Migrating birds take turns leading the flock

Birds in migrating flocks cooperate and take turns to lead a 'V' formation to conserve their energy, an Oxford-led research has found.
The research is the first convincing evidence for 'turn taking' reciprocal cooperative behaviour in birds.
The research, by an international team led by Oxford University scientists, studied the northern bald ibis, tracking precisely how this species maintains a 'V' formation when migrating.
Researchers found that birds took turns to take the very energy-depleting lead. This allowed every bird to take advantage of extra lift produced by the wings of the bird in front.
The researchers were able to track each bird in a flock, thanks to a unique conservation project by the Waldrappteam in Austria, which has raised northern bald ibises, and trained them to migrate behind a microlight aircraft, 'BBC News' reported.

Data loggers containing GPS-based tracking devices, that the team fitted to each bird, meant the scientists could track their exact positions.

Careful analysis of how and where the birds shifted position as they flew, showed that birds were working in pairs, repeatedly swapping around between follower and leader.
"What we saw was that, for each bird, there's a very clear correlation between the time it spent in front, and the amount of time it followed another bird," said lead researcher Bernhard Voelkl from the University of Oxford's department of zoology.
Overall, individuals spent an average of 32 per cent of their time benefiting by flying in the updraft produced by another bird's flapping wings and a proportional amount of time leading a formation, researchers said.

"Our study shows that the 'building blocks' of reciprocal cooperative behaviour can be very simple: ibis often travel in pairs, with one bird leading and a 'wingman' benefiting by following in the leader's updraft," said Voelkl.
"We found that larger formations of ibis were still made up of these 'turn-taking' pairs," said Voelkl.
"The checking that went on within these pairs was sufficient on its own to prevent any freeloaders hitching a free ride within a V-formation without leading," Voelkl said.
The research is published in the journal Proceedings of the National Academy of Sciences.