As a bird flaps its wings it disturbs the air and leaves whirling eddies behind. Some gregarious species, such as the Canada goose, have learned to take advantage of the upward disturbed air created off the wings of others in the flock by flying in a V formation. Each bird thus adds the lift lost by the bird ahead to its own. This "drafting" allows the geese to travel at an easier pace through their long flights. Researchers have found that geese flying in V's can travel as much as 70 percent further than they would otherwise have been able to.
When traveling long distances, tundra swans fly in the same V formations as geese and for the same reason. The resistance of the air is less as each bird flies in the widening wake of its predecessor. The leader has the hardest work to do as he or she "breaks the trail" but is relieved at intervals and drops back into the flock to rest.
Besides the many flocks of Canada geese and tundra swans we observe traveling in V or wedge-shaped formations, many other species of geese, swans, ducks, cormorants, shorebirds and gulls also regularly arrange themselves in that pattern.