Birds that sing duets with incredible rhythmic precision present a greater threat to other members of their species than those that whistle a sloppier tune, according to a study of Australian magpie-larks reported in the June 5th issue of Current Biology, published by Cell Press.

"When partners duet, they signal to other magpie-larks that they are working as a team to defend their territory," said Dr. Michelle Hall of the Max Planck Institute for Ornithology of the new findings. "The level of precision in their duets seems to let others know how good they aretheir ability and/or motivation to cooperate for territorial defense."

Coordinated displays are widely used among animals to defend shared resources, and may signal coalition strength so that groups can assess the relative competitive ability of rivals and avoid unnecessary fights. For example, lions roar in choruses that provide information about their groups size to intimidate rivals, as do gibbons, chimpanzees, and wolves, Hall said.

Paired Australian magpie-larks sing notes in rapid alternation to produce duets for territorial defense. One member of the pair repeatedly makes a call that sounds like peewee, and the other responds each time with wit, Hall said. Experiments have shown that the birds duets are more threatening territorial displays than songs sung solo.

However, magpie-lark pairs vary considerably in their singing skills. Highly coordinated partners create alternating notes so closely spaced that they can sound like a single bird. In contrast, others relatively poorer vocals often include gaps, overlaps, or irregular tempos. Yet the influence of those timing differences on the level of threat perceived by members of the birds listening audiences remained uncertain.

Hall and study collaborator Robert Magrath of Australian National University, Canberra, tested the function of duet precision by broadcasting coordinated and uncoordinated songs on t
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Contact: Erin Doonan
edoonan@cell.com
617-397-2802
Cell Press
4-Jun-2007