The secret of carrier pigeons' uncanny ability to find their way home has been discovered by scientists: the feathered navigators follow the roads just like we do.

Zoologists now believe the phrase "as the crow flies" no longer means the shortest most direct route between two points. They say it is likely that crows and other diurnal birds also choose AA-suggested routes, even though it makes their journeys longer.

Researchers at Oxford University spent 10 years studying homing pigeons using global positioning satellite (GPS) and were stunned to find the birds often don't navigate by taking bearing from the sun.

Instead they fly along motorways, turn at junctions and even go around roundabouts, adding miles to their journeys.

"It really has knocked our research team sideways to find that after a decade-long international study, pigeons appear to ignore their inbuilt directional instincts and follow the road system," said Prof Tim Guilford, reader in animal behaviour at Oxford University's Department of Zoology.

Guilford said pigeons use their own navigational system when doing long-distance trips or when a bird does a journey for the first time.

"But once homing pigeons have flown a journey more than once, they home in on a habitual route home, much as we do when we are driving or walking home from work," said Guilford.

"In short it looks like it is mentally easier for a bird to fly down a road. They are just making their journey as simple as possible."

(Agencies)