Nesting ecology of migratory golden eagles (Aquila chrysaetos) in Denali National Park, Alaska

Abstract

Between 1988 and 1993 I measured occupancy of nesting territories and reproduction of golden eagles (Aquila chrysaetos) in Denali National Park, Alaska. I collected data occupancy of nesting territories and three reproductive variables (pairs nesting, pairs producing fledglings, and fledgling production) at 74 nesting territories using three aerial surveys each year. During my study, annual fledgling production varied nearly threefold, from 20 fledglings in 1992 to 58 fledglings in 1989. Although rates of nesting territory occupancy did not vary significantly among years (yj = 8.21, d.f. = 5, P = 0.114), I noted significant variation in the proportion of pairs laying eggs (X2 = 33.12, d.f. = 5, P < 0.001) and the proportion of pairs fledging young (X2 = 16.03, d.f. = 5, P = 0.007) among years. Decreases in pairs laying eggs were correlated with decreases in average daily numbers of snowshoe hare (Lepus americanus) and willow ptarmigan (Lagopus lagopus) observed in the study area (rs = 0.83, P = 0.04).