When researchers attached advanced tracking devices to the legs of alpine swifts they weren't expecting to find the birds stayed in the air for six months straight.
"Up to now, such long-lasting locomotive activity had been reported only for animals living in the sea," Felix Liechti of the Swiss Ornithological Institute, said, New Scientist reported.
The researchers had been hoping to gain insight into the birds' energy expenditure during their migration from North Africa to their summer breeding grounds in Europe, the Smithsonian Blog reported.
"We wanted to learn about energy demands during migration. We expected to see how often they fly, how often they stop, that sort of thing," Liechti said.
When the researchers removed the alpine swifts' tags upon their return, they discovered the shocking information.
When we looked at the data, we were totally blown away," Lietchi said. "During their non-breeding period in Africa, they were always in the air."
For the entire 200 days the birds spent over Africa they never touched the ground. The chips only recorded data every four minutes, so there is a possibility that they snuck in a quick landing, but no evidence of this happening was ever recorded on the chips over the entire six month period.
This was the first time this kind of chip has ever been used to monitor birds' migration activity. The technology allowed the researchers to compare the birds' acceleration and pitch to see if they were actively flying, gliding, or resting on the ground.
The alpine swift relies on airborne plankton as a food source and have the ability to sleep in the air, which could explain how they stayed in the air for so long.
"It has been assumed that the birds 'sleep' only for seconds, or use only half if the brain while the other half is resting," Lietchi said, New Scientist reported.
Other groups have suggested that the bird doesn't sleep at all.
"Our group has shown that dolphins and killer whales remain active for at least 90 days without sleep and with greatly reduced sleep for up to 150 days after birth," Jerry Siegel, of the University of California at Los Angeles, said.
Siegel also said sandpiper birds stay awake throughout breeding season.
"What all this work tells us is that when it is adaptive for animals to remain awake, evolution allows that, so I think the idea that swifts must sleep and are therefore 'sleep-flying' is incorrect," Siegel said.
