Migrating birds fly in a V formation, allowing them to save energy, which could be a life saver in their long journey.

The formation, however, can be particularly difficult for the lead bird. How then do birds decide which of them takes this difficult spot?

Researchers of a new study published in the Proceedings of the National Academy of Sciences on Feb. 2 claim that what the birds do is to take turns in the lead position so no one gets exhausted.

Bernhard Voelkl from the Edward Grey Institute, Department of Zoology at the University of Oxford in the UK, together with colleagues, observed a flock of 14 young Northern bald ibis (Geronticus eremita) migrating from Australia to Italy.

The birds were equipped with data loggers that contained highly precise monitors to tell where they were relative to other birds.

The researchers found that the birds frequently changed positions and all equally shared the most difficult lead position. Individual birds were likewise found to spend less than a minute at the lead point of the formation before quickly switching places with one of the next birds.

"Surprisingly, we found no evidence of 'cheating' of any kind within these flocks with the level of cooperation, with individuals benefiting from following 32% of the time, significantly higher than expected," Voelkl said.

In an hour of flight, Voelkl observed, the birds would have made a pair-switch with its closest neighbor 57 times on average. Each of the birds would make hundreds of switches during a typical flight, which lasts between three to eight hours.

The researchers also said that the transition works almost seamlessly and takes only about a second to execute.

Scientists think that the high level of cooperation exhibited by the birds evolved as a necessity for survival. Migration can be risky, with over a third of young birds dying of exhaustion on their first migratory trip.

Birds that fly in a V formation can save energy by flying in the updraft of other birds in the flock. For migrating birds, saving 10 percent of their energy can be a matter of life and death.

"Cooperation in animals is an enigma because it contravenes the basic notion that evolution favors selfish genes that promote only their own well-being," the researchers wrote. "Bird migration in organized V-shaped or echelon formations constitutes such a cooperation dilemma."

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