Reducing bat mortality at operational wind facilities remains an important topic, particularly in consideration with several bat species being considered for regulatory protection at federal, state, and provincial levels. One such minimization tool are turbine-mounted acoustic deterrents to reduce the interactions between bats and wind turbines. The objective of this study is to evaluate the effectiveness of acoustic deterrents in reducing bat mortalities at two operational wind facilities in Ontario, Canada. This study used bat mortality data collected in southern Ontario, with 10 treatment turbines, across two facilities, included in the sample size. At each of the two facilities (10 turbines), one year of baseline fatality data was collected during normal operations. Two subsequent years of fatality data was then collected with blanket curtailment in place (5.5m/s; July 15 to September 30), followed by three years of mortality data with operational curtailment and acoustic deterrents installed. Across the six monitoring years, 293 bat mortalities were collected. This long-term study includes data from 2017-2022 and totals 60 turbine-years of data. The number of bat mortalities per turbine was compared during each treatment at the facilities, including baseline (normal operations), blanket curtailment, and blanket curtailment with an acoustic deterrent. The analysis compares the number of bat mortalities per turbine at the same 10 turbines across each year of the study. This allowed a direct comparison of data at the same geographic location and within the same landscape from year to year, as opposed to using control turbines with a different surrounding landscape, differing nearby habitat features, etc. Preliminary analysis of the combined mortality data indicates an overall reduction of 33.1% in bat mortalities from baseline data (normal operations) to blanket curtailment. The data suggests a further 40.5% reduction in overall bat mortalities following the addition of an acoustic deterrent, relative to blanket curtailment. Reductions in mortalities of individual species was also observed, with the largest overall reduction as a result of acoustic deterrent installation observed with Big Brown Bat (Eptesicus fuscus; 71%), and with species-specific reductions being noted in each of the three migratory bats, ranging from 13% to 36% reduction observed following the installation of an acoustic deterrent. This presentation will summarize the findings of the bat mortality analysis completed in this study, including overall reductions and species-specific results to inform the overall effectiveness of acoustic bat deterrents. The results of this study will further contribute to the knowledge surrounding efficacy of acoustic deterrents and their use in reducing bat mortalities at operational wind facilities, particularly in combination with a low-level blanket curtailment strategy. Furthermore, this study has management implications for the continued operation of wind facilities across North America as several bat species are considered for regulatory protection and state, provincial, and federal jurisdictions are tasked with defining minimization strategies.
