Nesting ecology and multi-scale habitat use of the black-capped vireo

Authors: K. N. Smith

Ecology and habitat use can vary substantially across a species breeding range. Most of the intensive studies on black-capped vireos have been in central Texas and Oklahoma. However, there is little information about black-capped vireo habitat use in the southern and western region of their breeding range. I monitored black-capped vireo territories and nests in 2009 and 2010 and utilized nest cameras to identify nest predators. I compared habitat used with what was available to the vireos at the landscape, territory and nest-site scale and determined if habitat used was adaptive on the territory and nest-site scale.

From March through July in 2009 and 2010 I territory mapped and monitored 64 Black-capped Vireo territories and 119 nests across 7 study sites. I observed 69 nests with cameras to determine nest predators. Nest success was 18.5% in 2009 and 44.7% in 2010. Both nest depredation and parasitism was >10% higher in 2009 than it was in 2010. Clutch size differed statistically in 2009 (3.4 ± 0.09) from clutch size in 2010 (3.8 ± 0.07). There was a large variety of nest predators compared to other areas of the black-capped vireo’s range that has been sampled. The most common nest predators were Brown-headed Cowbirds (n=4), snakes (n=4), and greater roadrunners (n=3). New predators identified that have not previously observed as Black-capped Vireo nest predators included bobcat (Lynx rufus), raccoon (Procyon lotor), Greater Roadrunner (Geococcyx californianus), and the greater arid-land katydid (Neobarrettia spinosa). Black-capped vireos primarily selected riparian areas and slopes of canyons and did not select mesas, low flats, or woodlands. The other areas highly used by BCVIs are the slopes of canyons and drainages, but unlike the riparian areas, slope habitat is widely abundant within the study area. Low woody cover is fundamental for black-capped vireos territories in the Devil’s River area, as it is in all other areas of their breeding range; however, mean cover within territories was higher in my study area (70%).

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