Migratory birds have many flight formations, called echelons. Each have their own set of advantages. The most common of these is the V shaped formation, which can be called a Skein. Anyone who sees a flight of migrating geese will see its distinct shape.
This flight pattern provides the birds with two main advantages. The most obvious being that since each bird is slightly behind the next, all of the birds can see the lead bird, and the bird immediately in front and to the side, allowing them to coordinate their flight paths and not crash into each other or get lost. This is the primary reason that fighter jets also fly in formation. The only real difference being that they also do this to increase their fields of view and defensive ability.
The second advantage, which is not as easy to see, is that this flight formation can increase the flight efficiency of the birds, allowing them to expend less energy in order to fly. This is essential for migrating birds that must travel long distances without landing, any conservation of energy is essential. the conservation of energy occurs because instead of flying on the same relative plane, each bird is at a slightly lower altitude than the other. this difference allows the birds to take “advantage of the upwash vortex fields created by the wings of the birds in front”(1). This results in a reduction of air resistance, reducing some of the drag that the birds would otherwise have to overcome. So every bird that is behind another feels a reduction in drag, but what about the bird in front? extended studies on migrating birds have shown that when the lead bird tires, it falls to the end of one of the V’s arms, and one of the nearest two birds take its place. This rotation allows the flock to fly for much longer than would otherwise be possible.
Amazingly, a group of researchers at Stanford have devised a flight pattern for airliners that borrows from this same energy saving mechanism to increase fuel efficiency. The proposed arrangement is to have three airplanes, spaced about 4 miles behind each other, and would have an increase of fuel efficiency of about 12 percent.
- Scientific American: Why do migratory birds fly in a V-formation?
- Stanford Press Release: Airliners could save fuel by taking a hint from birds flying in formation (May 2009)
- Everyday Mysteries: Why do geese fly in a V?
- AerospaceWeb: V-formation flight in birds