Altered nocturnal vocal activity patterns in Tropical Kingbird <i>Tyrannus melancholicus</i> (Passeriformes: Tyrannidae) at a site with artificial lighting

Artificial lighting at night (ALAN) modifies the vocal activity patterns of numerous birds. In this study, we evaluated the impact of ALAN on the vocal activity patterns of the Tropical Kingbird Tyrannus melancholicus on María Madre Island, located in the state of Nayarit, Mexico. Vocalizations were recorded using autonomous Song Meter Micro recorders at one site with ALAN and another without. We analyzed sound spectrograms to quantify vocalizations and performed behavioural observations. Our results showed differences in vocal activity between the ALAN site and the non-illuminated site. The ALAN site had higher total vocal activity, producing 3,947 vocalizations with at least one vocalization in every recording, compared to 228 distributed across 40% of the recordings at the non-ALAN site. Tropical Kingbirds at the ALAN site also had a substantially longer and earlier-shifted period of pre-dawn vocalization activity, from 0200 h to 0500 h, compared to a very brief period around 0500 h at the site without ALAN, as well as vocalizations throughout the night compared to a brief peak around twilight with no nocturnal vocalizations. Finally, we observed that individuals at the ALAN site continued to forage into the night, displaying increased agonistic interactions such as chases, wing-fluttering, and physical confrontations. Our results suggest that artificial light significantly alters the activity pattern of the Tropical Kingbird, extending its vocal and foraging activity. Our study could contribute to understanding the effects of light pollution on insectivorous birds in island environments and shows the importance of reducing the impacts of artificial light in natural habitats.