Darwin Finches
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Darwin's finches (also known as the Galápagos Finches) are 13 or 14 different but closely related species of finches Charles Darwin collected on the Galápagos Islands during the Voyage of the Beagle. 13 reside on the Galápagos Islands and one on the Cocos Islands.
The birds are all about the same size (10–20 cm). The largest differences between species are in the size and shape of their beaks, and the beaks are highly adapted to different food sources. The birds are all brownish or black. Their behaviour differs and they have different song melodies.
The finches and Darwin's theory
Although these birds were to play an important part in the inception of Darwin's theory of evolution by natural selection, at the time of the survey voyage of HMS Beagle he had no idea of their significance. It is often assumed that when he saw the finches on the islands this inspired the theory, but this is not true: Darwin believed that they were not closely related when he encountered them, indeed he thought that most of these birds were not finches at all (Sulloway 1982), although he realized the close relationship of those species which he did recognize as finches.
Following his return from the voyage, Darwin presented the finches to the Geological Society of London at their meeting on 4 January 1837, along with other mammal and bird specimens he had collected. The bird specimens, including the finches, were given to John Gould, the famous English ornithologist, for identification. Gould set aside his paying work and at the next meeting on 10 January reported that birds from the Galápagos Islands which Darwin had thought were blackbirds, "gross-bills" and finches were in fact "a series of ground Finches which are so peculiar" as to form "an entirely new group, containing 12 species." This story made the newspapers. In March Darwin met Gould again, learning that his Galápagos "wren" was another species of finch and the mockingbirds he had labelled by island were separate species rather than just varieties, with relatives on the South American mainland. Darwin had not bothered to label his finches by island, but others on the expedition had taken more care. He now sought specimens collected by captain Robert FitzRoy and crewmen. From them he was able to establish that the species were uniquely related to individual islands, giving him the idea that somehow in this geographical isolation these different species could have been formed from a small number of common ancestors so that each was modified to suit "different ends".
The term Darwin's Finches was first applied in 1936, and popularized in 1947 by David Lack. Later, Peter and Rosemary Grant conducted extensive research in documenting evolutionary change among the finches. Beginning in 1973, the pair spent many years tracking thousands of individual finches across several generations, showing how individual species changed in response to environmental changes.
The finch species
- Genus Geospiza
- Large Cactus-Finch (Geospiza conirostris)
- Sharp-beaked Ground-Finch (Geospiza difficilis)
- Medium Ground-Finch (Geospiza fortis)
- Small Ground-Finch (Geospiza fuliginosa)
- Large Ground-Finch (Geospiza magnirostris)
- Common Cactus-Finch (Geospiza scandens)
- Genus Camarhynchus
- Vegetarian Finch (Camarhynchus crassirostris syn. Platyspiza crassirostris)
- Large Tree-Finch (Camarhynchus psittacula)
- Medium Tree-Finch (Camarhynchus pauper)
- Small Tree-Finch (Camarhynchus parvulus)
- Woodpecker Finch (Camarhynchus pallidus) :
The Woodpecker Finch, Camarhynchus pallidus, is one of the so-called Darwin's finches. First seen by Charles Darwin on the Galapagos Islands, it is a unique species which uses a twig, stick, or cactus spine as a tool. The tool is used as compensation for its short tongue. The finch manipulates the tool to dislodge invertebrate prey such as grubs from trees. The same tool can be used many times on many different trees. Scientists have observed that the finches may shorten the stick or spine to make it more manageable. The finches may also try various sticks or spines at one site before finding just the appropriate one that can reach and extract the prey item. Tool use, however, is not a common behavior; most prey items are extracted using the beak in the usual manner. Woodpecker Finches occur widely in Galápagos, from sea level to high elevations.
- Mangrove Finch (Camarhynchus heliobates)
- Genus Certhidea
- Warbler Finch (Certhidea olivacea)
- Genus Pinaroloxias
- Cocos Island Finch (Pinaroloxias inornata):
The Cocos Island Finch or Cocos Finch, Pinaroloxias inornata, is the only one of Darwin's finches not native to the Galápagos Islands, and the only member of the genus Pinaroloxias. It is endemic to Cocos Island, approximately 360 miles south of Costa Rica, where it is the most common landbird.
It is a chunky 12 cm long finch weighing about 12.5 g and with a black decurved pointed bill. The male is entirely black, the female is brown, paler below and heavily streaked. The young are similar but have yellow bills.
The roughly spherical nest is built at the end of a branch, and the standard clutch is two brown-spotted white eggs.
The Cocos Finch is found in all available habitats and eats a wide range of plant and insect food.
This species qualifies as Vulnerable because it has a very small range.
- Cocos Island Finch (Pinaroloxias inornata):
Copyright: Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia.org
Related Web Resources: Galapagos
Care and Feeding:
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