In Greek folklore, vampire women with the power to transform themselves into birds of prey or other sinister animals. The striges derived from the Roman strix, a night demon, named for the screech owl. It was believed to attack infants and drain their blood. The strix appears across southern Europe, where it is known variously as strega (Italy), striges (Greece), and strigoi (Romania). The striges differed from other vampire creatures in that they were thought of as living members of the community rather than the returning dead.
Melton, J. Gordon. The Vampire Book: The Encyclopedia of the Undead. Detroit: Visible Ink Press, 1994.