In the Cobscook Bay area recently – near the easternmost part of Maine – I have been hearing the honks of Canada geese. I always look up to see them because I am fascinated by their flight in V-formations. But geese do not have a monopoly on V-formations. Many species of ducks, swans, cormorants, ibises, cranes and even some pelicans show the same behavior.

Have you ever wondered why these birds fly in such formations? The behavior yields a significant savings of energy.

As a bird flies, the tips of the wings deform on the powerful downstroke. Eddies of air swirl off the tips of the wings. Some ornithologists began to wonder if trailing birds could take advantage of these upward eddies to gain lift. Using a computer model developed by aviation engineers, these ornithologists found that birds flying in V’s could realize an energy savings of 71%, compared to birds flying alone. The model showed that the greatest benefit would result when a trailing bird has a wing overlap of about 5 inches with the next bird ahead. In other words, if a bird moved abreast to the next bird ahead of it, the wing of the trailing bird would overlap by 5 inches with the wing of the bird next in line. The model also showed that each bird except the leader should be between 1 and 3 yards behind the bird in front for greatest energy savings. The position is tricky because it is possible to lose efficiency if the position is affected by the downward eddies on the upstroke. Finally, the model shows that the birds in the flock should beat their wings in perfect synchrony.

Films of migrating Canada geese were used to see how well the positions of the geese agreed with the computer model. In many cases, the wing overlap was right around 5 inches, the most desirable position. Distance to the next bird and synchrony of flight were not always as predicted, probably because of turbulence in the air. Nevertheless, the performance of the geese suggested that an energy savings of 36% resulted from flying in V’s.

In a V of geese, the leader receives no benefit of the flight formation. Geese do switch positions, so they take turns as leader, and as well as at the end of the skein on either side. The social status of the leader(s) has not been studied.

One study on pelicans revealed that birds flying in a V had lower heart rates than birds flying solo. Let’s hear it for miniaturized heart monitors. Lone birds also beat their wings more frequently.

Research with juvenile Northern bald ibises in Europe provided information on learning how to fly efficiently in V formation. The ibises were fitted with small data loggers that recorded the position of birds and their flapping rate several times a second. When the migration was first begun, the ibises did not fly in a regular formation. No adults were present to teach them how to fly in a V. Nevertheless, they quickly discovered on their own the advantages of flying in a V. Soon, by trial and error, the ibises were maintaining the predicting spacing and beat their wings in synchrony in agreement with the mathematical models.

Aviation engineers have taken a lesson from birds flying in V formations. Immense vortices of air spin off the tips of the wings of a plane in flight. Experiments with the spacing of fighter jets in a V showed a decrease of fuel consumption of 10%. The engineers believe a 15% saving is possible.

Airbus is pioneering a program with spacing of two large commercial aircraft. One flies about 2 miles behind the first one. The second plane takes advantage of the updraft. Greater updraft is possible with closer distances, but at the expense of a turbulent ride. The 2-mile spacing results in a 5-10% fuel savings while providing the passengers with a smooth flight.

Herb Wilson taught ornithology and other biology courses at Colby College. He welcomes reader comments and questions at whwilson@colby.edu

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