- The Washington Times - Wednesday, February 14, 2007

Matching birds in a flying V formation, switching directions seemingly on cue, one would think a silent sky director choreographed the performance.

But the creatures’ talent is almost preternatural: Clustering or grouping together is an evolved and learned behavior that avian and marine life use to travel by air or sea.

Ducks, geese, swans and other migratory birds fly in V formation to save energy, while birds that remain within the same locale use flocks for protection. Most fish species, such as tuna, anchovies and mackerel, swim in schools for both protection and efficiency.

“The reason [birds] fly in V formation is aerodynamics,” says Nicholas Throckmorton, spokesman for the U.S. Fish & Wildlife Service.

Waterfowl migrate thousands of miles a year, he says. The birds breed in the Great Lakes area and north to Alaska and Newfoundland; then in the fall, they migrate south to warmer climates in California, the arid West, Mexico, Florida and the Chesapeake Bay.

The V formation is a symmetrical pattern of flight in which the lead bird forms the tip of a V and the other birds trail behind to form the edges. The birds behind the lead put their heads and bodies behind the tip of the wing of the bird in front of them, Mr. Throckmorton says.

“It’s easier for a bird to fly behind a bird of the same species with the same wingspan,” says Chandler Robbins, volunteer wildlife research biologist with the U.S. Geological Survey in Reston. He holds a doctorate in biology. “It only works with the large birds. Small birds flap so fast.”

Pelicans, sea ducks and cormorants fly in a line with each bird off to the side of the one in front, essentially creating one side of a V, Mr. Robbins says.

“Flying in V formation gives an advantage to trailing birds because the movement of the bird ahead creates lift for the bird behind,” says Hillary Cressey, assistant professor of biology at George Mason University in Fairfax.

Lift occurs as air ahead of the bird is pushed downward and air behind it is pushed upward, says Rajat Mittal, professor of engineering and applied science at George Washington University.

“If another bird comes in, it can make use of the extra air and extract from the energy the first bird has imparted into the air,” says Mr. Mittal, who holds a doctorate in applied mechanics. “Birds can sense a location behind the lead bird to get the best lift.”

A bird’s wings, and also those of an airplane, are flat on the bottom and rounded on the top, Mr. Throckmorton says. As the bird moves its wings, high pressure is created below and low pressure above each wing, he says.

“The air wants to move from high to low pressure. The wing is in the way, so it pushes the wing up,” Mr. Throckmorton says. “At the tip of the wing, the air kind of swirls around where it mixes, and you get a vortex at the end of the wing.”

The birds behind the lead bird use the vortexes coming off the tip of the wing of the bird in front, Mr. Throckmorton says.

“As air comes off the end of the wing, it causes an updraft, which gives the bird behind it a small bit of lift,” says Donald H. Messersmith, professor emeritus of entomology and ornithology at the University of Maryland in College Park. He teaches evening birding classes in Chevy Chase for the U.S. Department of Agriculture Graduate School in cooperation with the Audubon Naturalist Society of the Central Atlantic States. He holds a doctorate in entomology.

Birds flying in formation take turns being in the lead because the lead expends the most energy, Mr. Mittal says.

“The lead bird doesn’t always stay in the lead,” Ms. Cressey says. “As the lead bird gets tired, it can fall back, and another bird will take its place.”

When the birds take off, one of them takes the lead, usually an older, stronger bird, Mr. Messersmith says.

“It’s not a leader in a sense. It’s a bird who gets in the air first,” he says. “The lead bird stays until it gets tired because it’s not benefiting from those updrafts. It slips off, and the next one in line becomes the leader.”

With schools of fish, the lead fish has to push away the fluid in front of it to move through water, Mr. Mittal says. The lead fish reduces the drag for the fish following behind in its wake, a concept known as drafting, he says. The trailing fish expend less energy to move through the water, he says.

“Drag is a significant part of energy expended for birds, fish and planes,” Mr. Mittal says.

Dolphin drafting occurs when a calf swims beside its mother toward her rear half to save energy.

“By doing that, the calf is able to swim and keep up with its mother with little energy expenditure. The calf is able to take advantage of the flow created by the mother,” Mr. Mittal says.

Most ocean fish travel in schools; animals such as zebras move in herds; and birds such as pigeons, sandpipers and starlings, fly in flocks for safety.

“In bigger groups, each individual’s survival against predators increases,” Mr. Mittal says.

A predator is less likely to attack a large group of birds than a single bird and larger groups than smaller groups, Ms. Cressey says.

“Individuals that have strayed from the group or are at the edges are more likely to be picked off by a predator,” she says.

Flocks of birds, along with schools of fish, rapidly change direction to confuse and ward off predators, to evade a known predator that has been sighted and to search for food, Mr. Mittal says. Birds and fish use visual cues from those around them to change position, he says.

Predators will pick out a bird that is not in unison with the flock, says Russell Greenberg, head of the Smithsonian Migratory Bird Center in Northwest.

“All the birds are cued in to maintaining their position and direction in cue with the birds near them,” Mr. Greenberg says.

When the birds change direction, their effort is a highly coordinated cascading effect, Ms. Cressey says.

“It’s called the chorus-line effect, where birds can see this movement coming and have to react to it,” she says. “Birds have a very quick reaction time, so they can execute these very rapid movements in response to the individuals around them.”

The birds turn so quickly, it looks as if they are doing it in unison at the same time, Mr. Messersmith says.

“It’s a visual thing, not a vocal thing. One of them doesn’t squawk and say it’s time to turn,” he says.

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