It appears that by flying in this pattern the birds boost each other and increase their flight range as much as 71 percent. The theory is based almost entirely on laws of aerodynamics, rather than observations of birds in flight. But the V angles and spacings that specialists arrived at in their calculations are very similar to those seen in flights of migratory birds.
According to scientific conclusions, each bird in flight leaves a strong updraft or upward movement of air off its wing tips. By taking a position in the formation so as to have full advantage of this lift, the bird following is helped to fly forward more easily. This is very much like the way a hawk or glider pilot takes advantage of updraft to keep aloft. Flying in this way reduces the forward speed of the birds, but it extends their flight range. And when you consider how many hundreds of miles migratory birds travel you can appreciate why this type of flying is far more practical.
It might appear that in V-formation flying the lead bird would have to do the most work. But the specialists' calculations show that in this flying pattern the updraft from the birds on both sides of the leader extends far enough forward to help it too. However, this depends on the spacing of the birds and the shape of the V. Probably the leader does have to do more work, and, therefore, be the strongest bird, or maybe the best navigator. Also the birds at the outermost ends of the V can lighten their load by dropping back slightly.