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Information about Darwin's Finches

Darwin's Finches
Enlarge picture
Large Ground-finch, Medium Ground-finch
Small Tree-finch, Warbler Finch

Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Aves
Order:Passeriformes
Family:Emberizidae
Genera


Geospiza
Camarhynchus
Certhidea
Pinaroloxias
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. Thirteen reside on the Galápagos Islands and one on Cocos Island.

The birds are all about the same size (10–20 cm). 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 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 Darwin 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).

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-beaks" 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.[1]

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. By mid March he realised that the original immigrants had somehow become altered to produce an array of new species. 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."[2]

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 Beak of the Finch by Jonathan Weiner is a book about the finches, highlighting the Grants' research.

Taxonomy

Family

For some decades taxonomists have placed these birds in the family Emberizidae with the New World sparrows and Old World buntings (Sulloway 1982). However, the Sibley-Ahlquist taxonomy puts Darwin's finches with the tanagers (Monroe and Sibley 1993), and at least one recent work follows that example (Burns and Skutch 2003). The American Ornithologists' Union, in its North American check-list, places the Cocos Island Finch in the Emberizidae but with an asterisk indicating that the placement is probably wrong (AOU 1998–2006); in its tentative South American check-list, the Galápagos species are incertae sedis, of uncertain place (Remsen et al. 2007).

Species

Text from the Voyage of the Beagle

In the first edition of The Voyage of the Beagle Darwin simply described the finches without mentioning his thoughts at that time, merely stating that "It is very remarkable that a nearly perfect gradation of structure in this one group can be traced in the form of the beak, from one exceeding in dimensions that of the largest gros-beak, to another differing but little from that of a warbler."[3] The book was written in the months after John Gould had revealed that the birds which Darwin had thought to be unrelated were different species of finches.[4] The proofs were finished later that year, but the book did not go into print until 1939. By the time of the second edition in 1845 Darwin had brought together his theory, and he cautiously added two closing sentences hinting at his ideas.[5]
The remaining land-birds form a most singular group of finches, related to each other in the structure of their beaks, short tails, form of body and plumage: there are thirteen species, which Mr. Gould has divided into four subgroups. All these species are peculiar to this archipelago; and so is the whole group, with the exception of one species of the sub-group Cactornis, lately brought from Bow Island, in the Low Archipelago. Of Cactornis, the two species may be often seen climbing about the flowers of the great cactus- trees; but all the other species of this group of finches, mingled together in flocks, feed on the dry and sterile ground of the lower districts. The males of all, or certainly of the greater number, are jet black; and the females (with perhaps one or two exceptions) are brown. The most curious fact is the perfect gradation in the size of the beaks in the different species of Geospiza, from one as large as that of a hawfinch to that of a chaffinch, and (if Mr. Gould is right in including his sub-group, Certhidea, in the main group) even to that of a warbler. The largest beak in the genus Geospiza is shown in Fig. 1, and the smallest in Fig. 3; but instead of there being only one intermediate species, with a beak of the size shown in Fig. 2, there are no less than six species with insensibly graduated beaks. The beak of the sub-group Certhidea, is shown in Fig. 4. The beak of Cactornis is somewhat like that of a starling, and that of the fourth subgroup, Camarhynchus, is slightly parrot-shaped. Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends. In a like manner it might be fancied that a bird originally a buzzard, had been induced here to undertake the office of the carrion-feeding Polybori of the American continent.[6]

Notes

1. ^
2. ^
3. ^
4. ^
5. ^
6. ^

References

  • id="CITEREFDarwin1839">Darwin, Charles (1839), Narrative of the surveying voyages of His Majesty's Ships Adventure and Beagle between the years 1826 and 1836, describing their examination of the southern shores of South America, and the Beagle's circumnavigation of the globe. Journal and remarks. 1832-1836., vol. III, London: Henry Colburn.
    • id="CITEREFDarwin1845">Darwin, Charles (1845), Journal of researches into the natural history and geology of the countries visited during the voyage of H.M.S. Beagle round the world, under the Command of Capt. Fitz Roy, R.N. 2d edition, London: John Murray.
      • id="CITEREFDarwin1887">Darwin, Francis (1887), "Chapter 1, The Foundations of the 'Origin of Species'", in Darwin, Francis, The life and letters of Charles Darwin, including an autobiographical chapter., vol. 2, London: John Murray
        • id="CITEREFDesmondMoore1991">Desmond, Adrian & James Moore (1991), Darwin, London: Michael Joseph, Penguin Group, ISBN 0-7181-3430-3

          External links

          G. magnirostris

          Binomial name
          Geospiza magnirostris
          Gould, 1837

          The Large Ground-finch (Geospiza magnirostris) is a species of bird in the Emberizidae family.
          ..... Click the link for more information.
          G. fortis

          Binomial name
          Geospiza fortis
          Gould, 1837

          The Medium Ground-finch (Geospiza fortis) is a species of bird in the Emberizidae family. It is endemic to Ecuador.
          ..... Click the link for more information.
          C. parvulus

          Binomial name
          Camarhynchus parvulus
          (Gould, 1837)

          The Small Tree-finch (Camarhynchus parvulus) is a species of bird in the Emberizidae family. It is endemic to Ecuador.
          ..... Click the link for more information.
          Certhidea

          Species: C. olivacea

          Binomial name
          Certhidea olivacea
          Gould, 1837

          The Warbler Finch (Certhidea olivacea
          ..... Click the link for more information.
          Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. Scientific classification also can be called scientific taxonomy, but should be distinguished from folk taxonomy, which lacks scientific basis.
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          Chordata
          Bateson, 1885

          Typical Classes

          See below

          Chordates (phylum Chordata) are a group of animals that includes the vertebrates, together with several closely related invertebrates.
          ..... Click the link for more information.
          Aves
          Linnaeus, 1758

          Orders

          About two dozen - see section below

          Birds (class Aves) are bipedal, warm-blooded, egg-laying vertebrate animals.
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          Passeriformes
          Linnaeus, 1758

          Suborders
          • Acanthisitti
          • Tyranni
          • Passeri


          A passerine is a bird of the giant order Passeriformes. More than half of all species of bird are passerines.
          ..... Click the link for more information.
          Emberizidae
          Vigors, 1831

          Genera

          Over 70, see text

          The Emberizidae are a large family of passerine birds.

          They are seed-eating birds with a distinctively shaped bill. In Europe, most species are named as buntings.
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          Genera was an operating system and development environment for Lisp machines developed by Symbolics. It was essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI. The ~1.
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          Certhidea

          Species: C. olivacea

          Binomial name
          Certhidea olivacea
          Gould, 1837

          The Warbler Finch (Certhidea olivacea
          ..... Click the link for more information.
          Pinaroloxias
          Sharpe, 1885

          Species: P. inornata

          Binomial name
          Pinaroloxias inornata
          (Gould, 1843)

          The Cocos Island Finch or
          ..... Click the link for more information.
          species is one of the basic units of biological classification. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring.
          ..... Click the link for more information.
          Fringillidae
          Vigors, 1825

          Genera

          Many, see text

          Finches are passerine birds, often seed-eating, found chiefly in the northern hemisphere and Africa. One subfamily is endemic to the Neotropics.
          ..... Click the link for more information.
          Charles Robert Darwin

          At the age of 51, Charles Darwin had just published On the Origin of Species.
          ..... Click the link for more information.
          State Party  Ecuador
          Type Natural
          Criteria vii, viii, ix, x
          Reference 1
          Region Latin America and the Caribbean

          Inscription History
          Inscription 1978  (2nd Session)

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          second voyage of HMS Beagle from 27 December 1831 to 2 October 1836 was the second survey expedition of HMS Beagle, under captain Robert FitzRoy who had taken over command of the ship on its first voyage after her previous captain committed suicide.
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          The inception of Darwin's theory began with a search for explanations of contradictions in current faith based ideas, and led him to formulate his theory of natural selection which was eventually published in his book On the Origin of Species.
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          Natural selection is the process by which favorable traits that are heritable become more common in successive generations of a population of reproducing organisms, and unfavorable traits that are heritable become less
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          HMS Beagle was a Cherokee class 10-gun brig of the Royal Navy, named after the beagle, a breed of dog. She was launched on 11 May 1820 from the Woolwich Dockyard on the River Thames, at a cost of £7,803.
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          The Geological Society of London is a learned society based in the United Kingdom with the aim of "investigating the mineral structure of the Earth". It is the oldest national geological society in the world and the largest in Europe with over 9000 Fellows entitled to the
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          John Gould (14 September 1804 – 3 February 1881) was an English ornithologist. The Gould League in Australia was named after him. His identification of Charles Darwin's finches was pivotal in the development of the theory of The Origin of Species.
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          Ornithology (from Greek: ορνισ, ornis, "bird"; and λόγος, logos, "knowledge") is the branch of zoology concerned with the study of birds.
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