Galapagos birdlife & evolution - Ground finches

The four species of ground finches are similar in coloration -- adult males are black, and females streaked brown. They all have bills of the "crushing" variety, useful for feeding on seeds.

Sharp-beaked finch
(Geospiza nebulosa) of the humid highlands of the central and western islands is highly endangered, unfortunately since some ornithologists believe it may be the closest to the ancestral form of all Darwin's finches. On Wolf Island (or Culpepper, in the northwest corner of the archipelago) this finch is called the "vampire finch," for its habit of pecking at the skin of boobies until they draw blood, which they drink. Such a behavior may have evolved from eating the parasitic insects that are found in bird plumage (as ground finches do in other islands).

Small ground finch
(G. fuliginosa) is wide-spread throughout the archipelago except Genovesa and the smaller islands of the northwest, Darwin (Wenman) or Wolf.

Medium ground finch
(G. fortis) is also not present on smaller islands Espanola, Genovesa, Darwin and Wolf(where it may be extinct).

Large ground finch
(G. magnirostris), though less common than other ground finches, is found on all major islands except Genovesa and Wolf. All three species have similar appearance and behavior, and telling them apart is a challenge even for ornithologists.