Satellite Tracking Data Reveals High-Use Areas for Immature Bald Eagles from Kentucky

Abstract. Immature raptors often travel long distances and move nomadically from the time they leave their natal area to the time they are recruited into the breeding population. Emphasis on identifying the nesting and winter habitat of Bald Eagles (Haliaeetus leucocephalus) has overshadowed the need to understand the habitat and spatial use of young eagles prior to reaching maturity. We used satellite telemetry to track the movements of immature Bald Eagles hatched in western Kentucky during 2010–2016. We analyzed movement data to identify high-use areas for eagles in their first and second years during warm and cool periods. Five out of seven eagles migrated north to the Great Lakes region during their first year. Using Brownian Bridge Movement Modelling, we identified 47 noncontiguous high-use areas during the warm period and 67 during the cool period. Public lands comprised 17% of warm period high-use areas and 43% of cool period high-use areas. High-use areas were located in Illinois, Indiana, Kentucky, Arkansas and Tennessee, and were often near federally-owned dams, rivers with sandbars, or areas with abundant waterfowl. Our small sample of tracked eagles correctly identified known Bald Eagle concentration areas within the study area; thus, we infer that previously unrecognized high-use areas identified by this study are likely to be concentration areas important to the larger population. We further suggest remote sensing data, even in limited datasets, as an efficient way to identify Bald Eagle concentration areas.