Bird Intelligence Explained by Neuron Density

Birds have always been a bit of a mystery in neuroscience. Many birds, especially parrots and songbirds, have shown a striking amount of intelligence. Alex the African grey parrot, for example, had a vocabulary of over 100 words and showed a remarkable level of understanding in the 35 years he was studied. He was considered to have the general intelligence of a 5-year-old human child and the emotional intelligence of a 2-year-old. Crows also have excellent reasoning abilities and can learn to use tools. Songbirds create and memorize complex songs. This contradicts modern neuroscience, though, because birds have relatively small brains (Alex’s brain was about walnut-sized). Generally, science has assumed that smaller brains meant lower cognitive power. A brand new study, however, finally solves the mystery.  A paper published online in Proceedings of the National Academy of Sciences analyzed 28 species of bird and found that they have more neurons in general, especially in the parts of the brain responsible for high level learning.

The researchers dissected the brains of various bird species and then counted how many neurons there were and what parts of the brain they were from. They found that birds have twice as many neurons than primates with the same brain mass, with songbirds and parrots coming out on top. The extra neurons were especially focused in the forebrain, in sections normally dedicated to higher cognitive processes and learning. Interestingly, the bird neurons were very small, allowing more to be packed into a smaller brain.

This new research explains why so many bird species show advanced cognitive capabilities in spite of their tiny brains. The smaller than average neuron size also creates new questions. Were bird neurons always this small or did they shrink during evolution in order to accommodate flight? The researchers intend to investigate those questions in future studies.


Seweryn Olkowicz et al, Birds have primate-like numbers of neurons in the forebrain, Proceedings of the National Academy of Sciences (2016).

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