Frigate birds can spend two months in the air, study finds

Scientists have known frigate birds are capable of flying for long period of time, but researchers who conducted a recently-published study were likely shocked to find out just how long – nearly two months!

Published in the journal Science, the new study found great frigates, which inhabit the Indian and Pacific oceans, travel hundreds of miles by riding updrafts and flapping their massive wings once every 6 minutes.

The study team affixed featherweight devices on the nape of the birds’ necks. Linked to satellites, the small solar-powered devices included GPS tracking, heart rate monitors, accelerometers, and altimeters. They weighed only 10 grams, which made it achievable to follow the birds without impacting flight.

Researchers knew frigate birds have a very light body weight distributed over a large wing area, which helps kept them aloft. Because great frigates don’t have water-repellent feathers, they must stay aloft to keep from landing on water.

Discovering the flight patterns of the great frigates

The study team saw that great frigates soar and glide in long swoops by making the most of the distinct weather patterns in the heart of the Indian Ocean. All year round, enormous swaths of the Indian Ocean remain fairly windless, patches known as doldrums. Great frigates will keep to the perimeters of these doldrums, orbiting them over days and months because the weather patterns discovered at the edges are fairly constant and reliable, filled with updrafts birds can ride.

When floating near these doldrums, the birds spend about 10 percent of their time on the lookout for food. The remainder of their time is spent soaring from cloud to cumulus cloud, for up to 400 miles per day. The study team said they might somehow be sleeping in the air over these long journeys.

Prior to the study, researchers were confident great frigates avoided entering clouds due to the likely for chaotic turbulence. The researchers admitted that assumption appears to be wrong.

When the distance between clouds is substantial, great frigates will enter in the clouds and make use of its makeup to fly high into the air so they can float a greater distance. The researchers saw some birds in the study could soar up to 2.5 miles above the water, where the oxygen is thin and water freezes. On average, the birds tended to favor lesser heights, from 150 to 2,000 feet above the ocean.

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Image credit: AURÉLIAN PRUDOR/CEBC CNRS

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