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Darwin's finches (also known as the Galápagos finches) are a group of about fifteen species of passerine birds. They are often classified as the subfamily Geospizinae or tribe Geospizini. They belong to the tanager family and are not closely related to the true finches. They were first collected by Charles Darwin on the Galápagos Islands during the second voyage of the ''Beagle''. Apart from the Cocos finch, which is from Cocos Island, the others are found only on the Galápagos Islands. The term "Darwin's finches" was first applied by Percy Lowe in 1936, and popularised in 1947 by David Lack in his book ''Darwin's Finches''.〔Lack, David. 1947. ''Darwin's Finches''. Cambridge University Press (reissued in 1961 by Harper, New York, with a new preface by Lack; reissued in 1983 by Cambridge University Press with an introduction and notes by Laurene M. Ratcliffe and Peter T. Boag). ISBN 0-521-25243-1〕 David Lack based his analysis on the large collection of museum specimens collected by the 1905–06 Galápagos expedition of the California Academy of Sciences, to whom Lack dedicated his 1947 book. The birds vary in size from 10 to 20 cm and weigh between 8 and 38 grams. The smallest are the warbler-finches and the largest is the vegetarian finch. The most important 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 dull-coloured. == Darwin's theory == During the survey voyage of HMS ''Beagle'', Darwin was unaware of the significance of the birds of the Galápagos. He had learned how to preserve bird specimens while at the University of Edinburgh and had been keen on shooting, but he had no expertise in ornithology and by this stage of the voyage concentrated mainly on geology.〔Grant, K. Thalia and Estes, Gregory B. 2009 "Darwin in Galapagos: Footsteps to a New World" Princeton University Press, Princeton.〕 In Galápagos he mostly left bird shooting to his servant Syms Covington. Nonetheless, these birds were to play an important part in the inception of Darwin's theory of evolution by natural selection. On the Galápagos Islands and afterward, Darwin thought in terms of "centres of creation" and rejected ideas concerning the transmutation of species.〔 〕 From Henslow's teaching, he was interested in the geographical distribution of species, particularly links between species on oceanic islands and on nearby continents. On Chatham Island, he recorded that a mockingbird was similar to those he had seen in Chile, and after finding a different one on Charles Island he carefully noted where mockingbirds had been caught.〔 In contrast, he paid little attention to the finches. When examining his specimens on the way to Tahiti, Darwin noted that all of the mockingbirds on Charles Island were of one species, those from Albemarle of another, and those from James and Chatham Islands of a third. As they sailed home about nine months later, this, together with other facts, including what he had heard about Galápagos tortoises, made him wonder about the stability of species. 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 that 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 the birds from the Galápagos Islands that Darwin had thought were blackbirds, "gross-beaks" and finches were actually "a series of ground Finches which are so peculiar (to form ) an entirely new group, containing 12 species". This story made the newspapers. Darwin had been in Cambridge at that time. In early March, he met Gould again and for the first time got a full report on the findings, including the point that his Galápagos "wren" was another closely allied species of finch. The mockingbirds that Darwin had labelled by island were separate species rather than just varieties. Gould found more species than Darwin had expected, and concluded that 25 of the 26 land birds were new and distinct forms, found nowhere else in the world but closely allied to those found on the South American continent.〔 Darwin now saw that, if the finch species were confined to individual islands, like the mockingbirds, this would help to account for the number of species on the islands, and he sought information from others on the expedition. Specimens had also been collected by Captain Robert FitzRoy, FitzRoy’s steward Harry Fuller and Darwin's servant Covington, who had labelled them by island. From these, Darwin tried to reconstruct the locations from where he had collected his own specimens. The conclusions supported his idea of the transmutation of species.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Darwin's finches」の詳細全文を読む スポンサード リンク
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