Prominence of Female Birdsong Challenges Evolutionary Theory

Male birds attract females with their lavish plumage and crooning birdsongs, but a new study suggests the birds are not singing to a mute audience. Seventy-one percent of female birds sing, too.

The find goes against the grain of Charles Darwin's evolutionary theory that birdsong is a characteristic of male birds used to compete with other males and attract females.

Writing in the journal Nature Communications, Katharina Riebel, a biologist at Leiden University in the Netherlands, and her colleagues report their finds, several of which run contrary to standing beliefs on birdsong.

By conducting an analysis of all available literature on female birdsong, Riebel and her collaborators compiled the first worldwide survey of birdsong in female birds, as well as the first study of song in primitive songbird species.

The researchers used a genetic databank to map the evolutionary characteristics of female songbirds, determining that the ancestors of modern songbirds, both male and female, must have used song.

Riebel suggests that the origin of birdsong must not lie solely with male birds' sexual selection of females and competition with males, as Darwin's theory would suggest.

"It seems more probable that sexual and social selection also played a role in females: song allowed both males and females to compete for the resources necessary for survival and reproduction," she said.

The research challenges the current view that competition for partners led male birds to develop bright plumage and loud songs.

"Our study disputes the general validity of this view by showing that a) singing female songbirds are very widespread and b) both the females and the males of the ancestors of all modern songbirds must have had song," Riebel said. "This means that the preference of females for singing males cannot have been the first and foremost reason for the evolution of song. This is a starting point for alternative scenarios, that so far have not been taken into consideration in birdsong research."