Seasonal variation in resource selection by subadult golden eagles in the Great Basin Desert

Abstract

Golden eagles Aquila chrysaetos are a long‐lived and wide‐ranging species believed to be stable or in slight decline across North America. Golden eagles have an extended subadult stage (4–5 years) that is critical to maintaining recruitment into the breeding population and population viability. Compared to adult golden eagles, the ecology of subadult golden eagles (hereafter, subadults) has received little attention. We investigated patterns of resource selection for subadults in the Great Basin Desert of the western United States during summer and winter, 2013–2019. We monitored 46 subadults with GPS transmitters and related locations (n = 99 037) with predictors hypothesized to influence seasonal patterns of space use with mixed‐effects logistic regression. Subadults selected for ridges and upper slopes in summer and winter, but higher elevations in summer. Subadults showed weak selection for lower ridge density in summer, which was likely facilitated by selection for areas with greater thermal wind current potential. In contrast, subadults showed strong selection for higher ridge density in winter. Subadults selected areas further from roads in summer and closer to roads and electrical transmission lines in winter, which may be related to winter scavenging of road‐killed ungulates. Resource selection functions suggested subadults selected for shrublands and woodlands in both seasons, but odds ratios revealed that during winter subadults avoided shrublands and increased selection of woodlands relative to summer. Subadults selected for areas with infrequent fires in both seasons; areas with frequent fires were avoided in summer but selected for in winter. Seasonal changes in resource selection suggested that subadults used woodlands more than expected, potentially reflecting spatial partitioning by subadults to lower‐quality habitats to minimize competition with breeding adults during winter when energetic demands for thermoregulation were presumably higher and prey more limited.

Selección de sitios de anidación por el águila real Aquila chrysaetos (Linnaeus, 1758) (Accipitriformes: Accipitridae) en Janos, Chihuahua, México

“…En la actualidad, gracias al desarrollo de la tecnología, han aumentado en número las investigaciones en rapaces en torno a la telemetría satelital y la selección de hábitat (Sandgren et al, 2014;Domenech et al, 2015;Tikkanen et al, 2018;Hixson et al, 2022), y con ello se han hecho recomendaciones para el manejo del águila real y el hábitat asociado (Singh et al, 2016), que apoyan su conservación. Sin embargo, a pesar de las acciones como el monitoreo constante de las poblaciones reproductoras a largo plazo, conteos aéreos de nidos, paros controlados de la generación de electricidad con turbinas eólicas o ubicaciones apropiadas de los campos, prohibición de uso de pesticidas y leyes que protegen específicamente a esta rapaz, la mortalidad de esta especie es alta y requiere de más trabajo, como tener encuestas de sitios de anidación a largo plazo en toda el área de distribución del águila, así como el conocimiento de las tendencias poblacionales de forma local, el registro satelital de la distribución de individuos residentes y la asignación de fondos de todos los niveles para investigación e implementación de estas acciones (Kochert & Steenhof, 2002;Katzner et al, 2012).…”

Predicting the spatial distribution of wintering golden eagles to inform full annual cycle conservation in western North America

“…The vegetation and land-cover variables in our model were also broadly consistent with other studies of winter-season habitat selection by golden eagles in the western U.S., which found strong positive associations with tall sagebrush and shrubland vegetation, and other variables potentially representative of prey habitat, and some evidence for avoidance of agriculture [ 56 , 59 ]. By contrast, an analysis of subadult winter habitat selection in the Great Basin found higher winter use in mid-elevations, with more use of ridges, in shrub and woodland areas, closer to roads and powerlines, and at lower median wind classes [ 60 ].…”