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Airdate: Oct 03, 2000
Scientist: Luis Baptista

Bird Song - Why

Bird Song - Why
Why do birds sing? What may sound like light-hearted entertainment is often very serious business.


The trilling, tweeting and whistling of a song bird may sound like light-hearted entertainment, but in fact it's often serious business. I'm Jim Metzner and this is the Pulse of the Planet, presented by DuPont. Birds that sing apparently do it for two main reasons -- to defend their territory from would-be interlopers, and to attract a mate. According to Luis Baptista, former curator of ornithology at the California Academy of Science, male birds are much more vocal when they're seeking a mate than they are when they have a partner.

"Song is also used by the male to stimulate the female sexually, to make her produce hormones and to make her ovaries grow."

In some species, the female bird sings in response to the male's song, and it's her own singing that stimulates her reproductive system.

"When she sings, she stimulates a nerve that goes from the vocal chord right up to the brain, and then it causes hormones to come and her ovaries grow. So the male indirectly stimulates her to sing and she in turn stimulates her ovaries."

Scientists have discovered that female birds seem to respond more to some male birds' singing than others. For example, among mockingbirds, the males with a larger repertoire of bird imitations are better at attracting females and at holding on to territory. But do birds ever sing for the pure pleasure of it? Some experts, including Luis Baptista, think they do.

"Sometimes birds sing just because they're happy, they've had a good meal, they've nothing to worry about. This is an expression, if you will, of well-being."

Our series on bird song is dedicated to the memory of Luis Baptista, who passed away recently. Pulse of the Planet is presented by DuPont, bringing you the miracles of science, with additional support provided by the National Science Foundation. I'm Jim Metzner.