Birds Bored by the Same Old Song
WHITE-CROWNED SPARROWS, it seems, are not big fans of “golden oldies.”
To test female sparrows’ responses to old versus new versions of males’ springtime songs, biologist Elizabeth Derryberry, a graduate student at Duke University, played two tapes of the songs, one recorded in 1979 and the other in 2003. Although the differences between the versions appeared subtle—the newer song was slower and lower pitched—she found that females overwhelmingly preferred the modern tune, fluttering their wings, arching their backs and raising their tails and beaks—all indicators that the birds were ready to mate. Some of the 10 females Derryberry tested didn’t even wait for the two-and-a-half-second song to end before beginning their solicitous behavior. “It’s—boom—on,” she said. Male sparrows, meanwhile, acted less threatened when played older versions of songs from potential competitors.
While researchers have long known that the songs of many bird species—including white-crowned sparrows—vary from place to place, Derryberry’s work (published online in the journal Evolution) shows that songs from the same region are also changing over time.—Laura Tangley