Testing the feasibility and effectiveness of a fall Steller's eider molt survey in southwest Alaska

Since 1992, U.S. Fish and Wildlife Service, Migratory Bird Management has flown a spring aerial survey in southwest Alaska to monitor trends in the Pacific population of Steller's eiders and improve understanding of habitat use and timing of spring migration. Due to constraints with the traditional spring survey, we sought to test the feasibility of an alternative monitoring approach using photography of fall molting flocks along the Alaska Peninsula. Our goal was to determine whether different survey timing and methods could provide a more precise and cost effective annual index to track the Pacific Steller's eider population. We reasoned that a fall photographic survey could be more effective based on: 1) better timing (molt being easier to target than spring staging, as flocks are sedentary), improved flock estimation (better precision using photographs than ocular estimates alone), and weather (early fall typically has longer periods of favorable weather). From 27-30 August 2012, we conducted photographic surveys of molting Steller's eiders at major lagoons along the Alaska Peninsula (King Salmon to Izembek NWR), with replicate surveys at the Seal Islands and at Izembek and Nelson lagoons. Combined counts for the Alaska Peninsula totaled 50,404 birds, with an average of 9,764 birds at Seal Islands, 35,549 birds at Nelson lagoon, 4,418 birds at Izembek lagoon, and 943 birds scattered between Port Moller (602) and Port Heiden (341). Results from 2012 provided defensible population estimates and repeatable methodology. We discuss the feasibility of photographic methods, compare current and historic Steller's eider population surveys, and outline benefits and constraints of a fall survey as an index to the Pacific population.