Whether you’re a birdwatcher or not, you don’t have to go far to find American Crows (Corvus brachyrhynchos), arguably the most familiar bird species in North America.
Although these big, glossy black birds are common in fields and woods, they also thrive near human-altered habitats – from suburban backyards and parking lots to roadsides, city parks, golf courses, and garbage dumps.
Along with jays, magpies, rooks, and ravens, crows belong to the bird family Corvidae, a group of over 120 species.
In the Lowcountry, American Crows are year-round residents, along with Fish Crows, which look nearly identical but are more common near water. One way to tell the two apart is by their calls: the “caw” of Fish Crows is higher-pitched and more nasal.
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Both kinds of crows know how to make a lot of noise. And their vocalizations aren’t exactly melodic.
In the case of American Crows, scientists have begun to analyze their extensive vocal repertoire, which comprises various types of caws, along with assorted grunts, rattles, clicks, and murmurs. Crows also mimic the sounds of other animals, including humans, and different populations may exhibit regional “dialects.”
Certain vocalizations seem to have specific functions – to advertise a food source, for example, or to signify distress. It’s not uncommon for a flock of crows to “mob” a hawk or other potential predator, amidst a raucous din of alarm calls summoning other crows to the scene.
Although much remains to be learned, the large and varied vocabulary of American Crows is clearly key to a complex array of social behaviors.
During the breeding season, for example, the birds exhibit “cooperative breeding.” Offspring may stay with their parents for several years, helping them rear successive broods of young – in other words, their younger siblings.
Outside of the breeding season, these family units may join larger groups, and huge numbers of crows may gather together in noisy roosts.
Like other corvids, American Crows have large brains relative to their body size. Recent scientific observations, along with countless anecdotal accounts, have highlighted their intelligence, curiosity, and capacity for learning.
For example, crows can recognize individual human faces, form lasting memories, and pass this knowledge on to other birds.
In a notable series of studies at the University of Washington, researchers wore “caveman” masks while they captured, banded, and released some of the American Crows on campus. Afterward, the scientists were repeatedly mobbed and “scolded” by crows whenever they wore those masks again.
The harassment came not just from the birds that had been banded, but also, apparently, from other crows that had merely witnessed the disturbing event. The flock’s aversion to the caveman face persisted years after the original banding incidents, as additional birds joined in the mobbing scenes and learned to recognize this particular “enemy.”
Crows also demonstrate learning and versatility while foraging. American Crows eat a wide variety of foods, from seeds and fruits to earthworms, insects, spiders, snails, mice, frogs, carrion, and the eggs and young of other birds. They’re also adept at raiding trash cans and pilfering tidbits from the picnic lunches of unsuspecting humans.
Scientists have found that American Crows in urban California display fine-tuned strategies while feeding on walnuts, which they drop repeatedly from considerable heights to crack the shells. The birds drop black walnuts, which have hard shells, from greater heights than they use for English walnuts, which are easier to break. The birds also use higher drop heights over soft, grassy areas than over pavement.
And some corvids, such as New Caledonian and Hawaiian Crows — close relatives of our Lowcountry species — have taken foraging tactics to a new level of sophistication. These birds extract prey from wood crevices with the aid of small sticks – in other words, tools.
Vicky McMillan, a retired biologist formerly at Colgate University,lives on Hilton Head Island. She can be reached at firstname.lastname@example.org.