Vampire ground finch
The vampire ground finch (Geospiza septentrionalis) is a small bird native to the Galápagos Islands. It was considered a very distinct subspecies of the sharp-beaked ground finch (Geospiza difficilis) endemic to Wolf and Darwin Islands. The International Ornithologists' Union has split the species supported by strong genetic evidence that they are not closely related, and divergences in morphology and song. Other taxonomic authorities still consider it conspecific.
|Vampire ground finch|
Geospiza difficilis septentrionalis
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 on Wolf, a buzzing song on Darwin, and whistling calls on both islands; only on Wolf, a drawn-out, buzzing call is also uttered.
This bird is most famous for its unusual diet. When alternative sources are scarce 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. 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. Finally guano and leftover fish from other predators additionally serve as diet options. 
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. The reason for these peculiar feeding habits is 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.
- BirdLife International (2017). "Geospiza septentrionalis". The IUCN Red List of Threatened Species. 2017: e.T103815245A119461181. doi:10.2305/IUCN.UK.2017-3.RLTS.T103815245A119461181.en.
- 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. doi:10.1006/bijl.1999.0382
- Rothschild, W. and E. Hartert. (1899). A Review of the Ornithology of the Galapagos Islands. With Notes on the Webster-Harris Expedition. Novitates Zoologicae Vol. VI, No. 2, pp. 85-205, 2 plates.
- Farrington, Heather; Lawson, Lucinda; Clark, Courtney; Petren, Kenneth (29 July 2014). "The evolutionary history of Darwin's finches: speciation, gene flow, and introgression in a fragmented landscape". Evolution. 68 (10): 2932–2944. doi:10.1111/evo.12484. PMID 24976076.
- Schluter, Dolph & Grant, Peter R. (1984). Ecological Correlates of Morphological Evolution in a Darwin's Finch, Geospiza difficilis. Evolution 38(4): 856-869. doi:10.2307/2408396 (HTML abstract and first page image)
- Michel, Alice J.; Ward, Lewis M.; Goffredi, Shana K.; Dawson, Katherine S.; Baldassarre, Daniel T.; Brenner, Alec; Gotanda, Kiyoko M.; McCormack, John E.; Mullin, Sean W. (2018-09-19). "The gut of the finch: uniqueness of the gut microbiome of the Galápagos vampire finch". Microbiome. 6 (1): 167. doi:10.1186/s40168-018-0555-8. ISSN 2049-2618. PMC 6146768. PMID 30231937.
- Galef, Bennett G., Jr. Bekoff, Marc; Jamieson, Dale (eds.). Interpretation and Explanation in the Study of Animal Behavior. Volume I: Interpretation, Intentionality, and Communication. Boulder, San Francisco & Oxford: Westview Press. p. 78. ISBN 978-0-8133-7979-1.