Birds are remarkably intelligent, although their brains are small. Corvids and some parrots are capable of cognitive feats comparable to those of great apes. How do birds achieve impressive cognitive prowess with walnut-sized brains? Songbirds, parrots and owls share extremely high neuronal densities and disproportionately large numbers of neurons in the pallial telencephalon. Remarkably, numbers of pallial neurons in large-brained parrots and songbirds (especially corvids) equal or exceed those found in primates with much larger brains. In contrast, birds representing basal lineages, such as ostriches, tinamous and galliform birds, have lower neuronal densities, a proportionally smaller telencephalon, small telencephalic and dominant cerebellar neuronal fraction. Brains of birds situated phylogenetically in between these groups, such as pigeons or birds of prey, exhibit intermediate characteristics. Compared to mammals, avian brains are built in a more economical, spatially efficient way; even the lowest neuronal densities observed in brains of basal birds are equal to or higher than the highest densities found in homologous brain regions in mammalian species investigated so far. Avian brains thus have the potential to provide much higher "cognitive power" per unit mass than do mammalian brains. We therefore suggest that the large numbers of neurons concentrated in high densities in the telencephalon substantially contribute to the neural basis of avian intelligence.
Pavel Němec is a researcher from the Department of Zoology at Charles University in Prague. His research program mainly focuses on Neurosciences. He has made important contributions on sensory biology, comparative vertebrate neuroanatomy, neural basis of magnetoreception and magnetic orientation, and neurobiology of subterranean mammals. His most influential contributions include the finding that birds may have equal or greater number of neurons in the brain than primates with much larger brains, and the identification in mammals of neurons that are responsive to magnetic stimuli.
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