Traffic Reduction during COVID-19 Lockdowns Benefited Species Already Tolerant of Noise Pollution: An Acoustic Analysis.

AbstractHigh levels of anthropogenic noise pollution affect wildlife globally. Traffic noise contributes a ubiquitous source of noise pollution and shows high intensity at lower sound frequencies. Animals using high-frequency sounds or broad frequency bandwidths may, to some extent, escape energetic masking by traffic noise. Although it is difficult to disentangle effects of noise pollution from those of urbanization, COVID-19 lockdowns reduced traffic in a quasi-experimental manner that isolates the effects of noise. Comparing counts of North American songbirds before and during COVID-19 lockdowns, we show that, surprisingly, species with songs more resilient to interference by noise (wider-bandwidth songs, especially) experienced more favorable changes in abundance associated with stronger reductions in traffic. Such abundance changes in human-altered landscapes during lockdowns indicate that noise pollution can be detrimental even for noise-tolerant species and that conservation of less noise-tolerant species will require more extensive limitations to anthropogenic noise than during COVID-19 lockdowns.