Bat interaction with a solitary wind turbine along the Delaware coast
High bat mortality has been an unforeseen side effect of the rapid growth of the wind energy industry; this rapid growth has led to a need to assess bat behavior around wind turbines and reduce high bat mortality. We conducted a post-construction assessment of bat activity at a solitary wind turbine located along the shoreline near the Delaware Bay and Atlantic Ocean in Lewes, Delaware. Here we present data from the 2012-2013 flight/migratory season. Our objectives were to determine if the turbine is an attractant/repellent for bats, assess the turbine’s impact on local and migratory bats by monitoring bat activity, and examine correlations between turbine rotation, bat activity, and bat mortality. We monitored bat activity both near and away from the turbine via ultrasonic acoustic detectors and conducted carcass searches during the flight period using standardized protocols. We also implemented a raised turbine cut-in speed during 2013 to assess the effects of curtailment on mortality.
We found bat activity to be significantly higher in the area immediately surrounding the turbine as compared to farther away for both 2012 (Wald Chi-square = 381.71, df = 1, P < 0.001) and 2013 (Wald Chi-square = 39.56, df = 1, P < 0.001). During 2012 we found a total of 35 bat carcasses with no curtailment. For the 2013 season we found a total of 23 carcasses with significantly fewer (Pearson Chi-square = 170.62, df = 4, P < 0.001) carcasses found during curtailment weeks. The most common carcass found for both years was the migratory tree bat Lasiurus borealis (eastern red bat). Our data indicate that bats are attracted to the wind turbine or the area immediately surrounding the turbine; however, subsequent mortality can be significantly reduced by raising the turbine’s cut-in speed.