Anthropogenic city noise affects the vocalizations of key forest birds

Some urbanization impacts on biodiversity are often underestimated such as noise pollution generated by anthropogenic activities. Birds inhabiting urban and peri-urban areas suffer anthropogenic noise that impact their communication, affecting fitness components as reproduction, distribution, density and diversity patterns. We evaluate how anthropogenic sounds (automobiles, airplanes, and helicopters) affect vocalizations of four functionally important bird species of the Andean-Patagonian Forest: The Thorn-tailed Rayadito (Aphrastura spinicauda, arthropod predator), the White-crested Elaenia (Elaenia albiceps, seed disperser), the Green-backed Firecrown (Sephanoides sephaniodes, pollinator) and the Austral Parakeet (Enicognathus ferrugineus, large seed disperser). During the spring–summer of 2021 and 2022 we placed audio recorders (AudioMoth v 1.2.0) in wooded areas of a city surrounded by a National Park, in Argentine Patagonia. We selected recordings where an individual was vocalizing before, during, and after an anthropogenic noise. From each recording, we analyzed frequency (minimum, maximum and dominant frequency) and temporal bioacoustic parameters (duration of vocalization and pause length between syllables). We found that anthropogenic noise affected all bird species, but responses varied between species. During anthropogenic noise, frequency bioacoustic parameters changed in two studied species, whereas all species modified at least one temporal bioacoustic parameter. Some impacts continued even after the noise ceased. Our results show noise produced by human activities affected bird communication potentially threatening birds’ fitness and ecosystem functioning. Given the increase in urbanization over recent decades, and its associated anthropogenic noise increase, understanding the potential impacts of noise is essential for the conservation of bird populations and maintaining ecosystem functioning.