Researchers have discovered that migrating birds swap positions in the V-formation in order to share the burden of being the leader.
A group of international researchers led by a team from the University of Oxford, England, have reported on the phenomenon, where birds lead the migratory formation for a period of time before falling back in order to save energy by flying in the wake of another bird.
According to their report in the Proceedings of the National Academy of Sciences, the scientists witnessed the first conclusive evidence of reciprocal cooperative behavior in birds when they tracked a flock of juvenile Northern bald ibis on their migration from Austria to Italy.
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Birds’ energy efficiency
The birds were familiar with their human handlers, who had raised them to be “human imprinted.” Jim Algar of Tech Times writes that the birds followed their handlers, who were flying in powered parachutes, and positioning data was gathered from data loggers carried by the individual birds.
The scientists observed that the birds would repeatedly change positions in order to take advantage of the updraft produced by the flapping of another bird’s wings, which means that they save approximately 10-14% of their energy output.
“Our study shows that the ‘building blocks’ of reciprocal cooperative behavior can be very simple: ibis often travel in pairs, with one bird leading and a ‘wingman’ benefiting by following in the leader’s updraft,” says lead author Bernhard Voelkl, part of the Department of Zoology at the University of Oxford.
“‘We found that in these pairs individuals take turns, precisely matching the amount of time they spend in the energy-sapping lead position and the energy-saving following position.”
A matter of life or death
Large formations of birds also exhibit this behavior, and the researchers claim that energy savings can be even greater
“We found that larger formations of ibis were still made up of these ‘turn-taking’ pairs,” Voelkl says. “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.”
According to previous studies, up to 35% of young birds die from exhaustion during their first migration, testament to the risk involved in such journeys.
“We think that it is the extreme risks associated with long migration journeys that have driven the evolution of such cooperative behavior where something like saving 10 percent of your energy can make the difference between life and death,” Voelkl claims.