Vermilion flycatchers avoid singing during sudden peaks of anthropogenic noise

Abstract

In many animals, vocalizations are necessary for social interactions to occur; however, anthropic noise can pose a problem as it can disrupt acoustic communication. Oscine birds display a variety of strategies to presumably increase the chances of detection in noisy habitats. On the other hand, suboscines, a group of birds with arguably less vocal flexibility, have been less studied, and we have a poor understanding of the strategies that they may use to cope with noise. Anecdotal evidence suggests that vermilion flycatchers (Pyrocephalus rubinus), a suboscine that produces song bouts, interrupts its bouts in the presence of sudden urban noise (SUN, e.g., when a car passes by), avoiding peak noise. To test this idea, we conducted a playback experiment on 27 free-living males. We recorded the song bouts of each individual: before playback, during SUN playback, and after playback. Ambient noise and artificial light at night (ALAN) have been shown to influence bird singing. To evaluate if there is an association between these pollutants and birds’ response to SUN, we also measured mean ambient noise, ambient noise coefficient of variation, and ALAN in the males’ territories. We found that birds sang shorter bouts during the SUN treatment. Song bout length during the SUN treatment was not associated with mean noise levels or coefficient of variation in males’ territories; however, it was positively associated with ALAN. This result was dependent upon an influential point and should be taken cautiously. We found no association between singing recovery (latency to sing and song bout length after SUN relative to before SUN) and mean ambient noise, ambient noise coefficient of variation, and ALAN. Our results show SUN-induced temporal singing flexibility and suggest that vermilion flycatchers are well adapted to acoustically polluted environments, with males living in territories with more light pollution possibly being less affected by traffic noise peaks. A previous study showed that song bout length is an important signal during intra-sexual interactions; interrupting this acoustic component may have important consequences during social interactions.