Food habits of Bald Eagles wintering in northern Arizona

We used pellets collected from roosts to supplement incidental foraging obs ervations to identify prey species of Bald Eagles (Haliaeetus leucocephalus ) and to evaluate spatial and temporal trends in their food habits while wi ntering in northern Arizona between 1994-96. We analyzed 1057 pellets colle cted from 14 roosts, and identified five mammal and 13 bird species. Americ an Coot (Fulica americana, N = 447) and elk/deer (Cervus elaphus/Odocoileus hemionus, N = 412) were the most common prey remains we identified and the y 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 pellet s with identifiable bird prey (N = 701) than dabblers (1%), although Christ mas Bird Counts indicated 64% divers and 36% dabblers in the study area ( = 18 202; chi (2) 46.3, df = 1, P <0.01). Almost all pellets consisted mostl y of mammal or bird remains (N = 366 and 689, respectively). The overall ra tio of mammal to bird pellets was 59:41, with relative class frequencies va rying between years (<chi>(2) = 118.29, df = 2, P < 0.01). At roosts <3 km from water (N = 752), 90% of the pellets contained birds; whereas, at roost s >3 km from water (N = 303), 96% of the pellets contained mammals (chi (2) = 698.54, df = 1, P < 0.01). In three successive winters of varying weathe r conditions, wintering eagles foraged primarily on mammals, fish, and wate r fowl, respectively; but only mammals and waterfowl were accurately repres ented in pellets.