Golden Eagle Breeding Ecology
This project builds on an investigation of Golden Eagle nesting ecology started in 1962 by graduate students of John Craighead. Now in its fourth year, the project focuses on the nesting ecology, movements, and habitat preferences of adult, resident Golden Eagles. As one of three Golden Eagle studies at CBS, it complements our migration study and our research on sub-adult and juvenile eagles. This work adds to one of the oldest datasets on nesting eagles in the country, which is critical to understanding the population dynamics of this long-lived species. This project’s focus on adult eagles is completed, but we will continue monitoring nesting demographics for several years, while expanding the study’s scope to include tracking juvenile Golden Eagles in order to better understand eagle dispersal.
More on the Project:
Beginning in 1963 under the guidance of John Craighead, researchers began examining Golden Eagle Ecology in South-Central Montana. At that time, their focus was on nesting ecology, prey selection, and the effects of pesticides on the birds. The initial effort provided essential and timely information in the 1960s and also provided us with a baseline dataset for comparison of the breeding density in the future. In the mid-1990s, Derek Craighead returned to resurvey the study site his father had helped to research 30 years prior. Upon his return, Derek documented eagles in many of the previously located historic territories, and he also found similar nest density and productivity rates. In the 1990s, the Golden Eagle population in the Rocky Mountain region was thought to be stable and was of little concern to resource managers. However, this period marked the beginning of what became an annual decline in migrating Golden Eagle count numbers at established locations along known migration routes. This trend soon caught the attention of biologists and land managers, and they shifted their focus to Golden Eagles as concern grew for this apparent negative trend. More recently, concern over an increase in future threats, specifically the expansion of wind-energy development, has further focused attention on Golden Eagles in the west. As a result, efforts are underway at the state and federal level to create conservation guidelines. But in order to produce effective conservation actions, basic information on Golden Eagles must be readily available. With access to a historic dataset, we were in a unique position to help with the effort of supplying information necessary to ensure Golden Eagles persist into the future.
Since 2010, we have been annually monitoring the breeding Golden Eagle population in the Livingston, Montana, area. We have documented information including occupancy rates, nest initiation rates and productivity rates. We’ve also tracked 18 adult Golden Eagles breeding in the study area and nine nestlings. We used the information from the tracking data to produce models of habitat selection for the breeding eagles with the goal of providing conservation practitioners with the tools they need to effectively create management guidelines for this species. We continue to collect tracking data on nestlings and will begin analyzing this information in the upcoming year. We also are continuing to monitor breeding performance of the Golden Eagles in our study area to enhance our dataset and to provide an accurate assessment of the current status of the population and identify factors that are influencing the probability of breeding success.
Publications and Data
Spatial and temporal patters in Golden Eagle diets in the Western United States, with implications for conservation planning. 2017. Geoffrey Bedrosian, James W. Watson, Karen Steenhof, Michael N. Kochert, Charles R. Preston, Brian Woodbridge, Gary E. Williams, Kent R. Keller and Ross H. Crandall. Journal of Raptor Research 51: 347-367.
Patterns of spatial distribution of Golden Eagles across North America: How do they fit into existing landscape-scale mapping systems? 2017. Jessi L. Brown, Bryan Bedrosian, Douglas A. Bell, Melissa A. Braham, Jeff Cooper, Ross H. Crandall, Joe DiDonato, Robert Domenech, Adam E. Duerr, Todd E. Katzner, Michael J. Lanzone, David W. LaPlant, Carol L. McIntyre, Tricia A. Miller, Robert K. Murphy, Adam Shreading, Steven J. Slater, Jeff P. Smith, Brian W. Smith, James W. Watson, and Brian Woodbridge. Journal of Raptor Research 51: 197-215.
A comparison of nest survival between cliff- and tree-nesting Golden Eagles. 2016. Ross H. Crandall, Derek J. Craighead, and Bryan E. Bedrosian. Journal of Raptor Research 50: 295-300.
Habitat selection and factors influencing nest survival of Golden Eagles in south-central Montana. 2015. Ross H. Crandall, Bryan E. Bedrosian, and Derek Craighead. Journal of Raptor Research 49: 413-428.
Space use and habitat selection by adult migrant Golden Eagles wintering in the Western United States. 2015. Robert Domenech, Bryan E. Bedrosian, Ross H. Crandall, Vincent A. Slabe. Journal of Raptor Research 49: 429-440.