Threats to the viability of California spotted owls

Abstract

The California spotted owl (Strix occidentalis occidentalis) is a species of conservation concern owing to threats to its habitat and populations. Verner et al. (1992) first assessed the status of the California spotted owl "The California Spotted Owl: A technical Assessment of it’s current status" (CASPO) and identified four factors as either threats or potential threats to the viability of California spotted owl populations: (1) timber harvest and forest management, (2) wildfire, (3) development of gaps in owl distribution across the Sierra Nevada, and (4) human population growth and development. Since the publication of CASPO, other factors have emerged as threats to California spotted owl population viability: (1) the invasion of the barred owl (Strix varia) into the Sierra Nevada, (2) climate change that could affect owls and their habitat, (3) the invasion of West Nile virus in the owl’s range, (4) the potential impact to owls from secondary ingestion of rodenticides used to kill rodents that eat marijuana, Cannabis sp., and (5) reduction in genetic diversity. In this chapter, I review threats identified in CASPO and emerging threats to California spotted owls in the Sierra Nevada that have arisen since CASPO. I have relied on key findings from peer-reviewed literature of forest ecology and management and California spotted owl ecology.

Parent Publication

• The California spotted owl: current state of knowledge

Citation

Keane, John J. 2017. Threats to the viability 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: 185-238. Chapter 7.