Echolocation Monitoring Models Bat Occupancy Near Wind Energy Facilities
Bird and bat fatalities at wind energy facilities are a common occurrence. Although changes in facility siting and turbine design have reduced bird deaths, bat activity and migration are still poorly understood and casualties remain high. The amount of bat activity depends on the time of year and a number of environmental conditions, such as wind direction and speed, air temperature, and moon phase.
Forest Service scientists developed a new interactive tool that enables users to visualize how changes in the time of year and weather conditions affect the probability of bats being present near wind energy facilities. They used data from multiple echolocation detectors, at a site near Palm Springs, CA, to model weather conditions when bats were present at the site. Use of such models, when integrated into existing computer software in turbines, could optimize turbine mitigations and decrease the number of bats killed with minimal disruption to energy production.
Fatalities of migratory bats, many of which use low-frequency echolocation calls, have become a primary environmental concern associated with wind energy development. The scientists combined the results of continuous echolocation and meteorological monitoring to model conditions that explained presence of low-frequency bats at a wind energy facility in southern California. The scientists used a site-occupancy approach to model nightly bat presence while accounting for variation in detection probability among echolocation detector heights. Detectors at 22 and 52 meters had greater detection probabilities for the bats than detectors at 2 meters above ground. Bat presence also was associated with lower nightly wind speeds and higher temperatures.
The scientists suggest that use of multiple environmental variables to predict bat presence could improve the efficiency of turbine operational mitigations over mitigations based solely on wind speed. The scientists predict that if mitigation efficiencies can be increased, it could increase their use at wind energy facilities to the benefit of bat populations.