ABUNDANCE AND HABITAT PREFERENCES OF GRAY VIREOS (VIREO VICINIOR) ON THE COLORADO PLATEAU

Abstract

The Gray Vireo (Vireo vicinior; hereafter “vireo”) is a little-studied songbird with small breeding and wintering ranges. Because of uncertainty about vireo populations, conservationists are concerned about the future of this species. The goal of the present study was to provide new data on the ecology of the vireo to help determine its conservation status. During May and June 2001, I studied breeding habitat selection by vireos on the Colorado Plateau in northern Arizona and southern Utah. I surveyed for vireos and collected vegetation data on 31 transects in pinyon-juniper (Pinus edulis-Juniperus spp.) woodlands throughout this region. Estimated density of vireos was 0.064 ± 0.011 (mean ± SE) birds ha−1. Analysis at two scales showed that the vireo’s primary habitat preference was for areas where junipers predominate over pinyon pine. Vireos also preferred areas with some shrub cover, and they increased with the prevalence of sagebrush (Artemisia tridentata) among shrubs. Additionally, vireos were more common at lower elevations, an effect that was largely independent of vegetation characters. Habitats preferred by vireos are widespread in the southwestern United States and may be increasing in extent as woodlands expand into grasslands and shrublands. On the basis of these results, I suggest that vireo populations are relatively safe, at least for the short term. Additional data on vireo demography are needed to ensure the long-term conservation of this species. Abundancia y Preferencias de Hábitat de Vireo vicinior en la Planicie de Colorado