Abstract
The recent listing of the Northern spotted owl (Strix occidentalis caurina) by the U.S. Fish and Wildlife Service as a threatened species (Federal Register 1990) raises heated debate concerning the long-term survival of the species and perceived economic cost to timber industry (Thomas et al. 1988). Long term studies of the owls's ecology are necessary to provide information needed for ecologically based management plans (Dawson et al. 1987). Much is already known about the natural and life history of the Northern spotted owl (Forsman et al. 1984, Gutierrez et al. 1984, Gutierrez 1985, Franklin et al. 1990) as well as the California subspecies (S. o. occidentalis) (Gutierrez and Pritchard 1990). In contrast, the Mexican spotted owl (S. o. Iucida) is the least studied of the three subspecies (Ganey and Balda 1989). It is known that this latter subspecies inhabits rocky canyonlands and coniferous forests in the southwestern United States and Mexico (Kertell1977, Wagner et al. 1982, Webb 1983, Johnson and Johnson 1985, Ganey 1988, and Skaggs 1988) but there are few published studies on its ecology and habitat needs (Ganey 1988). Also, the effects of human activities, such as recreation, on the Mexican subspecies are unclear, particularly in isolated habitats (Gutierrez 1985). Therefore, in 1989, we initiated a two year investigation of abundance and distribution of Mexican spotted owls in Zion National Park. This report summarizes our 1990 survey effort and research findings.