Dr Gavin Hunt and Dr Russell Gray of the University of Auckland have spent the past decade studying feathered technology in New Caledonia, 900 miles north-east of Australia. After an intensive field survey of local crow industry, the scientists found that the birds rip the leaves of the pandanus tree to fashion three distinct types of tool for grub and insect extraction: wide, narrow and tapered.
Long ago, the birds discovered that they could rip the serrated edge off the leaves to make a wide tool. The skill spread and the crows honed tools with finer working tips, by either narrowing tools or tapering them. (Because the leaves are reinforced by tough parallel fibres, the tapered design is made in steps. The crow nips the leaf, rips along the fibres, makes another cut and tears again, repeating until it has a tool with usually two, three or four steps.)
Leaf tool manufacture is an example of culture: the birds leam through example and their tool-making wisdom grows in sophistication down the generations. The crows appear to have the cognitive requirements for cumulative, though rudimentary, technological evolution, said Dr Gray. Tool manufacture in New Caledonian crows shows striking flexibility and innovation.’ The ability of the birds to innovate is further shown by their making of other tools. They often strip a twig of leaves and cut it off just below a shortened offshoot to create a hook to get bugs out. They also use simpler tools to extract grubs from the dead wood of trees.
