Frigatebirds – The Sleep in Flight Bird Using Unihemispheric

On their wandering flights, frigatebirds can stay aloft for up to two months without touching down on land or water. Scientists recently discovered, Great Frigatebirds can sleep in 10-second bursts while remaining airborne for up to two months.

Frigatebirds are referred to as kleptoparasites as they occasionally rob other seabirds for food, and are known to snatch seabird chicks from the nest.

Frigatebirds are a family of seabirds called Fregatidae which are found across all tropical and subtropical oceans. The five extant species are classified in a single genus, Fregata. All have predominantly black plumage, long, deeply forked tails and long hooked bills.

The males have inflatable red-coloured throat pouches called gular pouches, which they inflate to attract females during the mating season. The gular sac is, perhaps, the most striking frigatebird feature. These can only deflate slowly, so males that are disturbed will fly off with pouches distended for some time.

The word frigatebird derives from the French mariners' name for the bird La Frégate - a frigate or fast warship. The etymology of the name was given by French naturalist Jean-Baptiste du Tertre when describing the magnificent frigatebird in 1667. English mariners referred to frigatebirds as Man-of-War birds.

Nonetheless, soaring frigatebirds appeared to use unihemispheric sleep to watch where they were going while circling in rising air currents. Despite being able to engage in all types of sleep in flight, the birds only slept for 0.7 h d?1 during flights lasting up to 10 days.

Magnificent Frigatebirds range along coasts and islands in tropical and subtropical waters. They nest and roost in mangrove cays on coral reefs and in low trees and shrubs on islands. Magnificent Frigatebirds forage over warm oceans far out to sea, along the coast, and in shallow lagoons.

Forages in the air, swooping close to water to take items from on or near surface, making very little contact with water. Never swims. Forages in the same way over land, taking prey from beaches without landing. Also feeds by piracy, chasing other birds, forcing them to drop or disgorge their food.

Unlike other species of birds, they likely do not mate for life. The oldest observed frigate bird was nearly 20 years old, but their average and maximum lifespans are not known.

Magnificent frigatebirds have one of the longest mating and incubation periods of any seabird, which totals nearly 60 days. In the breeding season, male magnificent frigatebirds have a bright red throat pouch that they puff out to attract a mate.

The males have inflatable red-coloured throat pouches called gular pouches, which they inflate to attract females during the mating season. The gular sac is, perhaps, the most striking frigatebird feature. These can only deflate slowly, so males that are disturbed will fly off with pouches distended for some time.

This bird does not need much food to survive; they have also adapted to useless amount of energy, in order to need the less amount of food. Their bones are filled with air making them very light, they barely need to move their wings when flying high and are the most efficient flyers of all.

"It's the only bird that is known to intentionally enter into a cloud," Weimerskirch says.

"And not just any cloud — a fluffy, white cumulus cloud. Over the ocean, these clouds tend to form in places where warm air rises from the sea surface. The birds hitch a ride on the updraft, all the way up to the top of the cloud., according to NPR

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