Breeding Biology of the Golden Eagle in Southwestern Idaho

In view of population declines in several species of raptors in North America and Europe in the last 25 years (Hickey 1969, Ratcliffe 1970, Cottam 1961), a great need exists for studies that help is ascertain norms in unaffected raptor populations and identify factors contributing to the declines. In this regard, in 1966 the U.S. Bureau of Sport Fisheries and Wildlife (Divsion of Wildlife Research and DIvision of Wildlife Services) initiated a study of Golden Eagles (Aquila chrysaetos) in southwestern Idaho and southeastern Oregon. That preliminary field work laid the foundation for a longer-term ecological study of Golden Eagles in southwestern Idaho, the results of which are reported here. In this paper we describe nesting success, density, mortality, and evaluate current population status of Golden Eagles in southwestern Idaho. During 1968 and 1969 we concentrated on obtaining basic information on food habits, productivity, nesting density, morality factors, and behavior of Golden Eagles. In 1970 and 1971 our objectives were: 1, to ascertain the reproductive success and density of the breeding population; and 2, to identify certain mortality factors