New data on the brain and cognitive abilities of birds

Abstract

New evidence of functional analogies and homologies of avian and mammalian brains is presented, as is a revised nomenclature of the most important brain structures. Comparative characteristics of the avian brain and criteria for its progressive development in the phylogeny have been considered. We studied the possibility to use Portmann’s index as one of the indicators of brain development in different avian species. We substantiated the necessity to chose for investigation new sets of avian species with medium ( Parus caeruleus and Loxia curvirostra ) and low ( Larus glaucescens ) levels of brain complexity to maintain fully valuable grounds for comparing the cognitive abilities in birds. The main experimentally supported proofs of the existence of elementary thinking and some other cognitive functions in the higher birds have been reviewed. The high levels of cognitive processes that underlie the tool using ability in birds, as well as the similarity to those processes in apes, have been demonstrated from the results obtained in the first decade of the 21st century. Comparative studies on proto-instrumental activity confirmed the ability of hooded crows and ravens to find urgent solution of tool-using tasks. Although birds with a medium level of brain complexity display seemingly rational behavior, it is plausible that they use simpler rules being unable to understand the task logic. It was shown that birds of different orders with a high level of brain complexity demonstrate similar dynamics in the development of abstract concepts. Crossbills, which have a medium level of brain complexity, were able to develop the same concepts at a lower level than the corvids; whereas the seagulls and pigeons, which possess a low level of cognitive abilities, were not able to operate any abstractions and were incapable of solving other cognitive tests. The fact that corvids, parrots, and apes have similar abilities to solve some cognitive tasks supports the hypothesis of the convergent evolution of the brain and cognition in birds and primates.