Birds take turns leading migratory V formations

In the world of migratory birds, when it comes to heading up the flock on a trip to new territory, leadership is a team game. One most important feature of several larger bird species is their annual migration in V-shaped or echelon formation.

A flock of lesser flamingos fly in formation. Photo by Nikunj vasoya/CC.

When birds are flying in these formations, energy savings can be achieved by using the aerodynamic up-wash produced by the preceding bird. As the leading bird in a formation cannot profit from this up-wash, but the question arises who is going to fly in front? 

According to new research, birds take turns leading the V formations during migration seasons. Flying in formation helps minimize energy expenditures by allowing birds to take advantage of updrafts created by the wings of the birds flying ahead of them. 

Bernhard Voelkl, a researcher in Oxford University's Department of Zoology said, "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."

"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," Voelkly said.

Not every spot in a V formation is equally advantageous, so birds mix it up -- constantly switching places to ensure every member of the formation gets an equal amount of aerodynamic assistance. As a result of this socialized approach to migratory travel, each member of a flock takes a turn at leading the formation.

To track the specific flying patterns of migrating ibis, researchers outfitted more than a dozen 'human-imprinted' bird specimens with tracking devices, and then led the birds on a migratory journey with a hang glider carrying the birds' handlers. 

Human-imprinted animals are those that are adopted by a human leader at a young and impressionable stage. Human-imprinted geese have been shown to follow their handlers in formations that mimic their wild peers. 

"We found that larger formations of ibis were still made up of these 'turn-taking' pairs," Voelkl added. "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. In fact, surprisingly, we found no evidence of 'cheating' of any kind." 

Previous research has shown that similar selfless cooperation improves the chances of self-preservation in other species - like penguins that rotate their position in huddles and on the march to share the advantages of insulation and ensure everyone stays warm. 

The new ibis study was published online this week in the journal PNAS.

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