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Nature

16
Jan

Why Do Birds Fly in Vs? Endangered Bird Solves the Mystery

Reteach an old bird old tricks, and you might learn something.

That’s what happened when Johannes Fritz and his colleagues at an Austrian conservation organization strapped tiny sensors on 14 northern bald ibises. The ibis—a large bird with a long, subtly hooked orange beak—became extinct in Central Europe in the 17th century. Fritz’s team is reintroducing it to its old migration routes.

The northern bald ibis. Not the prettiest bird around.

The scientists acted as “foster parents,” writes Flora Lichtman for The New York Times: 

Eventually, the foster parents taught the birds their 600-mile migration route from Salzburg to Orbetello, Italy, by flying alongside them. The birds wore custom-made data loggers that allowed the researchers to track flapping, speed and direction. Weighing less than an ounce, the devices included an accelerometer, a gyroscope, a magnetometer, a memory card, a battery, a microcontroller and a GPS unit “much better than on your iPhone,” Dr. Usherwood said. It is accurate to about one foot and refreshes five times per second — the resolution necessary to track the birds’ positions in relation to one another.

Northern bald ibises flying in migratory formation. Note the characteristic wave pattern of their wings from the lead bird on back.

But not only did these tech-laden birds enable Fritz and his team to monitor their migratory progress, but it also confirmed what ornithologists have long suspected: that birds fly in a V formation to conserve energy. Until today, expert hypotheses were based mostly on calculations of airflow around airplanes—no one had taken any direct measurements of V formation aerodynamics in birds. Reporting in the journal Nature, Fritz’s team can now confidently say that wind-borne birds take advantage of the upward-sweeping current, or upwash, that rolls off the wings of the bird that is diagonally to the fore. (Upwash in birds does, in fact, work similarly to how it does in airplanes.)

But here’s what’s really impressive. The ibis, pelican, goose, and others are doing this rather intelligently, while a fine eye for detail. Here’s Ed Yong, writing at Not Exactly Rocket Science:

As each bird flaps its wings, the trail of upwash left by its wingtips also moves up and down. The birds behind can somehow sense this and adjust their own flapping to keep their own wings within this moving zone of free lift. “They trace the same path that the bird in front traced through the air,” explains Portugal.

Imagine that a flying ibis leaves a red trail with its left wingtip as it moves through the air. The right wingtip of the bird behind would travel through almost exactly the same path. “It’s like walking through the snow with your parents when you’re a kid,” says Portugal. “If you follow their footprints, they make your job easier because they’ve crunched the snow down.”

Portugal explains that this is a much more elaborate and sophisticated process than his team had expected, and that it seems like it’s almost self-taught. But how do they all learn to do it? And how has V formation flight become so successful? Scientists don’t know yet, but they’re not waiting in the wings to find out.