Geese fly in a V-shaped formation to conserve energy and keep track of the locations of other geese. When flying in formation, the goose in the front reduces the wind resistance that the goose in the rear experiences.
Because the following geese expend less energy in moving forward than the lead goose, migrating geese take turns being the lead goose. The V-shaped formation also allows each goose to see all of the other geese. Fighter pilots often choose to fly in V-shaped formations for the same reason. No other aerial formation allows for this type of visual communication among group members.