11 May 1998

Birds Sing Autobiographies

Female birds listening to the melodic outpourings of eager males are every bit as rigorous as the judges at the Eurovision Song Contest. According to a new theory proposed by biologists at Duke University in the latest issue of American Zoologist, female birds scrutinize the quality of males' singing to deduce the "story of their lives" - how well they've coped with the stresses and strains of growing up. From this they judge how desirable a mate they might be.

"The hypothesis has to do with the fact that song is a learned trait," says professor of zoology Steve Nowicki, "and that this learning is supported by specific regions of the brain that develop during a particular period when the young bird is most likely to undergo stress."

The theory also tackles the thorny question of how exactly a female bird benefits from choosing a mate based on his song. "Bird song is far more complex than it needs to be for the information it conveys," explains Nowicki. "It can be as complex as human speech by such measures as the number of units per time, bandwidth, or the rate of acoustic modulations. But if a bird is only more or less just advertising its species, defending a territory or attracting females, why then are bird songs so complex?"

Because they paint a melodic picture of the male bird's life - how fit he is and how his parents raised him. The more complex the song, the more thorough the learning process. And the more thorough the learning process, the better the brain development. "It's because they were better nourished or less stressed during this critical period in the late nestling, early fledgling phase," says Nowicki.

Other studies reviewed by Duke biologists have confirmed that the quality or complexity of bird song does reflect genetic quality, as demonstrated by survival and survival of offspring. Still unclear, however, is precisely what quality the female is assessing when she critiques a male's song. Again, the parallels between the bird kingdom and the Eurovision Song Contest are uncanny. One can only wonder what female birds would have made of Dana.