Professor Albert Feng and colleagues at the University of Illinois said most female frogs don't call since most lack or have only rudimentary vocal cords. But the female concave-eared torrent frog (Odorrana tormota) emits a high-pitched chirp that, to the human ear, sounds like a bird.

The frogs live along streams in central China's Huangshan Hot Springs, where waterfalls and rushing water provide a steady din. The frog has a recessed unusual ear structure and the high-pitched calls are likely an evolutionary adaptation to the noisy environment, Feng said.

The male response to the female call is instantaneous, Feng said, and their ability to home in on the sound call was astonishingly precise. A typical male could leap toward the sound with an accuracy of more than 99 percent.

"This is just unheard of in the frog kingdom," he said.

The research that included Jun-Xian Shen at the Chinese Academy of Sciences and Peter Narins at the University of California-Los Angeles is detailed in the journal Nature.