Birds Asleep

Night is a dangerous time for birds and many are only half asleep. A bird’s life after dark is hidden from human view, and birds work hard to keep it that way. It’s rare to encounter a sleeping bird, since most are careful to cover their tracks on the way to and from their well-hidden sleeping spots.

Many birds become nervous, even fearful, as dusk approaches, because nighttime is a dangerous time for them. Their daytime vigilance is necessarily lowered as they slumber, leaving them extremely vulnerable to predators. Owls and other creatures that work the night shift are always on the lookout for a quick meal, and a sleeping bird is an easy target.

Birds are careful to select sleeping quarters that offer protection from predators (and weather). Not surprisingly, many birds roost at night in habitat similar to their nesting sites. Outdoor-nesting songbird, such as cardinals, catbirds and robins, lock their feet onto tree branches or twigs in dense shrubbery and doze away the night. Cavity-nesting birds like woodpeckers, chickadees and nuthatches, snooze in tree holes. Some birds that nest on the ground sleep there as well, including meadowlarks, white-throated sparrows, towhees and juncos.

Chimney swifts swirl down into tall chimneys or hollow trees, while many ducks float on water during the night, slowly paddling in place. Crows and other blackbirds gather in large groups, roosting together at the tops of trees. The northern bobwhite has one of the most fascinating sleeping styles in the bird kingdom. These small quail gather in a circle on the ground, heads out and tails in, ready to launch themselves into flight if a fox approaches.

Half Sleep

How deeply do birds sleep? Studies show that many species can sleep with one eye open and half their brain awake. Like marine mammals, they seem able to control this “half sleep” that allows them to remain at least partially alert for danger. They can switch between brain hemispheres to give one half a rest, then turn both off to enter full sleep if they feel safe.

During migration, most songbirds travel at night, which creates a major sleep deficit. They compensate by taking numerous small “power naps” during the day, most only a minute or two in duration. A few birds in the swallow family may even sleep while coasting in the air.

Some birds “talk” in their sleep, and some silently rehearse their species’s song repertoire while sleeping (brain tracking revealed this activity). Often, young birds will sleep bunched up on a branch with their siblings for the first few weeks after fledging, re-creating the shoulder-to-shoulder contact they experienced in the nest.

There’s still a great deal to learn about the sleeping life of birds. We do know that the amount they sleep varies with the seasons (longer sleeps on winter’s long nights) and that migration and nesting seasons push them to the brink of exhaustion.

A bird’s primary goal, as it heads into a tangle of shrubs, a tree hole, or leaf pile to spend the night, is waking up to greet the morning. Birds increase their odds by carefully selecting their sleeping quarters—and coming and going without attracting attention.

Sleep Aids

We can help birds get a good night’s sleep by providing a variety of places to roost in our backyards. Cavity nesters will use roost boxes attached to trees or posts. Find one at a wild bird store or check the Internet for building plans.

Plant evergreens, a great source of shelter in all seasons. Arborvitae shrubs and trees are a good alternative for yards that lack space for a full-sized conifer.

Build a brush pile from tree branches and twigs for shelter, the denser the better. In northern regions, snow accumulates on the pile, creating a “bird igloo.”

Leave nest boxes out at all seasons, since some birds will use them as nighttime roosts after the breeding season.

Val Cunningham, St. Paul MN. Val leads bird hikes for the St. Paul Audubon Society; writes about nature for local, regional and national newspapers and magazines; and can be reached at valwrites@comcast.net.