SPACE USE AND HABITAT SELECTION BY ADULT MIGRANT GOLDEN EAGLES WINTERING IN THE WESTERN UNITED STATES

Recently, there has been an increase in concern for Golden Eagle populations in the western United States, stemming from a marked decrease in the number of migrants and an increase in future threats from a variety of factors including, but not limited to, energy development. Part of an effective conservation strategy for Golden Eagles involves understanding basic requirements of the eagles during both the breeding and nonbreeding seasons. We used PTT and GPS/PTT transmitter data from 14 adult, migratory Golden Eagles captured near the Rocky Mountain Front in Montana to determine the location and size of winter ranges and habitat use and selection within chosen winter ranges. We found large variability in location and size of winter ranges in the western United States. Eagles showed high fidelity to core wintering areas but plasticity in annual range sizes. Adult, migrant Golden Eagles used habitat types associated with perches and primary prey species. Golden Eagles chose areas within winter ranges that were close to prey habitat, within conifer forests and riparian areas, in relatively low elevations, and in areas conducive to orographic uplift. Golden Eagles appeared to avoid urban areas, grassland, agriculture, and non-sagebrush-steppe habitat types. Our results suggest that an effective conservation strategy for migrant Golden Eagles wintering in the western United States should include a large geographic area with heterogeneous habitat allowing for adequate hunting perches and prey habitat, with little urban development or anthropogenic habitat conversion.