Abstract
Anthropogenic noise is one of the fastest growing, globally widespread pollutants, affecting countless species worldwide. A rapidly growing source of noise pollution is wind turbine infrastructure. Despite accumulating evidence on the negative impacts of wind turbines on wildlife, little is known about how the noise they generate impacts ecological systems. Songbirds may be susceptible to noise pollution due to their reliance on vocal communication and thus, in this field study, we examined how songbirds are impacted by wind turbine noise. We broadcasted noise produced by one wind-turbine in a migratory stopover site during the nonbreeding season. Throughout the study, we repeatedly monitored the acoustic environment and songbird community before, during and after the noise treatments. We found a significant decrease of approximately 30% in the daily number of birds in the presence of wind turbine noise, compared to the before or after phases. This reduction had a significant spatial pattern with the strongest decrease closer to the speaker and on its downwind side, fitting measured sound propagation. Although we found no impact on species diversity, two out of three most common species at our site showed clear avoidance behavior: 45% and 36% decrease in abundance for the Lesser whitethroat (Sylvia curruca) and Sardinian warbler (Sylvia melanocephala momus), respectively, with lingering effects on the Lesser whitethroat in the 'after' phase. Additionally, the age structure of the lesser whitethroat population was impacted, as only juvenile birds showed avoidance behavior. No difference in avoidance extent was found between migratory and nonmigratory species, but the impacts of displacement on migrants during stopover are especially troubling from a conservation perspective. Our results stress the need to address the impacts of noise pollution on wildlife when planning noise-generating infrastructures, such as wind turbines, to allow for sustainable development without threatening already declining songbird populations.