How Smart Are Crows? Facts About Corvid Intelligence

Crows and their relatives, such as ravens, magpies and jays, are among the most intelligent birds studied. Researchers have documented problem solving, planning and memory that rival some primates in specific tasks.

Key takeaways

• Corvids include crows, ravens, rooks, jays and magpies.
• New Caledonian crows make and use tools in the wild.
• Crows can recognise individual human faces and remember them.
• Some corvids appear to plan ahead and solve multi-step puzzles.
• Researchers are careful about how to compare bird and human intelligence.

The corvid family

Corvids belong to the family Corvidae, found on almost every continent. They have relatively large brains for their body size, and the part of the bird brain involved in complex thinking, the pallium, contains a very high density of neurons. Though bird brains are structured differently from mammal brains, they can support sophisticated cognition.

Tool users

The New Caledonian crow, native to islands in the South Pacific, is famous for making tools. In the wild, these crows shape twigs into hooks and tear pandanus leaves into barbed strips to extract insects from crevices. Experiments show that they can also solve puzzles that require using one tool to get another. Young crows learn from adults, and tool designs can vary between regions, suggesting a form of cultural tradition.

Aesop's fable experiments

In an old fable, a thirsty crow drops stones into a pitcher to raise the water level. Researchers tested a version of this with rooks and other corvids, and found that they dropped stones into water-filled tubes to bring a floating treat within reach. They also seemed to choose heavier or sinking objects over lighter or floating ones, suggesting some understanding of cause and effect, though how much they truly understand is debated.

Faces and memory

In studies led by biologist John Marzluff at the University of Washington, researchers wore distinctive masks when trapping and banding wild crows. Years later, crows scolded and mobbed people wearing the "dangerous" mask but not those wearing a neutral mask. Other crows that had not been trapped also learned to respond, suggesting information is passed between birds. This shows the ability to recognise individual people and remember them.

Planning and flexibility

Western scrub jays have been shown to hide food and later recover it, and they adjust where they hide it depending on whether they know another bird is watching. Experiments suggest that some corvids can plan for future needs. Ravens have been shown to choose a tool now because it will be useful later, in some tests, which was long thought to be uniquely human.

Social lives

Many corvids live in family groups or flocks, with complex social relationships. Ravens may form long-term pair bonds. Crows have been observed gathering around a dead crow, which some researchers interpret as a way of learning about danger, though it is also described as a funeral, and the interpretation is debated.

Communication

Crows have a range of calls, and some can mimic sounds, including human speech in captivity. Different calls convey alarm, food or identity. Research continues on how much information is carried by crow vocalisations.

Living alongside crows

In many cities, crows adapt well, using human food and structures. Some people enjoy feeding them, while others find them noisy. Treat wildlife with respect and follow local guidance.

Brains built differently

Bird brains look very different from mammal brains, and for a long time that led people to underestimate birds. In fact, the pallium, the outer part of the bird forebrain that handles complex thinking, contains many tightly packed neurons. Studies have found that corvid brains have a very high number of neurons for their size, comparable in some respects to those of primates. This suggests that intelligence can evolve in different ways, using different brain structures to solve similar problems.

A famous tool-making crow

In 2002, researchers at the University of Oxford reported that a captive New Caledonian crow nicknamed Betty bent a straight piece of wire into a hook to lift a small bucket of food out of a tube. She had not been trained to do this, and the team saw her do it repeatedly in different trials. Later studies showed that wild New Caledonian crows also craft hooked tools from twigs and leaf edges. Scientists debate how much insight the birds have, but the findings changed how people think about animal tool use.

Culture and teaching

Crows learn from each other. Young birds watch adults, and information can spread through a group, as in the mask studies where birds that had never been trapped still learned to scold the dangerous face. Different populations have different tool designs, which suggests that some behaviours are passed on socially, a form of culture. Corvids also have varied alarm calls and may recognise individual voices.

Living with crows

In cities, crows scavenge food scraps and nest in tall trees and buildings. In autumn and winter, some species gather in large roosts of hundreds or thousands. Most people can coexist with them by securing rubbish, not leaving food outside and avoiding feeding them directly. During nesting, a few crows may swoop at people who come close to the nest, which is defensive behaviour and usually short-lived. Crows also eat pests such as insects and rodents, and they clean up carrion.

Other clever birds

Corvids are not the only impressive birds. Parrots can learn large vocabularies and some understand concepts such as same and different. Magpies have passed versions of the mirror mark test, in which an animal tries to remove a mark visible only in a mirror, although scientists debate what this proves. Pigeons, which are often dismissed, have shown strong visual memory and have been trained to tell works of art apart and to recognise letters.

Frequently asked questions

Are crows as smart as apes?

In some tests, they perform similarly, but intelligence is hard to compare, as they excel at different tasks.

What is the difference between a crow and a raven?

Ravens are usually larger, with a heavier bill, a wedge-shaped tail and deeper calls.

Do crows hold grudges?

They can remember individuals who threatened them and warn others, according to studies.

Can crows count?

Experiments suggest that crows can keep track of small quantities and can learn to respond to a set number of items, and brain recordings have found neurons that respond to particular numbers. This is not the same as human counting with words, but it shows number sense.

How long do crows live?

In the wild, many crows live for around seven to eight years, though some reach their teens or older. In captivity, with protection from predators and disease, crows and ravens can live for twenty years or more.

Are crows dangerous to people?

Crows are not generally dangerous. Occasionally, a nesting crow will swoop at someone who is too close to its nest. Avoiding the area for a few weeks usually solves the problem, and the behaviour stops once the chicks have left.

Sources and further reading

• Corvidae (Wikipedia)
• Cornell Lab of Ornithology: American Crow