Frigatebirds Can Sleep While Flying in Short Midair Naps

Frigatebirds can sleep while flying, taking brief naps of about 10 seconds as they soar over the ocean.

Biology

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Frigatebirds have an unusual solution to a basic problem: how do you sleep when you spend long periods over the ocean and cannot simply settle on the water? Research on great frigatebirds showed that they really can sleep during flight, but far less than they sleep on land. Their airborne sleep comes in very short bursts, averaging around 10 seconds, and happens mostly at night while the birds are gaining height in rising air currents. The birds can sleep with one brain hemisphere at a time while the other remains active, and they can also occasionally sleep with both hemispheres at once. Keeping part of the brain awake may help them remain aware of their surroundings while flying. The study used small recording devices that measured brain activity and movement, giving researchers direct evidence rather than simply assuming the birds were asleep. The finding is especially striking because frigatebirds can remain at sea for extended journeys, sometimes staying airborne for weeks, while their reduced waterproofing and poorly adapted feet make resting on the water difficult. The research also showed that flight sleep is much shorter and less frequent than sleep on land, suggesting that staying alert while traveling and searching for food takes priority over getting a normal amount of rest.

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