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 (Grant et al. 2000).
The vampire finch is sexually dimorphic as typical for its genus, with the males being primarily black and the females grey with brown streaks. It has the largest and most pointed beak of all G. difficilis subspecies, and overall looks like a miniature Common Cactus-Finch rather than, as the other subspecies do, a large Small Ground-Finch with a straight bill (Schluter & Grant 1984). It has a lilting song on Wolf, a buzzing song on Darwin, and whistling calls on both islands; only on Wolf, a drawn-out, buzzing call is also uttered.(Grant et al. 2000)
This bird is most famous for its unusual diet. The Vampire Finch occasionally feeds by 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 (Schluter & Grant 1984). Curiously, the boobies do not offer much resistance against this. 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.
More conventionally for birds, but still unusual among Geospiza, they also take nectar from Galápagos prickly pear (Opuntia echios var. gigantea) flowers at least on Wolf (Schluter & Grant 1984). The reasons for these peculiar feeding habits are the lack of freshwater on these birds' home islands. Nonetheless, the mainstay of their diet is made up from seeds and invertebrates as in their congeners (Schluter & Grant 1984).
The vampire finch is endangered, being a small-island endemic. The Galápagos finch species collectively form a showcase example of Charles Darwin's theory of natural selection. The 12 or 13 species of Galapagos finches are often called "Darwin's Finches". They are used as an example of how the descendants of one ancestor can evolve into several species as they adapt to different conditions.
- Grant, Peter R.; Grant, B. Rosemary & Petren, Kenneth (2000): The allopatric phase of speciation: the sharp-beaked ground finch (Geospiza difficilis) on the Galápagos islands. Biol. J. Linn. Soc. 69(3): 287–317. PDF fulltext