Hixson, K. M. , S. J. Slater, R. N. Knight, and R. C. Lonsinger. 2022 Seasonal variation in resource selection by subadult golden eagles in the Great Basin Desert. Wildlife Biology 2022:e01002.
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 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 locational data (n = 99,037) with spatial predictors hypothesized to influence seasonal patterns of space use with mixed-effects logistic regression. Subadults selected for ridges and upper slopes in both seasons, 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. Subadults tended to select 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 suggest that subadults used woodlands more than expected, and this may reflect spatial partitioning by subadults to lower-quality habitats to minimize competition with breeding adults during winter when energetic demands were higher and prey more limited. Our models had high predictive power and can inform natural resource planning to promote golden eagle conservation.