Food Consumption and Growth Energetics of Nestling Golden Eagles

AasTaAcT. -Food consumption, energy metabolism, and growth of 12 wild Golden Eagle (Aquilu chrysaetos) chicks were compared with 4 captive chicks to evaluate the influence of food availability and sibling interaction on growth in wild nestlings. Captive female and male eaglets consumed and assimilated similar amounts of black-tailed jack rabbit (Lepus calijbrnicus). A linear relationship between age and maximum meal size was used in conjunction with field estimates of crop fullness to refine calculations of daily consumption. Growth of captive chicks was very similar to patterns exhibited by wild nestlings. Among wild nestlings, however, females had significantly heavier asymptotic body weights, but slower growth rates than males. Growth curve inflection points occurred 2.2 days later for females than for males, but the difference was not significant. The energy metabolized (ME) by captive and wild female eaglets showed similar increasing trends throughout the chickrearing period. ME values for captive and wild males, however, differed substantially. Wild male eaglets had reduced ME values during the sixth week of chick rearing, a time when captive males showed peak consumption rates. This difference may have been due to the presence of sibling competition, principally with females, for food. Received 20 May 1985, accepted 7 Mar. 1986.