The common swiftlet (Apus apus) holds the record for the longest flight with the ability to stay in the air for 10 months continuously .

Traveling nearly a day by plane is a tiring long-distance flight for humans, but that is nothing compared to the capabilities of the common swift ( Apus apus ). Many people will start to feel uncomfortable after just a few hours of flying, even if they just sit still. However, swiftlets can spread their wings for 10 months to fly continuously in the air.

Common swiftlets have the ability to fly continuously for 10 months. (Photo: Dilomski).

As far back as the 1970s, Welsh ornithologist Ronald Lockley suggested that common swifts could set flight time records. But it was not until decades later that a group of researchers at Lund University, Sweden, were able to confirm this. The study was published in the journal Current Biology in 2016.

A group of scientists monitored 13 adult swiftlets, attaching them to tiny data recorders. The device contains an accelerometer to record flight activity and a light sensor to locate the bird. Some of the birds have been tracked for years as they migrate from Sweden to the southern Sahara desert in winter and then return.

The results showed that common swiftlets spend most of their time in the air. The tracked birds only stay on land two months of the year, settling in to breed. Although some occasionally land a little during the remaining 10 months, their flight time still accounts for more than 99.5%. The three swifts stayed in the air for the entire 10 months of migration, an impressive feat considering their small size, each weighing only about 40 grams.

Researchers believe that the difference between swifts that fly long distances and those that land may lie in their plumage. Birds that land do not change their wing feathers, while those that fly continuously lose their feathers and grow new flight feathers (long, stiff feathers on the wings and tail that help birds fly).

“The presence or absence of molting reveals small differences in overall condition or parasite problems, and also explains the flight behavior of each individual within the species,” explains study author Anders Hedenström .

Researcher Anders Hedenström calls these data recorders “mini backpacks”. (Photo: A. Hedenström)

How can the swiftlet stay in the air for so long? Physical activity consumes energy, but the animals have adapted to use relatively little energy during long flights.

“Common swiftlets have evolved to be very efficient fliers, with streamlined body shapes and long, narrow wings that generate lift with little effort,” Hedenström explains. This helps the bird consume less energy. In addition, they can quickly replenish energy by eating flying insects.

For humans, in addition to in-flight snacks, sleeping is also a way to recharge. But scientists are not sure exactly whether swiftlets do the same thing or not. “They can act like sea cormorants and sleep while flying. Every day, at dusk and dawn, swiftlets fly to a height of about 2 – 3km. They probably sleep while flying down, but we not sure,” Hedenström said.