Changing cut in speeds is…

Changing cut in speeds is absolutely necessary to reduce the impacts to bats. However, more studies are needed to test changes in turbine cut-in speed among different sizes and types of turbines, wind regimes and habitat conditions before custom approaches can be assessed. Many research studies have only compared a few different levels of cut in speeds and typically always between 3.5 to 6.5 m/s. It is recommended that higher cut in speeds (e.g., 7 to 10 m/s) be used as a conservative approach if a blanket cut in speed is to be implemented during migratory periods. Future studies should implements a wider range of cut in speeds to test success. Custom approaches must be science based with recent location specific data that demonstrates successful mitigation. Monitoring to confirm that custom approaches remain successful over time should also be a requirement.

A standard method of comparing bat mortality at the turbine with actual bat activity in the area is necessary to ensure that any apparent reduction in mortality at the turbines are not confounded with the general declining trends in bat abundance. This should be incorporated as a mandatory aspect of developing a custom approach.