Resource Documents: Bats (61 items)
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Activity of forest specialist bats decreases towards wind turbines at forest sites
Author: Ellerbrok, Julia; Delius, Anna; Peter, Franziska; Farwig, Nina; and Voigt, Christian
Abstract
Worldwide, wind turbines are increasingly being built at forest sites to meet the goals of national climate strategies. Yet, the impact on biodiversity is barely understood. Bats may be heavily affected by wind turbines in forests, because many species depend on forest ecosystems for roosting and hunting and can experience high fatality rates at wind turbines.
We performed acoustic surveys in 24 temperate forests in the low mountain ranges of Central Germany to monitor changes in the acoustic activity of bats in relation to wind turbine proximity, rotor size, vegetation structure and season. Call sequences were identified and assigned to one of three functional guilds: open-space, edge-space and narrow-space foragers, the latter being mainly forest specialists.
Based on the response behaviour of bats towards wind turbines in open landscapes, we predicted decreasing bat activity towards wind turbines at forest sites, especially for narrow-space foragers.
Vertical vegetation heterogeneity had a strong positive effect on all bats, yet responses to wind turbines in forests varied across foraging guilds. Activity of narrow-space foragers decreased towards turbines over distances of several hundred metres, especially towards turbines with large rotors and during mid-summer months. The activity of edge-space foragers did not change with distance to turbines or season, whereas the activity of open-space foragers increased close to turbines in late summer.
Synthesis and applications. Forest specialist bats avoid wind turbines in forests over distances of several hundred metres. This avoidance was most apparent towards turbines with large rotors. Since forests are an important habitat for these bats, we advise to exclude forests with diverse vegetation structure as potential wind turbine sites and to consider compensation measures to account for habitat degradation associated with the operation of wind turbines in forests.
Julia S. Ellerbrok, Conservation Ecology, Department of Biology, University of Marburg, and Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
Anna Delius, Conservation Ecology, Department of Biology, University of Marburg, Germany
Franziska Peter, Natural Resource Conservation, University Kiel, Germany
Nina Farwig, Conservation Ecology, Department of Biology, University of Marburg, Germany
Christian C. Voigt, Evolutionary Ecology, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
Journal of Applied Biology: 09 July 2022, doi:10.1111/1365-2664.14249
Download original document: “Activity of forest specialist bats decreases towards wind turbines at forest sites”
Curtailment and acoustic deterrents reduce bat mortality at wind farms
Author: Good, Rhett; et al.
Abstract – The impacts of wind energy on bat populations is a growing concern because wind turbine blades can strike and kill bats, and wind turbine development is increasing. We tested the effectiveness of 2 management actions at 2 wind-energy facilities for reducing bat fatalities: curtailing turbine operation when wind speeds were <5.0 m/second and combining curtailment with an acoustic bat deterrent developed by NRG Systems. We measured the effectiveness of the management actions using differences in counts of bat carcasses quantified by daily and twice-per-week standardized carcass searches of cleared plots below turbines, and field trials that estimated searcher efficiency and carcass persistence. We studied turbines located at 2 adjacent wind-energy facilities in northeast Illinois, USA, during fall migration (1 Aug–15 Oct) in 2018. We estimated the effectiveness of each management action using a generalized linear mixed-effects model with several covariates. Curtailment alone reduced overall bat mortality by 42.5% but did not reduce silver-haired bat (Lasionycteris noctivagans) mortality. Overall bat fatality rates were 66.9% lower at curtailed turbines with acoustic deterrents compared to turbines that operated at manufacturer cut-in speed. Curtailment and the deterrent reduced bat mortality to varying degrees between species, ranging from 58.1% for eastern red bats (Lasiurus borealis) to 94.4 for big brown bats (Eptesicus fuscus). Hoary (Lasiurus cinereus) and silver-haired bat mortality was reduced by 71.4% and 71.6%, respectively. Our study lacked a deterrent-only treatment group because of the expense of acoustic deterrents. We estimated the additional reduction in mortality with concurrent deployment of the acoustic deterrent and curtailment under the assumption that curtailment and the acoustic deterrent would have reduced mortality by the same percentage at adjacent wind-energy facilities. Acoustic deterrents resulted in 31.6%, 17.4%, and 66.7% additional reductions of bat mortality compared to curtailment alone for eastern red bat, hoary bat, and silver-haired bat, respectively. The effectiveness of acoustic deterrents for reducing bat mortality at turbines with rotor-swept area diameters >110 m is unknown because high frequency sound attenuates quickly, which reduces coverage of rotor-swept areas. Management actions should consider species differences in the ability of curtailment and deterrents to reduce bat mortality and increase energy production.
Rhett E. Good, Goniela Iskali, John Lombardi, Trent McDonald, Karl Dubridge, Andrew Tredennick, Western EcoSystems Technology
Michael Azeka, EDF Renewables
The Journal of Wildlife Management, 08 May 2022, doi:10.1002/jwmg.22244
Wind turbines without curtailment produce large numbers of bat fatalities throughout their lifetime: A call against ignorance and neglect
Author: Voigt, Christian, et al.
Abstract – Bats are protected by national and international legislation in European countries, yet many species, particularly migratory aerial insectivores, collide with wind turbines which counteracts conservation efforts. Within the European Union it is legally required to curtail the operation of wind turbines at periods of high bat activity, yet this is not practiced at old wind turbines. Based on data from the national carcass repository in Germany and from our own carcass searches at a wind park with three turbines west of Berlin, we evaluated the magnitude of bat casualties at old, potentially poor-sited wind turbines operating without curtailment. We report 88 documented bat carcasses collected by various searchers over the 20-year operation period of this wind park from 2001 to 2021. Common noctule bats (Nyctalus noctula) and common pipistrelles (Pipistrellus pipistrellus) were most often found dead at these turbines. Our search campaign in August and September 2021 yielded a total of 18 carcasses. We estimated that at least 209 bats were likely killed during our field survey, yielding more than 70 casualties/wind turbine or 39 casualties/MW in two months. Since our campaign covered only part of the migration season, we consider this value as an underestimate. The 20-year period of the wind park emphasises the substantial impact old turbines may have on bat individuals and populations when operating without curtailments. We call for reconsidering the operation procedures of old wind turbines to stop the continuous loss of bats in Germany and other countries where turbine curtailments are even less practiced than in Germany.
Christian C. Voigt, Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany
Klara Kaiser, Samantha Look, Freie Universitäat Berlin, Germany
Kristin Scharnweber, Carolin Scholz, Universität Potsdam, Germany
Global Ecology and Conservation, Volume 37, September 2022, e02149
doi:j.gecco.2022.e02149
Download original document: “Wind turbines without curtailment produce large numbers of bat fatalities throughout their lifetime: A call against ignorance and neglect”
Behavioral patterns of bats at a wind turbine confirm seasonality of fatality risk
Author: Goldenberg, Shifra; Cryan, Paul; Gorresen, Paulo; and Fingersh, Lee
Abstract: Bat fatalities at wind energy facilities in North America are predominantly comprised of migratory, tree‐dependent species, but it is unclear why these bats are at higher risk. Factors influencing bat susceptibility to wind turbines might be revealed by temporal patterns in their behaviors around these dynamic landscape structures. In northern temperate zones, fatalities occur mostly from July through October, but whether this reflects seasonally variable behaviors, passage of migrants, or some combination of factors remains unknown. In this study, we examined video imagery spanning one year in the state of Colorado in the United States, to characterize patterns of seasonal and nightly variability in bat behavior at a wind turbine. We detected bats on 177 of 306 nights representing approximately 3,800 hr of video and > 2,000 discrete bat events. We observed bats approaching the turbine throughout the night across all months during which bats were observed. Two distinct seasonal peaks of bat activity occurred in July and September, representing 30% and 42% increases in discrete bat events from the preceding months June and August, respectively. Bats exhibited behaviors around the turbine that increased in both diversity and duration in July and September. The peaks in bat events were reflected in chasing and turbine approach behaviors. Many of the bat events involved multiple approaches to the turbine, including when bats were displaced through the air by moving blades. The seasonal and nightly patterns we observed were consistent with the possibility that wind turbines invoke investigative behaviors in bats in late summer and autumn coincident with migration and that bats may return and fly close to wind turbines even after experiencing potentially disruptive stimuli like moving blades. Our results point to the need for a deeper understanding of the seasonality, drivers, and characteristics of bat movement across spatial scales.
Migratory tree bats, like this silver-haired bat (Lasionycteris noctivagans) seen roosting on a tree trunk during autumn, are among the most frequently found dead at wind turbines in North America during late summer and autumn.
Shifra Z. Goldenberg, Conservation Ecology Center, Smithsonian Conservation Biology Institute, Front Royal, VA; Institute for Conservation Research, San Diego Zoo Global, Escondido, CA
Paul M. Cryan, US Geological Survey (USGS), Fort Collins, CO
Paulo Marcos Gorresen, University of Hawaii at Hilo, HI; US Geological Survey Pacific Island Ecosystems Science Center, Hawaii Volcanoes National Park
Lee Jay Fingersh, US Department of Energy, National Renewable Energy Laboratory, National Wind Technology Center, Boulder, CO
Ecology and Evolution, 18 March 2021
doi: 10.1002/ece3.7388
Download original document: “Behavioral patterns of bats at a wind turbine confirm seasonality of fatality risk”
