Biologists at the University of St Andrews, U.K. have studied Caledonian crows and found that they engage in a sophisticated tool-making activity. They pick the side branches of a plant and “craft” it to make a hook-like structure at the end which can be used to capture prey, says a study published in Current Biology . The researchers found that the depth of the hook depended both on the plant and the techniques the birds used to detach the branch from the plant. When the crows used careful cuts using their sharp beaks, the “hook” was deeper than when they simply pulled it off. They also found that adult crows were prone to the sloppy latter technique, unlike younger ones. The study can shed light into the evolutionary past of humans.
