Foraging ecology and forage availability for the black-capped vireo

Authors: D.T. Morgan

An individual’s survival and reproduction depends on its ability to capture prey and obtain energy. Current literature is lacking quantitative information on the foraging habitats or available foods of the federally endangered black-capped vireo (Vireo atricapilla). In 2010 and 2011, I monitored male black-capped vireo territories to collect foraging ecology and available foods data at the Balcones Canyonlands National Wildlife Refuge, Texas. I conducted foraging behavior, vegetative time-use, nesting productivity, and vegetation composition surveys in 30 and 58 breeding territories in 2010 and 2011, respectively. I observed 273 foraging events and recorded over 2000 minutes of time-use surveys from black-capped vireo territories in 2010 and 377 foraging events and over 3200 minutes of vegetation time-use surveys in 2011. I collected descriptive data on the use of vegetative substrates and compared male vireo foraging mean proportion of use versus vegetative species availability between species, year, within season sampling periods, and reproductive success. I collected branch clippings to sample available arthropod foods from a subset of 16 territories in 2010 and 20 territories in 2011. I compared mean arthropod abundance, biomass, and order richness between within season sampling periods and compared mean arthropod order biomass between vegetative species. Ashe juniper (Juniperus ashei), shin oak (Quercus sinuata), and live oak (Q. fusiformis) were the predominant foraging and time-use substrates. There was little difference in vegetation use and territory reproductive successfulness. Sampling available foods revealed variation in arthropod communities between sample years, within season sampling periods, and vegetative species. Ashe juniper is a species of interest because it is commonly removed from vireo habitat because of its tendency to encroach if not properly managed. These data should provide managers valuable information on vegetative species composition to provide vireos optimum foraging opportunities.

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