Unique amongst birds, the sharp-beaked ground finch is famed for the extraordinary feeding habits that have earned it the sinister pseudonym of the 'vampire finch' (3) (4). Like the other ground finches (Geospiza sp.), the adult male plumage is completely black, while the female is brown and streaked (2). However, different populations of this species exhibit greater variation in appearance and ecology than any other of Darwin's celebrated finches. Whereas some populations are similar in appearance to the common cactus-finch (Geospiza scandens) with its long pointed beak, others are slighter in build and bare a closer resemblance to the small ground-finch (Geospiza fuliginosa) (2) (5) (6). Indeed, so great is the morphological variation amongst populations, that questions have been raised about its status as a single species (2) (6).