HABITS OF BALD EAGLES WINTERING ALONG THE CROOKED RIVER, OREGON

Bald eagles (Haliaeetus leucocephalus) were observed in the upper Croo ked River drainage in central Oregon from January to April, 1986 and 1 987 to locate roosts and to describe roosting habitat, eagle abundance , and foraging behavior. The number of eagles peaked at almost-equal-t o 115 during the weeks of 10 March 1986 and 2 March 1987. Large mammal carcasses (deer and cattle) were the primary food source for eagles d uring January and February. Ground squirrels (Spermophilus spp.) were important food during March and April. Twelve communal night roosts we re generally in the largest trees in the vicinity of feeding areas and were isolated from human activities. All roost trees but one cottonwo od (Populus deltoides) were conifers and were the dominant, open-struc tured individuals in forest stands. Results indicate that: 1) substant ially more bald eagles (100+) utilize eastern Oregon in winter than wa s previously thought, 2) use of large mammal carrion by bald eagles ca n be enhanced by not placing carcasses in pits, opening intact carcass es to expose flesh and viscera, and placing carcasses at least 250 m f rom human activities, and 3) large (63-152 em diameter at breast heigh t) coniferous trees that are near feeding areas and isolated from huma n activities are chosen for communal night roosting. Management of bal d eagle roosting habitat should include maintenance of stands of large coniferous roost trees, planting of deciduous trees with horizontal l imb structure (e.g., cottonwood) near feeding areas, and protection of riparian zones from livestock grazing.