Evaluating methods for monitoring populations of Mexican spotted owls: A case study

Abstract

Monitoring population status of rare or elusive species presents special challenges. Understanding population trends requires separating signal (true and important changes in abundance) from noise (normal temporal and sampling variation; e.g., Block et al. 2001). This is particularly difficult when small numbers or elusive habits make it difficult to obtain precise estimates of population parameters (Thompson et al. 1998:68). We conducted a pilot study to evaluate a sampling design proposed for monitoring populations of the threatened Mexican spotted owl (Strix occidentalis lucida; USDI Fish and Wildlife Service 1995). Here, we discuss this effort as a case study illustrating some pitfalls and issues involved in sampling rare and/or elusive populations. We begin with a brief history of events leading up to the pilot study to provide a context for the study. We then describe study design and implementation and summarize results of the study and conclusions following from those results. Future monitoring efforts may benefit from our efforts and the lessons we learned.

Citation

Ganey, Jospeh L.; White, Gary C.; Bowden, David C.; Franklin, Alan B. 2004. Evaluating methods for monitoring populations of Mexican spotted owls: A case study. In: Thompson, W. L., ed. 2004. Sampling Rare or Elusive Species: Concepts, Designs, and Techniques for Estimating Population Parameters. Washington, D.C.: Island Press. p. 337-385.