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Title: Comparative habitat use of sympatric Mexican spotted and great horned owls

Author: Ganey, Joseph L.; Block, William M.; Jenness, Jeffrey S.; Wilson, Randolph A.;

Date: 1997

Source: Journal of Wildlife Research. 2(2): 115-123.

Publication Series: Miscellaneous Publication

Description: To provide information on comparative habitat use, we studied radiotagged Mexican spotted owls (Strix occidentalis lucida: n = 13) and great horned owls (Bubo virginianus: n = 4) in northern Arizona. Home-range size (95% adaptive kernel estimate) did not differ significantly between species during either the breeding or nonbreeding season. Home ranges overlapped considerably between species, but overlap in use of individual stands was limited. Relative area of 4 canopy-cover classes (<20, 20-39, 40-59, and [greater than/equal to] 60% canopy cover) and 3 cover types (ponderosa pine forest, pine-oak forest. and meadow) did not differ between ranges of spotted and great horned owls in either season. Use of canopy-cover classes differed between species in both seasons, however, and use of cover types differed during the breeding season. In general, great horned owls used meadows and open stands (canopy cover <40%) more than spotted owls, who roosted and foraged primarily in forests with [greater than/equal to] 40% canopy cover. Structural characteristics of forest stands within the home range also differed between species, as did characteristics of stands used for foraging and roosting. Differences in structural characteristics were consistent with observed differences in use of canopy-cover classes and cover types: stands used by great horned owls had lower log volume, less shrub and canopy cover, and greater herbaceous cover than stands used by spotted owls. The observed patterns of habitat use are consistent with morphological features suggesting that great horned owls are adapted to hunt in more open habitats than spotted owls. Our results suggest that silvicultural treatments that reduce canopy cover below 40% or create large openings within the forest will likely favor great horned owls, whereas maintenance of closed-canopy stands (canopy cover [greater than/equal to] 60%) should favor spotted owls. Such stands were rare in our study area, arguing for their conservation where they occur.

Keywords: Arizona, Bubo virginianus, great horned owl, habitat use, home range, Mexican spotted owl, pine-oak forest, radiotelemetry, Strix occidentalis lucida

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Ganey, Joseph L.; Block, William M.; Jenness, Jeffrey S.; Wilson, Randolph A. 1997. Comparative habitat use of sympatric Mexican spotted and great horned owls. Journal of Wildlife Research. 2(2): 115-123.


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