Timing is everything to catch a boost from a neighbor’s wing
A bird migrating with others in a V formation turns out to be a master of the well-timed flap, able to match the up-and-down path traced by the wing tip of the bird in front of it.
Fighter pilots know the benefits of flying in a V formation. Wings create a vortex of whooshing air trailing from their tips, and a rearward plane that keeps one of its wing tips in a vortex from the plane in front gets a boost from the upwash of air and can save fuel. But birds flap their wings, and the vortices spinning off their rising and falling wing tips swoop up and down. For a bird to catch the benefit of another’s wing trail, flap timing has to be right.