Habits of bald eagles wintering along the Upper John Day River, Oregon

We investigated the ecology of bald eagles (Haliaeetus leucocephalus) wintering along the upper John Day River in northeastern Oregon from late-November through March, 1991-92 and early-December through March, 1992-93. Our primary objective was to locate night roosts. Secondary objectives were to document eagle abundance, locate foraging areas, and describe food habits. The number of eagles peaked at 96 during early-February 1992 and 64 in early-March 1993. Midwinter Bald Eagle Counts and Christmas Bird Counts suggest that the number of bald eagles wintering in the area has increased recently. Primary foraging areas were the John Day River between Picture Gorge and Blue Mountain Hot Springs, the North Fork of the John Day River, and Fox Valley. Mammal carrion was an important food; fish, ground squirrels (Spermophilus spp.), and birds were also utilized. Sixty-one night roosts were located and 19 more were suspected. Eighty-five percent of roosts were used by less than or equal to 5 bald eagles. Only 16% of roosts identified in 1991-92 were used in 1992-93 because eagles moved frequently in response to small, scattered, and ephemeral food supplies. Sixty-six percent of the night roosts were in conifers, 33% were in black cottonwood (Populus trichocarpa), and one roost (2%) was in a mixed western juniper (Juniperus occidentalis), deciduous tree stand: 62% of roosts were on private land. Non-commercial and unregulated cutting of trees on private land is done to expand fields for agriculture, obtain firewood, or clear land for subdivision and other purposes, and commercial harvest of cottonwoods is becoming economical. Consequently, the potential for losing roosts is great, resulting in the possible degredation of wintering habitat for bald eagles. We conclude with management recommendations for monitoring the bald eagle population and managing their foraging and roosting habitats.