This report summarizes current knowledge on the status and ecology of the Mexican spotted owl within the Upper Gila Mountains Recovery Unit (UGM RU). It was written at the request of U.S. Forest Service personnel involved in the Four Forests Restoration Initiative (4FRI), a collaborative, landscape-scale restoration effort covering approximately 2.4 million ac (1 million ha) across all or part of four National Forests (Apache-Sitgreaves, Coconino, Kaibab, and Tonto National Forests) located within the UGM RU. The UGM RU supports >50% of the known population of Mexican spotted owls, and the central location of the UGM RU within the overall range of the owl appears to facilitate gene flow throughout that range. Consequently, the UGM population is viewed as important to stability within the overall range of the owl, and management that impacts owls within the UGM RU could affect owl populations beyond that RU. The UGM RU supports >50% of the known population of Mexican spotted owls.
KeywordsHabitat connectivity within the UGM RU is high relative to other RUs, allowing high levels of owl movements and gene flow, and the central location of the UGM RU within the overall range of the owl appears to facilitate gene flow throughout that range. Consequently, the UGM population is viewed as important to stability within the overall range of the owl, and management that impacts owls within the UGM RU could affect owl populations beyond that RU.We have little information on historical distribution of Mexican spotted owls within the RU. This owl currently is distributed widely in mountains and canyons featuring mixed-conifer, ponderosa pine-Gambel oak, and/or riparian forests. In other parts of the range, they occur in rocky canyons lacking extensive forest cover, but this appears atypical within the UGM RU.Mexican spotted owls in the UGM RU occupy large (up to 2,500 ac [1,012 ha]) home ranges. They typically concentrate use in smaller portions of this larger home range, with these "activity centers" typically comprising <50% of homerange area. Most radio-marked owls remain near their breeding areas year-round, but some migrate during winter. This migration, which has been observed in all populations studied, typically entails movement to lower elevations. Resident owls greatly expand their home range during the non-breeding season, but areas used during the breeding and non-breeding seasons overlap spatially. Thus, protection of breeding-season home ranges protects habitat that is used throughout the year.All studies in the UGM RU indicate that home ranges are located in areas containing greater amounts of mature forest than surrounding areas, or sometimes in areas of younger forest containing relatively large trees (>18 in [45.7 cm] diameter at breast height [dbh]). Differences between owl home ranges and randomly located areas are most pronounced near the nest area and decline as areas farther from nests and range centers are included.ii Mexican spotted owls appear to be more selective for habitat used for roostin...