Tail singers.

The sound effects of Anna's hummingbirds, widespread along the West Coast, have been misunderstood, according to a new test.

Some of the males' most dramatic noises aren't vocalizations, as has been thought. Instead, the birds make noises by whipping their tails through the air.

Males, with iridescent, rose-colored throats and heads, perform aerial dives when courting a female or confronting another male. For a display, a male flies high in the air and then drops nearly straight down. When he's plummeted to the level of his intended audience, he pulls out of the dive while sounding an explosive squeak.

In the late 1970s, ornithologists decided that those notes came from the birds' vocal organs. Chris Clark and Teresa Feo of the University of California, Berkeley have challenged that idea by removing some birds' outer tail feathers. A clipped male still dives, but he no longer makes the sound as he bottoms out. Clark also tested the tail feathers in a wind tunnel and was able to make noises like the birds'. The researchers reported their findings at the July 21-25 meeting of the Animal Behavior Society in Burlington, Vt.

Ornithologists have documented a wide variety of noises made by bird wings, from cricketlike rubbing sounds to aerial whistles. A tail-feather sound effect, though, is quite rare, says Clark.--S.M