London, Nov 29 (IANS): Birds and humans have evolved completely different organs for producing voice. But new research suggests that humans and birds use exactly the same physical mechanism to move their vocal cords and thus produce sound.

Humans use myoelastic-aerodynamic theory, or in short the MEAD mechanism, for speech and singing.

"We have now shown that birds use the exact same mechanism to make vocalisations. MEAD might even turn out to be a widespread mechanism in all land-dwelling vertebrates," said lead author Coen Elemans from University of Southern Denmark.

In the human voice box, or larynx, air from the lungs is pushed past the vocal cords, which then start moving back and forth sideways like a flag fluttering in the wind.

With each oscillation the larynx closes and opens, making the airflow stop and start, which creates sound pulses.

Birds do not make sounds with their larynx. Instead, birds produce sound using an organ unique to birds called the syrinx that is located deep in the body and therefore very difficult to study.

Elemans and colleagues studied six different species of bird from five avian groups. The smallest species, the zebra finch, weighs just 15 grams, and the largest one, the ostrich, weighs around 200 kg.

All studied birds were revealed to use the MEAD mechanism, just as humans do.

"We now managed to film sound production in birds from zebra finches to ostriches in detail using high-speed cameras. We show for the first time that birds also produce sound according to the MEAD theory," Elemans said.

The study appeared in the journal Nature Communications.