BC Conservation Data Centre: Conservation Status Report
Aechmophorus occidentalis
Western Grebe
| Scientific Name: | Aechmophorus occidentalis |
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| English Name: | Western Grebe |
| Provincial Status Summary | |
| Status: | S1S2B,S2N |
| Date Status Assigned: | April 27, 2023 |
| Date Last Reviewed: | April 27, 2023 |
| Reasons: | Small breeding population restricted to only three regular sites and vulnerable to human disturbance. Winter populations larger but experiencing declines and vulnerable to oil spills and other threats. |
| Range | |
| Range Extent: | E = 5,000-20,000 square km |
| Range Extent Estimate (km2): | 6000 |
| Range Extent Comments: | Regular breeding populations are restricted to Salmon Arm Bay on Shuswap Lake, Duck Lake near Creston, and possibly the north arm of Okanagan Lake (Howie 2015). Winter populations are widely distributed along the coast and sparsely and locally distributed on large, open bodies of water in the interior (Campbell et al. 1990). Formerly bred at Williams Lake (last breeding in 1964), and Swan Lake, near Vernon (last breeding probably in 1987). A colony at Kamloops Lake was used only in 1973 and a pair bred at Westham Island in 1986 (Campbell et al. 1990). |
| Area of Occupancy (km2): | C = 3-5 |
| Area of Occupancy Estimate (km2): | 3 |
| Area of Occupancy Comments: | Extremely localized distribution at very few locations. |
| Occurrences & Population | |
| Number of Occurrences: | A = 1 - 5 |
| Comments: | The colony near Salmon Arm is the main and largest breeding colony in the province, followed by Duck Lake near Creston (Howie 2015). The continued use or success of the Okanagan Lake colony could not be determined during the BC Breeding Bird Atlas, but was believed to be declining (Howie 2015). The species has had historical and/or ephemeral breeding activity at a number of other locations in the province, but these have not persisted. |
| Number of Occurrences with Good Viability / Ecological Integrity: | Rank Factor not assessed |
| Number of Occurrences Appropriately Protected & Managed: | B = 1 - 3 |
| Comments: | The Duck Lake breeding site is protected within the Creston Valley Wildlife Management Area. |
| Population Size: | C = 250 - 1,000 individuals |
| Comments: | Breeding population estimated at approximately 200 pairs in 1990s, and the species was considered never to have exceeded 300 pairs annually (Burger 1997). The Shuswap Lake colony is presumed to be the largest in the province (Howie 2015). From 1997-2018 the number of adults in the nesting area at Duck Lake annually ranged from 10 to 79, with between 0 and 44 nests (Van Damme 2020). The Okanagan Lake colony is presumed active, with nearly 200 individuals present in June 2021 (D. Cecile pers. comm.). Wintering populations previously contained upwards of 10,000 birds locally and were estimated to total 100,000 in some years (Burger 1997). There have been large survey-declines in wintering populations in the province, and Christmas Bird Counts province-wide now typically record numbers only in the low thousands (National Audubon Society ND; accessed 16 September 2021). |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | Rank Factor not assessed |
| Comments: | Human disturbance (primarily wave-wash from power boats) directly threatens nesting sites through increased annual reproductive losses and/or abandonment of colony (Campbell et al. 1990; Burger 1997). This is the probable cause of the loss of British Columbia colonies (Campbell et al. 1990). However, Western Grebes will even depart from nests in response to non-motorized craft such as kayaks. Extreme weather events and windstorms creating wave action can be a major cause of nest failure. An expanding colony of Ring-billed Gulls may be a potential threat to the colony at Shuswap Lake. Nearshore and foreshore development may degrade habitats. Large aggregations of wintering grebes are vulnerable to oil spills, though chronic, low-volume spills also cause mortality (Burger 1997). Western Grebes are also known to be exposed to and contain a number of toxic contaminants, such as dioxins and furans. |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | G = Relatively Stable (<=10% change) |
| Comments: | Breeding populations are presumed stable. Wintering populations have undergone significant regional declines. Abundance of Western Grebes in the Salish Sea (the predominant wintering area in the province) declined by about 95% between 1975 and 2010 (Wilson et al. 2013). During this same time period the continental population was estimated to have declined by 52% (Wilson et al. 2013). |
| Long-Term Trend: | FH = Decline of <30% to increase of 25% |
| Comments: | Breeding populations have potentially declined. Former regular breeding also at Swan Lake near Vernon and Williams Lake. The decline of the Swan Lake colony was coincident with the increase of the Okanagan Lake colony, and may represent a colony shift due to some factor(s) (Burger 1997). The Williams Lake colony was active in the 1930s until the 1960s at least (Burger 1997). Burger (1997) states that the provincial breeding population has likely always been fewer than 300 pairs. |
| Other Factors | |
| Intrinsic Vulnerability: | Rank Factor not assessed |
| Environmental Specificity: | Rank Factor not assessed |
| Other Rank Considerations: | |
| Information Gaps | |
| Research Needs: | The impact of gull predation on the Shuswap Lake colony should be investigated, as should competitive effects of increasing numbers of piscivorous species near all colonies. |
| Inventory Needs: | Reproductive success at breeding colonies should be monitored periodically but not annually (to avoid excessive disturbance). General activity at breeding colonies can be monitored annually from a distance. Significant winter concentrations should be inventoried annually. In particular the Okanagan Lake colony lacks recent information on the number of nests or breeding pairs. |
| Stewardship | |
| Protection: | |
| Management: | Unprotected breeding sites should be secured through habitat acquisition or administrative transfer. An area management plan for each colony should be developed in cooperation with all affected government agencies and stakeholders. Human activities, particularly but not exclusively power boating, should be prohibited or strictly regulated near colonies during the breeding season. Marine oil spill response plans (e.g., Howes and Wainwright 1993) should be evaluated and amended as necessary to address the needs of wintering Western Grebe populations. |
| Version | |
| Author: | S. Cannings and L. Ramsay, updated by N. Hentze (2021) |
| Date: | September 07, 2021 |
| References | |
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Burger, A.E. 1997. Status of the Western Grebe in British Columbia. B.C. Minist. Environ., Lands and Parks, Wildl. Branch. Working Rep. WR-87. 40pp.
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Campbell, R.W., N.K. Dawe, I.McT. Cowan, J.M. Cooper, G. Kaiser, and M.C.E. McNall. 1990. The Birds of British Columbia, Vol. 1. Nonpasserines: Introduction, Loons through Waterfowl. Royal B.C. Mus. in association with Environ. Can., Can. Wildl. Serv. 514pp.
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Cannings, R.J. 1998. The Birds of British Columbia - a taxonomic catalogue. B.C. Minist. Environ., Lands and Parks, Wildl. Branch, Victoria, Wildl. Bull. B-86. 266pp.
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Forbes, L.S. 1984. The nesting ecology of the Western Grebe in British Columbia. Can. Wildl. Serv. Rep., Delta, BC. 20pp.
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Howes, D.E., and P. Wainwright. 1993. Coastal resources and oil spill response atlas for the southern Strait of Georgia. Environ. Emergencies Coordination Off., B.C. Minist. Environ., Lands and Parks, Victoria, BC.
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National Audubon Society. No Date. The Christmas Bird Count Historical Results [Online]. Available http://www.christmasbirdcount.org [your access date]
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Resource Inventory Committee. 1997d. Standardized Inventory Methodologies for Components of British Columbia's Biodiversity: Colonial Freshwater Nesters, version 1.1. Prepared for the Resour. Inventory Comm., B.C. Minist. Environ., Lands and Parks, Victoria, BC.
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Storer, R.W., and G.L. Nuechterlein. 1992. Western and Clark's Grebe (Aechmophorus occidentalis and Aechmophorus clarkii) in A. Poole, P. Stettenheim and F. Gill, eds. The Birds of North America, No. 26. Acad. Nat. Sci., Philadelphia, PA, and Am. Orthinol. Union, Washington, DC. 24pp.
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Van Damme, L. 2020. A Passion for Birds - their life in the Creston Valley. Edited by R.W. Campbell, P. Huet and B. Denkers. Self-published.
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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. 2021. Conservation Status Report: Aechmophorus occidentalis. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 10, 2026).