The impressive cognitive capability of parrots and corvids (crows, jays, ravens, and jackdaws) has been extensively documented in scientific literature. These two have a large brain relative to body size. Apparently, this is true of all mammals that exhibit greater cognitive development. In the case of crows, which generally rank very low in human esteem, the relative size of the brain is the same as that of chimpanzees. But the size of the brain alone does not translate to higher cognitive capability. A study of all cognitively advanced animals, including some species of corvids and parrots, shows that they share a unique characteristic — a larger forebrain. The cerebrum that is associated with higher brain function such as memory, thought, and action is located in the forebrain. It is therefore not surprising that these birds — which have forebrains that are relatively the same size as that of apes — often demonstrate ape-like intelligence.
With the higher level of intelligence established, scientists have tried to compare the levels of cognition of parrots and corvids. Unfortunately, most of the experiments have used single tasks (either tool use or non-tool use) to arrive at a conclusion. Such an approach is not ideal as the tests tend to favour the natural ability of one species, and hence will not necessarily shed light on problem-solving capabilities. A paper published recently in the journal PLOS One assessed the problem-solving skills of six kea parrots and five New Caledonian crows by using a combination of four tests, two of which involved tool-use. Overall, the kea performed much better than the crows. While none of the crows employed more than one solution, the kea parrots were quicker in discovering multiple solutions. While the naturally stick-tool using crows scored over their competitors, they were slower than the parrots in the second tool-use test involving a ball. The kea is not known to use sticks in the wild and this may be due to its beak curvature. Yet one managed to insert a stick into the opening by employing a sophisticated technique. That the study brought out the innate characteristics — the neophobia of the crows, which hampered their performance, and the neophilia of the parrots, which allowed them to act even on novel objects — highlights the compelling need to use a combination of tests to compare relative cognitive capabilities and development.