hey tweets,

this is the last one for now, i promise! but i thought you might find
this interesting, too.

regards,

Devorah A. N. Bennu, PhD
Chapman Postdoctoral Fellow
Department of Ornithology
The American Museum of Natural History
Central Park West at West 79th Street
New York, NY 10024-5192
212.313.7784 (office) 212.313.6962 or 212.313.7773 (lab)
email:nyneve at amnh.org or nyneve at myuwnet.washington.edu
work page http://research.amnh.org/ornithology/personnel/bennu.htm
personal pages http://research.amnh.org/users/nyneve/

---------- Forwarded message ----------
Chicks Offer Insight Into Origin of Flight
By JAMES GORMAN


The behavior of chukar partridge chicks, which can run straight up the
side of a hay bale or a tree while flapping their wings, may offer a
new window on the origin of flight in birds.

Feathered dinosaurs may have done something similar, Dr. Kenneth P.
Dial of the University of Montana suggests in today's issue of Science.
He suggests that they too flapped their primitive wings to help them
climb, which brought them off the ground and closer to discovering the
aerial possibilities of their wings. Even incompletely feathered
proto-wings, Dr. Dial says, would have been useful in running up inclines.

One of Dr. Dial's findings, which has surprised other scientists who
study the evolution of flight, is that the chukar chicks did not use
their wings to raise them off the ground. The wing beats served the
same purpose as spoilers on race cars. The force generated by flapping
pressed the chicks into the surface on which they were running for
better traction. As Dr. Dial said of his finding, "It's not intuitive."

In fact, he came upon the behavior accidentally. His teenage son, Terry,
was helping him study the development of flight in chukar chicks. While
Dr. Dial was traveling, his son was keeping track of the young birds as
their feathers grew, and they gradually launched themselves on longer
flights, horizontally and vertically.

The vertical flights used hay bales as an obstacle. When Dr. Dial
returned from a trip, he said, his son told him the chicks were not
staying with the program. "They're cheating," Dr. Dial recalled his
son telling him, "They're not flying anymore. They're running up."

Dr. Dial had to see for himself. He then had to videotape the behavior
and to do experiments varying the incline and the surface the birds
were running up, and clipping the feathers at different lengths.

He found that the chicks were using a flight stroke, but changing the
angle to press their feet against the running surface. More feathers
meant more effective use of the wings, but partly feathered wings
provided a significant benefit.

Dr. Dial concluded that proto-birds with somewhat similar wings might
have done the same thing, and that the climbing ability they gained
would have given them an evolutionary edge, even if the wings were not
yet useful for full flight.

Once the proto-birds were up a bush, or wall or tree, they would be
in a position to discover what wings could do in the air. This
evolutionary path to flight, he says, is different than previous models
in which proto-birds first launched either from the trees or the ground,
called the arboreal and cursorial models. "It's both and neither," Dr.
Dial said.

The findings have intrigued other scientists. "First and foremost," said
Dr. Kevin Padian of the University of California, "it's telling us
something we never knew."

Dr. Padian, who studies the evolution of flight, said: "Nobody knew that
they ran up trees like this. Nobody knew that wings could generate this
kind of force. It's a terrific study for those reasons alone."

Dr. Padian said Dr. Dial's demonstration of this new use of wings added
to earlier research that had determined that the dinosaur ancestors of
birds had both feathers and the right limb structure to make a flight
stroke. Even without flying ability, he said, wings and feathers offered
evolutionary benefit, in terms of isolation and catching prey. Those
dinosaurs, he said, could have used a forward predatory grab similar to
a flight stroke. The new use of wings, he said, offers an additional
survival benefit for a proto-wing.

Dr. Alan Gishlick, a paleontologist who also studies the evolution of
flight, said, the research "for the first time gives us a modern analog
for terrestrial origin of flight."

Dr. Gishlick, who is at the National Center for Science Education in
Oakland, Calif., a nonprofit group that defends the teaching of evolution
in public schools, said the fossils of dinosaurs he has studied showed
they had the bone and muscle structure for this use of wings.

"Dinosaurs like velociraptor could have done this," he said.

He was not suggesting that velociraptors flew, since they seem to have
been a highly successful predator on their feet. A more likely candidate
to want to leave the ground, Dr. Gishlick said, was microraptor, a
feathered dinosaur the size of a pigeon that was chased enough to make
it want to run up into the sky.

--------------------------------------------------