Regulation of Bald Eagle Reproductive Rates in Southeast Alaska

Abstract

I examined the influence of food abundance and habitat quality on reproduction of Bald Eagles (Haliaeetus leucocephalus) in the Chilkat Valley, Alaska. The proportion of active nests was greatest and the timing of laying earliest in portions of the study area where food was most abundant. Clutch size was not related to food availability. Offspring survival was higher in breeding areas where food was experimentally provided than in control areas. Whether nests were active was also related to 2 of 11 habitat features measured at breeding areas. One habitat variable was associated with nest success. The findings suggest that variable productivity and a surplus of non breeders are the norm in the region as a result of high variability of annual food supplies and strong intraspecific competition. The results further suggest that the decline of this species in other parts of North America was at least partially due to alteration of eagle food sources and habitats by humans.