Food habits of bald eagles wintering in northern Arizona

Abstract

We used pellets collected from roosts to supplement incidental foraging observations to identify prey species of Bald Eagles (Haliaeetus leucoughalus) and to evaluate spatial and temporal trends in their food habits while wintering in northern Arizona between 1994-96. We analyzed 1057 pellets collected from 14 roosts, and identified five mammal and 13 bird species. American Coot (Fulica americana, N = 447) and elk/deer (Cervus elaphus/Odocmleus hemoinus, N = 412) were the most common prey remains we identified and they varied annually and inversely with each other (11-58% for coots and 21-78% for elk/deer). Diving ducks (92%) were more heavily represented in pellets with identifiable bird prey (N = 701) than dabblers (1%), although Christmas Bird Counts indicated 64% divers and 36% dabblers in the study area (N = 18 202; x² = 46.3, df = 1, P < 0.01). almost all pellets consisted mostly of mammal or bird remains (n = 366 and 689, respectively). the overall ratio of mammal to bird pellets was 59:41, with relative class frequencies varying between years (x² = 118.29, df = 2, P < 0.01). at roosts 3 km from water (N = 303), 96% of the pellets contained mammals (x² = 698.54, df = 1, P < 0.01). In three successive winters of varying weather conditions, wintering eagles foraged primarily on mammals, fish, and waterfowl, respectively; but only mammals and waterfowl were accurately represented in pellets.

Citation

Grubb, Teryl G.; Lopez, Roy G. 2000. Food habits of bald eagles wintering in northern Arizona. Journal of Raptor Research. 34(4): 287-292.