CANBERRA, March 5 (Xinhua) -- A team of international researchers has found that bird song is almost as common in female birds as in males, overturning long-held theories that bird song was an exclusively male trait.
The findings, released by Australian National University (ANU) on Wednesday, challenge long-held assumptions about sexual selection in birds, and pose new questions about Darwin's theory of sexual selection and the evolution of elaborate bird song.
The research, by the University of Maryland, Baltimore County, the University of Melbourne, the Australian National University and Leiden University in the Netherlands, has been published in the journal Nature Communications.
"Darwin focused on the evolution of song through sexual selection, and assumed birdsong was a male trait to attract females," said report joint author Dr Naomi Langmore, from the ANU 's Research School of Biology.
"Our findings suggest that bird song may have evolved through a broader process, called social selection, as both sexes competed for food, nest sites, mates and territories."
Darwin had suggested the primary role of female birds was to listen to the songs of the males, and instances of female bird song were traditionally dismissed as rare or the outcome of hormonal aberrations.
But the latest study found female song was present in the ancestors of all songbirds, and today remains in 71 percent of the songbird species surveyed.
In Australia, Dr Langmore said most present songbird species feature bird song from both males and females, including lyrebirds, fairy-wrens, honeyeaters, fantails, whistlers, and magpies.
She said the songs from male and female birds were equally melodic.
She said female bird song was less common in a recently-evolved group of songbirds that is more prevalent in Europe and North America, which may explain why the old assumptions lasted for so long.