This bird 'plays' its wings.

• Position: Mate club-winged manakin

Richard Prum, an ornithologist from Yale University, was hiking through an Ecuadorean forest 18 years ago when he had a strange experience: He watched a bird sing with its wings. The bird--a mate club-winged manakin--was hopping from branch to branch to attract females. He waved his wings over his back, producing a loud tone that sounded like a violin. "There's literally no bird in the world that does anything that prepares you for it," says Prum. "It's totally unique." The manakin family includes about 40 species of birds, many of which have feathers that enable them to make unusual sounds. Some pop like a firecracker; others make whooshing noises in fright. But the way in which the...