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Friday, December 09, 2011

What use is half a wing?

An oft repeated creationist canard is "What use is half a wing?" or something equally inane.  The University of Montana and the BBC shed some light on this that even a creationtard could possibly understand (assuming they got their fingers out of their ears long enough to listen).

Flap-running in birds is key to flight evolution

The ungainly sight of a bird furiously flapping its wings as its spindly legs propel it forward could be a peek at evolutionary history. 

"Flap-running", researchers say, may have been a key step in the evolution of flight.

Experiments with pigeons have shown that it helps birds ascend slopes and suggests the earliest flightless birds might have used the same technique.

The study was published in the Journal of Experimental Biology.

Brandon Jackson, from the University of Montana, US, who led the study, explained that he and his colleagues wanted to know why birds would flap-run when they were capable of flight.

His co-researcher, Ken Dial, noticed this behaviour when filming a type of partridge known as a chuckar.
As the rotund birds negotiated obstacles, they would run up the objects flapping their wings. When Dr Dial discussed this behaviour with local ranchers and hunters, some reported that adult chukars would flap to run up cliffs, rather than fly.
Diagram of pigeon flap-running up a slope (Image: Journal of Experimental Biology) 
The birds used far less energy when flap-running than when flying
 
Dr Jackson and his team decided to find out if the birds might be using the technique to save energy by measuring the amount of power generated by the flight muscles when birds flew and when they were flap-running.

They surgically implanted electrodes into the flight muscles of pigeons - closely related birds that often flap and run even though they are very good fliers.

The electrodes measured muscle activity in the birds as they flapped and ran up ramps of varying inclines, and as they flew parallel to those same ramps.

The team was most surprised by what they saw when they compared the birds' muscle activity on a ramp with a 65 degree incline.

Running up that ramp, explained Dr Jackson, "required about 10% as much power from the flight muscles" as flying.

"The signal was imperceptible at first, and we actually thought we had a problem with the recording equipment. But when we zoomed in, there it was, about a tenth the magnitude that it was during flight," he said.

"The birds seemed to be using hardly any power to flap their wings as they ran up the slopes."

The method, the researchers say, is also an essential learning step for fledging chicks.
CLICK HERE TO READ THE REST OF THE ARTICLE.

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