Experimental effects of human activity on breeding Bald Eagles

To assess the consequences of increased recreational activity in wilderness areas, we studied the effects of human activity on breeding behavior of Ba ld Eagles (Haliaeetus leucocephalus) in interior Alaska. Activity budgets o f breeding eagles changed considerably when humans were camped fur 24 h at a distance of 100 m from nests (treatment) compared to when they were campe d 500 m from nests (control) (P = 0.0036). With humans near nests, adult ea gles decreased the time they preened (percentage change from control to tre atment = -53%), slept (-56%), maintained nests (-50%), and fed themselves a nd their nestlings (-30%) and increased the time they brooded nestlings (+1 4%). Further, overall activity (total number of behaviors performed by adul ts at nests per day) decreased by 27% with humans near nests, as did the am ount of prey adults consumed (-26%) and fed to nestlings (-29%). In contras t, nest attendance did not change with humans near nests (percentage change = 0.3%, P = 0.9); however, the time adults were absent from the nest area (greater than or equal to 200 m from nests) increased by 24% with humans ne ar nests (P = 0.013). Throughout 24-h treatments, eagle responses to nearby humans diminished, suggesting that eagles habituated to the disturbance. D uring the last 4 h of treatment, however, adults still vocalized twice as f requently as controls, indicating continued agitation. Human activity near nests caused clear and consistent changes in behaviors of breeding eagles, suggesting that frequent human activities near nests could adversely affect nestling survival, and therefore reproductive success.