The Incredible Flight Endurance of Common Swiftlets: How They Can Fly for Up to 10 Months Continuously

The common swiftlet (Apus apus) holds the record for the longest flight of any bird, with the ability to stay in the air for up to 10 months continuously. While humans may find a day-long flight tiring, swiftlets can spread their wings and fly for months on end without rest.

In the 1970s, Welsh ornithologist Ronald Lockley suggested that common swifts could set flight time records, but it wasn’t until decades later that researchers at Lund University in Sweden were able to confirm this. A group of scientists monitored 13 adult swiftlets by attaching tiny data recorders to them. The device contained an accelerometer to record flight activity and a light sensor to locate the bird. Some of the birds were tracked for years as they migrated from Sweden to the southern Sahara desert in winter and then returned.

The results showed that common swiftlets spend most of their time in the air, with some birds only staying on land for two months of the year while others flew continuously for 10 months. Three swifts even stayed in the air for the entire migration period, an impressive feat considering their small size, each weighing only about 40 grams.

Researchers believe that the difference between swiftlets 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, which helps them fly efficiently.

Common swiftlets have evolved to be very efficient fliers, with streamlined body shapes and long, narrow wings that generate lift with little effort. This helps them consume less energy during long flights and quickly replenish energy by eating flying insects. Scientists are still unsure if swiftlets sleep while flying or not but they do know that they can soar to heights of about 2-3 km at dusk and dawn.

Overall, the ability of common swiftlets to stay in the air for such a long period of time is a remarkable feat of evolution and adaptation.