MISSOULA - Birds can be pretty intelligent, and biologists have long wondered why certain species of birds are smarter than others, and whether these abilities come from larger brains — which has been the general consensus for years — or from a greater number of neurons in specific areas of the brain.
A new publication in Nature has found that the answer is that it’s a little bit of both. A crow's brain is about the weight of three nickels, and if you compare a crows brain to an orangutan’s brain of the same mass, the crow’s brain will have 43 times more neurons than the orangutan. This means that certain birds can achieve primate-like levels of cognition.
The reason that the brains of birds can have so many more neurons is largely due to what is known as the pallium. The pallium in birds is the equivalent of the human cerebral cortex – the outer layer that is all squiggly and mushed together. This part of the brain is involved in memory, learning, reasoning, and problem-solving.
The reason a bird’s pallium is able to store so many neurons is because of its smoothness, which adds more surface area. Compared to our brains, our cortex seems clunky but, a bird’s has more room -- allowing them to be jampacked with neurons.
When researchers compared bird neuron numbers to over 4,000 foraging innovations, they found that the species with the higher numbers of neurons in the pallium were also likely to be the most innovative.
A key component to more neurons was also attributed to longer time spent in the nest as a baby. Larger species of birds like crows and parrots -- that are known for their intelligence -- spend a longer period of time in the nest. A sparrow spends about half as much time as a crow does in the nest.
Spending more time in the nest allows more time for the brain to grow and accumulate more neurons. The results of this recent study allow for more of an understanding of the evolution and significance of brain size and show how a life-history perspective helps to understand the evolution of brain cognition.