BC Conservation Data Centre: Conservation Status Report
Larus glaucescens
Glaucous-winged Gull
| Scientific Name: | Larus glaucescens |
|---|---|
| English Name: | Glaucous-winged Gull |
| Provincial Status Summary | |
| Status: | S4S5 |
| Date Status Assigned: | April 28, 2023 |
| Date Last Reviewed: | April 28, 2023 |
| Reasons: | Large range extent and number of occurrences and a large increase in populations from historic numbers but recent declines well documented by several sources. |
| Range | |
| Range Extent: | G = 200,000-2,500,000 square km |
| Range Extent Estimate (km2): | 242,506 square km (breeding) |
| Range Extent Comments: | Glaucous-winged Gulls are widespread breeders along the entire coast of British Columbia (Barry 2015), but breeders are absent from the interior except for one location in the Southern Interior Ecoprovince, where a few pairs nest annually on Grant Island (also known as Whiskey Island or Nahun Wenox) in Okanagan Lake since at least 2003 (Cecile cited in Barry 2015). Wintering birds are more widespread (range extent 444,180 km) with increasing number of birds being reported regularly from interior locations in the last twenty years in the Okanagan Valley, Revelstoke, Kokannee Creek Prov. Park and other locations. About half the Glaucous-winged Gulls in BC nest in the Strait of Georgia and 26% nest on the west coast of Vancouver Island (Rodway et al. 2016). Hybridization between this species and several others occurs frequently enough the hybrids have been given informal names: Glaucous-winged x Western Gull (Olympic Gull), Glaucous-winged x Herring Gull (Cook Inlet Gull), Glaucous-winged x Glaucous Gull (Seward Gull) and Glaucous-winged x Slaty-backed Gull (Commander Gull). Hybridization occurs most commonly with gulls breeding outside of British Columbia where ranges overlap, but there are records involving mixed pairings between Glaucous-winged and Western (Pearce 1946) and Glaucous-winged and Herring (Merilees 1974) and backcrosses occurring in BC. Hybrids, especially "Olympic" and "Cook Inlet" gulls are common during the nonbreeding season. Gulls banded on the central westcoast of Vancouver Island dispersed widely with returns from northern Vancouver Island, mainland BC, Washington, Oregon and California (with one return from Midway Island in the N. Pacific and another inland to Kamloops (Hatler et al. 1978). |
| Area of Occupancy (km2): | FG = 126-2,500 |
| Area of Occupancy Comments: | Easily exceeds 130 occupied grid cells for breeding locations. Breeding birds are increasing as urban nesters on rooftops, Rodway et al. (2016) list 389 colonies in British Columbia of 100 or more nesting birds and many smaller colonies exist. |
| Occurrences & Population | |
| Number of Occurrences: | E = > 300 |
| Comments: | Rodway et al. (2016) list 389 colonies in British Columbia of 100 or more nesting birds and there would be numerous smaller colonies and individual nesting pairs and scattered rooftop breeding in urban areas of Vancouver, Victoria and Nanaimo. |
| Number of Occurrences with Good Viability / Ecological Integrity: | Rank Factor not assessed |
| Number of Occurrences Appropriately Protected & Managed: | E = >40 |
| Comments: | Many Glaucous-winged Gull colonies are in parks and ecological reserves. Some examples of larger colonies (greater than 100 pairs) in protected areas include: SGang Gwaay (Anthony Island) (Gwaii Haanas National Park Reserve and Haida Heritage Site), Byers-Conroy-Harvey-Sinnett Islands Ecological Reserve, The Scott Islands (Anne Vallée (Triangle Island) Ecological Reserve, Sartine Island Ecological Reserve, Beresford Island Ecological Reserve), Solander Island Ecological Reserve, Big Bunsby Marine Provincial Park, Cleland Island Ecological Reserve, Seabird Rocks (Pacific Rim National Park and Reserve), Race Rocks Ecological Reserve, Mittlenatch Island Nature Provincial Park, Christie Islet Migratory Bird Sanctuary, Hudson Rocks Ecological Reserve, Rose Islets Ecological Reserve, Ballingall Islets Ecological Reserve, Java Islets and Imrie Island (Gulf Islands National Park Reserve), nc Chain Islets (Trial Islands Ecological Reserve and Victoria Harbour Migratory Bird Sanctuary). |
| Population Size: | F = 10,000 - 100,000 individuals |
| Comments: |
Breeding: About 15 percent of the global populations is thought to nest in British Columbia (Rodway et al. 2016). Global population estimates are uncertain, but probably number up to 300,000 pairs (Hayward and Verbeek 2020). Non-breeding: There is no estimate of the number of Glaucous-winged Gulls overwintering in BC (Rodway pers. comm). However, it is the most numerous gull on Christmas Bird Counts along the coast of BC and in the top ten most numerous species in BC. Very large concentrations in the nonbreeding season are found where there are food sources, most especially Pacific Herring (Clupea pallasii) (e.g., estimated more than 32,000 near Comox in March 2016 (https://ebird.org/checklist/S17457946) and Eulachon (Thaleichthys pacificus) spawning events (e.g., estimated 35,000 Glaucous-winged Gulls at Fishery Bay, near the mouth of the Nass River in March 2020 (eBird https://ebird.org/canada/checklist/S66465817) |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | CD = Medium - low |
| Comments: | In the past, egg collecting was thought to restrict growth of the Glaucous-winged Gull population along the BC coast, however with the adoption of the Migratory Birds Convention Act this threat was largely mitigated (Rodway et al. 2016). Persecution of gulls is an ongoing threat, however not considered to be a driver of population level declines. Harassment and predation of breeding gulls by Bald Eagles has been suggested as a cause of lower fecundity for colonial Glaucous-winged Gulls in the Strait of Georgia (Vermeer and Devito 1989). Significant declines in food availability for this species from changes in ocean conditions and over harvest of food fish (Blight et al. 2022) and changes in garbage management that reduce food for gulls (Davis et al. 2015) are thought to be additional factors driving short term declines. |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | EF = Decline of 10-50% |
| Comments: |
Bird et al. (2020) estimated a generation time for this species of 13.819 hence a 3 generation time of 41.45 years. Christmas bird count data from 1967-2021 indicate a decline of 0.62% year (95 % CL-1.17 to -.6) for period 1967-2021. This equates to a 22.2% decline over 3 generations. Declines in breeding birds have also been documented. Sullivan et al. 2022 report that from 1986 to 1999, the number of nesting Glaucous-winged Gulls at fourteen breeding colonies declined by 31% (1,610 nests) in the southern Strait of Georgia, British Columbia. Blight et al. (2015) estimated a decline in the colonial breeding sites in the Strait of Georgia of about 50% from 1980's to 2010. However, Rodway et al. (2016) note that some of the decline can be attributed to differences in how "active nests" were defined in the Blight et al. work compared to the historical accounts they were compared against, nor did the estimate take into account the increase in urban nesting gulls. Even with those caveats it is clear that this species is in decline in the Strait of Georgia and that is confirmed by eBird trend data (greater than a 30% decline in almost all grid cells from Alaska to California (Fink et al. 2021), Coastal Waterbird Surveys (-0.9 % per year (Ethier et al. 2020) = 32.82 % decline over 3 generations) and Christmas Bird Counts (CBC) (summarized above). Note that there is no range-wide survey of Glaucous-winged Gulls on their breeding grounds as a number of colonies are remote and difficult to access (Rodway et al 2016). Previous report of a 84% decline over 3 generations (17 years; 10% decline per year 1986-2006; Downes and Collins 2007) were characterized as having unreliable trend data and now appear to be much too high. Note also that the more recent estimate of generation time for this species (Bird et al. 2020) is a significant increase over past generation time estimates. |
| Long-Term Trend: | I = Increase of >25% |
| Comments: | Rodway et al. (2016) estimate that the part of the population in major colonies in B.C. tripled in size from 1930 to 1990, with the majority of the growth occurring up to about 1978, followed by a period of stability and then followed by declines in the 1990's. Vermeer (1992) reported a continuing growth of 9% in urban nesting gulls in a portion of Vancouver from 1983 to 1989. Despite recent declines, current populations (2022) are likely to be nearly double historical numbers from the turn of the century. |
| Other Factors | |
| Intrinsic Vulnerability: | C=Not intrinsically vulnerable |
| Comments: | Widespread along the BC coast, adaptable and feeds on a large range of items. |
| Environmental Specificity: | CD = Moderate to broad. |
| Comments: | Widespread along the BC coast, adaptable and feeds on a large range of items. |
| Other Rank Considerations: |
Despite recent declines range wide, the BC population is likely still larger than it was at the turn of the century. |
| Information Gaps | |
| Research Needs: | |
| Inventory Needs: | |
| Stewardship | |
| Protection: | |
| Management: | |
| Version | |
| Author: | Fraser, D.F. |
| Date: | December 20, 2022 |
| References | |
|
Merilees, W.J. 1974. A Glaucous-winged Gull mated to a Herring Gull on Okanagan Lake, British-Columbia. Canadian Field-Naturalist 88: 485-486. |
|
|
Pearse, T. 1946. Nesting of Western Gull off the Coast of Vancouver Island, British Columbia, and Possible Hybridization with Glaucous-Winged Gull. The Murrelet, 27:3, pp. 39?40. |
|
|
Barry, K.L. 2015. Glaucous-winged Gull in Davidson, P.J.A., R.J. Cannings, A.R. Couturier, D. Lepage, and C.M. Di Corrado (eds.). The Atlas of the Breeding Birds of British Columbia, 2008-2012. Bird Studies Canada. Delta, BC. http://www.birdatlas.bc.ca/accounts/speciesaccount.jsp?sp=GWGU&lang=en
|
|
|
Bird, J., R. Martin, H.R. Akçakaya, et al. 2020. Generation lengths of the world?s birds and their implications for extinction risk. Conservation Biology 34:1252?1261.
|
|
|
Blight, L. K., W. O'Shea, and G. T. W. McClelland. 2022. A comparison of historical and contemporary reproductive traits in a declining population of Glaucous-winged Gulls (Larus glaucescens). Avian Conservation and Ecology 17(2):41.
|
|
|
Blight, L.K., M.C. Drever and P. Arcese. 2015. A century of change in Glaucous-winged Gull (Larus glaucescens) populations in a dynamic coastal environment. Condor 117 1:1
|
|
|
Davis, M.L., J.E. Elliott, and T.D. Williams. 2015. Spatial and Temporal Variation in the Dietary Ecology of the Glaucous-winged Gull Larus glaucescens in the Pacific Northwest. Marine Ornithology. 43:189-198.
|
|
|
Downes, C.M., and B.T. Collins. 2007. Canadian Bird Trends Web site Version 2.2. Canadian Wildlife Service, Environment Canada, Gatineau, Quebec, K1A 0H3.
|
|
|
Ethier, D. et al. 2020. Twenty years of coastal waterbird trends suggest regional patterns of environmental pressure in British Columbia, Canada. Avian Conservation and Ecology 15:20. https://doi.org/10.5751/ACE-01711-150220
|
|
|
Fink, D., T. Auer, A. Johnston, et al. 2021. eBird Status and Trends, Data Version: 2020; Released: 2021. Cornell Lab of Ornithology, Ithaca, New York. https://doi.org/10.2173/ebirdst.2020
|
|
|
Hatler, D.F., R.W. Campbell, and A. Dorst. 1978.Birds of Pacific Rim National Park. B.C. Provincial Museum Occasional Paper No. 20, Victoria, BC. 194 pp.
|
|
|
Hayward, J. L. and N. A. Verbeek. 2020. Glaucous-winged Gull (Larus glaucescens), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.glwgul.01
|
|
|
Rodway, M, R.W. Campbell and M.J. Lemon. 2016. Seabird Colonies of British Columbia ? a Century of Changes. Wildlife Afield 13:1 and 2. 298 pp.
|
|
|
Vermeer, K. 1992. Population growth of the Glaucous-winged Gull (Larus glaucescens) in the Strait of Georgia, British Columbia, Canada. Ardea 80: 181-185.
|
|
|
Vermeer, K., and K. Devito. 1989. Population trend of nesting Glaucous-winged Gulls in the Strait of Georgia. Pp. 83-93 in K. Vermeer, and R.W. Butler, eds. The ecology and status of marine and shoreline birds in the Strait of Georgia, British Columbia. Spec. Publ., Can. Wildl. Serv., Ottawa.
|
|
Please visit the website Conservation Status Ranks for information on how the CDC determines conservation status ranks. For global conservation status reports and ranks, please visit the NatureServe website http://www.natureserve.org/.
Suggested Citation:
B.C. Conservation Data Centre. 2022. Conservation Status Report: Larus glaucescens. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 17, 2026).