By exposing the vocal muscle fibers to electrical stimulation, scientists clocked how fast the muscles expanded and contracted. Both female and male starlings moved at about 3.2 milliseconds per expansion or contraction. In zebra finches, females moved at 7.1 milliseconds, while males twitched at 3.7.
There are some competitors elsewhere in the natural world. Rattlesnakes come in a close second with the twitching muscles on both sides of their rattler. The muscles in swim bladders of certain fish also move strikingly fast.
"We had no idea muscles could work at these superfast rates," said Daniel Margoliash, a biologist at the University of Chicago. "That they can and do is just amazing."