The rustling and fluttering would be abrupt and startling. Dark, soundless mornings were quite often ripped open in this fashion, causing me to jump out of my skin every time.
It was some years ago, but the memories are fresh. I had a newspaper delivery route and the sleepy robotic monotony of those predawn walks was frequently interrupted by small birds suddenly flushing from bushes or other cover as I passed.
Those scenarios replayed in my mind the other day when a friend asked, “Where do birds sleep?” The question opens up a thread of thought worth discussing.
In researching this topic, I came upon an article in the Wilson Bulletin from 1945 written by A. D. Moore.
The opening paragraph reads in part, “Some birds creep into the space between loose bark and the tree trunk; some cling in trunk depressions; some pass the night in natural cavities in trees; while others chisel out their own cavities … (some) use thick bushes, vines next to buildings, or space in buildings. Other species find shelter in clumps of cattail or grass, or under clods.” That’s a fair quick-and-dirty answer. But the details, like most of nature, are where the delicious nuggets are found.
Perhaps it’s worth asking: Do birds really sleep? Yes. It turns out that every creature out there with a brain needs something resembling sleep in order to sustain life functions. But birds sleep in distinctly different ways than other organisms.
First, birds’ cycles of rapid eye movement sleep and non-REM sleep are much much shorter than ours; measured in seconds or a few minutes vs. minutes to hours in mammals.
Second - this is the cool part - a bird, like some animals, practices something called unihemispheric slow-wave sleep, meaning only half of its brain is sleeping while the other half is awake and alert to potential dangers. Birds, unlike those other animals however, are able to control how much of their brain is asleep by regulating how wide they keep their eyes open. It’s what allowed birds to immediately flush from those bushes as I once walked by. Contrast this idea with the typical slow groggy arousal we as mammals experience, the one needing two cups of coffee before we can even begin to function normally.
A tiny handful of bird species take this sleep thing to an extreme and practice something known to science as torpidity. A bird in a torpid state is one that is, for lack of a better description, hibernating. Its heart rate is reduced, its breathing and metabolism are slowed, its body temperature is greatly lowered, and its response to external stimuli is almost nonexistent. The bird most noted for this is the common poorwill, a species found in summer in the North Dakota Badlands.
Returning to the original query of where birds sleep, in general it is known as a roost. Like Moore described, roosts can occur in a variety of places, but can change with the season or even the time of day.
In broad terms, birds roost in the same general habitat where they nest. Waterfowl typically roost on the water, birds of the brush roost in the cover of brush, chimney swifts roost in chimneys, woodpeckers roost in tree cavities, and birds of the open prairie roost in the cover of grass.
Some species roost singly, others in large flocks, nearly always in winter. Locally, decent numbers of American crows can be observed settling into a tree for the night and wintering Canada geese from the Moorhead lagoons can number in the hundreds, but it’s the local flock of European starlings that impresses. Several thousand of the non-native birds call the Fargo sanitary landfill home. Yet even this pales in comparison to the historic roosts of the passenger pigeon. Gigantic - almost unimaginable - gatherings of this extinct bird once numbered in the billions and could cover hundreds of square miles.
It’s winter and deciduous trees are leafless in your neighborhood. Unless a person is looking for a hawk or eagle, those trees won’t hold many roosting birds. Most will instead be tucked in the cover of conifers or thickets of heavy brush. The birds might even be sleeping in that juniper next to your front door waiting to scare the heck out of the paperboy early tomorrow morning.
