Ducks are rather pragmatic when it comes to sleep. For them, it’s not a complete shutdown from the world around them, but more of a low-alert mode. During what is known as unihemispheric slow-wave sleep, one half of the brain can actually rest while the other remains alert to what’s happening around it. So one eye closes while the other stays open — just in case the world suddenly decides to remind them that it’s still there.
This becomes especially interesting when ducks sleep in a group. Those resting at the edge may keep the eye facing outward open, while those in the middle have less need to stay on guard. It’s a rather sensible system of collective security: the ones on the outside keep watch while the ones in the middle sleep. Then again, sometimes a duck tucks its head so confidently into its feathers that there’s simply no way to tell from the outside how alert it actually is.
Ducks can sleep on water or on land, standing on one leg or lying flat on the grass. The other leg can be tucked into their feathers, while the head is turned back and the bill rests on its back. From the outside, it all looks like a picture of absolute serenity.
In the end, a duck can sleep in practically any position — as long as some part of it is still keeping track of what’s going on.
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