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Golden Eagle
Aquila chrysaetos
Order
FALCONIFORMES
– Family
ACCIPITRIDAE
Authors: Kochert, M. N., K. Steenhof, C. L. Mcintyre, and E. H. Craig

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Welcome to BNA Online, the leading source of life history information for North American breeding birds. This free, courtesy preview is just the first of 14 articles that provide detailed life history information including Distribution, Migration, Habitat, Food Habits, Sounds, Behavior and Breeding. Written by acknowledged experts on each species, there is also a comprehensive bibliography of published research on the species.

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Introduction

Adult Golden Eagle, Goshute Mountains, Nevada, October 1999.
Figure 1. Distribution of the Golden Eagle in North America.

The Golden Eagle inhabits a wide range of latitudes throughout the Northern Hemisphere and uses a variety of habitats ranging from arctic to desert. Rare in the eastern half of North America, it is most common in the West near open spaces that provide hunting habitat and often near cliffs that supply nesting sites. Northern breeders migrate thousands of kilometers to wintering grounds; southern pairs tend to be resident year-round. As one of North America’s largest predatory birds, this eagle has been prominent in human lore and culture, inspiring awe, reverence, and sometimes fear and hatred. Humans kill Golden Eagles both intentionally and accidentally by trapping, shooting, poisoning, and electrocution; at the same time, urbanization, agricultural development, and wildfires encroach on this eagle’s traditional shrub-steppe foraging habitat. The species persists, but some U.S. nesting populations may be declining. In the twenty-first century, humans will determine the fate of this species and its habitat.

The Golden Eagle has astonishing speed and maneuverability for its size and uses a wide variety of hunting techniques to capture prey, including soaring, still-hunting from a perch, and low contouring flight. Although capable of killing large prey such as cranes, wild ungulates, and domestic livestock, this species subsists primarily on rabbits, hares, ground squirrels, and prairie dogs. Most do not acquire a nesting territory until they are at least 4 years old, after they have molted into Definitive plumage. Once an individual establishes a territory, it tends to stay there, defending an area of approximately 20–30 square kilometers from conspecifics. A territory may contain up to 14 nests, which a pair maintains and repairs as part of their courtship. The nesting season is prolonged, extending more than 6 months from the time eggs are laid until young reach independence. A typical Golden Eagle raises an average of only 1 young per year and up to 15 young over its lifetime. Pairs commonly refrain from laying eggs in some years, particularly when prey is scarce. The number of young that Golden Eagles produce each year depends on a combination of weather and prey conditions. The black-tailed jackrabbit (Lepus californicus) is a key prey species throughout much of the range, and eagle reproductive rates fluctuate with jackrabbit population cycles.

Although much information on Golden Eagle life history comes from studies in Europe (Watson 1997), important North American research has provided insights about developmental behavior (Ellis 1979), survival rates (Hunt 2001, Harmata 2002), and migration (Brodeur et al. 1996, Craig and Craig 1998, CLM). Much information about Golden Eagle ecology comes from southwestern Idaho, where research on this species has been conducted in and near the Snake River Birds of Prey National Conservation Area (NCA) for more than 35 consecutive years, beginning with Hickman (1968). NCA studies have focused on diet (Beecham 1970, Kochert 1972, Steenhof and Kochert 1988), food consumption/energetics (Collopy 1980, 1983a, 1983b), parental care and feeding ecology (Collopy 1984), long-term reproduction (Steenhof et al. 1983, 1997), dispersal (Steenhof et al. 1984), home-range characteristics (Dunstan et al. 1978, Marzluff et al. 1997), and effects of habitat alterations on nesting populations (Steenhof et al. 1997, Kochert et al. 1999). Despite the wealth of information from this one study area, much remains unknown about populations in other parts of this eagle’s range, particularly Alaska and western Canada. New work in these areas is shedding light on Golden Eagle ecology and may suggest differences between northern migratory populations and southern resident ones.