These geniuses in the sky make scientists question everything we know about animal intelligence.
Among the most intelligent creatures on the planet are crows. In fact, they rival primates and even human children when it comes to intelligence.
Over the past few decades, a series of scientific experiments have revealed behaviors so sophisticated that they force researchers to rethink what it means to be rational.
Here are some of the most surprising discoveries, according to , which explain why so many scientists consider these birds to be the true “brains” of the sky.
1. Think about cause and effect
In an experiment with New Caledonian crows, researchers placed the birds in an enclosure where, suddenly, a stick came out of hiding and moved. In half of the situations, the crows saw a human enter this hiding place, move the stick and then leave; in the other half, the human was invisible or was not seen moving anything.
When they knew that a person was there, the crows became much calmer after the human left: they mentally linked the movement of the stick to the presence of that agent. They started eating and behaving normally again. But when they had no visible explanation for the stick moving, they remained suspicious, cautious, as if something “invisible” could still be there.
For biologist Alex Taylor, these results show that crows can reason about hidden causes, a way of thinking about the world that is very close to what humans do in similar situations.
2. Understand water displacement
Another famous experiment tested whether crows can understand the principle of water displacement.
The scientists offered the birds transparent tubes with water and a snack that floated, but out of reach of their beak. Near the tubes, there were stones and other heavy objects. The crows began throwing objects into the water until the level rose high enough for them to reach the food.
Even more impressive, when given the choice between tubes with different water levels, or between objects that sank and others that floated, the crows systematically preferred the options that required less effort to obtain the reward. According to the researchers, the performance of these animals was comparable to that of human children of around seven years old.
3. Holding a grudge and passing the warning on to everyone
Anyone who studies crows knows that it is wise to wear a mask. It’s not a whim: birds recognize human faces and remember who treated them badly.
Biologist John Marzluff, who specializes in corvid behavior, discovered this in the loudest way possible. During experiments in which he captured and marked crows, he wore a specific mask. He quickly realized that, whenever he appeared with that “face”, the birds reacted with screams and agitated flights.
Years later, Marzluff discovered something even more extraordinary: even without new incidents, an increasing number of crows began to “insult” the dangerous mask. Two weeks after the first capture, about a quarter of the birds reacted with alarm; 15 months later, the value had risen to a third; three years later, two thirds of the local population were already participating in the collective scandal.
In other words, crows not only hold grudges but also seem to teach others to distrust certain humans. Bad reputations in the corvid world spread quickly.
4. “Funerals” to learn about danger
Anyone who has ever seen a group of crows screaming around a dead individual may have thought that it was some kind of funeral. Biologist Kaeli Swift decided to investigate the phenomenon systematically.
When exposing flocks of crows to the bodies of other crows, or to the skins of predators, he observed that the birds came together, vocalized intensely and adopted an alert posture. The conclusion of the work was clear: these “vigils” serve to learn about threats in the environment.
There are practical examples of this collective learning. In the city of Chatham, Canada, authorities tried to ward off migrating crows with air bullets. Before long, the birds began to systematically fly a little higher than the shooting range. The “survival lesson” seemed to have been passed on from one to another.
5. Rationality and “healthy paranoia”
Crows are not the only corvids with advanced mental abilities. Studies with cormorants have shown that these birds have something close to the so-called Theory of Mind – the ability to recognize that others also have intentions, knowledge and perspectives different from ours.
This hypothesis arose after observing that, when guarding food, cormorants are much more discreet if they know they are being seen by others. To test the idea, researchers taught birds to peer through a hatch and see a human hiding food in a neighboring room. Then, they placed the cormorant in the food room in two different conditions: with the shutter closed, in silence, or with the shutter open but only with sounds of other cormorants emitted by a column.
When the hatch was open and other cormorants were heard, the birds behaved as if they were actually being watched by a rival, hiding the food more cautiously. They seemed to be able to imagine the point of view of a potential thief, generalizing from their own experience.
6. Solve complex puzzles in several steps
In the BBC program Inside the Animal Mind, scientists decided to create the most complex puzzle ever to test a wild crow, nicknamed 007.
The challenge had eight steps that had to be solved in a specific order to free a piece of food. The crow should collect different tools, use them in sequence: for example, use a small stick to obtain a longer one, and so on, until reaching the final objective.
Although I already knew each tool individually, I had never been faced with the need to combine them. Still, 007 managed to solve the entire puzzle, demonstrating an impressive ability to plan several steps ahead, adapt and learn quickly.
7. Who doesn’t have a dog…
If nature doesn’t offer them the right tool, the crows invent one. In 2015, through tiny cameras placed in their tail feathers, researchers recorded tool-making by crows for the first time in the wild.
The images show the birds breaking small branches, removing leaves and bark and shaping the end into a hook. They then use these instruments to probe cracks, trunks and holes in search of insects and other hidden prey.
In one of the videos, a crow drops the tool and returns shortly afterwards to retrieve it, suggesting that it values the object and does not see it as something disposable for a single use. This is a level of planning and utility appreciation that, until recently, was thought to be exclusive to primates.
8. Justice: whoever steals is left without a partner
Cormorants’ social relationships also reveal sophisticated rules of fairness and cooperation. In an experiment conducted at the University of Vienna, pairs of cormorants had to simultaneously pull two ropes to bring a platform with two pieces of cheese closer, one for each.
When an individual took advantage of the opportunity to keep both pieces, the deceived partner refused to collaborate with him in subsequent rounds. However, he was willing to cooperate with other “fair” cormorants, who shared the reward equally.
This type of selective ostracism had already been observed in humans and chimpanzees. Seeing similar behavior in birds reinforces the idea that social intelligence evolved convergently across multiple lineages.
9. Self-control and delayed gratification
Crows don’t just react on impulse. Like the children in Stanford University’s famous “marshmallow experiment,” they are also capable of waiting for a better reward.
In a 2014 study, researchers first determined each bird’s favorite foods by offering them grapes, bread, sausages, fried fat and other snacks. Then, they would give them a less appealing food, with the possibility of exchanging it, after some time, for something better, for example, a grape in exchange for meat.
Many crows chose to wait until they could make the switch. In some cases, they spent up to 10 minutes waiting for the superior reward, ignoring the immediate temptation. Interestingly, they were less motivated to delay gratification when the reward was just “more” of the same food, and not something of better quality.
10. Plan the future and do “business”
Cormorants have also shown a remarkable ability to plan for the future and assign value to objects they know they can use later.
In one experiment, birds were trained to release a treat by inserting a tool into a hole in a box. The researchers then removed the box and, after a while, offered the cormorants a selection of objects, including the right tool. When the box later reappeared, most of the birds had chosen and kept precisely the instrument they would need – even when the interval between choosing and having the opportunity to use it was up to 17 hours.
In another phase of the study, cormorants learned to exchange a symbol (a “token”) for food with a human experimenter. Later, they were placed in front of a tray with several objects, including this token and an unappetizing food. In most trials, they chose the token, kept it and, when the experimenter returned, exchanged it for a more valuable reward.
For the study authors, these results suggest that cormorants are capable of making decisions for a future that they cannot yet see or smell – a form of planning considered, until now, typical of great primates.
11. Remember who was fair — or who was a cheat
If there are corvids that don’t forget an affront, they also don’t forget those who treat them well. In addition to numerous reports of crows bringing shiny little “gifts” to people who regularly feed them, there is experimental evidence that they distinguish fair from unjust humans.
In a study with cormorants, the birds were trained to exchange bread (of lesser value) for cheese (much more appetizing). Two human experimenters participated in the task: one always fulfilled the agreement and delivered the cheese; the other kept the cheese for himself after receiving the bread.
Days and even a month later, when the cormorants were again placed in front of the two humans and a neutral third, with a piece of bread to exchange, they mostly preferred the “fair” experimenter. They remembered who had respected the “contract” and avoided what had deceived them.
12. Communicate with gestures, like human babies
Before they learn to talk, babies point, show objects and use gestures to communicate. For a long time, it was thought that this type of gestural communication was exclusive to primates. Until someone started looking closely at wild cormorants.
Researchers from the Max Planck Institute and the University of Vienna observed several interactions between pairs of cormorants. On dozens of occasions, the animals used their beak as if it were a hand: they picked up a piece of moss, a branch or other object and showed it to a partner; in others, they extended the object to their partner, almost as if offering something.
These gestures were not random: they occurred mainly between individuals of opposite sexes and were often the prelude to closer interactions, such as touching nipples or manipulating the object together. In functional terms, they are very similar to the gestures of “look here” or “do you want this?” of humans.
13. The pleasure of the game
Finally, there is a trait that brings these birds even closer to us: they genuinely like to play. Crows repeatedly gliding across snow-covered roofs, throwing objects into the air to catch them again, or performing acrobatics in flight, without any obvious food objective, are scenes that have already been widely documented.
This playful behavior seems to play an important role in learning, in strengthening social relationships and, perhaps, simply in the search for pleasure. In a world where it is necessary to always be aware of predators, human dangers and food shortages, the ability to set aside moments to play can be another expression of their remarkable mental flexibility.
