ANNUAL MIGRATIONS OF BALD EAGLES TO AND FROM CALIFORNIA

Abstract

We fitted four nestling Bald Eagles (Haliaeetus leucocephalus) with Doppler-based satellite Platform Transmitter Terminals (PTTs) in northern California in 1997–1999. We also fitted immature and adult Bald Eagles with apparent origins in Canada with PTTs on their wintering grounds in central and southern California in 1997–2002. Post-fledging California eagles moved northward in their first summer, three to coastal and near-coastal central British Columbia and one to Great Slave Lake in Canada's Northwest Territories (ca. 1200–1400 and 2200 km by straight line, respectively). Three eagles with still-functioning PTTs returned to California between October and April. In subsequent years, the California-fledged eagles returned to or near their original northern summer areas in British Columbia or Northwest Territories annually for as many as 2 yr. Migrations of one young California eagle to and from Great Slave Lake were geographically similar to those of adult and immature Bald Eagles we studied concurrently that spent the breeding season in Canada and wintered in California, but timing of movements differed. In migrations subsequent to their first year, California eagles departed California later (late May to late July) than wintering migrants of all ages (mid-February to mid-March), and returned as early as September, while the winter migrants did not arrive in California until December–January.