The Vampire ground finch (Geospiza septentrionalis) or Vampire finch is a small bird native to the Galápagos Islands. A member of the Darwin's finches group, it is known for its unique parasitic behavior of feeding on the blood of other birds. It is endemic to Wolf and Darwin Island. The species was previously considered a very distinct subspecies of the sharp-beaked ground finch (Geospiza difficilis),
Description
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 a lilting song along with a drawn-out, buzzing call on Wolf, a buzzing song on Darwin, and whistling calls on both islands. This behaviour may have evolved as a symbiotic relationship, with the finches removing ectoparasites from the boobies' feathers, but has become a parasitic relationship over time. While boobies will typically swat at pecking finches, several finches may feed on a single booby at once, making defense impractical. The finches also predate the boobies' eggs, making their hosts reluctant to leave their nests to stop the blood-letting.
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 Island.