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Dinosaurs' flapping led to flight?

By Marsha Walton
CNN

Flapping may have helped some ancestors of avians get away, researcher says.
Flapping may have helped some ancestors of avians get away, researchers say.

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(CNN) -- The feathered forelimbs of some species of small, two-legged dinosaurs may have helped those ancient animals run up hills or other inclines to escape predators. This half running, half flapping may have evolved into an ability to fly, researchers say.

The findings of Kenneth Dial, a researcher at the University of Montana, support theories that the ability to fly evolved gradually in land animals. Feathers may have first acted to protect animals from cold and wet weather, then been used out of necessity when something with big teeth was chasing them.

Fossils show some structures common to birds and dinosaurs, leading many scientists to the theory that birds evolved from dinosaurs about 225 million years ago.

Birds' ancient cousin

Even before their wings develop enough to fly, scientists say some young birds in today's world use them to improve their traction, and to gain speed. The flapping action of the wings is often enough to keep the young birds from becoming somebody's lunch.

"They hit the ground running when they're born," Dial said.

Dial studied non-migratory birds, like partridges, that are only capable of limited flight time. When it comes to energy output, "It's a heck of a lot cheaper to run than it is to fly," Dial said.

So these baby birds, born with big feet and big, powerful legs, use them in combination with their wings, first to stay balanced and grounded, and then to take on steeper and steeper inclines. Birds in the turkey and quail families use the same techniques.

Using this "wing assisted incline running," Dial reports in this week's issue of Science magazine that chukar partridges can negotiate 50 degree inclines from the time they are born, 60 degree slopes when they're just four days old, and at 20 days, can perform a vertical ascent with all the skill of Spiderman.

"The wings help them stick to the ground," said Dial, who studied videotapes of birds running up various inclines. The wings only come into play on steep angles. Birds don't flap to run faster on level ground or on very gentle slopes.

But at about a 50 to 60 degree incline, he says, the birds start slipping. That's when they begin a head to tail movement, like a reptile, that pushes them to the ground to enhance the traction of their legs.

"They used their wings like spoilers on a race car, to give their feet better traction," he said.

Wings assist in running

Use of this wing- assisted running doesn't stop when the birds are old enough to fly. Adult birds capable of flight often choose the running and flapping option instead of flying, because for some species it is much more energy efficient. They also use the technique to reach trees, cliffs, boulders and other high refuges.

In additional studies, the researchers attached two accelerometers to the front and backside of the birds, to measure the direction of wing movement and the "physics of flapping." Those movements change depending on the mode and speed of flight.


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