These are White Pelicans. The following birds benefit from the upwash produced by the wings of the bird ahead of them. Researchers have found that the heart rate of pelicans is much lower when flying in formation than when they are flying alone. It has also been shown that birds in formation can fly 70% farther than a solo bird using the same amount of energy.

Even the lead bird gets some advantage, as the wing beats of the birds just behind offset some of the drag. When the lead bird starts to tire, it falls back and another bird takes its place.