Characteristics of nest trees and nest sites of California spotted owls in coniferous forests of the southern Sierra Nevada

Abstract

We described 86 nest sites of California spotted owl (Sh-ix occidentalis occrdentalzs) and tested for differences in vegetation structure at nest locations rn conifer-dominated stands in 2 study areas, the Sierra National Forest (SNF) and Sequoia and Kings Canyon National Parks (SNP), California. All nests were between 1061 and 2414 m in elevation, 52 were side-cavity nests, 18 topcavity nests, and 9 platform nests. All nests were in live trees (69) or snags (17): 41 in fir (Abies spp.), 17 in black oak (Quercus kelloggii), 14 in pine (Pinus spp.), and 14 in @ant sequoia (Sequoiadendron gzganteum). Nest trees had a mean diameter of 118.5 cm (SD = 32.1), except for giant sequoia whlch were much larger in diameter (462.9, SD = 144.5 cm). Pines were the only species where we detected a significant difference (P = 0.0001) in diameter of nest trees between study areas, with larger diameter nest trees located on the SNP. Nest sites were evenly distributed topographically, from near the ridge tops to the bottoms of drainages. Slopes and aspects at nest sites differed (P < 0.05) between study areas with the SNF having the greatest number of nests in the 0-10% slope class on north and west aspects, while the SNP had the greatest number in the 10- 20% slope class on east aspects. Nest sites in both study areas had dense canopy cover (89%) with multiple vegetative layers. Overall, nest site characteristics on the SNF and SNP were similar despite the long history of timber harvest on the SNF and the lack of harvest on SNP.

Citation

Steger, George N.; Munton, Thomas E.; Johnson, Kenneth D.; Eberlein, Gary E. 1997. Characteristics of nest trees and nest sites of California spotted owls in coniferous forests of the southern Sierra Nevada. Transactions of the Western Section of the Wildlife Society, 30:30-3