Scientists have just discovered that Fregata minor, the great frigatebird, can fly for up to two months without a break. The details are in a paper just published in the journal Science. Scientists fitted the birds with tracking devices and then analyzed the data, finding that the birds are able to cover amazing distances without resting at all.
The great frigatebird is a large seabird found in the Pacific, Atlantic, and Indian oceans. They spend most of their life at sea, only venturing onto land during breeding season. This has made them difficult to study in the past and there was little knowledge on their flight patterns. Frigatebirds are unusual for seabirds in that their feathers are not waterproof. This means that a frigatebird can’t land in the water without drowning, a serious problem for a bird that spends most of its life above the open ocean. They get around this problem by stealing food from other birds and catching fish that jump out of the water, such as flying fish. Great frigatebirds were known to migrate great distances but their exact flight movements had never been studied.
The researchers captured a small group of great frigatebirds when the birds were nesting on land. They attached small, lightweight tracking devices and then set the birds free. The tracking devices wouldn’t interfere with flight and included heart monitors. After analyzing the data, the scientists were surprised to learn just how high the birds were flying. The frigatebirds soared up to 4,000 meters, the highest elevation any bird has flown above the ocean. At this height, the air becomes thin and frigid. These frozen conditions seem harsh for a tropical seabird but the monitors showed that the birds handled these extreme temperatures without problems. In addition to flying at such high elevations, the frigatebirds managed to cover astonishing distances without stopping. They could fly for up to two months without landing and their heart monitors showed that this wasn’t an issue for the birds.
The frigatebirds were apparently taking advantage of strong winds caused by the doldrums local to their area. In addition to this technique, frigatebirds will fly into cumulus clouds, using the updrafts to quickly soar north. Once above the cloud, the birds will glide down for miles until reaching the next cumulus cloud. This is an unusual strategy; most bird species purposely avoid flying into clouds. Frigatebirds save a lot of energy utilizing this method and one of the tagged birds managed to fly over 40 miles without flapping its wings. The authors also noted that frigatebirds have a very low body weight, allowing clouds to carry them easily.
The researchers were surprised by these findings and are now studying how the birds sleep. They speculate that frigatebirds might catch quick naps during their effortless cloud gliding. The great frigatebird is an interesting species, breaking multiple records for seabird flight and using unique strategies to conserve energy.
Weimerskirch et al. Frigate birds track atmospheric conditions over months-long transoceanic flights. Science (2016).