The fastest-moving muscles known to man have been found in the vocal cords of two tiny songbirds whose chirping is said to have inspired Mozart and who can sing an aria's worth of notes in the blink of an eye.

Temporal and acoustic diversity of calls is elemental to surviving and thriving in the animal kingdom. But the way small birds do it — in particular the European starling and the Indonesian zebrafinch — defies accepted notions of what exactly is going on when they burst into song.

"Superfast" vocal cord contractions have previously been found in less cheerful vertebrates such as the rattlesnake, in a few types of fish and the ringdove, according to the study published in the July 9 edition of the Public Library of Science's online journal PLoS ONE.

"We now have shown that songbirds also evolved this extreme-performance muscle type, suggesting that these muscles — once thought extraordinary — are more common than previously believed," said lead author Coen Elemans, a former postdoctoral researcher in biology at the U., who is now at the University of Southern Denmark.

Many species of songbirds use complex songs to communicate with one another, and many of those are able to change the volume and/or the frequency of their song faster than ordinary vertebrate muscles are able to contract, Elemans said. However, no direct evidence had existed that avian vocal muscles could produce such rapid and precisely timed vocal changes recorded in the study.

The zebrafinch and European starling can contract and relax their vocal muscles in 3 to 4 milliseconds — three-thousandths to four-thousandths of a second. That's 100 times faster than the 300 milliseconds to 400 milliseconds (three-tenths to four-tenths of a second) it takes a human to blink.

Their vocal folds are similar to human, but there, too, humans are bogged in molasses by comparison. The birds' capacity for changing pitch and volume during a song is 250 times faster than the "modulation frequencies" of any human counterpart, whether in the spotlight on-stage or belting it out in the shower.

Finding out that "the twitch kinematics of these so-called superfast muscles" is producing the unique calls of these birds makes the songbirds that humans can never hope to match even more a source of inspiration somehow, Elemans said, noting his study was motivated by a common parking terrace variety bird — pigeons.

"They have amazingly fast vocal muscles but have really boring, slow songs. That made me wonder what the muscles in songbirds were like, so I decided to find out."

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