The flight patterns of geese:
Flying in the shape of a "v" allows geese to have an equal field of vision while conserving energy, using wingtip vortices to decrease any drag in flight. The bird in the front is working the hardest, but when the leader grows weary it rotates to a position farther back and allows another feathered pilot to take its place. This formation is so successful in conserving energy that birds who fly in "v" formations have been recorded to have lower heart rates than those who do not. If one of the birds flies out of formation, they will feel the increase in drag nudging them back into position.