London, Jan 24 : Researchers have answered the long-debated question of how birds first took to the skies, by finding that it was the right angle of their wings which made the aerials fly.
For more than a century, the evolution of birds has been a debatable issue, with some scientists arguing that wings began with two-legged ground dwellers attempting to become airborne to catch insects and others that they emerged to allow tree-dwellers to leap from branch to branch and glide down to make soft landings.
However, scientists from the University of Montana say that whether the first bird to fly took off from the ground or glided off a tree or even a cliff-edge is insignificant.
Lead author Prof Kenneth Dial explains that the key to understanding the origin of flight doesn't lie in the wings, but the precise narrow angle of the wing-stroke.
He said that the secret of flight itself, begins with learning the optimal wing-to-ground angle needed to generate force.
It appears that both young and adult birds use the same angle for many types of locomotion leading up to level flight, he added.
The researchers came to the conclusion by studying just the wing-stroke of quail-like ground birds called chukars (Alectoris chukar), as part of a broad range of studies that rely on wind tunnels, sensors and high speed video to tease out the nuances of flight.
"Birds use [undeveloped wings] to improve their locomotive performance and escape predators. Even if you take out the evolutionary implications, the ecological implications of that are enormous," Nature quoted Dial, as saying.
"They really only need one wing stroke, and they use [their wings] the day they hatch in an aerodynamically meaningfully way-even though they can't fly," he added.
Dial further explained that the way in which vulnerable young birds use their wings while transitioning into adult bodies could be a model for how their ancestors developed the ability to fly.
"When you step back and look at the fossils they are finding, the long-legged dinosaurs with half a wing, they look very uncannily like today's birds that are going through the juvenile stage," he said.
"When you look at the development of these animals, you may in fact be looking at the strategies that their ancestors employed to get through transitional states [in evolution]," he added.
Kevin Padian, an expert on the origins of flight at the University of California, Berkeley, said the work is of incredible importance for flight theory.
"This is really a good insight," said Padian, who was unaffiliated with the research. Essentially it says to me that [birds] are always going 'up and forward' in some sense, whether flying or running up trees, and so the angle of attack of the wings is sensibly the same, or nearly so," Padian said.