These Birds Take Turns So No One Gets Too Tired Flying in Formation

“Reciprocal altruism” in a migrating flock of birds means that the more exhausting lead position is deliberately and equally shared

Flying birds
Andrew Bertuleit Photography/Corbis

Friendly skies are a real thing, at least for one migrating flock of northern bald ibises recently studied by scientists examining the birds’ in-flight behavior.

In a recent article, researchers described their observations of a flock of 14 juvenile ibises on a fall migration from Austria to Italy. Individual birds were found to frequently switch positions, equally sharing the more exhausting lead. That front position is typically burdened with forging through strong air currents while those behind the lead bird save energy riding its wake, Science reported.

"For whichever combination of two birds we looked at, we saw that the time bird A was flying in front of bird B matched closely the time bird B was flying in front of bird A," the study’s lead author, Bernhard Voelkl said, according to New Scientist.

The position changes happened quickly and consistently with most of the interchange occurring in pairs. Sixty percent of the observed formations involved only two birds, each contributing a nearly equal share of the work.

The find is a rare example of a phenomenon called “reciprocal altruism,” an idea first proposed in the 1970s “to explain how organisms could help each other without being exploited by cheats,” writes New Scientist. But examples are hard to come by, especially because care provided between related animals (like grooming habits in a family of gorillas) doesn’t make the cut. Such behavior is thought tied to “kin selection,” an evolutionary strategy that favors those in an animal’s own genetic line. 

But the ibis flying patterns demonstrate a communal technique that benefits each member of the flock, regardless of their relationship with each other. Ultimately, reciprocal altruism helps the birds save energy and better ensure survival.

The team gathered their data with the use of GPS data loggers and an ultralight plane that guided the flock, which, according to Science, had been hand-raised. A previous study performed by authors of the study using northern bald ibises found that the birds have a wing-flapping rhythm that also aids in energy conservation during migration.

The new research may help scientists identify other kinds of birds that exhibit the same kind of cooperative behavior and provide further understandings about how such conduct evolved.

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