Evaluation of two GIS habitat models and initial characterization of nesting and breeding-season roosting microhabitat for Mexican spotted owls in the Guadalupe Mountains

The Mexican spotted owl (Stix occidentalis lucida ) is a federally threatened species inhabiting mixed conifer forests and canyon systems throughout the southwestern United States and Mexico. This subspecies has been found in steep-walled canyons and less frequently in mixed-conifer forests of the Guadalupe Mountains of West Texas and Southeast New Mexico. Prior to this study, no quantitative study of spotted owl habitat in this region had been conducted. The purpose of this study was to characterize and quantify the breeding-season habitat of Mexican spotted owls at two spatial scales based on their occupancy in the Guadalupe Mountains. I determined the distribution of high-quality habitat at a landscape scale by assessing the predictive ability of two existing GIS-based habitat models initially designed from data outside this region. I quantified 21 microhabitat features surrounding known nest and roost sites to characterize the site-specific conditions within canyon habitats.;I found Mexican spotted owls utilizing steep, narrow canyons with strong vegetative components. The overlapping high-quality habitat predicted by both models had the strongest association to known nest and roost sites and higher occupancy estimates compared to the high-quality habitat predicted by either model alone, making it the most efficient description of Mexican spotted owl breeding-season habitat at a landscape-scale. Canopy-cover, saplings, and rocky debris were significant microhabitat characteristics of nest and roost sites within this region. Canyon morphology, species composition, and ground cover vegetation at nest and roost sites were homogenous compared to random canyon sites.;This study was the first attempt to quantify and describe the breeding-season habitat of Mexican spotted owls using the predictions of GIS-based habitat models and quantitative sampling methods in the Guadalupe Mountains. This study reaffirms the utility of GIS-based habitat models as an effective means for predicting Mexican spotted owl breeding-season habitat and the importance of steep, cool canyons for nesting and roosting sites in the Guadalupe Mountains.