Multiscale Nest‐Site Selection by Black‐Capped Vireos

Abstract

Abstract: We used an information‐theoretic approach to investigate nest‐site selection by black‐capped vireos (Vireo atricapilla) at the landscape and habitat‐patch scales on Fort Hood Military Reservation in central Texas, USA, during 2003 and 2004. We used a use‐availability sampling design and logistic regression to compare woody cover characteristics at nests to random points in the landscape to determine habitat selection at the landscape scale. At the habitat‐patch scale, we used matched case‐control logistic regression to compare habitat measures at nests and random non‐nest points to evaluate support for hypotheses concerning the influence of woody cover, nest‐patch, and nest‐site characteristics on black‐capped vireo nest‐site selection. At the landscape scale, we found strong support (Akaike wt [wj] = 1.0) for a model with a cubic effect of percent woody cover and woody cover edge density. Sites with the greatest predicted probabilities of use had woody cover values between 30% and 60% and increasing amounts of edge. We found strong support (wi = 0.93) for the global model at the habitat‐patch scale that included characteristics of the nest site, nest patch, and woody cover within 25 m. Based on odds ratios and confidence limits, percent woody cover, cover below 2 m, cover type, and substrate height had the greatest effect on nest‐site selection. The predicted probability a site was selected for a nest site increased with foliage cover below 2 m, taller substrates, deciduous cover, and decreased at high levels of percent woody cover (especially >80%). Texas red oak (Quercus buckleyi) was the most used nest substrate (100 of 358 nests), followed by shin oak (Q. sinuata var. breviloba; 86 of 358 nests) and Ashe juniper (Juniperus ashei; 44 of 358 nests). Black‐capped vireos used Texas red oak and shin oak in greater proportion to their availability, whereas Ashe juniper was used less in proportion to its availability, suggesting vireos avoided this species. We suggest that managers promote dense deciduous cover for nesting habitat and maximize edge‐to‐area ratios to maintain spatial and structural heterogeneity.