Skilled tool use is considered a sign of intelligence, but a study of crafty crows shows that it takes the right physical attributes too.
New Caledonian crows (Corvus moneduloides; pictured) extract prey from nooks and crannies with tools that they craft from sticks and other items. Jolyon Troscianko at the University of Birmingham and Christian Rutz now at the University of St Andrews, both in the UK, and their colleagues studied the birds' visual fields and bill shapes. Compared with related species that do not use tools, New Caledonian crows have a larger field of binocular overlap. Using a video camera in the base of a baited tube, the team found that New Caledonian crows bring both eyes forward during tool use, which allows them greater visual control. Moreover, the straighter bill of C. moneduloides compared to related species gives the bird better control over a tool within its field of binocular vision.
Like the flexible wrists and opposable thumbs of humans, these traits provide a rare example of physical adaptations for tool use.
Nature Commun. http://dx.doi.org/10.1038/ncomms2111 (2012)