Bat Mortality at Ontario Wind Farms Quantified and Compared Using Four Candidate Estimator Equations

Bethany G. Thurber, Ontario, CanadaFollow
Catherine B. Jardine, Birds CanadaFollow
J. Ryan Zimmerling, Environment and Climate Change CanadaFollow

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This work is licensed under a Creative Commons Attribution 4.0 License.

Abstract

Wind farm development is expanding globally. While wind energy is a low-cost option for new electricity supply, the impacts to wildlife populations, including bats (Chiroptera), are of ecological concern. To quantify these impacts, scientists have developed estimator equations to estimate bat mortality, which vary in assumptions related to correction factors. We compared the results of 4 estimators applied to post-construction monitoring data from Ontario, Canada, wind farms to evaluate the effects of field methods and correction factors on estimator consistency. To conduct our study, we obtained data from 21 wind farms between 2011 and 2017 for a total of 26 wind farm survey years, because some wind farms supplied fatality monitoring data in >1 year, to estimate mortality. The Ontario Ministry of Natural Resources and Forestry estimator (OMNRF) tended to be highest, while the Huso, Schoenfeld-Erickson, and GenEst estimators produced similar results. Huso and Schoenfeld-Erickson estimates tended to fall within 95% confidence intervals for GenEst, while OMNRF estimates tended to be higher than the upper confidence interval for GenEst. The results from the OMNRF estimator were consistent with the other candidates when carcass persistence times were >6.5 days but inconsistent when carcass persistence times were shorter. Our results demonstrated the degree to which mortality estimates can vary among estimators and highlight the need for a consistent estimator in comparative studies. We recommend GenEst for such studies, as this estimator can incorporate more inputs with flexibility to reflect site-specific field conditions and produces highly consistent results. Conversely, the OMNRF estimator produced consistently higher estimates than the other candidate estimators, and assumptions related to carcass persistence were regularly violated. We recommend that these limitations be acknowledged when interpreting results from this estimator and that its use be reconsidered when assumptions related to carcass persistence are not met.

Recommended Citation

Thurber, Bethany G.; Jardine, Catherine B.; and Zimmerling, J. Ryan (2022) "Bat Mortality at Ontario Wind Farms Quantified and Compared Using Four Candidate Estimator Equations," Human–Wildlife Interactions: Vol. 16: Iss. 1, Article 9.
DOI: https://doi.org/10.26077/0413-08f4
Available at: https://digitalcommons.usu.edu/hwi/vol16/iss1/9

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