Mexican spotted owl home range and habitat use in pine-oak forest: Implications for forest management

To better understand the habitat relationships of the Mexican spotted owl (Strix occidentalis lucida), and how such relationships might influence forest management, we studied home-range and habitat use of radio-marked owls in ponderosa pine (Pinus ponderosa)-Gambel oak (Quercus gambelii) forest. Annual home-range size (95% adaptive-kernel estimate) averaged 895 ha +/- 70 (SE) for 12 individuals and 997 ha +/- 186 (SE) for 7 pairs of owls. On average, the 75% adaptive-kernel contour (a probability contour containing 75% of the owl locations) included 32 and 30% of the annual home range for individuals and pairs, respectively, suggesting high concentration of activity in a relatively small portion of the home range. Relative area of three cover types (ponderosa pine forest, pine-oak forest, and meadow) did not differ between seasonal ranges, and owls used these cover types in proportion to their relative area during both breeding and nonbreeding seasons. In contrast, relative area of four canopy-cover classes varied between seasons. Breeding-season ranges contained greater proportions of areas with canopy cover greater than or equal to 60% and lower proportions of areas with 20-39% canopy cover than nonbreeding-season ranges. Owls roosted and foraged in stands with greater than or equal to 60% canopy cover more than expected during both breeding and nonbreeding seasons, and used stands with 20-39% canopy cover less than expected except for foraging during the breeding season. Stands used for foraging did not differ in structure between seasons and had greater canopy cover and less rock cover than stands with no documented use. Stands used for roosting differed between seasons in a multivariate comparison, but no individual habitat variables differed between seasons in subsequent univariate comparisons. In both seasons, stands used for roosting had greater canopy cover than stands with no roosting use. Closed-canopy forests, which were used heavily by owls, were relatively rare on the study area, suggesting that such forests warrant special protection in areas managed for spotted owls. This may conflict with efforts to restore more open conditions in ponderosa pine forests.