Geospiza difficilis

The Sharp-beaked Ground Finch (Geospiza difficilis) is a species of bird in the Darwin's finch group of the tanager family Thraupidae. This rather small, slender-billed bird is endemic to the Galápagos Islands, where found on Fernandina, Santiago, Pinta, Genovesa, Darwin and Wolf. On the first three islands, it breeds in the humid highlands and disperses afterwards, but on the remaining smaller and lower islands the Sharp-beaked Ground Finch is found in the arid zone year-round. Formerly it was also present in the highlands of several other islands, and it is possible it still occurs on Isabela.

The subspecies on the islands of Darwin and Wolf has gained a level of notoriety due to its habit of feeding on blood of large birds, notably boobies, gaining it the common name Vampire Finch. Other subspecies do not exhibit this behavior, insteading feeding mainly on insects.
References

BirdLife International 2004. Geospiza difficilis. 2006 IUCN Red List of Threatened Species. Downloaded on 25 July 2007.
Sharp-beaked Ground Finch media at ARKive