Bird Brains Have More Neurons Than Mammal Brains

In Animals by Woodz, June 16, 2016

For decades, scientists have been amazed by the cognitive prowess of birds which is surprising looking at how small their brains are. Certain species, such as crows and ravens, are known to use tools, solve problems and even recognize themselves in the mirror. They are somehow very intelligent even though their brains are the size of a walnut. Now, researchers studying brains from dozens of species reveal that bird brains contain very large numbers of small, tightly-packed neurons.

Additionally, songbirds are capable of vocal learning – something only a few species have a capacity for, while parrots not only learn human words, they can use them to communicate with us. Yet the brain of a common raven is 15.4 grams on average, and that of the hyacinth macaw is 24.7 grams. As an example, a chimpanzee’s brain weighs 420 grams.

hyacinth macaw bird brains more neurons mammals

“On average, Hyacinth Macaw brains weigh only 24.7 grams but are still very intelligent” by Tambako The Jaguar is licensed under CC BY 2.0

This new study out in the Proceedings of the National Academy of Sciences focused on 28 species: 11 parrot species, 13 vocal learning songbird species (including six corvids), and four other birds (an emu, barn owl, red junglefowl, and a pigeon). The study was performed by an international team of researchers, and the results were astounding.

Bird brains are about twice as neuron-dense as mammals of the same size

The researchers also found that large parrots and corvids (crows, ravens etc.) had especially dense clusters of neurons in their forebrains. As the hypothesis goes, the more neurons, the more cognitive ability. If so, these two groups of birds may have much higher cognitive power per unit mass than mammals. Furthermore, compared to mammals, a greater proportion of bird neurons are located in the forebrain, the area associated with intelligent behavior.

Though brain structures may be different in classes of animals, it is not necessarily the size, or even the structure, that makes a brain more advanced. Suzana Herculano-Houzel of Vanderbilt University, the study co-author, explained: “Bird brains show that there are other ways to add neurons: keep most neurons small and locally connected and only allow a small percentage to grow large enough to make the longer connections; This keeps the average size of the neurons down”.