It is more aerodynamic and each bird provides lift for the ones behind it. It can be proven by some advanced physics, but that's basically how it works.

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. This decrease in drag occurs thanks to the formation of wingtip vortices. Creation of trailing vortices due to a difference in pressure above and below a lifting surface These vortices are generally undesirable because they create a downwash that increases the induced drag on a wing in flight. However, this downwash is also accompanied by an upwash that can be beneficial to a second wing flying behind and slightly above the first. A bird flying in one of these upwash regions essentially gains free lift so that it can fly at a lower angle of attack. As angle of attack is reduced, the induced drag is also lowered so that the bird does not need to flap its wings as hard or as often to generate the thrust needed for forward flight. Flapping the wings less often means that the bird's muscles do not work as hard and its heart rate drops. As a result, the bird does not tire as quickly and is able to fly farther. Other studies have estimated that a flock of 25 birds in formation can fly as much as 70% further than a solo bird using the same amount of energy. Theoretical investigations further support these observations of birds in formation flight. By spacing themselves apart properly, birds can achieve optimum positions that reduce the drag of every bird in the formation. However, not all birds benefit equally. 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. Another theory as to 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. To see the diagrams etc. go to: http://www.aerospaceweb.org/question/nature/q0237.shtml

Two reasons. First, it conserves their energy. Each bird flies slightly above the bird in front of him, resulting in a reduction of wind resistance. The birds take turns being in the front, falling back when they get tired. In this way, the geese can fly for a long time before they must stop for rest. The second benefit to the V formation is that it is easy to keep track of every bird in the group. Fighter pilots often use this formation for the same reason.

wat i knw is.. Head of the family leads the way... It can be Male or Female... Rizwan..

birds fly in v shape because this is another one of Gods awsome designs that screams to us that he is the creator of the universe and everything that is in it including us .