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It has long been known that flying in formation saves birds precious energy, which they need for long migrations.

Now, a study claims that migrating birds 'share the pain' of leading a v-formation so that all members of the flock can take turns saving energy by following in another avian's wake.

The new research is the first convincing evidence for 'turn taking' reciprocal cooperative behaviour in birds.

Ibis take turns saving energy by following in another bird's wake (pictured), according to a new study. It is thought to be the first example of 'turn taking' reciprocal cooperative behaviour in birds

It is also only the second good example of reciprocal cooperation in animals, following a study that revealed how vampire bats shared blood to keep other unrelated individuals alive.

An international team of experts led by Oxford University studied 14 juvenile Northern bald ibis (Geronticus eremita) migrating from Salzburg in Austria to Orbetello in Italy. 

The birds followed a powered parachute carrying their handlers and each wore small data loggers, enabling the researchers to examine how individuals within a flying v-formation interacted.

The researchers found that individual birds changed position frequently within the flock, flying in formations of between two and 12 birds.

Individuals spent almost a third of their time flying in the updraft produced by another bird's flapping wings – letting them save energy - and a similar amount of time leading a formation, according to the study published in the journal PNAS. 

The researchers found that individual birds (stock image) changed position frequently within the flock, flying in formations of between two and 12 birds

Illustrating how risky migrations are for birds, a previous study has shown that up to 35 per cent of juvenile birds can die of exhaustion on their first migration.

Flying in formation helps them save vital energy. For example, geese are thought to make energy savings of 10 to14 per cent by gaining lift from flying in the updraft of other birds.

The scientists investigated why 'selfish' individuals would 'altruistically' use up more of their energy leading a formation, as well as how flocks guard against 'free-loaders' that never take the lead, preferring instead to save energy by following.

Lead author Dr Bernhard Voelkl of Oxford University's Department of Zoology, explained: '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.

'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.'

By travelling in a pair, the energy costs for both individuals are reduced and larger formations bring even greater energy savings.

'We found that larger formations of ibis were still made up of these "turn-taking" pairs,' Dr Voelkl said.

'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 within these flocks with the level of cooperation, with individuals benefiting from following 32 per cent of the time, significantly higher than expected.

'We think that it is the extreme risks associated with long migration journeys that have driven the evolution of such cooperative behaviour where something like saving 10 per cent of your energy can make the difference between life and death.'

Experts are planning on studying how the cooperative behaviour of the juvenile ibis develops over time and whether they learn to fine-tune their energy-saving tactics.

The team also say more research is needed to quantify the energy-saving benefits for individuals by fitting the birds with sensors to monitor heart rate and respiration, for example. 

...V-SHAPE AND TIMING FLAPS ENSURES A FLOCK IS AERODYNAMIC 

Migrating birds precisely time the flapping of their wings and adjust their position to make the best of the subtle effects of air turbulence, researchers discovered last January.

In this way, each bird takes advantage of 'upwash' thrown up by the wings of the flyer in front while avoiding lift-sapping 'downwash'.

Scientists learned the aviation secrets of migrating birds after attaching tiny logging devices to a flock of 14 northern bald ibises that not only tracked their position and speed by satellite but measured every flap of their wings.

Why do birds fly in V formations? Secrets revealed

The birds were studied as they flew alongside a microlight on their migration route from Austria to their winter home in Tuscany, Italy.

Lead researcher Dr Steve Portugal, from the Royal Veterinary College, University of London, said: 'The intricate mechanisms involved in V-formation flight indicate remarkable awareness and ability of birds to respond to the wingpath of nearby flock-mates. 

'Birds in v-formation seem to have developed complex phasing strategies to cope with the dynamic wakes produced by flapping wings.'

When flying in a v-formation, the birds' wing flaps were approximately 'in-phase', meaning all the wing tips followed roughly the same path, the scientists found. This helped each bird capture extra lift from the upwash of its neighbour in front.

Occasional shifts of position within the formation meant that at times birds flew directly one behind the other. When this happened, the birds altered their wing beats to an out-of-phase pattern to avoid being caught by downwash.