PARIS, June 30 (UPI) -- New data has revealed frigate birds as the animal kingdom's most prolific soarers.
A team of researchers led by Henri Weimerskirch, an ornithologist at the National Center for Scientific Research in Paris, used transmitters to track the flights of frigate birds in the Indian Ocean and South Pacific. They published their findings this week in a paper in the journal Science.
The large, black seabirds coast on air currents for days and weeks at a time. One bird covered 40 miles without a single wing flap. Most covered an average of 300 miles a day, riding roller coasters of air up and down.
Researchers say they are the only species of bird seen purposefully entering clouds.
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"They're doing it right through these cumulus clouds," Curtis Deutsch, an oceanographer at the University of Washington who aided the research, told NPR. "You know, if you've ever been on an airplane, flying through turbulence, you know it can be a little bit nerve-racking."
Frigate birds boast a 6-foot wingspan, as well as the highest ratio of wing surface area to body weight of any bird species.
The frigate bird's mastery of air currents, thermals and trade winds, and the seemingly effortless soaring it enables, is essential for the species' survival. The frigate bird is the only seabird without waterproof feathers. Should a frigate bird become wet, it would be unable to take back to the air and would drown within minutes.
Instead of diving for fish, the frigate bird circles high in the air waiting for surface activity -- a feeding frenzy. When larger scaled predators push bait fish to the surface in a panic, frigate birds gather and pluck escaping minnows from the air.
"It's a very, very specific niche and way of attacking prey," Weimerskirch told the Washington Post. "But the prey are very patchy ... it takes days and days to encounter one opportunity. So they have to cover very long distances to find it."
Researchers say the swirling currents that arrive with cumulus clouds are associated with calmer seas, which means the frigate brids can not only ascend and descend to scout and feed, but are also less threatened by waves when approaching a surface-level fish fracas. Calmer surface water also allows upwelling to push nutrients to the top of the seas, attracting smaller fish and the predators that chase them.
Frigate bird parents spend a much longer time teaching their offspring to fly than other bird species, which can explain their adeptness at navigating air currents.
