It's a summer evening, and the sun is just setting leaving a beautiful sunset on the horizon, and you see a flock of birds migrating to someplace else, in that well known V shape. No matter if they are turning left or right they still rigidly keep to the V shape.
For many years the reasoning behind the flock formation was unknown, but now scientists from the Royal Veterinary College have fitted data loggers to a flock of rare birds (Ibis') as they were being trained to migrate following a microlight plane.
It seems that when in formation a bird positions itself in such a way, in relation to the other birds in the formation so that it gives them the best aerodynamic advantage. They do this in order to make the most of the air moving upwards from the bird in front of them (this is called upwash, and is created when a bird flies forward and the air is pushed downwards beneath its wings). Moreover all the birds in the formation do not beat their wings in time with each other but instead flap them to get the upwash from the bird in front. So they are all slightly off time with each other. This helps the birds to be as efficient as possible which is a necessity when they have to migrate long distances.