The Pacific Flyway Winter Brant Survey (WBS) has been conducted annually since 1981 as part of a cooperative effort by the U.S. Fish and Wildlife Service, Canadian Wildlife Service, Mexico, and the Pacific U.S. states, to estimate the abundance of the Pacific black brant (Branta bernicla nigricans) in their principal wintering areas along the Pacific Coast (in Baja, Mexico, California, Oregon, Washington, British Columbia, and Alaska). The survey is conducted each winter in January-February by a composite of ground and aerial crews, with the Alaska portion being conducted by the Alaska Region of USFWS Migratory Bird Management. The primary objective of the Alaska survey component is to provide an annual index of abundance of wintering brant in Alaska. Results from the Alaska component of the winter brant survey are combined with brant counts made by partner agency and non-governmental organizations in portions of British Columbia, Washington, Oregon, California, and Mexico. The combined WBS count is compared to population thresholds defined in the Pacific Flyway Management Plan for Pacific Brant which determines harvest strategy for the subsequent year. In addition to its relevance in the WBS, the Alaska winter brant survey also documents distribution and abundance of emperor geese (Anser canagicus) and Steller’s eiders (Polysticta stelleri), and generates counts of other waterbird and mammal species regularly encountered on the survey. The Alaska survey is completed by an aircrew of two individuals in an amphibious Cessna 206 aircraft flown at approximately 160 km/hr (100 mph) and altitude of 45m (150 feet) above sea level (ASL). The survey area includes shorelines and estuaries from Bechevin Bay to Moffet Lagoon along the Bering Sea side of the Alaska Peninsula; Kinzarof Lagoon, Morzhovoi Bay, and northwestern Cold Bay on the Pacific Ocean side of the Alaska Peninsula; and shorelines of nearby Sanak and Caton islands and surrounding islets (collectively Sanak Islands). Georeferenced observations are recorded from both sides of the aircraft using custom software. Counts are reported in 17 survey segments. Adequate coverage of these segments is accomplished by flying along systematic flight paths using real-time aircraft tracks with allowance to deviate to confirm size and species composition of large flocks. The pilot navigates using panel-mounted computers and GPS units, as well as paper topographic maps (scale 1:63,360) denoting section boundaries. Three to five repeated surveys are completed each winter in close succession, as weather allows, with the exception of Sanak Islands which is sampled once. Segment bird count totals are summed per replicate. Survey results are reported as an average of annual replicates. Final results are communicated to the Pacific Flyway Representative for the U.S. Fish and Wildlife Service who combines the Alaska component of the WBS with those from British Columbia, Pacific coastal states, and Mexico. In addition to supporting harvest management, the Alaska survey has helped detect distributional shifts in the winter brant population from Mexico to Alaska – documenting impacts of climate change; as the population shifts to more northern (increasingly ice-free) wintering grounds.
