Intelligence runs in the crow family, a diverse group of more than 120 bird species. And, as with most geniuses, crows and their relatives tend to be misunderstood.
Known as corvids, this family of birds includes not just crows, but also ravens, rooks, jays, jackdaws, magpies, treepies, nutcrackers and choughs. They range from the 1-ounce dwarf jay, a small forest bird found only in Mexico, to the 3-pound common raven, a wily opportunist found across the Northern Hemisphere.
Corvids are incredibly clever overall, with the largest brain-to-body-size ratios of any birds, but those in the genus Corvus tend to be especially brainy. This genus includes the crows, ravens, rooks and jackdaws, accounting for about a third of all corvid species. Many of these have a brain-to-body-size ratio (or "encephalization quotient") you'd expect from an ape, not a bird. In fact, according to one study, "the crow brain is the same relative size as the chimpanzee brain."
Humans have long recognized the craftiness of crows and ravens, as seen in centuries of folklore casting the birds as thieves, tricksters, problem solvers, wise advisors to gods or even deities themselves. Yet we also tend to stereotype these birds, overlooking many of their complexities to brand them as spooky, troublesome or outright nefarious. Fortunately, our appreciation of their intelligence has soared in recent years, thanks to research exploring what corvids can do with all that brainpower. Below is just a sampling of what we've learned about their mental and social lives, focusing mainly on crows but also including ravens and other relatives:
1. Crows have shrewd ways to get food.
Crows tend to be opportunistic and creative, commonly exploiting new food sources or adopting new feeding strategies to make their lives easier. The American crow is known to catch its own fish, for example, in some cases even using bread or other food as bait to lure fish closer, as captured in the video below.
At the same time, this species often steals food from other animals, sometimes even secretly following victims back to their nests or food caches. In one case, a group of American crows was seen distracting a river otter so they could steal its fish, according to the Cornell Lab of Ornithology, while another group followed common mergansers to intercept minnows the ducks had been chasing into shallow water.
Many crows also drop snails and hard-shelled nuts from the air while flying, using gravity and the ground to do the hard work for them. This is done by other birds, too, but some crows seem to have taken this a few steps further. Crows in Japan, for instance, place walnuts on roads so cars will crush the shells, then wait for the traffic light to change so they can safely collect the opened nut.
2. Crows don't just use tools; they also make them.
In the early 1960s, primatologist Jane Goodall shocked the world with her discovery that wild chimpanzees use twigs as tools to catch termites, debunking the idea that humans are the only tool-using species. Tool use does require a certain level of cognitive sophistication, but we now know lots of other animals also use tools in the wild, and not just our fellow primates. In fact, one of the most studied examples of non-primate tool use comes from a corvid: the New Caledonian crow.
Many corvids use tools, but New Caledonian crows are especially advanced. Like chimps, they use sticks or other plant matter to fish insects out of crevices. That alone is impressive, especially without hands, but it's just one of many tricks up their sleeves. In addition to choosing tools that are naturally well-shaped for a particular task, New Caledonian crows also manufacture tools in the wild, which is much rarer than just using found objects. This ranges from trimming the leaves off a stick to creating their own hook-shaped tools from twigs, leaves and thorns.
In controlled experiments, New Caledonian crows have also bent pliable materials into hooked tools, and even shown spontaneous "metatool use" — the ability to use one tool on another. Great apes like chimps and orangutans can solve metatool tasks, researchers noted in one study, but even monkeys are known to struggle with them. These crows have used a short stick to reach a longer stick that can reach a reward, for example, but have also made new compound tools from two or more otherwise non-functional elements. As one of the study's authors told the BBC, that requires imagining what a tool will do before it exists, then making it exist.
"They have never seen this compound tool, but somehow they can predict its properties," said Alex Kacelnik, professor of behavioral ecology at the University of Oxford. "So they can predict what something that does not yet exist would do if they made it. Then they can make it and they can use it."
3. Crows can solve puzzles on par with human kids.
In Aesop's Fable "The Crow and the Pitcher," a thirsty crow encounters a pitcher with a little water in it, but is initially thwarted by the low water level and the bottle's narrow neck. Then the crow starts dropping pebbles into the pitcher, however, eventually raising the water level high enough for it to drink.
Not only has research verified that crows can do this, but it shows they can pass the water-displacement test at a level similar to human children between the ages of 5 and 7. Crows have conquered a variety of other convoluted tests, too, like the eight-step puzzle in this BBC video. They can also plan their tool use, according to one recent study in the journal Current Biology, which found crows could solve a metatool problem when each step was out of sight of the others, planning ahead three behaviors into the future. The birds showed an ability to "mentally represent the goals and sub-goals of metatool problems," the researchers wrote, and even successfully ignored an extra tool that was planted in their path to distract them.
4. Crows hold funerals for their dead.
Crows are famous for holding "funerals" when one of their kind has passed away. It might be a lone individual or a group of crows — known as a murder, of course — and it may be solemnly quiet or cacophonous. In some cases the crows may keep a vigil over the fallen bird for days on end. Could they really be mourning?
Maybe, explains Kaeli Swift, a postdoctoral researcher and corvid expert at the University of Washington. As Swift writes on her blog, although she holds "little doubt that they have emotional intelligence," testing this possibility remains scientifically problematic, since "there's still no way we can truly know what's happening on an emotional level in an animal's head."
So, without necessarily ruling out grief, Swift and other researchers have focused more on "danger learning" as a likely motivator for corvid funerals. "If I were to find a dead person in the woods I might be feeling sad, but I'd also be alarmed and likely looking for the cause of death to make sure I'm not next," Swift writes. "Perhaps the crows are doing the same thing, looking for the source of danger and remembering key elements of the experience that will help keep them safe in the future."
5. Crows gossip, hold grudges and know who you are.
Several kinds of corvids have demonstrated a knack for recognizing human faces. Magpies and ravens, for example, are both known to scold specific researchers who have gotten too close to their nests in the past, regardless of what the researchers wear. Some of the best evidence of this ability comes from crows in Washington state, where Swift and her colleagues have done extensive testing on the birds' reactions to human faces they've learned to distrust.
Led by John Marzluff, a professor of wildlife science at the University of Washington, the testing was born from the realization that crows seem to hold grudges against specific people who'd netted and banded them for research. Researchers began wearing a rubber caveman mask when they did this, which revealed how the crows were identifying their enemies. Crows scolded and mobbed anyone who wore the caveman mask, regardless of who was actually underneath. In later tests, researchers achieved a similar effect by wearing masks while holding a dead (taxidermied) crow, which resulted in crows pestering future wearers of those same masks. "The interesting part was that not a whole lot mattered except the face," Marzluff told the National Wildlife Federation (NWF).
When wearing masks to test crows, researchers also carry signs that explain what they're doing for any curious (or nervous) human bystanders. (Photo: Willamette Biology [CC BY-SA 2.0]/Flickr)
Lots of other animals can also recognize human faces, but crows still stand apart, both for the length of their memories and for how they share information among themselves. Years after the study began, crows "continue to harangue the banding mask," the NWF explains, "even though they see it only twice a year for a few hours at a time." But this animosity isn't just from crows who saw the original banding event. The percentage of birds scolding and mobbing the caveman mask grew over time, roughly doubling within seven years, even though most had never been banded and were unlikely to have personally witnessed the mask doing anything offensive. Some were even young crows not born yet when the grudge began. The crows are apparently transmitting important information — the identity of a seemingly dangerous person — to their families and companions.
As Kat McGowan wrote for Audubon Magazine in 2016, "Nearly all of the birds originally trapped by the caveman are likely dead by now, yet the legend of Seattle's Great Crow Satan still grows."
Learning to identify humans could be a valuable skill for urban crows, since some of us are dangerous, some neutral and some helpful. Wild crows seem largely indifferent to the faces of people who haven't wronged them, and can also form positive relationships with us — like the girl in Seattle who famously received a collection of trinkets from the crows she'd been feeding.
6. Crows mate for life, but they're also 'monogamish.'
Crows are not only social birds, but also more family-oriented than many people realize. They mate for life, meaning a mated pair will typically stay together for the rest of their lives, but their family lives may also be a little more complicated than that suggests. Crows are "monogamish," Swift writes, adding a more scientific clarification that they're considered "socially monogamous but genetically promiscuous." This means they generally stay with one partner for life, but genetic analyses show that male crows only father about 80% of their family's offspring.
Some crows also lead a "double life," according to the Cornell Lab of Ornithology, splitting time between their families and big communal roosts. American crows maintain a territory year-round, for example, where the entire extended family lives and forages together. "But during much of the year, individual crows leave the home territory to join large flocks at dumps and agricultural fields, and to sleep in large roosts in winter. Family members go together to the flocks, but do not stay together in the crowd. A crow may spend part of the day at home with its family in town and the rest with a flock feeding on waste grain out in the country."
7. Young crows may stay home for a while to serve as 'helpers.'
American crows start to nest in early spring, building their nests from sticks and lining them with soft materials like grass, fur or feathers. (They may also build decoy nests if they think someone suspicious is watching them.) Young crows will remain dependent on their parents for a couple months after they fledge, but they also tend to stay near their family for a while longer, even after moving out of the nest. These chicks are still fiercely defended by their parents, Swift writes, creating a sort of extended adolescence that allows them time and energy for play behaviors, which might be important for their development and cultural learning.
Young crows will eventually start spending less time with their parents and more time with larger flocks, and face a decision as fall and winter set in. "They can either take off to 'float' before finding a mate and establishing a territory of their own," Swift writes, "or remain on their home turf and act as a 'helper' for next year's brood." The latter is known as cooperative breeding, in which more than two individuals help take care of offspring in a single brood.
In most American crow populations, older offspring continue to help their parents raise new chicks for a few years, according to the Cornell Lab. A crow family may include as many as 15 individuals, with offspring from five different years all pitching in to help. It's unclear why this evolved, Swift writes, but it may help delay the dispersal of young crows when there isn't enough open territory nearby for them to claim. ("See," she adds, "millennials are just doing what comes naturally.")
It's common for people to vilify crows, often focusing on unwanted behavior but overlooking more relatable or redeeming qualities. The American crow, for one, has been the subject of extermination attempts in the past, including the use of dynamite on large winter roosts. Those efforts ultimately failed, however, and thanks largely to its intelligence and adaptability, the American crow is now more common than ever across a range of habitats, including farms, towns and big cities.
Other corvids have similarly adjusted to or even capitalized on civilization, but being intelligent is no guarantee these birds are safe from us. The Hawaiian crow, for instance, is a smart corvid with a penchant for tool use, yet it was declared extinct in the wild in 2002 after being wiped out by a combo of disease, invasive predators, habitat loss and human persecution. Fortunately, scientists saved enough of the birds to start a successful captive-breeding program, and are now in the process of carefully reintroducing the species to the wild.
Crows do sometimes raid farms and gardens, but any damage they cause may be offset by ecological benefits like seed dispersal and eating pest insects. Plus, while any species has an inherent right to exist, we're especially lucky to have brainiacs like corvids living among us. They can help us learn more about our own intelligence, but also remind us how much we still have in common with the wildlife all around us.