GOLDEN EAGLE ABUNDANCE IN ALASKA: MIGRATION COUNTS AND MOVEMENT DATA GENERATE A CONSERVATIVE POPULATION ESTIMATE

Estimating species density and abundance is challenging but important for establishing conservation and management strategies. Significant progress has been made toward estimating Golden Eagle (Aquila chrysaetos) abundance in the conterminous United States of America (USA) but much less is known about eagle abundance in Alaska. Here, we paired migration count and GPS-tracking data collected near Gunsight Mountain, Alaska, in a Bayesian framework to estimate the number of Golden Eagles in southcentral Alaska. We estimated 1204 (95% credible interval: 866, 1526) potentially breeding (similar to 4 yr old) Golden Eagles annually moved through the Gunsight Mountain migration corridor and summered over an area of 150,325 km(2) in south-central Alaska, equating to a density of 0.80 potentially breeding eagles/100 km(2). By extrapolating across the species' nesting range in Alaska (1,180,489 km(2)) and incorporating published productivity and age-specific survival rates for eagles <4 yr old into our hierarchical model, we estimated 12,717 (95% credible interval: 9043, 16,349) Golden Eagles of all ages occur in Alaska, annually. We propose this as a conservative statewide population estimate because we used methods that likely underestimated population size. Even so, our estimate is three to five times larger than previous estimates and likely represents about one quarter of the USA's population.