Swifts often spend 10 months in constant flight, study reveals
Common swifts often stay constantly airborne for 10 months of the year, scientists say.
Researchers attached flight activity monitors to 19 of the birds and followed them as they migrated from their breeding site in Sweden to central Africa.
They found that apart from when they were breeding, a large proportion of the swifts spent more than 99% of the remaining 10 months of the year in constant flight.
While some birds came down to earth at some point, others never did.
Flight activity was lowest during the day, when the birds were able to save energy by soaring on warm air currents.
Scientists still cannot explain how the birds sleep, but it is thought they are able to slumber on the wing - possibly during slow descents at dawn and dusk.
Lead researcher Professor Anders Hedenstrom, from Lund University in Sweden, said: "When the common swifts leave their breeding site in August for a migration to the Central African rainforests via West Africa, they never touch ground until they return for the next breeding season 10 months later.
"Some individuals may roost for brief periods, or even entire nights in mid-winter, but others literally never landed during this period."
He added: "The accumulated flight distance equals seven round-trip journeys to the moon."
Surprisingly, considering the high energy costs of so much flying, swifts have long life spans, the scientists said..
There are documented cases of common swifts living to the age of 20.
While other species such as the frigate bird are known to remain in flight for periods of months, none can match the common swift, the scientists believe.
The research is reported in the journal Current Biology.