Use of a barbed tool by an adult and a juvenile woodpecker finch (Cactospiza pallida)

Here we describe the modification and use of a new tool type in the woodpecker finch (Cactospiza pallida). This species is known to habitually use twigs or cactus spines to extract arthropods out of tree holes. We observed an adult and a juvenile bird using several barbed twigs from introduced blackberry bushes (Rubus niveus) which the adult bird had first modified by removing leaves and side twigs. The barbs of blackberry tools provide a novel functional feature not present in tools made from native plants and de-leafing of twigs never has been observed before. Both birds were observed using several of these tools to extract prey from under the bark of the native scalesia tree (Scalesia penduculta). They oriented the twigs such that the barbs pointed towards themselves; this rendered the barbs functional as they could be used to drag prey out of a crevice. The juvenile bird first watched the adult using the tool and then used the tool that the adult bird had left under the bark at the same location and in the same way as the adult. Our observation highlights the fact that opportunities for the transmission of social information do occur in the wild and indicates that woodpecker finches are flexible in their choice of tool material and tool modification.