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

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 \u3e1 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 \u3e6.5 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

Landscape Movements of Migratory Birds and Bats Reveal an Expanded Scale of Stopover

Many species of birds and bats undertake seasonal migrations between breeding and over-wintering sites. En-route, migrants alternate periods of flight with time spent at stopover – the time and space where individuals rest and refuel for subsequent flights. We assessed the spatial scale of movements made by migrants during stopover by using an array of automated telemetry receivers with multiple antennae to track the daily location of individuals over a geographic area ∼20×40 km. We tracked the movements of 322 individuals of seven migratory vertebrate species (5 passerines, 1 owl and 1 bat) during spring and fall migratory stopover on and adjacent to a large lake peninsula. Our results show that many individuals leaving their capture site relocate within the same landscape at some point during stopover, moving as much as 30 km distant from their site of initial capture. We show that many apparent nocturnal departures from stopover sites are not a resumption of migration in the strictest sense, but are instead relocations that represent continued stopover at a broader spatial scale

Timing and Weather Offer Alternative Mitigation Strategies for Lowering Bat Mortality at Wind Energy Facilities in Ontario

Relatively high mortality of migratory bats at wind energy facilities has prompted research to understand the underlying spatial and temporal factors, with the goal of developing more effective mitigation approaches. We examined acoustic recordings of echolocation calls at 12 sites and post-construction carcass survey data collected at 10 wind energy facilities in Ontario, Canada, to quantify the degree to which timing and regional-scale weather predict bat activity and mortality. Rain and low temperatures consistently predicted low mortality and activity of big brown bats (Eptesicus fuscus) and three species of migratory tree bats: hoary bat (Lasiurus cinereus), eastern red bat (L. borealis), and silver-haired bat (Lasionycteris noctivagans). Bat activity occurred in waves with distinct peaks through the season; regardless of seasonal timing, most activities occurred in the first half of the night. We conclude that wind energy facilities could adopt a novel and more effective curtailment strategy based on weather and seasonal and nocturnal timing that would minimize mortality risks for bats while increasing the opportunities for power generation, relative to the mitigation strategy of increasing cut-in wind speed to 5.5 m/s

Economic Impacts of Curtailing Wind Turbine Operations for the Protection of Bat Populations in Ontario

Wind energy is a growing industry in Canada to meet the demand for a renewable supply of energy. However, wind turbine operation represents a high mortality risk for bat populations, and regulators often require that steps are taken to mitigate this risk. The result is concern among operators about lost revenue potential. This study was, therefore, designed to estimate the theoretical financial impact of curtailing turbine operations to mitigate for bat mortality for all wind farms that were constructed and operating in Ontario, Canada, as of 1 January 2020 (n = 87 wind farms). Empirical data from the Canadian Wind Farm SCADA and meteorological systems are not publicly available; thus, we were compelled to use data from the Canadian Wind Turbine database, the Environment and Climate Change Canada Wind Atlas, and the Independent Electricity System Operator to calculate the total theoretical energy production for all wind turbines in the province using manufacturer power curves and a measure–correlate–predict linear regression method. We estimated the financial impacts for all wind farms on the assumption that operations were curtailed when the Wind Atlas modelled local wind speed was <5.5 m/s between 6 pm of one day and 6 am the following day, between 15 July and 30 September, using the lower and upper limits of power-purchase agreement rates for Ontario wind farms: 115 and 150 CAD/MWh. We used generalized linear modelling to test whether the variability in production loss was predicted based on factors related to turbine design and site wind speeds. We estimated that total annual wind energy production would be reduced from 12.09 to 12.04 TWh if all Ontario wind farms implemented operational curtailment, which is equivalent to a difference of 51.2 GWh, or 0.42%. Production loss was related to turbine cut-in speeds and average site wind speeds recorded between 15 July and 30 September. The estimated profit losses were 6.79 ± 0.9 million CAD compared to estimated earnings of 1.6 ± 0.21 billion CAD, which suggests that mitigating bat mortality may represent a small cost to the industry relative to the conservation benefits for bat populations

Long Point, Lake Erie, ON, Canada showing tower locations (Points A–E) used in fall 2009.

<p>The directions each antenna were pointing (fall 2009) are shown with red arrows. In fall 2008 and spring 2009 towers A and B were not present and tower D was fitted with 4 antennae and situated approximately 4 km W of the location noted. Banding locations were within 200 m of towers as follows: Mainland (A), Old Cut (C), Tip (E).</p