Do Birds Sleep?
Have you ever wondered what happens to birds at night? Where do they go? What do they do? Do birds really sleep?
The answer is yes…but it’s a little more complicated than that. Birds have several techniques for when they need to get a little shut-eye. Check out some of these below!
Day flyer or night rider?
If you’ve ever seen an owl, then you may know that some birds prefer to fly primarily at night. Nocturnal birds, like owls and nighthawks, wake up as the sun sets and hunt at night. During the daytime, they find a safe place and close their eyes to block out the light. By contrast, most birds are diurnal, meaning they’re awake during the day and asleep at night. These species will find something to perch on, like a branch or a windowsill, for the night. Then, the bird will fluff out its down feathers, turn its head around, tuck its beak into its back feathers, and pull one leg up to its belly before falling asleep. Sounds uncomfortable, right?
Actually, it’s quite warm for the snoozing bird. Down feathers, the short fluffy feathers under the sleek outer ones, hold in heat. The bare parts of the bird (the beak and the legs) are tucked in to keep warm under the thick blanket of feathers as temperatures drop for the night.
Won’t birds fall off their perch as they sleep?
Actually, it is very unlikely that roosting birds will fall from their perch. When the bird places weight on its feet, the muscles in the leg force the tendons of the feet to tighten, keeping the foot closed. This gives the bird a vice-like grip around any branch it may be resting on, so the bird doesn’t slip off.
Not all birds sleep on branches however. Waterfowl and shorebirds sleep near the water. Ducks often stand at the water’s edge or on a partially submerged stick or rock and tuck one foot into their body, much like birds do on perches. Wherever birds can get a good footing, they tuck themselves in for a rest. Chimney Swifts have been documented resting when clinging to the insides of chimneys!
No rest for the feathered!
With so much to worry about— the cold, predators, noisy neighbors— how do birds get a good night’s rest?
Well…they don’t, at least not in the way humans think of a good night’s sleep. Unless they are in a state of torpor, birds tend to sleep in small snatches until startled awake either by a predatory threat, neighbor, or cold conditions.
Some can even sleep with one eye open, as half of their brain is alert while the other is asleep. This is called unihemispheric slow-wave sleep (USWS) and it allows the sleeping bird to spring into action quickly from rest if a threat approaches while still being able to satisfactorily rest if no threat arises. Ducks and waterfowl are particularly good at this, though other birds such as Peregrine Falcons and Eurasian Blackbirds can do this as well. Species that use this adaptation may even be able to sleep while flying!
Migrating birds may also rely on USWS to rest. The long migration flights of many species don’t allow for many chances to stop and rest. But a bird using USWS could both sleep and navigate at the same time. There is evidence that the Alpine Swift can fly non-stop for 200 days, sleeping while in flight!
Kind of makes you wish you could sleep like a bird, doesn’t it?