Sex ratios of Brazilian free-tailed bat (Tadarida brasiliensis) fatalities at wind energy facilities in California and Texas

Abstract

Fatalities at wind energy facilities may threaten some bat populations more than others. The Brazilian free-tailed bat (Tadarida brasiliensis) is the most common wind turbine-bat fatality in the Southern Great Plains and the western United States. In California, the population is considered non-migratory with an even sex ratio, whereas in Texas, the population is migratory and female-skewed. If these underlying differences in population sex ratios are reflected in collision fatalities, measures to reduce fatality rates may benefit the female-skewed migratory population more. We used molecular methods to determine the sex ratio of fatalities at wind energy facilities. In California, the proportion of female fatalities did not differ significantly from 0.5 and was stable over the survey years, but the time of peak fatalities was inconsistent. In Texas, the proportions of female fatalities differed across facilities, perhaps influenced by the proximity of roosts, and became less female-skewed over the years surveyed.