Dr. Keith W. Sockman, assistant professor of biology in UNC's College of Arts and Sciences, studies mating behavior in songbirds and the songs that play such a central role in their reproduction.
"From people to praying mantises, individuals invest everything from their homes to their heads to attract a member of the opposite sex," Sockman said. "When male songbirds sing to attract a mate, they expend energy during times they could otherwise be foraging for seeds and grubs.
"They may also increase their exposure to predators," the biologist said. "This led us to predict that when females are in short supply or infertile, unmated males should reduce these 'costs' by singing less."
In a paper published in the new issue of the journal Biology Letters, Sockman and colleagues Dr. Thomas P. Hahn and Kendra B. Sewall of the University of California at Davis and Dr. Gregory F. Ball of Johns Hopkins University in Baltimore, report that male songbirds are frugal in their efforts to attract a mate.
Studying Cassin's finches, which breed in the Sierra Nevada Mountains of California, the scientists found that males sang the most in response to the loss of a prospective mate but sang very little either in the presence of a mate or when females were unlikely to be nearby.
The researchers concluded that male Cassin's finches adjust their mate-attraction efforts according to their need for a mate and the likelihood of attracting one.
"But the story gets better," Sockman said. "After the breeding period was over, we determined the relative fertility of females by measuring when each began feather molt."
Because molt begins when fertility ends, the scientists could infe
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Contact: David Williamson
919-962-8596
University of North Carolina at Chapel Hill
2-Feb-2005