Evolution of the avian brain and intelligence

Abstract

Some birds are capable of cognitive feats which put most mammals to shame. In the rainforests of New Caledonia and Mare, New Caledonian crows use and construct a number of different tools which are used to gain access to large grubs found in the crevices of trees. These tools are crafted from raw materials (sticks and Pandanus leaves), and there is a suggestion that, like chimpanzees, crow tool use is a form of culture. In the laboratory, New Caledonian crows are equally impressive, demonstrating some understanding of ‘folk physics’ (the common sense view of how the world works). Perhaps the best demonstration of this is Betty the crow, who appeared to spontaneously bend a piece of wire into a hook to gain access to out-of-reach food.Other corvids are equally impressive, providing evidence of cognitive abilities thought to be uniquely human. Western scrub-jays, for example, are the first non-human animals to demonstrate episodic-like memory — the ability to remember the ‘what, where and when’ of a specific past event. In these studies, jays cache different types of food which decay at different rates in specific locations. In order to recover food that is still fresh and edible, the jays had to remember ‘what’ type of food they cached, ‘where’ they cached and ‘when’ they cached it. Scrub-jays are also extremely wary of the presence of conspecifics during caching. If an observer is watching when scrub-jays cache, the storers come back later when alone and move their caches to new places that the observer does not know. Interestingly, storers only do this if they have been thieves themselves in the past. This suggests that experienced scrub-jays may attribute others with the intention of pilfering, and so implement strategies to reduce this possibility in the future. Scrub-jays also protect their caches by reducing the amount of information available to an observer at the time of caching, by hiding caches behind barriers, in the shade or as far from an observer as possible. All this suggests that western scrub-jays may demonstrate another supposedly unique form of human cognition: theory of mind. Parrots, such as Alex the African grey, have also demonstrated intellectual abilities which rival primates, such as understanding whether objects are the same or different, their number (including zero), their colour and shape.Our new appreciation of the complexity of the avian brain is closely tied with a new appreciation of the complexity of the avian mind, particularly with respect to corvids and parrots. It is now the job of behavioural biologists, comparative psychologists and neuroscientists to determine how one translates into the other.