Crows often get a bad rap. In many Western cultures, they’ve been associated with death, disease, and bad omens. Farmers accuse crows of stealing crops and city dwellers consider them a nuisance. But the birds are fascinating creatures, adaptable and brainy to an extent that’s almost scary. Here are a few facts about these crafty corvids that might surprise you.
1. All crows and ravens belong to the same genus.
Members of the genus Corvus can be found on every continent except Antarctica and South America (although other close relatives live there). To date, scientists have identified 40 species that are commonly called ravens, crows, rooks, and jackdaws.
In the U.S., the American crow (Corvus brachyrhynchos) and the common raven (Corvus corax) are the most widespread corvids. The common raven is much larger, about the size of a red-tailed hawk. It also has a wedge-shaped tail compared the crow’s slightly rounded tail. And the birds’ calls are different: crows emit a caw-caw call along with rattling and clicking sounds, while a raven’s is a croaking, deeper-pitched onk-onk.
2. Older crow siblings can help their parents raise newborn chicks.
Like a lot of intelligent animals, most crows are quite social. American crows spend most of the year living in pairs (they usually mate for life) or small family groups. During the winter months, they’ll congregate with hundreds or even thousands of their peers to sleep together at night in a sprawling communal unit called a roost.
A mated pair of crows might be lucky enough to receive chick-rearing help. Juvenile birds are frequently seen defending their parents’ nest from predators. Other services they can provide include bringing food to the parents or feeding their younger siblings directly. One study found that 80 percent of American crow nests surveyed had a helping hand. And some birds become regular nest assistants, providing aid to their parents for over half a decade.
3. When a crow dies, its neighbors may have a funeral.
The sight of a dead crow tends to attract a mob of a hundred or more live ones. During this ritual, the live crows almost never touch the dead one, which rules scavenging out as a motive. Some studies suggest that the mass gathering is part of a survival strategy: The birds are learning about threats and seem hesitant to revisit any spot where they’ve encountered a dead crow, even if food is plentiful there.
4. Crows have caused blackouts in Japan.
Since the 1990s, crows have experienced a population boom in Japan, where delicious garbage is more plentiful than ever. Urban crows like to nest on electric transformers and will often use wire hangers or fiber-optic cables as building materials for their nests. One result was an epidemic of crow-caused blackouts in major cities: Between 2006 and 2008, the corvids stole almost 1400 fiber-optic cables from Tokyo power providers, and according to the Chubu electric company, crows are responsible for around 100 power failures per year in their facilities.
Chubu started installing artificial nests in 2004. Made with non-conductive resin, the nests are placed on company towers high above the power lines, where the birds are unlikely to cause any trouble. The strategy seems to be working: two-thirds of the faux nests have been used.
5. Proportionally, some crows’ brains are bigger than yours.
Crows are so smart and so good at improvising that some zoologists call them “feathered apes” (that’s a compliment). The New Caledonian crow’s brain weighs 0.26 ounces and accounts for 2.7 percent of its overall weight. That’s proportionately much larger than a human’s three-pound brain, which accounts for 1.9 percent of overall weight.
Crows, ravens, and parrots have the biggest brain-to-body size ratios of all living bird species. They’ve shown levels of cognition that put them on par with the great apes. In lab tests, they have shown a much higher density of neurons in their forebrains than primates do. The number of neurons in this region is thought to correlate with a given animal’s intelligence. Theoretically, having more neurons translates to better cognitive reasoning.
A 2020 study looked at whether crows, like humans and great apes, can demonstrate consciousness. Crow brains lack a cerebral cortex, where most of the primate brain’s conscious perception happens. Researchers tracked the brain activity in two crows as they performed different tasks, and discovered that they could perceive sensory input—suggesting that there is much more to understand about the evolution of consciousness.
6. Crows have regional dialects.
Apart from their famous caw-caw, crows emit other sounds. Each one sends out a different message; cawing can be used as a territorial warning or a way for crows to signal their location to relatives.
Two different populations of crows may have slight differences. As ornithologist John M. Marzluff and author Tony Angell noted in their 2005 book In the Company of Crows and Ravens, the calls these birds use “vary regionally, like human dialects that can vary from valley to valley.” If a crow changes its social group, the bird will try to fit in by talking like the popular kids. “When crows join a new flock,” they write, “they learn the flock’s dialect by mimicking the calls of dominant flock members.”
7. Some crows can read traffic lights.
In Japan, carrion crows (Corvus corone) use cars like oversized nutcrackers. The birds have learned to take walnuts over to road intersections, where they put them down onto the pavement. The crow then waits for a passing vehicle to smash the nut, after which it will swoop down and eat the delicious interior.
The crows aren’t usually run over because (unlike some people) they’ve figured out what traffic lights mean. Carrion crows wait until the light turns red before flying down to place the un-cracked nut on the road. The second the light goes green, the crow takes off to watch the nut get run over from afar; it will even wait for the next red to scoop up the nut’s meat. American crows have been observed doing the same thing in California.
8. Crows can recognize your face—and hold a grudge.
You don’t want a crow for an enemy. In a 2011 paper, a team from the University of Washington tested how well the birds could identify human faces using two Halloween masks (one resembling a caveman to be used as the aggressor, the other resembling Dick Cheney for the control).
At five sites, a scientist donned the caveman mask before catching and banding some wild crows. Getting trapped is never a fun experience, and upon their release, the crows loudly scolded their assailant with threatening caws. Seeing this, other birds swooped down to harass the captor. Over several years, researchers wore the masks on strolls through all five test spots. The crows—including many who’d never been captured or banded—scolded and dive-bombed the “caveman” while ignoring “Dick Cheney”.
The younger crows, who were born after the initial experiment, also scolded the “caveman.” The grudge had been passed on. Mind your manners around crows. Because if you mistreat them, they won’t forget you and neither will their friends—or the next generation.
9. New Caledonian crows make and use tools.
Lots of non-human animals, including chimpanzees and orangutans, create useful implements which help them survive in the wild. The New Caledonian crow (Corvus moneduloides) is one of only two species on the planet that can craft its own hooks in the wild. (The other is Homo sapiens.) The South Pacific crow uses the hooks, which are made from pliable twigs that the crows bend using their beaks and feet into a J-shape, to extract insects from tight crevices.
Another surprising attribute is this species’ bill. Unlike virtually all other birds, the New Caledonian crow has a bill that does not curve downwards. For years, the quirk went unexplained, but scientists now think that their unique beak evolved to help it grasp tools more easily, as well as to better see what the tool is doing.
The New Caledonian crow isn’t the only implement expert in the corvid family. In 2016, scientists at the University of St. Andrews demonstrated that the ultra-rare Hawaiian crow, or ‘Alalā (Corvus hawaiiensis), is similarly adept at using and modifying tools.
10. Crows fight off predators by ganging up on them.
Crows have to deal with a menagerie of predators, such as hawks, owls, coyotes, and raccoons. To ward them off, the corvids exploit the fact that there can be strength in numbers. Upon seeing a would-be attacker, crows are known to gather, with some groups consisting of a dozen birds or more. Individual crows then swoop down to deliver passing blows with their beaks, often inflicting serious bodily injury in the process. If all goes well, the target will back off—though it may kill a few of the dive-bombers before they retreat. Corvids are by no means the only avians that mob would-be attackers. Swallows, chickadees, and even hummingbirds have all been documented doing this. In fact, crows are sometimes at the receiving end of mob violence as smaller songbirds often feel threatened by them and lash out collectively.
11. Crows understand impulse control.
A 2014 study shows that at least some corvids can resist the urge for instant gratification—if you make it worth their while. The research was led by University of Göttingen graduate student Friederike Hillemann, whose team assembled five common ravens and seven carrion crows. Through careful note-taking, the scientists figured out what the favorite meal items of all 12 animals were. Then the experiment began.
With an outstretched hand, one of the researchers gave each of their birds a morsel of food. Then, the animals were shown a different piece of grub. The corvids were made to understand that if they liked the second option better, they could swap snacks—but only if they were willing to sit patiently for a certain period of time first. If a bird ate the original treat during that stretch, it forfeited the chance to trade it for a new one.
Hillemann’s results showed that the crows and ravens didn’t mind waiting around for an improved snack option. As such, a bird with a piece of bread was content to sit quietly if it knew that some fried pork fat would eventually be gained in the trade-off. However, if that same bird’s second choice was another piece of bread, sitting tight would be pointless. So understandably, corvids who were put in this kind of situation tended to go ahead and eat whatever they’d been given. Why wait for more of the same?
12. Some scientists would prefer you not call a group of crows a murder.
According to the Oxford English Dictionary (OED), the correct term for a group of crows is a murder, an expression bird-watchers and poets have been using since at least the 15th century, which the OED speculates may allude “to the crow’s traditional association with violent death, or … to its harsh and raucous cry.” But maybe it’s time to come up with a replacement. Ornithologist Kevin McGowan hates the phrase murder of crows. To him, it only feeds the public’s negative outlook on the animals. “These birds aren’t a gang of nasty villains,” he tells Sy Montgomery in her book Birdology. “These birds are just birds.”
A version of this story ran in 2017; it has been updated for 2023.