Why They Fly in V-Formation

THE recent conclusion of two aerodynamic specialists at the California Institute of Technology is that large migrating birds fly in V-formation for practical reasons. 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 these specialists arrived at in their calculations are very similar to those seen in flights of migratory birds.

According to their conclusion, 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.

Now, what helps the birds to stay in their place as they fly in this way? The analysis is that if a bird gets ahead of its proper position, it immediately feels an increased work load. This will move it to drop back into its proper place. If it falls behind, it does less work but then it is suspected that “social pressure” is applied to force it to keep up. The analysts reason that perhaps the continuous honking of wild Canada geese when on the wing is really a calling to the lazier birds to keep in their place.