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Canopy Closure around Nest Sites of Mexican Spotted Owls in Northcentral Arizona

Teryl G. Grubb, Joseph L. Ganey and Sharon R. Masek
The Journal of Wildlife Management
Vol. 61, No. 2 (Apr., 1997), pp. 336-342
Published by: Wiley on behalf of the Wildlife Society
DOI: 10.2307/3802589
Stable URL: http://www.jstor.org/stable/3802589
Page Count: 7
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Canopy Closure around Nest Sites of Mexican Spotted Owls in Northcentral Arizona
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Abstract

We analyzed variation in canopy closure around 47 Mexican spotted owl (Strix occidentalis lucida) nest sites and 47 random forest sites on the Coconino National Forest in northcentral Arizona. We mapped distinct habitat polygons on 1:15,840 color aerial photographs, assigned each polygon to one of 4 canopy-closure classes (<10, 10-40, 41-70, or >70%), and measured the area in each canopy class within 5 concentric analysis zones with radii of 0.1, 0.4, 0.8, 1.2, and 1.6 km (delineating rings of about 4, 47, 150, 252, and 352 ha). Landscape composition differed between spotted owl nest and random sites (P < 0.001). Differences were greatest within 0.4 km of nest and random sites but persisted across all analyses zones. Nest sites contained more area in the >70% canopy-closure class and less area in the < 10% class. The most abundant canopy class was 41-70%, except within 0.1 km of nests, where >70% canopy predominated. Nesting spotted owls selected areas with denser canopy than randomly available forest landscapes, but outside the immediate nest area (>0.8 km) canopy closure approached that of the surrounding forest.

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