Birds fly in a distinctive V formation to arrange themselves in "aerodynamically optimum positions" while precisely timing the flapping of their wings, scientists have found.
Flying in a V formation helps each bird take advantage of
"good air" (upwash) thrown up by the wings of the flyer in front while avoiding detrimental 'bad air' (downwash), according to researchers from the University of London's Royal Veterinary College.
They found that birds also flap their wings at just the right time so as maximise an updraft and minimise a downdraft.
These aerodynamic accomplishments were previously not thought possible for birds because of the complex flight dynamics and sensory feedback that would be required to perform such a feat, researchers said.
"The distinctive V-formation of bird flocks has long intrigued researchers and continues to attract both scientific and popular attention, however a definitive account of the aerodynamic implications of these formations has remained elusive until now," said Steven Portugal, lead researcher at the Royal Veterinary College.
"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," Portugal said.
Researchers studied a free-flying flock of northern bald ibises as they flew alongside a microlight on their migration route from Austria to Italy.
They used specially developed GPS biologging technology to measure the position, speed and heading of all birds in a V formation.
The team recorded the position and every wing flap of all individuals within the V during 43 minute of migratory flight.
They found each bird stayed about 45 degrees to the bird ahead and 1.2 metres to the one behind.
"Here we have shown that ibis flight in V formation does, on average, match predictions of fixed-wing aerodynamics, although of course the flock structure is highly dynamic," Portugal said.
"Birds flying in V formation flap with wingtip path coherence, meaning that their wingtips take the same path to maximise upwash capture.
"In contrast, birds flying in line flap in spatial antiphase, with wingtip paths maximally separated, to avoid adverse downwash," he said.
The study is published in the journal Nature.
