Why do geese fly in formation?
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The arctic tern (Sterna paradisaea) migrates the longest distance of any bird. They breed from subarctic regions to the very limits of land in the arctic of North America and Eurasia. At the end of the northern summer, the arctic tern leaves the north on a migration of more than 11,000 miles (17,699 kilometers) to its southern home in Antarctica. A tern tagged in July on the arctic coast of Russia was recovered the next May near Fremantle, Australia, a record 14,000 miles (22,526 kilometers) away.
Aerodynamicists have suspected that long-distance migratory birds, such as geese and swans, adapt the “V” formation in order to reduce the amount of energy needed for such long flights. According to theoretical calculations, birds flying in a “V” formation can fly some ten percent farther than a lone bird can. Formation flying lessens the drag (the air pressure that pushes against the wings). The effect is similar to flying in a thermal upcurrent, where less total lift power is needed. In addition, when flying, each bird creates behind it a small area of disturbed air. Any bird flying directly behind it would be caught in this turbulence. In the “V” formation of Canada geese, each bird flies not directly behind the other, but to one side or above the bird in front.