Improving Methods for Estimating Fatality of Birds and Bats at Wind Energy Facilities

The California Energy Commission awarded a Public Interest Energy Research grant to the California Wind Energy Association (CalWEA) to evaluate the procedures provided in the California Guidelines for Reducing Impacts to Birds and Bats from Wind Energy Development for estimating mortality of birds and bats associated with wind energy facilities. eFormative Options is partnering with CalWEA to manage the project.

The goal of the research was to improve the accuracy of methods for estimating the number of bird and bat fatalities by evaluating the effect of time-dependency on the probability of bird and bat scavenging and removal (carcass persistence) and detection by searchers (searcher proficiency).

Data collected from the Altamont Pass Wind Resource Area from January 7 to April 30, 2011 were used to create traditional carcass persistence and searcher proficiency functions and new functions in which searcher proficiency and persistence are modeled as a function of time, ecological condition, and carcass age. This study is the first to document that searcher proficiency and carcass persistence are time-based processes, and offers lessons and implications for experimental designs and the field monitoring recommendations provided in the Guidelines.

The study also investigated the fatality estimation equation provided in the Guidelines, and three other equations from the literature used to adjust mortality observations for searcher proficiency and carcass persistence.