Do birds fly for days while over the ocean? How do they sleep?
In: Biology
Scientists have found that migrating birds can fly for 200 days straight, eating and sleeping while soaring through the sky.
The species the researchers studied is the Alpine swift, a swallow-like bird found in Europe, Africa, and Asia. Some of the swifts breed in Switzerland, then wing their way across the Sahara to Western Africa for the winters.
Based on radar data, scientists “have claimed that some swifts may stay on the wing for almost their whole lifetime except for breeding,” the study authors write in Nature Communications. But, they add, “no data are available at the individual level confirming such long-lasting flights so far.” Long flights aren’t unheard of among birds: Sea birds, for example, may fly for days at a time while searching for food.
To find out the swifts’ endurance limits, the team caught six Alpine swifts in Switzerland and tagged them with data loggers. The devices recorded information about light levels (which helped the researchers determine the birds’ locations) and acceleration (which provided information on activity levels). After the birds migrated to Africa and back, the researchers caught three of them and tried to reconstruct the birds’ flight patterns.
The team found that the birds tended to flap their wings more at dawn and dusk during the winters. But the most impressive finding was that the swifts appeared to fly nonstop when they weren’t breeding. According to the study, this is the first time that scientists have shown such sustained activity in a non-marine animal.
The swifts eat bugs in mid-air, so that explains why they don’t starve. But the results “raise the question of how or whether these birds sleep,” the authors write. The swifts’ activity appeared to rise and fall during flight, and the researchers speculate that the birds might still be able to control their flying while sleeping. The team concludes that “swifts do at least to some extent sleep while airborne.” — Roberta Kwok | 11 October 2013
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