DAYTIME HABITAT SELECTION BY RESIDENT GOLDEN EAGLES (AQUILA CHRYSAETOS) IN SOUTHERN IDAHO, USA

Energy and other anthropogenic development are increasing throughout the range of Golden Eagles (Aquila chrysaetos) in western North America, and both private and government agencies have expressed concern about indirect and direct effects on Golden Eagles. To facilitate sustainable development and reduce risk to Golden Eagles, the U.S. Fish and Wildlife Service has established guidelines to assist developers in project planning and siting. A major component of environmental impact assessment is documenting Golden Eagle spatial use near a project site before development. Unbiased estimates of habitat selection (spatial use) in and near a proposed project area are possible with location data collected by Global Positioning System (GPS) transmitters attached to a sample of Golden Eagles in the area. During spring 2011, we identified occupied Golden Eagle territories within a study area in southern Idaho, and deployed four GPS and Argos tags on resident adult Golden Eagles. We developed seasonal resource selection functions (RSFs) for each monitored Golden Eagle, and estimated seasonal daytime habitat selection by the average Golden Eagle by averaging predictions from four RSFs. The final RSFs estimated that relative probability of selection by Golden Eagles was highest closer to nests and over moderately rugged terrain. Other predictor variables such as brightness (a measure of non-vegetated habitats) and slope were also seasonally important. Model validation indicated the models reliably predicted Golden Eagle use within the study area. This is the first study estimating Golden Eagle habitat selection based on a combination of GPS and nest locations. The process we developed may be used to improve our understanding of Golden Eagle habitat selection and to provide valuable information to help minimize risk to Golden Eagles from different land management practices.