Built for gliding, frigate birds of Europa Island in Africa have been found to stay in the air for more than two months by gliding on updrafts and global wind patterns.
With ultra lightweight aerodynamic bodies and wingspans that can reach more than seven feet, frigate birds have long been known for their ability to glide non-stop through the air for days and even weeks at a time, but new research has shown the seabird can stay aloft for much longer than previously known — more than two months in some instances.
Led by Henri Weimerskirch of the French National Center for Scientific Research (CNRS), an international team of researchers tagged and tracked the flight patterns, elevation, heart rate and wingbeats of approximately 50 frigate birds (Fregata minor) around Europa Island in the Mozambique Channel off the east coast of Africa.
Researchers used electronic tags that automatically download data to track the flight patterns and various physical measures of frigate birds. Credit:Screenshot from Independence Days, in the tracks of young marine predators, a film by Aurélien Prudor and Henri Weimerskirch.
“The juveniles in particular, who leave their birthplace for the first time, travel thousands of kilometers and, even more surprisingly, can remain airborne for over two months without touching ground,” according to a media release by CNRS.
Data collected from the tags showed that by following the trade winds and using updrafts produced by large cumulus clouds the birds are able to gain altitude without flapping their wings, thereby conserving energy and enabling them to soar continuously over more than 6,500 miles from their birthplace on Europa Island across the Indian Ocean to the island of Sumatra.
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“Once they have reached the bottom of a cumulus cloud, at an altitude of 600 or 700 meters, they glide down over kilometers without expending energy,” according to CNRS. “In order to glide over longer distances in less cloudy areas, frigate birds regularly climb to very high altitudes (of 3,000 to 4,000 meters) by flying inside cumulus clouds, where they can take advantage of strong updrafts.”
A frigate bird on the Island of Europa. Credit: Screenshot from Independence Days, in the tracks of young marine predators, a film by Aurélien Prudor and Henri Weimerskirch.
A video of the research, which was published on July 1 in the journal Science, can be found here.
The frigate bird’s lengthy flight time is particularly remarkable as the birds can not swim or land in water as they do not not have waterproof feathers (unlike all other marine birds, according to CNRS) and rely entirely on catching flying fish as they leap from the water.
Stranger yet, the birds not only eat in mid-flight, but according to CNRS the researchers believe short periods of inactivity while gliding might suggest they also sleep in flight.
Entirely dependent on wind patterns, the future may prove to be more difficult for frigate birds due to climate change, according to an excerpt from the video, →, in the tracks of young marine predators, a film by Aurélien Prudor and Weimerskirch.
“In the tropical zone scenarios of climate change suggest their will be an increase in the intensity of cyclones,” according to the video. “They will therefore have to deal with much stronger constraints in the future. Their adaptive capacity will be the key to their survival.”
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