How Early Do Birds Start Chirping? Dawn Chorus Onset and Peak Times in a Neotropical City

Urbanisation poses important challenges for animal communication. Avian dawn choruses are a prominent component of urban soundscapes and have received attention in recent urban ecology studies. Current evidence based on comparisons of urban and non-urban sites suggest that urbanisation is associated with earlier dawn chorus singing activity. However, this phenomenon remains mainly unexplored in tropical cities. We here assessed dawn chorus onset and peak times in two contrasting conditions of the urbanisation intensity gradient (i.e., intra-urban and peri-urban forested areas) of a Neotropical city, Xalapa in Mexico, assessing relationships with noise at sunrise and artificial light at night. We found no differences in dawn chorus onset or singing peak times when contrasting intra- and peri-urban areas. However, we found non-significant trends for earlier chorus onsets and peak times with increasing noise levels. Our results show no relationship between artificial light at night and dawn chorus timing, adding evidence to recent studies showing that light pollution does not seem to be determinant in the dawn choruses of tropical birds. Further research is needed to include a wider array of urbanisation conditions and drivers of the singing routines of urban tropical birds.