Scientists have long questioned the cognitive abilities of birds in relation to their tiny brain size; in certain areas they resemble or even outperform mammals. A new study carried out by researchers from the Universities of Prague, Vienna, and Rio de Janeiro has revealed how birds are able to perform such cognitive feats with brains the size of a walnut. What if Hitchcock were right?

Among birds, corvids (crows, magpies, and jays for example) and parrots appear to be cognitively superior; they may even rival the great apes. They are able to make and use tools, understand cause and effect mechanisms (in both directions), recognize themselves in a mirror, plan for future needs, or even infer the thoughts and intentions of other species, including humans (what we call “theory of mind”). Not to mention, parrots can learn words and use them to communicate with us. To explain the cognitive performance of birds, the researchers believed the connections in the avian brain might differ from primates, but studies have shown this not to be true.

Neuroscientist Suzana Herculano-Houzel and colleagues studied the brain cellular composition of 28 bird species by systematically measuring the number of neurons, from tiny finches to large emus. They discovered that bird brains contained more neurons than mammal brains, even of a similar mass. A parrot has as many neurons in his walnut sized brain as a Macaque monkey, which has a brain the size of a lemon. For example, among the parrots studies, according to the weight of the brain (from 23 to 1008 g), the number of neurons varied from 227 million to 3.14 billion. This means that the neuronal density far exceeds that of mammals; song bird and parrot brains possess about two times more neurons than primate brains of the same size. They also have a large number of neurons in their pallium, the part of the brain that corresponds to the cerebral cortex and which performs superior cognitive functions such as planning for the future.

According to S. Herculano-Houzel, “In designing brains, nature has two parameters it can play with: the size and number of neurons and the distribution of neurons across different brain centers, and in birds we find that nature has used both of them.”

So if anyone calls you a bird-brain, you can now take it as a compliment!