Researchers revealed the first solid evidence that migrating birds take turns leading the flock.
The findings are the second to show "turn taking reciprocal cooperative [behavior]" in birds, the University of Oxford reported.
To make their findings, the researchers looked at 14 Northern bald ibis (Geronticus eremita) migrating from Salzburg in Austria to Orbetello in Italy. The birds were raised by humans and followed by their handlers using high-powered parachutes. The birds were also outfitted with 23g data loggers that allowed the researchers to track how each individual flew within the v-formation.
The researchers found the birds changed position frequently within the flock. The team determined the average bird spent about 32 percent of their flying time in the updraft produced by other birds' flapping and about the same amount of time in leadership positions.
Migration comes with significant risks; it has been determined about 35 percent of juvenile birds die of exhaustion during their first migrations, and these flying formations could help prevent these unfortunate incidents.
"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 lead author Bernhard Voelkl of Oxford University's Department of Zoology. "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."
Even when the birds traveled in pairs (as opposed to flocks), the energy costs for both individuals were significantly reduced and the savings were even greater in larger groups of birds.
"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 concluded.
In the future, the researchers hope to determine how the behavior of juvenile birds develops in the flock over time, and if these energy-saving tactics are learned behaviors.
The findings were published in a recent edition of the journal PNAS.
