A bit of altruism makes V-shaped flocks of birds possible

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A bit of altruism makes V-shaped flocks of birds possible

It seems like a job no bird would want. The leader of a V-shaped flock works the hardest, fighting strong air currents while others save energy by traveling in his wake. So why would any bird volunteer to be in front? From an evolutionary standpoint, helping others makes sense if all the migrants are related. But that’s not always the case with migrating flocks. To find out how birds manage this dilemma, scientists outfitted a flock of 14 juvenile bald ibises (Geronticus eremita, pictured) with GPS data loggers and guided them in an ultralight plane from Austria, where they’d been hand-raised, to Italy on an autumn migration. The loggers recorded each bird’s geographical location, velocity, and position within the flock. Eight of the birds were unrelated, and there were three pairs of siblings. On their journey, the ibises flew in formations of two to 12 birds, changing positions frequently. The researchers’ analysis showed that the birds were working cooperatively, sportingly taking turns to lead and follow. Indeed, the researchers discovered that the ibises precisely matched the amount of time spent in the lead and trailing positions regardless of their genetic relationship, they report online today in the Proceedings of the National Academy of Sciences. The birds’ cooperative travels provide a rare and “convincing example” of reciprocal altruism in animals, the scientists say. All the birds had a chance to surf in another’s wake, and all spent time doing the hard work at the front. And they switched positions so often and with such rapidity (taking less than a second to move), that the benefits of cooperating were immediate. The findings may help explain how such “you scratch my back, I’ll scratch yours” behaviors can evolve.

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