Cooperative Fish and Wildlife Research Units Program: Texas
Education, Research and Technical Assistance for Managing Our Natural Resources

The Mexican spotted owl (Stix occidentalis lucida) is protected as a threatened species under the federal Endangered Species Act. In Texas it is listed by Texas Parks and Wildlife Department as threatened and considered as a S1B species, which indicates it is critically imperiled in the state because of extreme rarity (often 5 or fewer occurrences) or because of other factors making it especially vulnerable to extirpation from the state. Listing of the Mexican spotted owl as threatened was based primarily on loss of habitat due to timber harvest practices. Currently, the primary threat to Mexican spotted owls is landscape-scale stand-replacing wildfires. The species is distributed Utah, Colorado, Arizona, New Mexico, west Texas, and southward into northern states of Mexico. Across its distribution, Mexican spotted owls are distributed irregularly due to the patchy distribution of its habitat. Mexican spotted owls require mature pine forests or canyons with rocky cliffs for roosting and nesting habitat. Currently, the species’ distribution in Texas is based primarily on a very few documented observations at isolated locations in the Davis Mountains and the Guadalupe Mountains. However, the actual distribution and occurrence of Mexican spotted owls in Texas is, from a quantitative perspective, unknown. This is because no focused effort has been made to assess the true distribution and habitat associations of Mexican spotted owls in Texas. The landscapes and habitat used by this species, the fact that conventional surveys must be done at night and are time consuming (i.e., expensive), have rendered conventional surveys very challenging in the Trans Pecos region.

We propose to assess the distribution of Mexican spotted owls in Texas by taking advantage of 1) modern technology and 2) the increased number of private landowners in the Trans Pecos allowing wildlife researchers to access to their properties. Owls announce their presence and breeding territories by species-specific, identifiable, vocalizations at night. We will use passive audio monitors (PAMs) to sample the nocturnal hours for Mexican spotted owl vocalizations. Each PAM will be programmed to record during the Mexican spotted owl breeding season (~February – April). Each PAM will then be retrieved, data downloaded and analyzed for detections of Mexican spotted owls and other owl species. For example, Elf Owls (Micrathene whitneyi) and Flammulated Owls (Otus flammeolus) are both Texas species of conservation concern and may be seasonally sympatric with Mexican spotted owls, and there is concern the Barred Owl (Strix varia) may be expanding its range and begin competing with Mexican spotted owls. Our final product will address knowledge gaps for the Mexican spotted owl distributions in Texas and serve to facilitate informed voluntary conservation planning; support science-based management decisions; provide useful information for ESA species status assessment, critical habitat designations, and recovery efforts; and provide accessible data and methodologies to the US Fish and Wildlife Service, Texas Parks and Wildlife Department, and other interested entities. Further it will guide future research on the species. For example, we will pursue other funding from other sources to support research visits to locations where Mexican spotted owls are detected for in-person surveys to locate nest sites and conduct nesting habitat descriptions and assessment.