Birds don’t sleep in their nests. They don’t.
The mental image is a cute one - a little bird, tuckered out after an early morning of worm-getting, peeling back a tiny leaf blanket in its cozy little nest - but it’s just not the case.
Nests (for birds that even make nests - many of them don’t) are for keeping eggs and chicks in place. When nesting season is over, nests are a mess - splattered in the droppings of the fledglings and, in some cases, a dead chick. These messes can attract parasites and predators, and birds just don’t need the nests anymore.
So where do birds sleep?
Lots of places. When birds settle down to sleep, it’s called “roosting,” and the main things they’re looking for are safety and warmth.
Songbirds have to keep off the ground to avoid cats and raccoons, and out of the open to avoid owls. Dense brush or foliage does fine.
Bigger birds have more options and can sleep on the water, on a branch or even just right on the ground.
Few roosts are completely safe, though, so some birds have developed the ability to sleep with one eye open. The eyes of most birds (unlike in humans) send information to only one side of the brain.
Unihemispheric slow-wave sleep allows birds to slide one hemisphere of their brain into a deep sleep while leaving the other hemisphere awake and alert.
Birds can turn this on and off depending on how safe their roost is: For example, when a large flock of ducks is roosting on an open lake, the birds in the safety of the center of the flock can shut down completely, while the more vulnerable birds at the edge of the flock may enter the one-sided sleep to stay alert.
What’s more, scientists suspect that some birds use one-sided brain sleep to sleep while in flight.
OK, so birds don’t sleep in their nests. Let’s get more specific than that. There are a lot of different kinds of birds, and they roost in different ways. So here’s how a bunch of different families of birds prefer to roost.
Geese and ducks
A coyote would love nothing more than to run up on a big, fat, delicious, sleeping goose. Their bigness and fatness, along with their webbed feet, make it impossible for waterfowl to sleep in the safety of a tree. Most of the time, geese and ducks sleep at night right on the water.
Eagles and hawks aren’t a threat because they also sleep during the night, and any predator swimming after the birds would send vibrations through the water, waking them up.
Small islands work, too. Waterfowl also sleep on the shore, usually standing on one leg (tucking the other one up into the warmth of its feathers).
Herons and egrets
These big wading birds really have only equally large predators to worry about: alligators and eagles. Sometimes herons and egrets roost in the shallows, relying on vibrations in the water to warn them of reptiles, but they’re most often seen roosting in large flocks in waterside trees.
Shorebirds
Spending most of their time out on open beaches, birds like sandpipers and plovers are vulnerable to dive-bombing raptors even when they’re awake. Not being equipped to sit in trees or float on the water, for them sleeping is an even more dangerous proposition.
Shorebirds simply do the best they can, roosting on open beaches in large flocks (to help raise alarm) and almost certainly using one-sided brain sleep to remain alert.
Hawks, eagles and owls
You know that old joke about where the 800-pound gorilla can sit? Hawks and eagles follow the same rule: anywhere they want to. Big raptors don’t have to worry about predators as long as they’re off the ground, so they’ll usually just find a tree branch somewhere.
Owls also sleep in trees, usually during the day, either in dense foliage (to keep the light out) or, for certain species, in tree cavities.
Grouse and quail
Sleep is perhaps most dangerous for these guys - fat and juicy and, typically, with a poor ability to fly. Everything eats them. They sleep in the safest places they can find and use one-sided brain sleep and camouflage in their defense.
Birds, such as ruffed grouse, that live where there are trees, will fly up and sleep on branches. Where there aren’t trees but only smaller vegetation, birds like the willow ptarmigan will sleep in the vegetation. Where there’s nothing at all, no trees or bushes, say, and the land is covered in snow, birds like the white-tailed ptarmigan trust in their all-white plumage and nestle down on a snowy hillside.
Woodpeckers
Most woodpeckers roost in tree cavities, either ones they’ve used as nest holes or sometimes ones they’ve chiseled out just for sleeping. Lots of birds roost in tree cavities, or really any hole or covered area, for that matter. Humans have helped, creating protected nooks under roofs, bridges, barns and ledges.
Crows, swallows, swifts, starlings
These birds aren’t closely related, but they share some incredible communal roosting behaviors.
Some species, for social or safety reasons or for warmth, choose to sleep together - sometimes in gigantic flocks. The spectacle of these flocks gathering at dusk is amazing to some people, eerie to others, but impossible to look away from. Youtube.com contains clips of hundreds of crows in Maryland, thousands and thousands of tree swallows in Florida, chimney swifts wheeling into a middle school in Wisconsin, and a much-viewed starling “murmuration” in the United Kingdom.
Pretty much everything else
The bulk of the remaining birds - more than half of all bird species - are perching birds from the order Passeriformes. Classic bird-birds: sparrows, warblers, cardinals, jays, buntings, etc. For the most part, all these perching birds use dense vegetation - bushes, hedges, trees - to sleep. They just fly in at dusk, grab hold of an appropriately sized twig, and conk out.
How do perching birds stay attached to their perch while they’re asleep? Passerines have “flexor tendons” in their legs that involuntarily clasp shut when a bird squats on a perch. The tendons won’t relax until a bird straightens its leg, so a bird physically can’t leave until it’s ready. The grip is so tight that some birds, including hummingbirds, have been seen sleeping upside down.
To see a bird sleep while hanging upside down from a feeder, search Youtube for “Sleeping Torpor Hummingbird in Bellevue Tennessee.”
Looks plenty comfortable to me, and no nest required.
ActiveStyle, Pages 23 on 02/10/2014