Darwin's finches

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Darwin's finches

or

Galapagos finches

(gəlä`pəgōs'), species of small perching birds, constituting the subfamily Geospizinae of the tanagertanager
, any of the small, migratory perching birds of the family Thraupidae, chiefly of the tropical New World. Only five species migrate to North America; of these the scarlet tanager (Piranga olivacea) has the widest range in the United States. It is about 7 in.
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 family. Not related to the true finches, this group of at least fifteen species is confined to the Galápagos Islands, except for a single species found on Cocos Island, about 600 mi (960 km) northeast. Their special adaptations to various habitats were important evidence considered by Charles DarwinDarwin, Charles Robert,
1809–82, English naturalist, b. Shrewsbury; grandson of Erasmus Darwin and of Josiah Wedgwood. He firmly established the theory of organic evolution known as Darwinism.
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 in formulating the theory of evolutionevolution,
concept that embodies the belief that existing animals and plants developed by a process of gradual, continuous change from previously existing forms. This theory, also known as descent with modification, constitutes organic evolution.
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; they are a striking example of adaptive radiationadaptive radiation,
in biology, the evolution of an ancestral species, which was adapted to a particular way of life, into many diverse species, each adapted to a different habitat.
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.

Geographically isolated and without competition from similar species, Darwin's finches developed distinctive anatomy (particularly beak size and shape) and behaviors, with each species exploiting a unique feeding niche. The bill is adapted in the different species for different purposes, such as crushing seeds, pecking wood, and probing flowers for nectar. The woodpecker finch, Camarhynchus pallidus or Cactospiza pallida, an insect-eater, holds twigs and cactus spines in its beak to fish out larvae in tree cavities. Darwin proposed that the Galapagos finches evolved on the islands from a single bird species from mainland South America. Modern methods of DNA (genetic) analysis have confirmed his insight. Darwin's finches are classified in several genera of the phylum ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
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, subphylum Vertebrata, class Aves, order Passeriformes, family Thraupidae, subfamily Geospizinae.

Bibliography

See P. Grant, Ecology and Evolution of Darwin's Finches (1986).