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Ancient condor rode thermals to soar above Argentina
2007-07-03 04:30:50 Xinhua English

Argentavis magnificens was a big birdthat used its 20-foot wingspan to soar at up to 40 mph above the plains ofArgentina some 6 million years ago.

BEIJING, July 3 (Xinhuanet) -- Argentavis magnificens was a big bird that used its 20-foot wingspan to soar at up to 40 mph above the plains of Argentina some 6 million years ago.

Scientists have known the ancient condor could fly, but they didn't know ifthe largest bird ever to take to the skies, flapped its wings or simply glided. Now, with computer simulations based onthe bird's fossil bones, scientists reveal that Argentavis did both.

Sankar Chatterjee of the Museum of Texas Tech University and his colleagues estimated flight information from the predatorsfossil bones, and they input the data into two computer programs originally used for helicopters.

They found flight muscles account for about 17 percent of a bird's body mass, and the major bulk of that muscle comes from pectoralis, or breast, muscles. However, a bird gains weight faster than its wings can grow. So a big, heavy bird like Argentavis requires more muscle power to stay aloft than a smaller bird.

The scientists calculated Argentavis's pectoralis muscle would have weighed about 24 pounds, which could not have produced the flapping power needed to carry such a heavy animal through the air.

Like many land birds today, Argentavis could have hitched a ride onrising air columns. Updrafts caused by wind getting deflected upward by a ridge or cliff would have been common along the Andean slopes.

The researchers calculated thegiant condor would sink at a rate of three feet per second. With updrafts of that speed over the Andean slopes common occurrences, the scientists said, Argentavis could stay airborne. The birds also could have taken a "thermal elevator" into the sky. Thermals of rising air can form continuous chimneys or doughnut-shaped bubbles.

"As it reaches the top of the thermal, the bird can glide straight to an adjoining thermal and gain height again by riding the rising air," the scientists write in a report of their research published online this week in the journal Proceedings of the National Academy of Sciences.


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