Why Zebra Finches May Sing More Intensely Before Dawn

Dawn is welcomed by bird choruses across the globe, yet scientists still do not know why our feathered neighbours create such a commotion each morning.

A new study, which has not yet undergone peer review, examines this behaviour in captive zebra finches (Taeniopygia guttata). It found that the force of their singing may be shaped by hours of anticipation before sunrise.

Zebra finches and the dawn chorus

In a brightly lit laboratory, male zebra finches will spontaneously produce hundreds of songs. In total darkness, however, they do not make a single sound. This prompted researchers to investigate how the shift from night to day influences the dawn chorus.

When the researchers artificially postponed sunrise by three hours, leaving the lights off for longer, the finches began singing earlier and at a greater rate than they did when sunrise was not delayed. They appeared to be eager for the day to start.

Delayed light increases morning singing

Keeping dawn light away for several extra hours did not allow the birds a lie-in. They woke at their usual time and moved actively about in the dark, while holding back their song.

Their apparent impatience was also supported by an experiment giving them a switch that provided 10 seconds of early light. Birds subjected to the delayed ‘dawn’ frequently activated the light. By contrast, they did not do this when dawn came earlier than normal.

"Birds wake up in the dark long before dawn, likely through the hormonal mechanisms associated with melatonin, and their intrinsic motivation to sing increases while spontaneous singing is being suppressed by the darkness," writes the team led by senior author and cognitive behavioral neuroscientist Satoshi Kojima of the Korea Brain Research Institute.

This particularly vigorous morning song could help birds prepare their vocal abilities after resting overnight, rapidly refining their performance and potentially improving their chances of reproductive success during the day.

"Since a vocal exercise function has been proposed for the dawn chorus in wild songbirds as well, we propose that these mechanisms and function… may be applicable, at least in part, to the dawn chorus generally observed in wild birds," the team writes.

The preprint was published on bioRxiv.