Birds and bats can be killed in collisions with operating wind turbines. Wind companies conduct post-construction monitoring (PCM) to estimate the number and composition of these fatalities. Data from some of these studies are publicly available, but some are confidential and unavailable for analysis. The American Wind Wildlife Information Center (AWWIC) was developed to encourage voluntary contributions of confidential data from U.S. wind energy projects to a secure and anonymized database. AWWIC contains more than 250 PCM studies representing more than 25% of the installed wind energy capacity in the U.S. We standardized the estimated number of collision fatalities for birds and bats from these studies and used Generalized Linear Mixed Models to evaluate variation in bird and bat collision risk among species and geographic regions. Improving our understanding of the variability in species composition and spatial patterns in collision risk will guide efforts to minimize this risk.
Results/Conclusions
A total of 281 of approximately 600 bird species and 22 of 47 bat species whose range overlaps with wind energy projects in the U.S. were reported as collision fatalities during scheduled searches in the studies contained in AWWIC. For both birds and bats, fatalities are concentrated in a few species: four bat species constitute approximately 80% of bat fatalities and 15 bird species constitute approximately 48% of all bird fatalities. Bat fatalities have a distinct seasonal peak typically in late summer-early fall, whereas bird fatalities are distributed more evenly although modest increases in bird fatalities are discernible during spring and fall migrations. Bat fatality estimates are higher than bird fatality estimates in some geographic regions, and there is significant variation in bat fatality estimates among regions. Most collisions represent relatively few species and collision risk is high at relatively few projects. Future research should focus on understanding this variation in collision risk among species and geographic regions.