Artificial light at nigh drives early dawn chorus onset times of the Saffron Finch (Sicalis flaveola) in an Andean city

Urban birds around the world have to cope with dominant city stressors as anthropogenic noise and artificial light at night by adjusting the temporal and spectral traits of their acoustic signals. It is widely known that higher anthropogenic noise and artificial light levels can disrupt the morning singing routines, but its influence in tropical urban birds remains poorly explored. Here, I assessed the association between light and noise pollution with the dawn chorus onset of the Saffron Finch (Sicalis flaveola) in an Andean city of Colombia. I studied 32 urban sites distributed in the north of the city, which comprise different conditions of urban development based on the built cover. I annotated the time when the first individual of the Saffron Finch was heard at each site and then I obtained anthropogenic noise and artificial light at night measurements using a smartphone. Findings of this study show that Saffron Finches living in highly developed sites sang earlier at dawn than those occupying less urbanized sites. Unexpectedly this timing difference was related to artificial lighting instead of anthropogenic noise, suggesting that artificial light could drive earlier dawn chorus in a tropical urban bird. Saffron Finches could take advantage of earlier singing for signaling territorial ownership among neighbors, as expected by the social dynamic hypothesis. However, findings of this study should be interpreted carefully because the dawn chorus is a complex phenomenon influenced by many multiple factors. Future studies need to assess the influence of ALAN on the dawn chorus timing of Neotropical urban birds by taking into account the influence of confounding factors related to urbanization as well as meteorological, ecological, and social drivers.