For the Birds Radio Program: Sleeping Tight
The winter solstice is the shortest day and longest night of the year, the day birds get more sleep than on any other. Most birds eat a large meal just before they go to sleep, to ensure fuel enough to keep their metabolic furnace burning during those long hours of darkness. At first light, they start shivering fiercely, which heats up their muscles and raises their body temperature. Then they quickly race to the nearest feeder or other food source to pig out. The minutes between waking up and finishing the first meal are critical. One frigid morning when I went out to fill my feeders, a tree sparrow dropped out of a tree, dead at my feet. Interestingly, on cold mornings, hummingbirds do better at feeders without perches. Their flapping wings keep their bodies warm as they fill up with cold sugar water. There are several records of hummingbirds sitting on perches during their first meal of the day, and dropping off, suffering from hypothermia.
Where do birds sleep? Many cavity nesting birds also spend their nights in cavities which are sometimes called “dormitories.” Bluebirds and tree swallows, in woodpecker holes or bird houses, snuggle together in groups, sharing body heat. But some birds are solitary at nighttime, even in winter. Woodpeckers and chickadees each sleep in their own dormitory. To survive cold nights all alone, chickadees may allow their body temperature to drop over twenty degrees while sleeping. I don’t know if some saw-whet owls sleep in cavities during winter, but I’ve found them sound asleep in the branches of spruce trees. Screech owls do sleep in their cavities, sometimes with their mate or possibly siblings, outside of the nesting season. The smaller a bird is, the more body heat is lost through the surface area.
Robins, blackbirds, and crows fly into protected stands of trees, where they roost in large numbers. Waxwings, finches, and grosbeaks sleep in branches, too, often shoulder to shoulder to conserve heat. Brown creepers snuggle together in a sheltered part of a tree trunk. Hawks and eagles usually sleep alone. All these birds are most often found in conifers, which provide much more shelter from the elements and from predators than winter’s leafless deciduous trees.
Ducks and geese often sleep on shore, but during severe cold, they’re more likely to sleep swimming, in open water that is never colder than 32 degrees.
How do birds sleep? Most northern birds tuck their beaks into the feathers on their backs, making their bodies as spherical as possible, to reduce heat loss. While sleeping, they fluff up their down feathers. A sleeping chickadee looks surprisingly like a fuzzy golf ball with a spike tail.
Some birds sleep very soundly, but others wake at the tiniest sound. When I was rehabbing birds, I noted that chickadees were very difficult to rouse at night. Crows, on the other hand, were almost impossible to catch in the act of sleeping. No matter how softly I would creep into a room, a crow always had its eyes open, and followed my movements in the darkness. Yet despite their alertness, crows are shockingly docile at night. Whenever I had to administer medicine or re-bandage a wing for a crow, I’d wait until dark. One of my children would hold a flashlight while I worked. and even the bravest. fiercest crows always let me work without resisting at night. A few weeks ago, my neighbor went out on her deck and threw some cooking water into her backyard. Suddenly she heard a crow cawing and flapping. This is the first time I’ve ever heard of any crow activity at nighttime.
Do birds dream? No one knows for sure. but it’s likely that they do. Many songbirds have been discovered to learn (and even practice) their songs while sleeping. But whether they dream or not. they awaken refreshed, facing the new day with song and activity, without even a cup of coffee needed to start their engines.