V-formation

Why Birds Fly in a V Formation: A new study finds that big-winged birds carefully position their wingtips and sync their flapping, presumably to catch the preceding bird’s updraft—and save energy during flight.

Scientists used a microlight plane to show hand-raised birds their ancestral migration route from Austria to Italy. A flock of 14 juveniles carried data loggers specially built by Usherwood and his lab. The device’s GPS determined each bird’s flight position to within 30 cm, and an accelerometer showed the timing of the wing flaps.

Just as aerodynamic estimates would predict, the birds positioned themselves to fly just behind and to the side of the bird in front, timing their wing beats to catch the uplifting eddies. When a bird flew directly behind another, the timing of the flapping reversed so that it could minimize the effects of the downdraft coming off the back of the bird’s body.

http://news.sciencemag.org/biology/2014/01/why-birds-fly-v-formation