Vocal communication shapes animal social networks, connecting multiple individuals over space and time via information, facilitating mate attraction and resource defense. Despite evidence that both the physical and social environment affect signaling behavior, few studies consider variation in individual responses to rapid environmental change within a social context. For example, in response to anthropogenic noise, male songbirds adjust their signal structure. But change in signaling behavior may not be driven by the noise disturbance alone, and social factors may also play an important role in song adjustments. We test the hypothesis that male House wrens (Troglodytes aedon) plastically adjust their songs in response to their immediate noise environment, but that adjustments may depend on social context. We recorded paired males prior to clutch initiation, quantified ambient noise in the moments before signaling, and define social context within pairs as female fertile status and between males as number of conspecific neighbors. We used a series of random regression mixed models to determine whether males plastically adjust song traits, and if so, whether males vary in the level of expressed plasticity.
Results/Conclusions
Both social factors and noise affected temporal structure of songs, whereas frequency adjustments were driven by the social environment. Males plastically respond to increasing noise by changing their song duration, but whether they shorten or length songs depends on the number of conspecific neighbors. Males with no or few neighbors increase their song length with increase noise, whereas males that have several neighbors decrease song length. Spectral adjustments were predicted by social context; males sang songs at lower minimum frequencies when their mates were fertile. Because males vary in their ability to adjust songs, but adjustments depend on social factors, selection might favor males who exhibit greater plasticity, modifying songs as needed to improve signal transmission, while singing songs preferred by females during periods of low noise. Over time, noise could drive changes in signaling patterns; resulting in selection against songs with characteristics that transmit poorly, compared to those able to reach intended receivers. Our study is an essential step towards understanding drivers of flexibility in male signaling behavior, and expands our understanding on how both the social and physical environment may drive selection on male vocal signals.