Multi-scale habitat use of fledgling Black-capped Vireos across two temporal scales

Authors: M.T. Martinez

Knowledge of post-fledging habitat needs is limited for avian species. To better understand this life stage I examined how fledgling black-capped vireos (Vireo atricapilla; hereafter vireo) respond to woodland landcover by assessing habitat use at a landscape scale (>100 ha) and local scale (0.04 ha circular plot) at sites with low, medium, and high woodland availability (WA). I used post-fledging season and post-fledging age as scales to identify temporal trends in habitat use at the two spatial scales.

I established study sites across Balcones Canyonlands National Wildlife Refuge and private properties in central Texas. During the 2013 and 2014 vireo breeding seasons, I located and monitored fledglings, conducted behavioral surveys, and conducted vegetation sampling at fledgling locations, study site-wide locations, and nest locations. Though fledglings occupied woodland areas, fledglings used non-woodland areas considerably more than woodland areas. Probability of post-fledging woodland use was greatest at sites where woodland availability was high (>60%). Fledglings used nonwoodland areas significantly more than woodland areas regardless of the post-fledging season or their age. Although woodland use varied over the post-fledging season and with age class, the differences were not statistically significant.

Fledglings used areas with higher canopy, shrub cover, and compositions of Ashe juniper, live oak, and shin oak than what was average at the site. The vegetation characteristics of post-fledging habitat differed significantly between low, medium, and high WA sites, which suggest post-fledging habitat is highly variable across the landscape. Young fledglings used areas with 10% more shrub cover than old fledglings, and shrub cover at nest locations was about 10% higher than fledgling locations.