Nesting Ecology of the Black-Capped Vireo in Southwest Texas

Abstract

Abstract There is little information about nesting ecology of the federally endangered Black-capped Vireo (Vireo atricapilla) in the southern and western region of its breeding range, which is characterized by xeric thornscrub and patchy low-growing vegetation. We mapped territories and monitored 119 Black-capped Vireo nests across seven study sites in 2009 and 2010 in Val Verde County, Texas in the Devil's River region on the western edge of the Edwards Plateau. We observed 69 nests with cameras to identify nest predators. Clutch size was significantly smaller in 2009 (3.4 ± 0.82) than in 2010 (3.8 ± 0.43). Both nest depredation and parasitism by Brown-headed Cowbirds (Molothrus ater) were >10% higher in 2009 than in 2010. There was a large diversity of nest predators identified including Brown-headed Cowbird (n = 4), snakes (n = 4), and Greater Roadrunner (Geococcyx californianus) (n = 3). Species identified that have not been previously observed as Black-capped Vireo nest predators were bobcat (L...