Ranking habitat for Marbled Murrelets: New conservation approach for species with uncertain detection

Abstract

An essential element in the conservation of rare species is the ranking of some aspects of habitat quality. We developed a method to rank the importance of individual habitat patches to Marbled Murrelets (Brachyramphus marmoratus) in 26 old-growth forest stands in northern California, using estimates of stand occupaqcy as an index of nesting activity. We used survey data collected in the stands from 1992 to 1997. The analysis was based on an adjustment that incorporates uncertainty of detection into a binomial model. Maximum likelihood estimators were used for the proportion P of the stands occupied by murrelets and the conditional probability p of detection with each visit to an occupied survey station, and bootstrapping methods were used for error estimates. We were able to rank a single stand most important, three other stands second in importance, and eight additional stands third in importance to murrelet nesting activity. For the murrelets in our study area, these results provided information useful in negotiations between government agencies and a private company in efforts to preserve some of the stands. Our methodology also has potential application for other flora and fauna of management concern, when sampling for presence or absence with uncertain detection. This technique can be applied at a variety of scales depending upon the species and habitat. Although conservation issues require consideration of many factors, including political, social, economic, and biological, our methods are helpful in providing science-based information from sample data to assist in the decision-making process.

Citation

Stauffer, Howard B.; Ralph, C. John; Miller, Sherri L. 2004. Ranking habitat for Marbled Murrelets: New conservation approach for species with uncertain detection. Ecological Applications 14(5): 1374-1383