Thaindian News

Sydney, Oct 28 (IANS) How birds manage to zip effortlessly through restricted spaces without hitting obstacles, could help improve versatility of pilot-less aircraft, new research done by a team including two Indian-origin scientists has found.

Birds weave quickly and safely through dense forests and narrow corridors by using their eyes to sense the speed of background image flow on both sides and adjust their flight according to it.

“These findings can contribute to the technology of guiding unmanned aerial vehicles where aircraft have to fly through obstacles in cluttered environments or through canyons and gorges or under bridges,” said Mandyam Srinivasan, professor at The Vision Centre.

“As animals travel forward, things that are close seem to speed by, and things that are farther away seem to travel more slowly,” said Srinivasan whose team made the discovery.

“It’s the same for birds. We found that they try to achieve a safe ‘balance’ by ensuring that the background images are passing at the same speed in both eyes,” the journal Current Biology quoted him as saying.

To find out how birds navigate through narrow passages and away from danger, the research group trained budgerigars to fly along a corridor with walls lined with horizontal or vertical stripes, said Partha Bhagavatula of The Vision Centre and The National Vision Research Institute.

“We found that birds fly the fastest when both walls are lined with horizontal stripes, because the stripes are parallel to the bird’s flight direction, and the birds don’t ’see’ a strong image flow in the background,” Bhagavatula said.

“But when both walls have vertical stripes, birds slow down significantly due to the strong image motion, which shows that birds also regulate their flight speed according to what they see,” Bhagavatula added.

When the walls were set up with different orientations - one with vertical and the other with horizontal stripes, the group found that birds flew significantly closer to the horizontal stripes.

“As vertical stripes project a stronger image flow to their corresponding eye, they veer away to restore the balance between the flows experienced by their two eyes,” said Bhagavatula.

Flight behaviour in birds is very similar to insects such as honeybees, bumblebees and flies, Srinivasan said adding, “This suggests that this principle of visual guidance may be shared by all day-active flying animals.