Some seabirds appear to doze while flying, taking brief naps during long migrations over open water.

The longer version

Tracking devices on frigatebirds and some other seabirds recorded long flights over open water where wing beats continued while the birds showed brief quiet periods with reduced brain activity, including short bursts of one-sided slow-wave sleep. Electrodes recorded the brain directly, which allowed the researchers to distinguish quiet rest from wakeful gliding.

The recordings suggest naps of only a few minutes taken while gliding on rising air, since a bird over water has nowhere to land. Total sleep on such flights falls far below what the same birds get onshore, and they appear to recover afterwards. The measurements are technically demanding, and only small numbers of birds have been studied this way so far.

Where this entry sits

This collection gathers curious details about sleeping and dreaming, from nightly brain stages and body clocks to naps, yawns and unusual animal habits. It also covers how bedtime customs have changed across centuries, without offering any advice. The full list sits on the Sleep and Dreams page, where every entry is listed in order.