Swifts spend ten months in the air
THINK you’re busy and spend the whole time flying around? Then spare a thought for the swift.
The bird spends an incredible ten months in the air without landing, research shows.
It only spends two months on the ground during the breeding season, although it can mate in mid-air, too. The species survives on insects caught in flight – and is even thought to sleep on the wing.
The theory that swifts spend nearly all their time aloft was first put forward in 1970.
But it has taken until now to prove it right using hi-tech gadgets to track individuals migrating between the Sahara and Sweden.
Biologists from Lund University in Sweden tracked the ‘extreme lifestyle’ of the birds as they migrated to and from the Sahara. Pro- fessor Anders Hedenstrom said: ‘This discovery significantly pushes the boundaries for what we know about animal physiology.
‘A ten-month flight phase is the longest we know of any bird species – it’s a record.’
Thirteen birds were fitted with tracking devices, some for up to two years. The device detected whether it was in flight, its acceleration, and its location.
The results, published in the journal Current Biology, showed that some birds landed for a short time at night, while three of the 13 spent the whole night in the air.
Even the birds that landed over night ‘spent 99. per cent of their ten-month migration and hibernation period in the air’. Others, presumably ones with greater stamina, spent all their time in the skies.
Incredibly, the birds that stayed aloft had moulted and gained new flight feathers. However, birds that landed did not always moult.
Professor Hedenstrom said: ‘Whether they moult could indicate small differences in their condition or burden of parasites, and explain the flight behaviour of individual birds.’
The findings create a puzzle for science: How do the birds maintain energy consumption and fly and sleep at the same time?
Professor Hedenstrom said: ‘They might do as the frigate bird and sleep while gliding. Every day, at dusk and dawn, the common swift rises to two to three kilometres. Perhaps they sleep during a declining glide.’