Can Crows Count? The Science Behind Their Numerical Abilities

Crows are renowned for their intelligence, with a well-documented ability to use tools and recognize human faces. This complex cognitive life raises the question of whether they can count. Exploring this topic reveals not just the capacities of these birds, but also the different ways animals can process the concept of numbers.

Understanding Animal Numerical Abilities

When scientists investigate if an animal can “count,” they are looking for skills more complex than simple recognition. True symbolic counting, the way humans do with words or numerals, is one specific skill. However, many animals display other forms of numerical competence that are foundational to this ability.

One skill is “numerosity,” the capacity to perceive and compare the number of items in different groups without assigning a specific number to them. For example, an animal might consistently choose a pile with more berries over one with fewer. Another related ability is “subitizing,” the instant recognition of a small quantity of objects, typically up to three or four. This is similar to how a person can glance at a die and know the number of dots without consciously counting each one.

These non-symbolic systems are thought to be the evolutionary precursors to more complex counting. Many species, from honeybees to lions, possess an inherent sense of numbers that helps them make decisions. Distinguishing between these abilities is important for understanding what happens when a crow appears to engage with numbers.

Evidence from Crow Studies

Early experiments into avian numerical skills often involved birds choosing between sets of items that differed in number. For instance, a pigeon might be trained to select a container holding a specific quantity of grain to receive a reward. These studies suggested birds could discriminate between amounts but did not fully demonstrate a controlled use of numbers.

More recent research has provided stronger evidence of intentional counting in crows. A study in the journal Science revealed that carrion crows (Corvus corone) can be trained to produce a specific number of vocalizations on command. This work, led by neuroscientist Diana Liao, is the first to show an animal other than humans counting aloud in a controlled way, moving beyond simple estimation.

In the experiment, three carrion crows were trained to respond to both visual and auditory cues. The cues, such as an Arabic numeral on a screen or a specific sound, were associated with numbers from one to four. The crows learned to produce the corresponding number of caws and then peck a target to signal they had finished, receiving a food reward for a correct answer.

The crows were highly accurate, particularly with lower numbers, and their mistakes were typically off by just one. This indicates they weren’t just guessing but were actively planning and executing a specific number of vocalizations. The study demonstrated a combination of numerical understanding and vocal control not previously observed in non-human animals.

How Crow Brains Process Numbers

Behavioral evidence for crow numeracy is supported by neuroscience findings that explore how their brains handle numbers. Studies have identified specific neurons in a region of the crow brain called the nidopallium caudolaterale (NCL) that respond to distinct numerical quantities. These “number neurons” fire when a crow sees a specific number of items, with different cells tuned to different numbers, including the concept of zero.

The NCL is considered the functional equivalent of the primate prefrontal cortex, a brain region involved in higher-order thinking. Until these findings, number-associated neurons had only been identified in the prefrontal cortex of primates. The avian brain is structured very differently from the mammalian brain, lacking the layered neocortex found in humans.

Crows and primates, which last shared a common ancestor over 300 million years ago, independently evolved similar neural solutions for processing numbers in an example of convergent evolution. This suggests that having dedicated brain cells to represent quantities is an effective way to handle numerical information. The crow brain, though small, is densely packed with neurons, giving it enormous processing power.

The Evolutionary Advantage of Counting

The development of numerical skills in crows provides tangible benefits for survival and reproduction. The ability to process numbers enhances an animal’s capacity to exploit food sources, avoid predators, and navigate complex social dynamics. These skills are highly functional for a species like the crow.

One practical application is in foraging. A crow might use its numerical sense to remember how many food items it has stored in various caches or to assess which foraging patch is likely to yield a greater reward. Numerical competence can also be used in social situations, such as assessing the number of rivals in a territorial dispute. Deciding whether to fight or flee can depend on a quick calculation of which side has the numerical advantage.

This ability may also extend to communication. Some bird species, like black-capped chickadees, alter the number of notes in their alarm calls to signal the level of threat posed by a predator. While not yet proven in crows, their demonstrated ability to control vocalizations suggests that numerical information could be a component of their social communication, coordinating actions within a group.