A scientific team led by Henri Weimerskirch of the National Center for Scientific Research in France found the frigate bird species uses air currents to spend little energy flying over 250 miles a day for months at a time. (Aurelien Prudor/Henri Weimerskirch CEBC CNRS)
Europeans named the birds "frigate" for their resemblance to the swift warships. They look powerful, with their forked tails and long, slender wings; the shadows they cast on the sea surface could just as easily belong to a flock of pterodactyls. They make incredible feats of endurance — flying for two months without once setting foot on land, for instance — seem almost effortless: They ascend to altitudes of 2,000 feet and drop back down to sea level again with just a single flap of their wings.
"It is impressive," said Henri Weimerskirch, an ornithologist at the National Center for Scientific Research (CNRS) in France. "There is no other bird species like them."
Weimerskirch would know — he spent two years tracking 80 frigatebirds to understand their behavior, which seems to defy all laws of gravity and biology. Though they feed exclusively on fish, the creatures cannot swim. Instead they fly for weeks, even months, across the oceans of the tropics in search of food that swims close enough to the surface for them to snatch it out of the water.
They're able to do this, Weimerskirch reports Thursday in the journal Science, because of an incredible, intuitive mastery of air currents. Combining data from GPS trackers, heart rate monitors and accelerometers affixed to the birds with local weather reports, he and his colleagues figured out how frigatebirds take advantage of thermals and trade winds to fly over vast distances for long periods of time — all without expending much more energy than they would sitting in a nest.
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