Abstract
Anthropogenic noise can interfere with animal behavior through masking of acoustic communication. In response to masking, animals may change their acoustic signals as an apparent adjustment strategy, but this may have a drawback on signal quality. Songs and calls may show noise-dependent changes in frequency and duration, which may yield some masking avoidance, but may also constrain other acoustic parameters that might carry information about the sender. In the present study, we investigated whether noise-dependent reduction in frequency bandwidth or song duration restricted syllable diversity or song elaboration in a Neotropical songbird, the bananaquit (Coereba flaveola). We show that bananaquits sing higher frequency songs, of narrower bandwidth, in noisier territories, independent of variation in territory density, without significant variation in song duration. We also show that songs with higher minimum frequencies, narrower bandwidths, and shorter durations have on average a lower number of syllable types and higher syllable rates. This finding is in line with an acoustic restriction and may reflect a functional trade-off between audibility and signal value: higher frequencies may be more audible but less elaborate songs may weaken the message of sender quality. Consequently, noise pollution may not only alter avian communities, but also shape acoustic diversity and processes of sexual selection in urban environments.
Highlights
Anthropogenic noise has increased in natural and human-altered habitats (Mennitt et al, 2015; Buxton et al, 2017), where it might negatively affect vocally communicating animals
Three out of four of the spectral song measurements were significantly related to the ambient noise level
We found that the frequency bandwidth was significantly related to noise level, with a narrower frequency range in noisier conditions (Table 1)
Summary
Anthropogenic noise has increased in natural and human-altered habitats (Mennitt et al, 2015; Buxton et al, 2017), where it might negatively affect vocally communicating animals. The elevated noise levels can cause acoustic interference by masking the functional variation in frequency and amplitude of vocal signals, for example in frogs, birds, and mammals (Wollerman and Wiley, 2002; Lohr et al, 2003; Erbe et al, 2016). Anthropogenic noise may negatively impact vocal function and undermine survival and reproductive success (Halfwerk et al, 2011b; Potvin and MacDougall-Shackleton, 2015; Kleist et al, 2018), for example through reduced foraging efficiency while avoiding predation, and less success in territory defense and mate attraction (Quinn et al, 2006; Halfwerk et al, 2011a; Kleist et al, 2016). A solution to the problems, at least to some extent, would be to adjust acoustic signals in such a way that would reduce masking by anthropogenic noise
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