Chicks that stay in the nest for a long time become more intelligent

It is well known that there are high-flyers among birds. In terms of intelligence, crows, cockatoos and ravens are hardly inferior to primates. The clever fowl has a larger brain and more neurons in certain areas of the brain than its dumber counterparts. As a current study shows, this development is particularly possible in nest squatters – when the brain still has plenty of time to grow and mature after hatching.

Unlike mammals, birds do not have a cerebral cortex. They use the pallium, a region in the front of the head, to solve complex mental tasks. To further unravel the mysteries of feathered animals’ minds, Daniel Sol from the Center for Ecological Research in Catalonia and his international team took a closer look at the brains of 111 bird species from 24 families.

Neurons make you smart

It turned out that the bird species that are considered to be particularly intelligent and innovative have a higher number of brain cells on average. This connection remained even when the researchers included body size and mass. “The willingness to innovate is higher in birds, whose brains have a disproportionate number of neurons in relation to their body size,” report Sol and his colleagues. Although geese or owls have a relatively large brain, they have significantly fewer brain cells than parrots or corvids of the same size.

Uneven distribution of gray cells

Further analysis revealed that the additional neurons are not evenly distributed in the brain. Above all, the number of cells in the pallium – the evolutionarily youngest and most highly developed part of the brain of birds – has proven to be decisive for the intelligence of a bird species. “Our results thus confirm the hypothesis that intelligence reflects the ability to devote as many neurons as possible to a task,” explains the team.

Precocials aren’t that smart

In addition, Sol and his colleagues investigated whether developmental stages differ in more intelligent and less intelligent bird species. And indeed there were striking differences: Bird species with less neuron-rich brains are mostly precocial – their chicks hatch almost fully developed from the egg and can immediately walk, swim and eat. Examples are chickens, ducks or geese. Their brain and, above all, their pallium are still developing in the egg – but hardly grow any further after hatching, as the researchers determined in comparative analyses.

Unfinished chicks develop more neurons

The situation is different, however, with the chicks of crows, parrots and other “clever” birds: They are mostly altricial that hatch naked and blind and only mature slowly. Analyzes showed that the brains of these chicks form a disproportionately large number of new neurons during this nestling period – significantly more than in precocials. “The period during which the chicks mature in the nest could therefore play a crucial role in the development of their intelligence,” says co-author Louis Lefebvre from McGill University in Canada.

Long childhood conducive to brain growth

These results confirm that brain volume alone says little about cognitive performance in birds. Instead, the size and cell density, especially of the higher brain regions, plays an important role. And similar to us primates, a relatively long childhood also appears to be conducive to brain growth and intelligence in birds.

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