Study shows frigatebirds can sleep while in flight

Max Planck Institute for Ornithology researchers studied frigatebirds on the Galapagos Islands reveals their research.

The Max Planck Institute is perhaps best know as a leader in theoretical physics.  There are, however, many different disciplines under the Max Planck name, including the Max Planck Institute for Ornithology.

It is well-known that some songbirds, shorebirds, and seabirds can and do fly non-stop for several days or even weeks at a time. Some seabirds may remain at sea and aloft for a month or more. The Alpine Swift can remain airborne for 6 months.  

So what about sleep? Can birds fly and sleep at the same time? If so, how do they know where they are going, how do they avoid collisions or even not just fall out of the sky?

One theory is that birds can turn off half of their brain, getting their needed rest while still able to perform basic functions like staying aloft.

Dolphins and other creatures have this ability, called "unihemispheric slow-wave sleep."

Or maybe some birds can go long periods without sleep?  

To learn more, researchers at The Max Planck Institute attached small flight data recorders to nesting Great Frigatebirds.  The birds then carried the recorder during non-stop foraging flights lasting up to ten days and 3000 kilometers (1800 miles). The data collected monitored two kinds of sleep: slow wave sleep (SWS) and rapid eye movement (REM) sleep.  The results indicated that the frigate birds sleep about 40 minutes a day while airborne - sometimes with one cerebral hemisphere asleep at a time or sometimes with both hemispheres asleep simultaneously. They seem to make up for lost sleep, if that is possible, by sleeping up to 12 hours a day when back on land.

How they can function for up to 10 days at time with so little sleep is amazing.

References:
Max Planck Institute for Ornithology - First evidence of sleep in flight