Parental Care and Feeding Ecology of Golden Eagle Nestlings

Abstract

AbstractA field study of Golden Eagles (Aquila chrysaetos) nesting in and near the Snake River Birds of Prey Area was conducted during 1977-1979. Patterns of parental care differed between female and male eagles during incubation and chick rearing; males consistently captured more food throughout all phases of brood rearing (1.2 vs. 0.6 prey/day), while females typically fed and tended the offspring. During the 7th through 9th week of chick rearing, when the food requirements of nestlings were greatest, the female contributed 43% of the prey biomass. No differences were observed in mean daily capture rates between 1978 and 1979 or between parents of one-chick broods and parents of two-chick broods. Although there were no differences between the sexes in the mean weight of prey captured, there were significant differences among pairs, suggesting differences in prey availability or hunting ability. The daily food consumption of eaglets increased as chick rearing progressed and peaked between the 7th and 9th week. Comparisons between eaglets in different-sized broods revealed that individuals in multiple-chick broods received more food from adults than those in one-chick broods. Late in chick rearing, however, those chicks competing with siblings for food had lower consumption rates.