IDENTIFYING ENVIRONMENTAL FACTORS INFLUENCING GOLDEN EAGLE PRESENCE AND REPRODUCTIVE SUCCESS

Declining populations of plant and animal species is a major concern threatening global biodiversity. If we want to conserve threatened species, we must understand the requirements of the species. Recent data suggests Golden Eagle populations in the Western United States are declining. Future threats from expanded energy development, habitat loss and climate change are also a concern. Apparent declines and perceived threats have caused management agencies to classify the Golden Eagle as a species of concern requiring the creation of conservation plans. Yet, an effective conservation plan is dependent on information that is currently lacking. To address this lack of available information, I studied a population of breeding Golden Eagles in south-central Montana which has increased in the last 50 years. I was interested in determining which factors were responsible for the increase in the population and changes in measures of breeding performance. I used information from the current phase to identify which environmental factors are important for the eagles now and assessed whether the identified factors were responsible for the documented changes since the 1960’s. I found that Golden Eagles in the current phase were selecting areas for nesting territories based on prey habitat and terrain ruggedness. Within their territories, Golden Eagles selected areas conducive to uplift dependent on proximity to prey habitat, on a western aspect and closer to their nest. My results related to measures of breeding performance were unclear. I found prey habitat was likely not limiting the probability of territories being occupied between phases but instead, anthropogenic disturbance was likely limiting the historic population. My results suggest management plans should focus current protection on areas with prey habitat in close proximity to topography eagles can use to exploit uplift. To better understand the current population trends, I suggest expanding monitoring efforts to areas without a large degree of habitat loss in the last 50 years and to unprotected areas. Golden Eagle populations in these locations may be more indicative of the current status of the population range-wide