Skagit River Bald Eagles: Movements, Origins and Breeding Population Status - 1998 Progress Report

In the winter of 1997-98 we completed the second season of an investigation into the origins and breeding population status of bald eagles (Haliaeetus leucocephalus) on the Skagit River, Washington. We captured 14 adult eagles and 5 subadult eagles, for a total of 23 adults and 37 eagles captured during the study. As of July, 1998, 17 of the 23 satellite transmitters (PTTS) deployed on adult eagles were transmitting, and 4,760 satellite locations had been received. Satellite monitoring of adult eagles during spring migration (16 February to 5 April, n = 25 movements), and fall migration (8 August and 14 December, n = 5 movements) found eagles migrated along the coastal corridor from Washington to southeast Alaska, and through interior British Columbia along the Fraser River. Of 20 telemetered eagles, 40% originated from British Columbia, 35% from Alaska, 20% from the Northwest Territories, and 5% from the Yukon Territory. Breeding adults comprised 50% of the 16 adults for which nesting status was determined. Four of 5 eagles captured in winter 1996-97 returned to the Skagit River for nearly 3 weeks (average = 20 ± 23 days) of the 8 weeks (average = 55 ± 28 days) they spent in Washington and southwestern British Columbia in winter 1997-98. With the exception of 1 eagle that moved to the Feather River in northern California, winter movements of the 23 eagles in Washington were confined to the area east from the San Juan Islands to the Columbia River. In winter 1998-99, we plan to complete deployment of PTTS, and conduct further behavioral observations of telemetered eagles to assess daily movements and activity patterns.