Modeling Late-Summer Distribution of Golden Eagles (Aquila chrysaetos) in the Western United States

Abstract

Increasing development across the western United States (USA) elevates concerns about effects on wildlife resources; the golden eagle (Aquila chrysaetos) is of special concern in this regard. Knowledge of golden eagle abundance and distribution across the western USA must be improved to help identify and conserve areas of major importance to the species. We used distance sampling and visual mark-recapture procedures to estimate golden eagle abundance from aerial line-transect surveys conducted across four Bird Conservation Regions in the western USA between 15 August and 15 September in 2006–2010, 2012, and 2013. To assess golden eagle-habitat relationships at this scale, we modeled counts of golden eagles seen during surveys in 2006–2010, adjusted for probability of detection, and used land cover and other environmental factors as predictor variables within 20-km2 sampling units randomly selected from survey transects. We found evidence of positive relationships between intensity of use by golden eagles and elevation, solar radiation, and mean wind speed, and of negative relationships with the proportion of landscape classified as forest or as developed. The model accurately predicted habitat use observed during surveys conducted in 2012 and 2013. We used the model to construct a map predicting intensity of use by golden eagles during late summer across our ~2 million-km2 study area. The map can be used to help prioritize landscapes for conservation efforts, identify areas where mitigation efforts may be most effective, and identify regions for additional research and monitoring. In addition, our map can be used to develop region-specific (e.g., state-level) density estimates based on the latest information on golden eagle abundance from a late-summer survey and aid designation of geographic management units for the species.

Integrating citizen-science data with movement models to estimate the size of a migratory golden eagle population

“…Of these, an estimated 19,000-35,000 golden eagles reside in the western contiguous United States (Good et al, 2007;Millsap et al, 2013;Nielson et al, 2011).…”

“…In contrast, the eastern population likely increased through the late 20th century (Farmer et al, 2008a). Estimates of the size of the eastern population ranges between 1000 and 5000 individuals Ombalski and Brandes, 2010), less than a quarter of the number of golden eagles in western North America-i.e., 19,000-35,000 (Good et al, 2007;Millsap et al, 2013;Nielson et al, 2011). Eastern golden eagles are counted in the hundreds at hawk-count sites in the central Appalachians.…”

Spatial and Host-Related Variation in Prevalence and Population Density of Wheat Curl Mite (Aceria tosichella) Cryptic Genotypes in Agricultural Landscapes

“…Predicting species distributions and population densities has become a fundamental goal of many of basic and applied ecological disciplines [1–3], including practical applications such as conservation and wildlife management and forecasting parasite and pest population dynamics (e.g. [4–9]). Niche models that are routinely employed for predicting species distributions often focus solely on abiotic factors when evaluating the potential habitat suitability for a species of interest (e.g.…”

Review and synthesis of research investigating golden eagle electrocutions

“…Poles in eagle habitat with few natural perches also can present high electrocution risk because eagles tend to perch on these poles (Benson , Harness and Wilson , Schomburg ). Generally, late summer densities of golden eagles in the western United States are in areas with higher elevation, wind speed, solar radiation, percentage of undeveloped habitat, and percentage of unforested habitat (Nielson et al ), and these behaviors dictate fundamental levels of electrocution risk. Pole density also can influence risk where poles occur in eagle habitats.…”

“…Years of electrocution State, province, or region Juvenile Subadult Immature Adult Total Beecham and Kochert (1975) percentage of undeveloped habitat, and percentage of unforested habitat (Nielson et al 2016), and these behaviors dictate fundamental levels of electrocution risk. Pole density also can influence risk where poles occur in eagle habitats.…”