Aphid galls as a double food source for woodpeckers

An adult female and a young great spotted woodpecker Dendrocopos major were found exploiting galls of the elm balloon-gall aphid Eriosoma lanuginosum by eating both the insects and their honeydew. Literature offers sparse and indirect information to explain this behavior. Taking both aphids and honeydew from within galls is reported here for the first time for a bird species. Only one other vertebrate, the Eurasian red squirrel Sciurus vulgaris, would show similar behavior. In contrast with the seeming rarity of such a feeding way, likely advantages in the double food source suggest it may have been overlooked.