FOR human pilots, formation flying takes years to master, but migratory birds have it down to a fine art. Yet the reason why geese, for example, fly in a V-shape has long been something of a mystery.
Now a computer model has combined two competing theories. The first suggests that the formation has an aerodynamic advantage - each bird creates an upwash behind its wing tips, giving those following it an extra lift. The second holds that flying in a slightly skewed position relative to the bird in front allows for unimpaired vision.
Valmir Barbosa and Andre Nathan at the Federal University of Rio de Janeiro, Brazil, created computer models of flocks of between 15 and 35 birds, taking both theories into account. Each bird was allowed to seek out the one nearest to it, and to position itself so that its view was not blocked. It could then adjust its position to take advantage of any improved aerodynamics (www.arxiv.org/cs/0611032).
The results showed that both theories hold true. Previous computer models that did not take both into account were unable to reproduce V-formations, says Barbosa, "but we have found that these formations occur regardless of how the birds are positioned initially". The artificial birds also settled into other patterns seen in nature, such as W-formations. "This is an appealing instance of how complexity emerges from simple rules."Font NewScientist