Say It with Feathers

All to impress a female

WHEN A MALE Anna's hummingbird wants to impress a female, he makes a daring display, zooming 100 feet or more into the air, then plummeting back to earth with a noisy chirp. But the distinctive sound, it turns out, comes not from the hummer's throat but from its tail feathers, according to a new study from the University of California-Berkeley. Using a high-speed camera, researchers recorded the display and were able to determine that the sound coincides with a brief spreading of the tail feathers--faster than the blink of an eye--that occurs at the low point of the dive. The noise emitted is not a whistle but a rapid vibration, not unlike the sound created by the reed of a clarinet. The study surmises that the tiny birds, which have tiny song boxes, or syrinxes, may have evolved the tail chirp to "escape the intrinsic constraints on vocal sound volume."