Abstract
Worldwide, many countries aim at countering global climate change by promoting renewable energy. Yet, recent studies highlight that so-called green energy, such as wind energy, may come at environmental costs, for example when wind turbines kill birds and bats. Using miniaturized GPS loggers, we studied how an open-space foraging bat with high collision risk with wind turbines, the common noctule Nyctalus noctula (Schreber, 1774), interacts with wind turbines. We compared actual flight trajectories to correlated random walks to identify habitat variables explaining the movements of bats. Both sexes preferred wetlands but used conventionally managed cropland less than expected based on availability. During midsummer, females traversed the land on relatively long flight paths and repeatedly came close to wind turbines. Their flight heights above ground suggested a high risk of colliding with wind turbines. In contrast, males recorded in early summer commuted straight between roosts and foraging areas and overall flew lower than the operating range of most turbine blades, suggesting a lower collision risk. Flight heights of bats suggest that during summer the risk of collision with wind turbines was high for most studied bats at the majority of currently installed wind turbines. For siting of wind parks, preferred bat habitats and commuting routes should be identified and avoided.
Highlights
Over the past two decades, wind turbines have been installed in large numbers worldwide
Evening trips of female (n = 3) and male (n = 5) N. noctula differed in duration (U = 15, p = 0.04, n = 8) and distance travelled (U = 15, p = 0.04, n = 8), yet we note that females and males were recorded at different months
Comparing the speed of bats when traversing cropland, we found that male N. noctula flew almost 1.5 times faster than females (Fig. 2)
Summary
Over the past two decades, wind turbines have been installed in large numbers worldwide. Miniaturized GPS devices became available, which enables current researchers to record the foraging behaviour of even small to medium-sized bats at high spatial resolution[18]. We used such devices to track the movements of common noctule bats, Nyctalus noctula (Schreber, 1774), in north-eastern Germany, an area characterized by farmland that is heavily used for both agriculture and wind power production. Lehnert et al.[21] recently found that about 28% of N. noctula killed by wind turbines originated from distant places such as Poland, Baltic countries and Belarus, whereas the majority (72%) were of regional origin This emphasizes the need to better understand how local bat populations respond to wind turbines. We tested if N. noctula are attracted by visible prominent structures such as wind turbines and linear structures such as hedgerows and treelines
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