Abstract Buteo plagiatus (Gray Hawk), state-listed as threatened in Texas, occupy a narrow, increasingly fragmented portion of its range in the United States, where ongoing habitat loss may jeopardize long-term persistence. To quantify resource selection, we used GPS-tracking data and resource selection functions for adults and fledglings in the Lower Rio Grande Valley of Texas, modeling them separately at population and individual levels. We found that across life stages, seasons, and sexes, B. plagiatus consistently selected areas with taller trees, with differences by life stage and scale of selection. Tree height and tree height variability, rather than land cover classes or proximity to riparian zones, were the strongest predictors of use. In contrast with our hypotheses, distance to water, a presumed proxy for riparian zones, was not a consistent predictor of use. Within their home range, both age classes favored taller trees, with adults also responding to tree height variability, but fledglings exhibited greater individual variability. At the nest-site scale, nests were located in wooded areas with greater tree height variability, with taller trees (β = 0.37), less barren land cover within 1,500 m (β =—0.56), and closer to cropland (β =—0.70), all strongly supported predictors of nest-site placement. Many were also near urban areas with higher proportions of developed land (β = 0.31). Individual-level models highlighted variability in selection, especially at fine scales, emphasizing the importance of accounting for behavioral diversity in conservation planning. Our findings suggest that protecting and restoring wooded patches with taller trees and greater tree height variability, including those within urban areas, will be critical for sustaining B. plagiatus at the northeastern edge of its range, where landscapes face continued degradation and fragmentation, and conservation actions must balance pressures from urban expansion, agriculture, and alteration of riparian areas.
Stewart et al. (Wed,) studied this question.