NatureCounts - The State of Canada's Birds

Summary

National

Trend

Moderate Increase

Confidence: Low

Goal

Within Goal Range

The entire world's population of Heermann's Gull breeds on just a few islands in the Gulf of California, Mexico, with over 90% at a single colony on Isla Raza (Kushlan et al., 2002, Islam, 2002). After the breeding season, many of these birds undertake an unusual "reverse" migration, heading northward up the coast of North America from roughly July to October, as opposed to the usual southward direction of most North American migratory bird species. Most of the overwintering population occurs along the Pacific coast from Oregon to Guatemala, but as much as 7% of the population, approximately 23,000 individuals, reaches southwestern British Columbia. Surveys of the Salish Sea since the late 1990s and Christmas Bird Count results from the northern Pacific since the early 1970s (including Washington, and Oregon) both suggest an increase in abundance over time. However, because the Salish Sea surveys began relatively recently and the Christmas Bird Count data are not specific to Canada, confidence in the trend for Canada is only low. Heermann's Gull is within its goal range.

Migration Strategy

Seasonal visitor

Canadian Responsibility

Very Low

Population Estimates

Breeding 0

Annual 23,000

Global 350,000

Population Trends

The breeding population of Heermann's Gull has experienced wide fluctuations, but generally increased following the establishment of Isla Raza as a refuge in 1964 (Islam, 2002). There are no reliable long-term data specific to Canada for Heermann's Gull. Christmas Bird Count data for the northern Pacific region (spanning Alaska to northern California) indicate a change of +22% relative to 1970, but this likely samples less than one-quarter of the population, and may not accurately reflect changes in the portion of the population visiting Canada. Over a shorter period, data from the British Columbia Coastal Waterbird Survey suggest a large increase relative to the late 1990s, but they are relatively imprecise and the survey does not cover the majority of species' range in British Columbia. Overall, it appears likely that the Canadian population has experienced a moderate long-term increase, although confidence in this assessment is low because of the temporal and spatial limitations associated with the estimate.

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Population Goals

The goal for Heermann's Gull is to remain at or above its recent population level, based on the British Columbia Coastal Waterbird Survey. Trend data show that Heermann's Gull is currently within its goal range.

National

Canada

Population Goal

Maintain recent abundance

Population status relative to goal

Within Goal Range

Goal is based on BC Coastal Waterbird Survey

Designations

Designation	Geographic Area	Status
IUCN	Global	Near Threatened
Partners in Flight	Western Hemisphere	Yellow Watch List
Wild Species	Canada	Unrankable

References

Islam, K. 2002. Heermann's Gull (Larus heermanni), The Birds of North America Online (A. Poole, Ed.). Cornell Lab of Ornithology, Ithaca, New York. https://birdsna.org/Species-Account/bna/home.
Kushlan, J.A., M.J. Steinkamp, K.C. Parsons, J. Capp, M.A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Ellio, M. Erwin, S. Hatch, S. Kress, R. Milko, R.S. Miller, K. Mills, P. Richard, R. Phillips, J.E. Saliva, B. Sydeman, J. Trapp, J. Wheeler, and K. Wohl. 2002. Waterbird Conservation for the Americas: The North American Waterbird Conservation Plan, Version 1. Waterbird Conservation for the Americas, Washington, DC, U.S.A., 78 pp. http://www.waterbirdconservation.org/nawcp.html.