Katharine Johnson, age 13, of Waverly, Va., for her question:

Why do birds fly in a V formation?

Canada geese are whopping big game birds that migrate north and south with the seasons. In the fall, their V formations fly down to our southern states. In spring, they fly north to spend the summer in Canada. Some of these powerful fliers are almost 3 feet long.

Many peop1e ignore birds, but no one can resist watching a flock of geese in a V shaped dart across the sky. We wonder why they choose this formation. Perhaps the neat squadron is led by a wise old goose who happens to be the boss of the flock. Perhaps the leader is elected because he has a good sense of direction.

Bird admirers have been puzzled about the V formation for generations. Even now, we are not sure that we can Explain all the details. But on the basis of some recent studies, the experts think that the matter can be explained in very reasonable terms. And they assure us that the spearhead of the flock is not the boss goose. Nor is he elected to office because of his special talents.

Careful watching has proved that the leader of the squadrons is not always the same bird. The leader role is taken over by first one bird and then another. In a long flight, after a certain distance, the leader drops back in line and another bird flies forward to take his place.

In order to fly planes, we had to learn the tricks of aerodynamics. This is the manner in which air moves and flows around solid objects in certain directions. There are complex and invisible currents and movements, stresses and strains in moving air. Geese and other V flying birds have been coping with these problems for ages. And bird experts began to think of the V formations in terms of aerodynamics.

The lead bird cuts through an invisible wall of air. This sets up currents of air flowing behind him. The other birds take advantage of these windy drafts. The pioneer work of the lead bird is hard and after a while he becomes tired. Then he drops back and relaxes somewhat in the streaming currents created by the new lead bird who now plunges a path through the air.

Birds tend to fly in V formation only on their long migration journeys. On short hops between their feeding grounds, the flock goes off in the same direction, but they do not fly in any special formation. So when we see the geese flying high in their V shaped squadrons, we can be sure that they are flying between their winter and their summer home.