for National Geographic News
In the bird world, male brown-headed cowbirds (Molothrus ater) perform a choreographed song and dance routine that would be the envy of any American Idol contestant.
Using sophisticated monitoring devices and high-speed video cameras, two biologists have revealed just how complex a routine it is. Their research is part of a broad effort to understand how the birds' song and dance works as a communication tool and how songbirds communicate in general.
While female cowbirds don't sing, male cowbirds belt out a small repertory of songs, each one less than a second long. The short riffs begin with a low frequency note complex and almost all end with a high-frequency whistle.
Intriguingly, while all male cowbirds can sing without dancing, they never dance without carrying a tune. Precisely what the birds are trying to communicate, however, remains a mystery.
The research by Franz Goller and Brenton Cooper, biologists at the University of Utah in Salt Lake City, is described in tomorrow's issue of the journal Science.
Song and Dance
Employing video cameras and other monitoring equipment, Goller and Cooper correlated the songbirds' breathing and muscle patterns with their song and dance routine.
The pair found that some of the songbirds' wing—or dance—movements appear to make their singing flow more easily. However, during the most complex wing movements, the songbirds went silent.
While silence is expected when the birds breathe in, it's unusual when they exhale. "Cowbirds are the first species to show a long silent period during expiration. It actually looks like they are holding their breath and pushing to exhale at the same time," said Cooper.
The biologists suggest that this silence avoids the most severe biological and mechanical conflicts between singing and dancing. It may also give the cowbirds a musical rest that helps "keep the beat," said Cooper.
Stephen Rothstein, a zoologist and cowbird expert at the University of California Santa Barbara (UCSB), said he has always considered the visual display component of the routine important. But that he and other researchers didn't appreciate how complex it was until looking at Goller and Cooper's paper, he said.
Come Again?
|
SOURCES AND RELATED WEB SITES
|
