Scientists who have studied formation flight believe that birds fly in this way for two reasons. The first reason is that the shape of the formation reduces the drag force that each bird experiences compared to if it were flying alone...
teamwork
Even though the V formation benefits all of the birds, the bird in the lead position has to work the hardest. When this bird tires, it will drop out of the lead position and fall further back into one of the lines of the V. Another bird from further back will rapidly move forward to take the leading position and maintain the formation. The two birds in the furthest trailing positions also tire more rapidly than those in the middle, so these positions are also rotated frequently to spread the most fatiguing locations throughout the flock. This cyclical rearrangement gives all birds the responsibility of being the leader as well as a chance to enjoy the maximum benefits of being in the middle of the formation. This sense of teamwork comes naturally since even the youngest members of the flock rapidly realize that it takes less work to fly in a V formation than it does to fly alone.
communicate more easily
A second reason that may explain why birds fly in formation is that this orientation allows the birds to communicate more easily. The V formation provides the birds with good visual contact of each other to keep the flock together. This communication minimizes the possibility of losing birds along the way as the formation crosses vast distances during migration.
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However, military planes do still operate in V formations, but they are typically spaced too far apart to enjoy the benefits of reduced drag. These aircraft instead fly in formation primarily to maintain visibility of all the aircraft in the squadron in the same way that birds do.
A nice book with further information on how birds and insects fly is Nature's Flyers: Birds, Insects, and the Biomechanics of Flight by Steven Vogel.
- answer by Jeff Scott, 17 July 2005
