New Caledonian crows are known for their toolmaking, but Alex Taylor and his colleagues wanted to understand just how advanced they could be.

Crows from New Caledonia, an island in the South Pacific, can break off pieces of a branch to form a hook, using it to pull a grub out of a log, for instance. Once, in captivity, when a New Caledonian male crow had taken all the available hooks, its mate Betty took a straight piece of wire and bent it to make one.

“They are head and shoulders above almost every other avian subjects” at toolmaking, said Irene Pepperberg, an avian cognition expert and research associate in Harvard University’s department of psychology. “These crows are just amazing.”

Dr. Taylor, a researcher at the University of Auckland in New Zealand, and several European colleagues wondered how the crows, without an ability to talk and showing no evidence of mimicry, might learn such sophisticated toolmaking.