While the species of the crow family

While the species of the crow family – including jackdaw, magpie, crow, rook and raven – are renowned in myth and legend for their intelligence, a scientific basis for this has been hard to establish. Until, that is, researchers discovered a crow species living on the South Pacific islands of New Caledonia that manufactured tools more complex even than those used by humans' closest relatives, the chimpanzee.The original report from the 1990s described how the crows' tool making displayed three characteristics not seen before outside of humans: a high degree of tool standardisation, distinct tool designs that involve obvious imposition of form onto raw material, and the use of hooks. Sharing some traits with those of stone age humans' tools, this led to a surge of interest in the species.

Research over the past ten years has found a great deal of interesting behaviour in New Caledonian crows. They have been shown to make tools out of novel materials, use tools in novel ways to solve physical problems at which our close primate relatives fail, and to solve problems in a way that suggests abstract reasoning. Their impressive problem solving skills appear to be backed up by a relatively large brain, but more important than relative brain size is the neurological hardware inside it.There is some evidence that the crows, like primates, have a relatively large forebrain where most decision making occurs. The crows and certain other birds have distinct cell clusters in the forebrain, consisting of a neuron surrounded by supporting glial cells.

The density and distribution of these clusters in the forebrain varies between species, but the New Caledonian crow has a high density of them. If these clusters, as is believed to be the case in humans, play an important role in underpinning cognitive skills, they may help explain the crows' sophistication.In a new volume on tool use as adaptation from the Royal Society, the New Caledonian crow figures prominently. One study questions whether the birds know that the hooked end of a hooked stick is the functional end.A similar question has been asked in a previous study about the hooks they fashion from screw pine leaves.