Population distribution and trends of California spotted owls

Abstract

Following Verner et al.’s (1992) technical assessment of the California spotted owl (CASPO), we divided the range of the California spotted owl (Strix occidentalis occidentalis) into two major physiographic provinces: the Sierra Nevada and the mountains of southern California (Tehachapi Pass was the demarcation between the regions). Verner et al. (1992) noted that these provinces are geographically distinct and that movement of owls between them is probably rare, which remains true today (see "Population and Conservation Genetics of California Spotted Owls" section below). The California spotted owl is also found in the coastal mountains north to Monterey Bay, but much less is known about owl numbers and locations along the coast (see figs. 4-1 and 4-2). That portion of the southern Cascade Range that abuts the Sierra Nevada has been considered to encompass the range of the California spotted owl on the east side of California (see chapter 2). Where the ranges of the northern (S. o. caurina) and California spotted owls meet, a hybrid zone occurs in the area of contact near the Pit River (Barrowclough et al. 2011; see chapter 2). Hereafter, we refer to owls occurring south of the Pit River as belonging to the Sierra Nevada population of California spotted owls.

Parent Publication

• The California spotted owl: current state of knowledge

Citation

Tempel, Douglas J.; Gutiérrez, R.J.; Peery, M. Zachariah. 2017. Population distribution and trends of California spotted owls. In: Gutiérrez, R.J.; Manley, Patricia N.; Stine, Peter A., tech. eds. The California spotted owl: current state of knowledge. Gen. Tech. Rep. PSW-GTR-254. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 75-107. Chapter 4.