DOI: 10.5061/dryad.vx0k6djxg
title: Forest bat activity declines with increasing wind speed in the proximity of operating wind turbines

description: The increasing use of onshore wind energy is leading to an increased
 deployment of wind turbines in structurally rich habitats such as forests.
 Forest-affiliated bats, in turn, are at risk of colliding with the rotor
 blades. Due to the legal protection of bats in Europe, it is imperative to
 restrict the operation of wind turbines to periods of low bat activity to
 avoid collisions. However, bats have also been observed to avoid wind
 turbines over several hundred meters distance, indicating a displacement
 that cannot solely be explained by modifications to the habitat. This
 avoidance suggests a displacement of bats by indirect factors related to
 wind turbine operation, e.g., wake turbulences and noise emissions.
 Therefore, we investigated whether the activity of forest-affiliated bats
 is influenced by operation mode (on/off) under variable wind conditions
 along transects from 80 to 450 m distance to wind turbines. We divided
 recordings by foraging guild, i.e., either narrow-space (Myotis,
 Plecotus), edge-space (Pipistrellus, Barbastella), or open-space foraging
 bats (Nyctalus, Eptesicus, Vespertilio), and analyzed the effects of wind
 turbine operation and wind speed on the recorded bat guild activity with
 mixed effects models. The acoustic activity of narrow-space foraging bats
 decreased by 91% with increasing wind speed when wind turbines were
 operating, while bat activity remained unaffected by wind speed when
 turbines were not operating. This was neither observed for open-space
 foraging bats nor for edge-space foraging bats, and neither wind turbine
 operation nor wind speed (ranging between 0 – 4 m/s at 10 m height above
 ground) were found to affect bat activity when considered alone. Wind
 turbine noise emissions are known to increase with rotor speed and
 consequently, wind speed, thus presenting a likely explanation for the
 interactive negative effect of turbine operation and wind speed
 specifically on noise-sensitive narrow-space foraging bats. To understand
 potential ecological long-term consequences for bat populations in forest
 areas with wind turbines and to design effective conservation measures,
 future research should focus on disentangling the effects of different
 disturbances related to turbine operation.
description: Bat calls were recorded with automated ultrasonic recorders at
 increasing distances to wind turbines in forests. 12 study sites, 8
 sampling periods between 2020 and 2021. Wind turbine
 data was provided by the respective companies.
description: Open commented R-script (R_analyses.Rmd) in RStudio and run it
 chunk by chunk.
description: # Wind turbines operating at high wind speeds have a negative impact on
 the activity of forest bats --- Data set contains bat calls from 12
 forests with wind turbines, recorded in increasing distance to turbines.
 Further, it contains information on operation status and weather at the
 time of recording as well as data characterizing the habitat structure.
 Based on this data set, we investigated how bat call activity is
 influenced by wind turbine operation at different weather conditions. Our
 main finding: Bats of the narrow-space foraging guild (forest specialist)
 are decreasing activity with increasing wind speed, but only around
 operating wind turbines. This pattern suggests that avoidance behavior of
 bats towards wind turbines, which was observed in various recent studies,
 is caused by factors related to turbine operation, for example noise
 emissions. ## Description of the data and file structure
 R_analysis_dryad.Rmd: Commented R-script. Use the R-script to load and
 analyze the data from the excel-tables. final_data_narrow.xlsx:
 Excel-sheet containing the bat data for the narrow-space foraging guild
 plus environmental and wind turbine data. Excel-sheets contain
 descriptions of the content of each column on the second page.
 final_data_open_edge.xlsx: Excel-sheet containing the bat data for the
 open-space and edge-space foraging guild plus environmental and wind
 turbine data. Excel-sheets contain descriptions of the content of each
 column on the second page. ## Sharing/Access information Wind turbine
 operation data was provided by the respective companies. Data on wind
 turbine size, age and capacities was retrieved from:
 Climate
 data were downloaded from: ERA5-Land hourly data from 1981 to present.
 Copernicus Climate Change Service (C3S) Climate Data Store (CDS).
 10.24381/cds.e2161bac All other data were collected by us in the field. ##
 Code/Software Open the file "R_analyses_dryad.Rmd" with the
 program RStudio. Make sure R is installed on your computer (we used
 version 4.2.2). The file is divided in chunks. Begin from the start and
 run each chunk, one after another, by clicking the little green arrow in
 the top right corner.