By Dr. Becker
If you've ever gazed up into the sky and wondered why some migratory birds like ducks and geese travel in a V formation, here's the reason: The "V" offers substantial benefits in the efficiency and range of flying birds, especially when traveling long distances. The first bird takes off, and all the remaining birds fly in what is called the "upwash" from the circular patterns of rotating air that develop behind a wing as it generates lift. The upwash helps each bird support its own weight while in flight.
In a V formation of, say, 25 birds, each can reduce drag force by up to 65 percent, which results in an increase in range of 71 percent.1 That's a huge savings for birds that may fly up to 600 miles in a single day. The birds positioned at the front and each tip of the "V" are rotated in a timely fashion to insure flight fatigue is spread equally among all birds in the formation.
So that's the why of it, but in case you're curious as to how, exactly, birds manage to stay in position in a V formation over long distances, a new study offers an explanation.
It's All in the Timing
A bird flying in V formation must be able to match the up-and-down pattern of the wing tip of the bird in front of it. Unlike the stationary wings of fighter planes that fly in formation, birds flap their wings, making the task of following the movement of another bird's flapping wing quite a bit more challenging. In order for bird #1 to reap the benefit of bird #2's wing trail, bird #1's wing flaps must be precisely timed.
A team of European researchers led by Steven Portugal of the University of London's Royal Veterinary College used sensitive monitoring devices to discover that northern bald ibises coordinate the up-and-down motion of their wings for optimum efficiency when flying in a V formation. Their findings were published in a recent edition of the journal Nature.2
While in the "V," the birds flap in such a way that one of their wing tips follows the pattern of the nearest wing tip of the bird in front. This isn't to say that the birds' wings always rise and fall at precisely the same time, but that bird #1's wing tip pursues bird #2's wing tip along the same path, which allows bird #2 to take advantage of the upwash created by bird #1.
By contrast, when bird #2 flies directly behind bird #1 rather than in a "V," #2 tends to flap his wings in an opposite pattern to bird #1. When #1's wing tip is down, #2's wing tip is up. The opposing rhythm helps #2 avoid the considerable downwash of air experienced by flying directly behind another bird.
How the Researchers Collected Their Data
In their rather ingenious study, Portugal and his team trained captive-bred ibises, a critically endangered species, to migrate from Austria to Italy. In order to do that, the researchers had to convince ("imprint") newly hatched chicks to view human volunteers as their mothers.
When it came time to migrate, the "moms" flew in the rear of a microlight aircraft and called for the young ibises to follow. The ibises were outfitted with tiny backpacks that held equipment to monitor the location of each bird and its flapping phase. The researchers later collected the equipment to recover the data after the birds had spent some time flying in real-world situations.