Vocal activity of the rufous nightjar (Antrostomus rufus) in subtropical Yungas Andean forests of Argentina

Nightjars (Family Caprimulgidae) are insectivorous birds with crepuscular and nocturnal habits. Their coloration and cryptic behavior make this group extremely difficult to register, being more easily heard than sighted. The rufous nightjar (Antrostomus rufus) is a widely distributed species from Southern Central America to Northern Argentina, but most aspects of its life history remain unknown. By the employment of an acoustic remote unit, we evaluated the vocal activity and environmental variables of vocalizations by rufous nightjars during a complete annual cycle at one site in the Yungas Andean Forests of Northwestern Argentina. The results, based on one sampled site, indicate that the vocal activity of this species is performed during the breeding season (between September and November). During these months, this species showed a peak of vocal activity at midnight (between 00:00 and 01:00 hs) and at dawn (06:00 hs). In addition, most vocalizations were recorded during full moon nights, and temperature was negatively related to the vocal activity. We highlight the importance of using passive acoustic monitoring as a tool for understanding the life history of nocturnal neotropical birds.

Automated summary

Nightjars are difficult to study due to their secretive behavior and coloration. In this study, we used acoustic remote units to investigate the vocal activity and environmental variables of a species of nightjar, the rufous nightjar, in Northwestern Argentina. The results show that this species is most active during the breeding season, with peak vocal activity at midnight and dawn. Vocalizations were more common on full moon nights, and temperature was negatively correlated with vocal activity. This study highlights the importance of passive acoustic monitoring for understanding the life history of nocturnal neotropical birds.