Between September and November each year, nearly the entire world population of Pacific black brant (Branta bernicla nigricans) stages at Izembek Lagoon and surrounding estuaries (hereafter: Izembek Complex). The Izembek Complex is a unique area of protected brackish waters, supporting one of the world’s largest eelgrass beds and a diverse array of wildlife. The Alaska Fall Brant Survey has been conducted annually since 1976 in late-September through October, to provide an index of abundance for the entire post-breeding Pacific black brant population (Branta bernicla nigricans), while secondarily, providing annual fall population indices for cackling geese (Branta hutchinsii), emperor geese (Anser canagicus), and Steller’s eiders (Polysticta stelleri). The primary objective of the survey is to provide an annual index of the entire post-breeding Pacific brant population. To help account for sampling error among surveys of dense, multi-species aggregations within the Izembek Complex, crews conduct repeated fall surveys (long-term average [1976-2019] = 4 surveys) each year, and use the average of survey counts as the annual population indices (i.e., for the four primary species of interest: brant, cackling, and emperor geese, and Steller’s eiders). The coefficient of variation among repeated surveys is used as a minimum estimate of variance among counts. The Alaska Fall Brant Survey provides an alternative overall population metric to the Winter Survey – the primary survey specified in the Pacific Flyway Management Plan to determine harvest strategy for the subsequent year. The Alaska Fall Brant 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. Georeferenced observations are recorded from both sides of the aircraft using custom software. Counts are reported in 13 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. Five repeated surveys are completed each fall in close succession, as weather allows. Segment bird count totals are summed per replicate. Final survey results are reported as an average of annual replicates and included in the Pacific Flyway Databook table for Pacific Black Brant.
