We evaluated foraging and nesting behavior, territory size, and nest success of Golden-cheeked Warblers (Dendroica chrysoparia), a federally endangered songbird, relative to mountain biking trail use. We conducted our study at two mountain biking sites and two control sites at Fort Hood Military Base and in Austin, Texas, in spring 2002 and 2003. Territories of male Golden-cheeked Warblers in biking sites (2.2 ha) were >1.5 times as large as those in non-biking sites (1.4 ha). Mayfield nest success in biking sites (n  =  33) was 35% compared to 70% in non-biking sites (n  =  22). Nest abandonment was three times greater in biking areas (15%) than non-biking areas (5%). Seven nests were depredated in biking sites, but only two nests were depredated in non-biking sites. Texas rat snakes (Elaphe obsoleta) were the most frequent nest predator at biking sites, accounting for 71% of the predations. We conducted behavioral observations of male Golden-cheeked Warblers in biking (n  =  139) and non-biking (n  =  204) sites. Males spent similar amounts of time in diurnal behaviors in biking and non-biking sites. We used video-camera systems to record female nesting behaviors at 17 nests in biking sites and 15 nests in non-biking sites. Nesting behaviors of females did not differ between biking and non-biking sites. The cumulative effect of disturbance from mountain biking trail use on Golden-cheeked Warbler foraging and nesting behavior appears to be minimal, but fragmentation and alteration of habitat by mountain biking trails may reduce quality of nesting habitat for Golden-cheeked Warblers.