<P> A V formation (sometimes called a skein) is the symmetric V - shaped flight formation of flights of geese, ducks, and other migratory birds . V formations also improve the fuel efficiency of aircraft and are used on military flight missions . </P> <P> The V formation possibly improves the efficiency of flying birds, particularly over long migratory routes . All the birds except the first fly in the upwash from one of the wingtip vortices of the bird ahead . The upwash assists each bird in supporting its own weight in flight, in the same way a glider can climb or maintain height indefinitely in rising air . According to a 1970 paper, in a V formation of 25 members, each bird can achieve a reduction of induced drag and as a result increase their range by 71% . The birds flying at the tips and at the front are rotated in a timely cyclical fashion to spread flight fatigue equally among the flock members . Canada geese are a common example demonstrating the V formation . </P>

What kind of birds fly in a v formation