When a bird flaps its wings it disturbs the air and leaves whirling eddies behind.
An individual gets a little extra lift from the wake of a bird out front (and slightly below it) when they fly in V-shaped formations. The wake widens out as a V just like what you see on a lake from a passing boat.
Some gregarious bird species, such as the Canada goose, have learned to sync their flapping and take advantage of the updraft of air created off the wings of others in the flock by flying in a wedge or V formation. Thus each bird adds the lift lost by the bird ahead to its own and saves energy. This "drafting" allows the geese to travel at an easier pace through their flight. Researchers have found that geese in the V shape can fly as much as 70% farther than they would individually.
Ornithologists think geese honk from behind to encourage those up front to keep up their speed. The leader has the hardest work to do as he or she breaks the trail. They are relieved at intervals. Often as geese or other birds are flying in formation, one side of the V has many more individuals and looks like a wedge. Because they seldom fly directly into the wind, the downward part of the formation can be easier to fly in. One side of the formation can end up longer.
Besides saving energy, another benefit of flying in V formation is to keep track of every bird in the group. Flying in formation might assist with the communication and coordination within the group. Military fighter pilots often use the V formation for the same reason, and it also improves fuel economy.
Besides the numerous flocks of Canada geese and tundra swans we observe traveling in V or wedge-shaped patterns, other species of swans and geese, plus ducks, sandhill cranes, white pelicans, cormorants, shorebirds, and gulls also use that model.
For many years, during October and into November, each evening at sunset I have watched as one V formation after another of Franklin's gulls makes its way to Lake Waconia, where these social birds will spend the night as a huge surface water flock.
Jim Gilbert's observations have been part of the Minnesota Weatherguide Environment Calendars since 1977, and he is the author of five books on nature in Minnesota. He taught and worked as a naturalist for 50 years.