Biologists were curious to see how exactly frigate birds manage to stay in flight for days at a time, without having any stops to rest. The secret appears to lay in their wing surface.
A team of researchers from Paris used transmitters to monitor the flights of frigate birds over the oceans.
The seabirds soar on air currents for days at a time. One bird was found to cover 40 miles without moving any of its wings. The vast majority managed to fly an average of 300 miles each day, all through the use of air movements.
Frigate birds have a 6-foot wingspan. When compared with their body weight, the wing surface area is higher than in any other bird species.
Another interesting fact about frigate birds is that they are the only known bird species that intentionally enters clouds.
“They’re doing it right through these cumulus clouds. You know, if you’ve ever been on an airplane, flying through turbulence, you know it can be a little bit nerve-racking,” said Curtis Deutsch, an oceanographer at the University of Washington.
The frigate birds are masters of air currents and winds. Their efficiency in long-distance soaring is essential for survival, as they are the only species that does not have waterproof feathers and a fall into the water would make them drown in a couple of minutes.
As a consequence, the bird does not dive for food. It usually circles in the air and waits for surface activity, and when fish jump out of the water in a panic, they pluck the creatures directly from the air.
This very specific and opportunistic way of attacking prey involves days of wait. Frigate birds usually cover long distances to find food and to get the chance for fish to be driven out of the waters by other predators.
The birds have learned that cumulus clouds are associated with calmer seas and swirling currents. Therefore, they use them when looking for their prey as a means to ascend and descend towards the water surface and back.
The cumulus clouds are a sign that the waters have no waves that can threaten the bird. Moreover, inside calm waters, the nutrients are pushed more to the surface, which means smaller fish and their predators would also come closer to the sea level and expose themselves to frigate birds.
Another evolutionary trait is the fact that the species consumes more time in teaching their children how to fly, as the behavior is critical for their survival.
Frigate birds can flight at altitudes of more than 12,000 feet, which is impressive for a tropical bird that is not used to the cold.
Image Source: Flickr