Ecosystem processes, land cover, climate, and human settlement shape dynamic distributions for golden eagle across the western US

Abstract

Species-environment relationships for highly mobile species outside of the breeding season are often highly dynamic in response to the collective effects of everchanging climatic conditions, food resources, and anthropogenic disturbance. Capturing dynamic space-use patterns in a model-based framework is critical as model inference often drives place-based conservation planning. We applied dynamic occupancy models to broad-scale golden eagle Aquila chrysaetos survey data collected annually from 2006 to 2012 during the late summer post-fledging period in the western US. We defined survey sites as 10 km transect segments with a 1 km buffer on either transect side (n = 3540). Derived estimates of occupancy were low (4.4-7.9%) and turnover ratesthe probability that occupied sites were newly occupiedwere high (88-94%), demonstrating that annual transiency in occupancy dominates late summer behavior for golden eagles. Despite low philopatry during late summer, variation in golden eagle occupancy could be explained by a suite of land cover and annual-varying covariates including gross primary productivity, drought severity, and human disturbance. Our summary of 13 years of predicted occupancy by golden eagles across the western United States identified areas that are consistently used and that may contribute significantly to golden eagle conservation. Restricting development and targeting mitigation efforts in these areas offers practitioners a framework for conservation prioritization.

Golden Eagle Occupancy Surveys and Monitoring Strategy in Coastal Southern California, United States

“…Our analysis and results showed that the presence of golden eagles in coastal southern California was most strongly associated with the spatial arrangement of remote and rugged terrain conditions, developed land cover, and to a lesser extent, scrubland vegetation cover. These findings were in general accordance with predicted habitat associations of golden eagles from previous studies of site occupancy that we used to guide model development (Wiens et al, 2018;Tack et al, 2020). Moreover, our findings echoed those from historical surveys (Dixon, 1937;Scott, 1985) and more recent telemetry studies of individually marked birds (Tracey et al, 2018a(Tracey et al, , 2020 that emphasized the sensitivity of golden eagles to expanding human development.…”

“…The field of occupancy estimation and modeling (MacKenzie et al, 2006) provides a rigorous and repeatable framework for monitoring the status of wide-ranging terrestrial wildlife species like golden eagles. Occupancy-based studies focused on monitoring sites (e.g., a territory or other predefined area) have been increasingly used to examine the population dynamics of golden eagles and to evaluate how landscape features or human land use might influence those dynamics (Martin et al, 2009;Stahlecker et al, 2017;Wiens et al, 2018;Tack et al, 2020;Watson et al, 2020). A common strength of these studies is that they accommodate imperfect detection of golden eagles during surveys, which, if not accounted for, can lead to inaccurate inferences about site-use, population status, distribution, or nesting success.…”

Developmental stage shapes the realized energy landscape for a flight specialist

“…Additionally, older transient golden eagles are more susceptible to potentially deadly conflicts with territorial adult birds, influencing their movement decisions as they avoid established territories 38 affecting their landscape of fear and thus their decision landscape overall [39][40][41] . The distri-bution of anthropogenic features could also impact the eagles' decision-making on where to fly 42 . The strong individual variation that we observed in the birds' response to distance to ridge lines (Fig.…”

Importance of Power Pole Selection When Retrofitting for Eagle Compensatory Mitigation

“…Assuming bald and golden eagles are more numerous in high-quality habitat, it follows then that electrocution risk is greater within high quality habitats (Bedrosian et al 2020, Watts et al 2015. In Lehman et al (2010), the Rangely Oil Field, Uintah Basin, and High Desert study areas each were comprised of medium to high-quality golden eagle habitat (Dunk et al 2019;Tack et al 2020), but habitat variability did not fully account for differences in electrocution rates among poles. This finding suggested that habitat is a component of electrocution risk, but habitat alone cannot determine which poles pose a high risk of electrocution.…”