).

More importantly, however, the intensive and extensive use of glyphosate and other herbicides has undoubtedly resulted in a great reduction in floral resources in treated landscapes, and has thus likely contributed to reduced bumble bee colony and reproductive success. Because of increased genetic resistance to glyphosate and the lack of new herbicides, Health Canada and the Canadian Food Inspection Agency have recently approved genetically engineered crops that are resistant to the herbicides 2,4‑D and dicamba (Canadian Biotechnology Action Network 2018).

In Canada, an average of 116,000 hectares of publicly-owned forest lands are treated with glyphosate herbicides annually (ForestInfo 2018); however, there is no reported use of herbicides for forestry north of 60°N, where the majority of the McKay’s Bumble Bee range extends (National Forestry Database 2019).

Fungicides

There is increasing evidence suggesting that fungicides may have detrimental effects on bees. Bernauer et al. (2015) demonstrated that colonies of the Common Eastern Bumble Bee produced fewer workers, had less bee biomass, and had smaller mother queens following exposure to chlorothalonil, a widely used fungicide on crop and ornamental plants. Fungicides may also interact with other bumble bee threats; in fact, a study by McArt et al. (2017) found that the level of chlorothalonil in the regional (county) environment was the strongest predictor of the prevalence of the pathogen V. bombi in four declining bumble bee species, including the Western Bumble Bee. The use of fungicides is widespread in agricultural regions; in the eastern United States, Pettis et al. (2013) found that 100% of European Honey Bee-collected pollen in agricultural landscapes contained fungicide residue. However, as mentioned above for insecticides, intensive agriculture is sparse within the range of McKay’s Bumble Bee, so the threat remains low.

Climate change and Severe weather (IUCN-CMP Threat 11) – Low and Unknown Impact

Climate change and severe weather are a threat to bumble bees worldwide (Williams and Osborne 2009; Soroye et al. 2020). In general, bumble bees are cool-adapted species that live in temperate areas. Kerr et al. (2015) assembled long-term bumble bee data for Europe and North America and showed that, as climate warms, bumble bees are disappearing from the southern edges of their ranges but not correspondingly shifting northward at the northern edges. These effects were independent of changing land uses or pesticide applications. Across a range of climate change scenarios and assumptions about the capacities of bumble bees to disperse into new areas, range declines are expected to continue and even to accelerate among North American bumble bees (Sirois-Delisle and Kerr 2018; Soroye et al. 2020). However, Guzman et al. (2021) show that the species-specific trends of Soroye et al. (2020) may not be reliable enough to link changes in occupancy with changes in climate.

Bumble bee species with narrow climatic tolerances are also shown to be more vulnerable to extrinsic threats (Williams et al. 2009). Rasmont and Iserbyt (2012) attribute some declines in European bumble bees to increasing occurrences of extreme heat waves. There are no direct estimates for the McKay’s Bumble Bee, but climate change scenarios modelled by Rasmont et al. (2015b) predict that the climatic niche of its close relative the Buff-tailed Bumble Bee will decline by 34% to 71% by the end of this century.

Pollen serves as the only source of protein for developing larvae. Recent research has shown that the rise in carbon dioxide levels in the atmosphere has led to a 33% decline in protein content in Canada Goldenrod (Solidago canadensis) pollen since the beginning of the industrial era, and that a similar drop is expected in most flowering plant species (Ziska et al. 2016). Heavy metals can also have adverse effects on flowering plants and the pollinators that rely on them (Musah 2024). Heavy metals are released into the atmosphere by forest fires and permafrost thaw, both of which are expected to increase with climate change and severe weather in the Mackay’s Bumble Bee range.

Longer growing seasons can be problematic for bumble bees in a number of ways. Ogilvie et al. (2017) studied the effects of growing season length in the United States Rocky Mountains, and found that longer seasons had a negative effect on the interannual abundance of three species of bumble bees. This result was attributed to more days of low flower availability within the longer growing season. Warmer springs or increased snowpack may also shift the timing of peak flower abundance. Research suggests bees are unable to shift their reproductive timing as quickly as their floral resources in response to climate change, resulting in a mismatch between when peak nutritional needs of nesting bee colonies and availability of those resources (Pyke et al. 2016, Stemkovski et al. 2020).

Climate change and severe weather can also disrupt the phenology of bumble bees during the winter. In areas of moderate winters (such as those in the southern United Kingdom), bumble bees can become winter-active, especially if autumn temperatures are above normal (Owen et al. 2013). Although the Buff-tailed Bumble Bee (a close relative of the McKay’s Bumble Bee) workers can rapidly adapt to cold winter temperatures while active, they will die if they remain outside the colony overnight when the temperatures fall to about -10°C. This is not anticipated to be a major threat to McKay’s Bumble Bees in Canada, since they are not present in areas with moderate winters.

5. Management objective

The McKay’s Bumble Bee was assessed by COSEWIC as Special Concern because of large and apparently moving northwards declines in abundance in its close relative the Western Bumblee Bee, in southern Canada (primarily south of the boreal forest). The management objective addresses the COSEWIC reason for designation.

Management objective:

• to maintain the abundance and distribution of the species throughout its suitable habitat across its Canadian range

Short-term statements toward meeting the management objective:

• to determine population trend estimates and distribution through repeatable surveys across its Canadian range
• to fill knowledge gaps about the impact of threats including pathogens, pesticides, and competition from managed bumble bees and honey bees

Rationale

The McKay’s Bumble Bee is facing potential threats such as pathogen spillover and spillback from managed bumble bee populations in greenhouse operations, and an increase in pesticide use (COSEWIC 2014). Threats also include climate change, severe weather and, to a smaller extent, habitat loss within farmland. The distribution of the species has not yet shown a decline, while the population trend is unknown. Therefore the management objective aims to maintain abundance and distribution within suitable habitat within the current range of this species in Canada. However, there is uncertainty in how the distribution of suitable habitat, and thus this species’ range, may shift in the future with climate change.

The lack of effective monitoring of bumble bees is a stumbling block in their management. There are a number of information gaps in planning the conservation of the McKay’s Bumble Bee, including its former and present abundance throughout much of its range and the effects of the various identified threats. Proper evaluation of the management objective will require implementing repeatable monitoring methods designed to measure an index of abundance, as well as widespread inventories to delineate its range limits.

Maintaining the current population will also require the mitigation or elimination of threats, especially those from managed populations of bumble bees and European Honey Bees, and those from pesticides. Knowledge gaps around threats will have to be addressed. Increased outreach and communication with industry (especially the agricultural sector), landowners, and the general public will assist in achieving the management objective.

6. Broad strategies and conservation measures

6.1. Actions already completed or currently underway

Actions contributing to McKay’s Bumble Bee management and recovery have been implemented by various government agencies, academic institutions, non-profit groups, and citizens within Canada (Table 3).

6.2. Broad strategies

To achieve the management objective, the following broad strategies are recommended and are intended to serve as guidance to the jurisdictions and authorities responsible for the management of McKay’s Bumble Bee. Conservation measures are organized under eight broad strategies (numbers refer to Conservation Measures Partnership (2016) Conservation Actions Classification (v2.0), not the order of importance.

1. Land management
2. Species management
3. Awareness raising
6. Conservation designation and planning
7. Legal and policy framework
8. Research and monitoring
9. Education and training
10. Institutional development

6.3. Conservation measures

The following table outlines conservation measures and an implementation schedule that, if undertaken, would support achieving the overall management objective.

^a “Priority” reflects the degree to which the measure contributes directly to the conservation of the species or is an essential precursor to a measure that contributes to the conservation of the species. High priority measures are considered those most likely to have an immediate and/or direct influence on attaining the management objective for the species. Medium priority measures may have a less immediate or less direct influence on reaching the management objective, but are still important for the management of the population. Low priority conservation measures will likely have an indirect or gradual influence on reaching the management objective, but are considered important contributions to the knowledge base and/or public involvement and acceptance of the species.

6.4. Narrative to support conservation measures and implementation schedule

High priority: Essential

Pathogens

Pathogens and pathogen spillover are perceived to be the most serious threats to the Western Bumble Bee and the Yellow-banded Bumble Bee, the closest relatives of the McKay’s Bumble Bee (COSEWIC 2014, 2015), so the control of these pathogens and their carriers are likely to be key to the conservation of this species as well.

We currently have a limited understanding of the impact of pathogens on McKay’s Bumble Bee populations, the extent of their prevalence, and the degree to which commercial bumble bees and honey bees are introducing them to this species. While we can extrapolate from related bumble bee species, more targeted research on pathogens in McKay’s Bumble Bee, and better information on the occurrence of managed bees and their associated pathogen loads within its range are essential for addressing this threat.

In the meantime, more regulation and oversight of the managed European Honey Bee and commercial bumble bee industry are needed. It is important to know how many managed bees are being moved, and where they are being moved to. There should be regular testing for diseases within production facilities, and protocols to minimize disease spread to the wild (for example greenhouse vent covers, freezing of colonies before disposal, etc.). The “Bumblebee Sector Guide” to the National Bee Farm-level Biosecurity Standard (Canadian Food Inspection Agency 2013) should be updated and followed. Because it is impossible to prevent all escapes from greenhouses, and because (elsewhere at least) some colonies of commercial bumble bees are being placed directly into open fields there should be no shipment of managed bumble bees outside their natural ranges. Finally, commercial bumble bees should be reared and distributed within their natural ranges (that is, even if a commercial species is native to the range of McKay's Bumble Bee it shouldn't be reared in an eastern facility and shipped back to the northwest for use in agriculture).

However, these pathogenic organisms and their effects on these bumble bees are not well known. Important research questions include: What is the geographic origin of these pathogens; that is are they exotic or native? How are they transferred from bee to bee? Why is the prevalence of Varimorpha related to the concentration of fungicides in the environment?

Pesticides

There is now considerable evidence showing that neonicotinoid and other insecticides have serious sub-lethal effects on bumble bees (see 4.2 Description of Threats). Reduction and control of insecticide use through regulations and best practices is vital to the conservation and recovery of bumble bee populations in agricultural areas. Although insecticide use is limited within the range of McKay’s Bumble Bee, its use is not tracked; continuing development of integrated pest management methods to offer growers alternatives to pesticides is a key part of this management plan (Labrie et al. 2020). The widespread use of herbicides in both agriculture and silviculture has reduced the floral resources needed by bumble bees; best practices need to be followed to minimize the destruction of bee forage. Particular attention needs to be paid to drift of herbicides beyond the crop boundaries (even by a few metres) during mechanical or aerial spraying.

Continued pesticide research is essential to the conservation and recovery of this and other bumble bee species, especially research into the sub-lethal effects of insecticides (including the relatively new insecticides that are being developed to replace neonicotinoids), documentation of the effects of herbicides on pollinator forage resources, and the link between fungicides and bumble bee pathogens.

Competition

The introduction of exotic bumble bee species for pollination, whether inside or outside of greenhouses, needs to be controlled and monitored. The issue of potential competition with European Honey Bees also needs to be studied and, if deemed necessary, appropriate limits placed on European Honey Bee densities in McKay’s Bumble Bee habitat.

Climate change and severe weather

More research is needed to understand impacts of climate change and severe weather on McKay’s Bumble Bee. This includes research into how McKay’s Bumble Bee populations may be affected by temperature extremes, droughts and forest fires. Understanding how McKay’s Bumble Bees may or may not be able to respond to changing environmental conditions, by either being able to tolerate a wide range of climatic conditions or by shifting their range, is key in planning for future conservation efforts for the species.

Climate change can also interact with and amplify other threats, such as increasing pathogen prevalence or enabling range expansion of potential native bee competitors, but these interactions are poorly understood. Indirect effects of climate change, such as shifts in timing, quality and abundance of floral resources caused by earlier springs or increased snow pack, are also largely unknown. Research to increase understanding of the indirect and interactive effects of climate change on this species would enable better assessment of the cumulative impacts of the threats this species faces.

Monitoring

Widespread monitoring is needed to document population trends in the McKay’s Bumble Bee (and other bumble bees) in Canada, to measure progress in conservation efforts, and to achieve the management objective for the species. Surveys should be done late in the season (late July through early August) in order to maximize the probability of encountering bumble bees.

Examples of monitoring include standardized roadside netting surveys and blue vane trap surveys. Each method has its advantages and disadvantages; the key feature is that they can be repeated year after year and the results can be compared directly among years. It would be ideal if one survey type would be used across Canada, so that results could be summarized and compared nation-wide. Data and specimens from the surveys should be kept in central repositories (for example, data in provincial/territorial Conservation Data Centres, and specimens in recognized research collections).

Successful monitoring is dependent on investments in the training of paid and volunteer biologists and naturalists; including training in monitoring protocols, bumble bee identification, specimen preparation, and database entry. Training could occur within government, First Nations, the agricultural sector, and non-government organizations. Because monitoring necessarily involves specimen capture, investments also must be made in both specialist taxonomic skills and in regional natural history collections infrastructure in order to safely store specimens collected. Monitoring of bumble bees could be done within the context of a broader plan to monitor all bees, or even all pollinators.

Medium priority: Necessary

Outreach

Public education about the threats to bees and the enhancement of habitat for bees will support the broader conservation and recovery of bumble bees in a number of ways. Raising awareness with relevant government agencies (including Indigenous governments, organizations and co-management boards), greenhouse operators, beekeepers, land owners and managers is essential. The engagement of interested people through citizen science programs such as iNaturalist (iNaturalist 2024) and Bumble Bee Watch (Bumble Bee Watch 2019) will help monitor and map bumble bee distributions while conservation and recovery efforts take place. Public outreach about the best practices to mitigate or reduce pesticide use and pathogen transmission would promote stewardship actions within communities.

For this wide-ranging species with complex needs, partnerships focused on coordinating conservation implementation, knowledge generation and sharing will be necessary in conservation efforts. Indigenous governments and organizations such as Indigenous environment committees should be engaged to contribute local and Traditional Knowledge. Workshops on the habitat needs of bees and how the public can assist will not only help habitat restoration but raise general awareness of the bees and their needs as well.

Additional research

Additional studies on clarifying the boundary between B. mckayi and B. occidentalis ranges in northern British Columbia, effective population sizes, demographics, life history (for example overwintering and nest site selection) and other basic population ecology work would also inform conservation of these bumble bees (for example, Liczner and Colla 2019). As mentioned in the other sections above, research on the scale and impact of threats in the far northwest would be very helpful in the management of this bumble bee.

Low priority: Beneficial

Protected areas and habitat stewardship

Although private land is limited in the Canadian range of the McKay’s Bumble Bee, conservation easements could be a strategy in the enhancement of habitat in certain key areas. Many other habitat conservation options are available on public and private lands, including land use planning. Small protected areas could be useful (on a local scale) to help augment bumble bee populations. Protected areas in general should have pollinator management plans that may help establish populations in areas that otherwise have limited habitat available.

In areas where habitat for bumble bees has been degraded by development, restoration and ongoing maintenance using bee-friendly native vegetation will benefit local populations of all bumble bees, including McKay’s Bumble Bees. The intensification of agriculture and general ‘tidying’ of the landscape in developed regions has resulted in a loss of bee habitat. Programs that promote voluntary stewardship of pollinators would be valuable in this regard. It will be important to concurrently mitigate more serious threats in areas of habitat restoration, in order to ensure that these efforts are successful.

7. Measuring progress

The performance indicators presented below provide a way to measure progress towards achieving the management objective and monitoring the implementation of the management plan.

By 2034:

• there is no observed or estimated reduction in the abundance of the McKay’s Bumble Bee
• the geographic range of the McKay’s Bumble Bee is maintained

Measuring these indicators will require a range wide monitoring effort; for example, repeatable roadside netting surveys, to better understand the current abundance of McKay’s Bumble Bees, as well as widespread inventories designed to delineate its range limits.

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Appendix A: Plant food sources for the McKay’s Bumble Bee (Bombus mckayi)

Bumble bees are generalist feeders; these are examples of flowers co-occuring with McKay’s Bumble Bees that the species or close relatives have been recorded foraging on. Sources: Macfarlane (1974), Colla and Dumesh (2010), and Williams et al. (2014). English names compiled from Brouillet et al. (2020).

Latin name : Common name

Anaphalis margaritacea Pearly Everlasting

Aquilegia canadensis Red Columbine

Arctostaphylos uva-ursi Common Bearberry

Astragalus spp. Milk-vetches

Caragana arborescens Siberian Pea Shrub

Chamaenerion [=Epilobium] angustifolium Fireweed

Heracleum lanatum American Cow Parsnip

Rhododendron [=Ledum] groenlandicum Common Labrador Tea

Linaria vulgaris Butter-and-eggs

Lupinus sp. Lupines

Melilotus albus White Sweet-clover

Medicago sativa Alfalfa

Mertensia sp. Bluebells

Ribes nigrum European Black Currant

Rosa sp. Roses

Rubus sp. Brambles

Salix sp. Willows

Senecio sp. Groundsels

Solidago spp. Goldenrods

Sonchus oleraceus Common Sow-thistle

Sorbus americana American Mountain-ash

Spiraea latifolia Broad-leaved Meadowsweet

Symphyotrichum sp. Waxberry

Syringa vulgaris Common Lilac

Taraxacum officinale Common Dandelion

Trifolium hybridum Alsike Clover

Trifolium pratense Red Clover

Trifolium repens White Clover

Vaccinium spp. Blueberries and relatives

Vicia cracca Tufted Vetch