Sunday, October 02, 2005

ENV: Cracking the Chickadee Code

Biologists Crack Code of Chickadee Song
By Elise Kleeman, DISCOVER Vol. 26 No. 10, October 2005, Biology & Medicine

Who would have guessed that when a chickadee opens its tiny beak, it has a lot to say? Biologists studying the alarm calls of black-capped chickadees found the bird’s songs signal not only the presence but also the size of nearby predators. “This level of complexity is certainly new, in terms of alarm responses especially,” says Chris Templeton of the University of Washington in Seattle. His study shows chickadees have one of the most sophisticated means of communication discovered in animals.

Templeton had been working with a flock of the pint-size songbirds on another project when he realized they responded differently to each species of bird of prey tethered in their enclosure. “Most of the variations are really subtle and are too fine to pick up with our ears,” Templeton says. “But one of them we can hear is the dee.” The more dangerous the predator, he says, the more dee notes in their eponymous chick-a-dee-dee-dee call.

It isn’t large birds of prey that the chickadees fear most, though. “Smaller predators are more maneuverable, and they’re the only ones that can really catch a chickadee,” Templeton says. His team showed that small raptors like pygmy owls prompted an average of 3 and a half extra dees—and as many as 23. The great gray owl, which has a wingspan four times larger than the pygmy owl’s, elicited only an extra half dee on average. The same trend also held when Templeton introduced a cat and a ferret, which both eat birds, but not when he added a small yet harmless bobwhite quail, which suggests that chickadees base their calls on more than size.

The biologists also found that the more dees in an alarm cry, the larger the mob of other chickadees that formed to attack the intruder and the closer they approached in their attacks. “The more closely we look at animal calls, the more information we find,” Templeton says. “It’s surprising and really exciting to know that there is such sophisticated information being passed along in the calls you can hear almost every day.”