The Vampire Finch (Geospiza difficilis septentrionalis) is a small bird native to the Galápagos Islands. It is a very distinct subspecies of the Sharp-beaked Ground Finch (Geospiza difficilis) endemic to Wolf and Darwin Islands. Most finch species eat seeds and migrate to more hospitable climates in the winter months.
The vampire finch does not migrate, rather it supplements its diet by occasionally drinking the blood of other birds, chiefly the Nazca and Blue-footed Boobies, pecking at their skin with their sharp beaks until blood is drawn. Despite the seabirds (masked boobies) being much larger, the finches are apparently able to extract their grisly nourishment from the booby birds with impunity.
It has been theorized that this behavior evolved from the pecking behavior that the finch used to clean parasites from the plumage of the booby. The finches also feed on eggs, stealing them just after they are laid and rolling them (by pushing with their legs and using their beak as a pivot) into rocks until they break.
Charles Darwin used the dozen or so different species of Finch found on the Galapagos Islands to illustrate his newly formulated theory of evolution in his ground-breaking book The Origin Of Species.