Serins respond to anthropogenic noise by increasing vocal activity

Increasing levels of anthropogenic noise interferes with the acoustic communication of birds. Adaptive shifts in song characteristics (frequency and amplitude) and in the spatial and temporal patterns of singing behavior in the face of noise pollution have been documented. We provide evidence for another response, increased time spent singing, in a successful suburban bird, the serin Serinus serinus. Serins increased the proportion of time spent singing at posts in relation to changes in noise levels both in space and in time up to a threshold at approximately 70 dBA, whereas time spent at singing posts was not related to noise levels. This response could be related to the characteristics of the serin's song (high pitch and presumably low metabolic and neuromuscular costs) that would reduce the relative effectiveness of song shifts. However, vocal activity decreased sharply above the 70 dBA threshold, suggesting that this strategy is costly. Because singing time may trade off with vigilance time, our data suggest that bird populations in noisy city environments may face an increased challenge for survival compared with quiet areas, even for species whose song characteristics reduce the interference of urban noise with acoustic communication. Copyright 2011, Oxford University Press.