Winter ecology of the endangered golden-cheeked warbler

We studied the ecology of the Golden-cheeked Warbler (Dendroica chrysoparia) during three winter seasons, 1995-1998, in Honduras, Guatemala, and Mexico. Individuals of this species occurred almost exclusively as members of mixed-species flocks, occupying sites with greater densities of encino oak and ground cover and fewer pines than random sites. Most foraging observations were recorded in mid-story, encino oak. Commonly-observed foraging maneuvers were gleaning and sally-hovering. Eighty-three percent of foraging maneuvers were directed at the outermost portions of the oak foliage. Flocks in which Golden-cheeked Warblers occurred contained an average of 20.5 individuals and 12.9 species other than Golden-cheeked Warblers. The most frequently co-occurring species were Wilson's Warbler (Wilsonia pusilla), Black-throated Green Warbler (Dendroica virens), Hermit Warbler (D. occidentalis), Townsend's Warbler (D. townsendi), and Blue-headed Vireo (Vireo solitarius). The ratio of males to females observed was not substantially different from 1:1, and there was little evidence of sexual differences in habitat use. Golden-cheeked Warblers appeared to be tolerant of moderate levels of logging and grazing, but understory clearing to promote grazing for cattle may pose a significant threat to winter habitat availability.