Abstract

The diurnal behavior and nocturnal roosting patterns of 28 bald eagles outfitted with tail-mounted radios were investigated in Rush Valley, Utah between January and March 1982-1984. Casting analysis and feeding observations indicated the principal food source was jackrabbit carrion. Jackrabbit availability declined from 1982 to 1984 and eagles responded by; 1) roosting closer to feeding sites, 2) shifting from canyon to valley roosts, 3) arriving later at and departing earlier from roosts, 4) decreasing diurnal activity, and 5) decreasing residence time. Foraging efficiency appeared to be maximized by experienced eagles using familiar feeding areas and by naive birds monitoring their activity. There appeared to be a slight (8.6%) energetic advantage to roosting at valley sites because of their proximity to feeding areas. This saving was presumably dissipated under adverse weather conditions when eagles selected the sheltered microclimate of canyon slopes. Twelve eagles were tracked during spring migration and all followed northward routes.

Degree

PhD

College and Department

Life Sciences; Plant and Wildlife Sciences

Rights

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