Anthropogenic and natural factors are associated with bird dawn chorus onset in subtropical East Asia

Anthropogenic factors such as artificial lighting at night (ALAN) and natural factors including temperature and moonlight can affect the dawn chorus pattern in birds. However, most studies are conducted in temperate regions. We investigated the effect of anthropogenic and natural factors on dawn chorus timing in eight species of bird across Hong Kong, a subtropical city in East Asia. Passive recorders were set at 20 sites and recorded the dawn chorus for 32 days simultaneously. We found dawn chorus started earlier with increased ALAN in six species. The dawn chorus started earlier with higher temperatures in five species; one species delayed dawn chorus on cloudy days, and another species started singing earlier with later dates. Unexpectedly, four species showed a later dawn chorus with higher moon illumination. The effect of ALAN on dawn chorus timing was stronger than other variables, and larger species that started singing earlier were more strongly affected. Our results show that, even in a location with little variation in the time of sunrise across the year, ALAN can cause changes in dawn chorus timing. Our results also highlight another issue; one of the most strongly affected species was the Asian Koel Eudynamys scolopaceus , which has very loud calls. Complaints about the noise of the calls from this genus can be found across Asia and Australia. ALAN could worsen this human–wildlife conflict, as noisy calls occur even earlier in the presence of ALAN.