Light and noise at night reduce sleep and alter vocal output in common mynas

With the continuous expansion of urban areas anthropogenic nocturnal disruptors, such as light and noise pollution, are increasingly common. Such disturbances are likely to affect sleep in free-living birds. Lack of sleep can hinder the performance of many waking behaviours, including vocal communication. For many birds, vocal communication is essential for territory acquisition, mate attraction and other social interactions. However, few studies have investigated the direct effects of noise or light at night on bird vocal performance during the day. Here, we tested the effects of light and noise at night on common mynas’, Acridotheres tristis , sleep behaviour and vocal output. Each sleep disturbance experiment consisted of one night of normal sleep (baseline) followed by one night of disturbance (light or noise). We analysed the sleep behaviour of each bird during the experiments and their vocal output the day after. Common mynas slept less during both light and noise at night than during baseline. After the light treatment, common mynas spent less time singing but did not alter their call frequency when compared to baseline. After noise at night, they spent less time singing but more time calling than after baseline. Our results indicate that even short periods of sleep disturbances can affect how much birds vocalize, suggesting that light and noise pollution may influence avian communication through their effects on sleep. Future work should test whether chronic and co-occurring exposure amplifies these effects and whether timing or intensity thresholds determine the magnitude of vocal change.