The sun has set on the quad, and naturally, I am beneath a blanket of American crows.
Not literally, of course. But crows crowd the trees so closely that it almost looks like spring leaf-out has come early this year. And the air is filled with their sounds – the squawks, rustles, and wingbeats. To see so many of them in one place – thousands – is astounding. I am nothing short of awed.
Of course, not everyone feels this way. Walking back to my dorm, I hear one student exclaim to another: “It feels like a bad omen has come across campus!” And I understand. Crows, dark, strangely intelligent birds, can be a bit menacing. Historically, they’re associated with witches, dark magic, and death, partly because they’re opportunistic scavengers and partly because their calls sound oddly human.
But the Bates crows are not here to summon evil and pestilence across us all. Rather, they’re involved in a pretty common physiological phenomenon: roosting.
“Roosts are places where anywhere from a small handful to hundreds of thousands of individuals may converge to spend the night together,” Dr. Kaeli Swift, corvid expert, wrote in 2017. Swift said that roosting provides crows a safe place to sleep, especially in winter when the birds don’t have nests of young.
Crows are members of the corvid family, which also includes ravens, jays, magpies and several other groups. Corvids are characteristically smart among their bird cousins, with a brain-to-body-size ratio similar to that of a chimpanzee, according to one 2005 study. Crows, for instance, have been observed to use tools, a trait once thought to be singularly human.
And, though we may not understand it, crows have their own language that is composite and complex. If you listen, you’ll recognize different calls. While roosting, the crows often utter a guttural sound that sounds like a stick on a washboard: “k-k-k-k.” Likely as a form of communication between each other, American crows also sound the iconic “caw” (Maine’s other species, the fish crow, virtually indistinguishable visually, sounds a nasal, backwards “wac-wac”).
Observe the crows for a few minutes, and you’ll notice that while the bulk of them are motionlessly resting, some are alert, with necks constantly on a swivel. Unlike humans, who experience REM (rapid eye movement) deep sleep in periods of up to an hour, birds can achieve REM sleep in just ten seconds. This allows them to sleep in bursts and still stay alert to their surroundings, cycling between who’s on the lookout. This is why you still hear the crows even after they’ve roosted for the evening: some are always awake and on alert.
By communicating so closely and watching out for each other in large numbers, crows can stay safe from threats.
“For crows, roosts act in large part as predator protection,” Swift wrote. “The odds of successfully fleeing an incoming owl are much better when there are thousands of you, rather than just you and your mate.”
You can observe this yourself by watching crow roosts. Even the smallest of triggers – a broken twig, a lit phone screen below, a shout from across the quad – triggers a massive exodus of crows from a treetop. Often, the birds circle and re-land nearby or in the same spot.
Some threats we cannot see or hear ourselves. Maine-native predator barred owls, for example, are nearly silent on the wing and challenging to see at night. The crows are vulnerable to this obliviousness, too, but the more eyes and ears, the better.
There are many other reasons for roosting in vast numbers, including spreading information on food and other resources and preserving warmth, Swift noted. The roosts are particularly large in winter in part because crows don’t have to sit on a nest then, permitting them to gather in larger numbers. The largest of these roosts can number in the hundreds of thousands or even millions of crows.
“This kind of mass sleepover…isn’t unique to crows, but it certainly captures our attention in ways most other birds don’t,” Swift wrote.
The crows may choose Bates for a variety of reasons: perhaps it is the high viewpoint Mount David offers, or the relatively thin tree cover of the quad. Whatever it is, the birds choose Bates as a central roosting point every year.
While the birds may be loud, and occasionally messy, they’re not here to cause us harm – just to survive the cold Maine winter (which I suppose we’re all trying to do). People are legally barred from disturbing birds such as American crows by the Migratory Bird Treaty Act, which protects most native birds in the U.S. So, since there’s nothing to do about them but watch, why not enjoy the magnificence of hundreds of black dots in the sky, swooping between the clouds in tandem?
And while you stare up among rustling branches of wings, perhaps ponder: why so much hatred for the crows? With such complex intellect and companionship, they ought to fit well into our Bates community.
