Do woodpecker finches acquire tool-use by social learning?

Tool-use is widespread among animals, but except in primates the developmen t of this behaviour is poorly known. Here, we report on the first experimen tal study to our knowledge of the mechanisms underlying the acquisition of tool-use in a bird species. The woodpecker finch Cactospiza pallida, endemi c to the Galapagos Islands, is a famous textbook example of tool-use in ani mals. This species uses modified twigs or cactus spines to pry arthropods o ut of tree holes. Using nestlings and adult birds from the field, we tested experimentally whether woodpecker finches learn tool-use socially. We show that social learning is not essential for the development Of tool-use: all juveniles developed tool-use regardless of whether or not they had a tool- using model. However, we found that not all adult woodpecker finches used t ools in our experiments. These non-tool-using individuals also did not lear n this task by observing tool-using conspecifics. Our results suggest that tool-use behaviour depends on a very specific learning disposition that inv olves trial-and-error learning during a sensitive phase early in ontogeny.