Functions and mechanisms of the dawn chorus: Updates since the previous presentation

초록

Songbirds from many species sing intensely in the early morning. This phenomenon has been widely known as the “dawn chorus (DC)”, and it is recognized as one of the most prominent biological signs of the break of the day around the globe since ancient times. However, despite such ubiquity and prominence, the functions and underlying mechanisms of the DC remain surprisingly elusive. In my presentation, I will suggest a novel mechanism and function of DC-like singing based on laboratory experiments in zebra finches. We previously found that temporary suppression of spontaneous singing in the daytime (by turning off ambient light) enhances singing motivation, resulting in intense singing immediately after release from suppression (Kim et al, 2022). We demonstrate here that such “suppression-driven rebound singing” also occurs after the dark of nighttime, resulting in DC-like intense singing in the morning. Moreover, we found evidence that birds tend to wake up a few hours before lights are on in the morning and increase singing motivation in the dark. We also demonstrate that physical suppression of spontaneous daily singing for 2 weeks causes significant deterioration of song structure. Taken together, these results suggest that DC-like singing functions to compensate for the loss of vocal practice during the night and enables birds to quickly re-optimize their song structure to prepare for breeding activity. These results shed light on the mechanisms and functions of DC in songbirds, and provide an important first step toward understanding neurophysiological mechanisms of DC.