Darwin's finches
Encyclopedia
Darwin's finches are a group of 14 or 15 species
of passerine
birds. It is still not clear which bird family
they belong to, but they are not related to the true finches. They were first collected by Charles Darwin
on the Galápagos Islands
during the second voyage of the Beagle
. Thirteen are found on the Galápagos Islands and one on Cocos Island
.
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. The birds vary in size from 10 to 20 cm and weigh between 8 and 38 grams. The smallest is the Warbler Finch
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-colored.
HMS Beagle
, Darwin had no idea 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. 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 of transmutation of species
. From Henslow
's teaching he was interested in 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 the mockingbirds on Charles Island were of one species, those from Albemarle
of another, and those from James
and Chatham Islands of a third species. As they sailed home about nine months later this, together with other facts including what he'd heard about Galápagos tortoise
s, 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 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 finch
es 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.
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 mockingbird
s Darwin had labelled by island were separate species rather than just varieties. Gould found more species than Darwin had anticipated, 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 America
n 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 where he had collected his own specimens. The conclusions supported his idea of the transmutation of species.
), he described Gould's findings on the number of birds, noting that "Although the species are thus peculiar to the archipelago, yet nearly all in their general structure, habits, colour of feathers, and even tone of voice, are strictly American". In the first edition of The Voyage of the Beagle
Darwin said 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".
In 1839 Darwin conceived of his theory of natural selection
, and by the time of the second edition in 1845 Darwin had brought together his theory. He now added two closing sentences: "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".
spent just five weeks in the Galápagos, and David Lack
spent three months, Peter and Rosemary Grant
and their colleagues have made research trips to the Galápagos for about thirty years, particularly studying Darwin's finches. Here we look briefly at the case of the large cactus finch Geospiza conirostris on Isla Genovesa (formerly Tower Island) which is formed from a shield volcano, and is home to a variety of birds. These birds, like all well-studied groups, show various kinds of morphism
.
Males are dimorphic in song type: songs A and B are quite distinct. Also, males with song A have shorter bills than B males. This is also a clear difference. With these beaks males are able to feed differently on their favourite cactus, the prickly pear Opuntia
. Those with long beaks are able to punch holes in the cactus fruit and eat the fleshy aril
pulp which surrounds the seeds, whereas those with shorter beaks tear apart the cactus base and eat the pulp and any insect larvae and pupae (both groups eat flowers and buds). This dimorphism clearly maximises their feeding opportunities during the non-breeding season when food is scarce.
If the population is panmixic
, then Geospiza conirostris exhibits a balanced genetic polymorphism and not, as originally supposed, a case of nascent sympatric speciation
. The selection maintaining the polymorphism maximises the species' niche
by expanding its feeding opportunity. The genetics of this situation cannot be clarified in the absence of a detailed breeding program, but two loci with linkage disequilibrium
is a possibility.
Another interesting dimorphism is for the bills of young finches, which are either 'pink' or 'yellow'. All species of Darwin's finches exhibit this morphism, which lasts for two months. No interpretation of this phenomenon is known.
with the New World sparrows and Old World buntings (Sulloway 1982). However, the Sibley-Ahlquist taxonomy
puts Darwin's finches with the tanager
s (Monroe and Sibley 1993), and at least one recent work follows that example (Burns and Skutch 2003). The American Ornithologists' Union
, in its North America
n 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 America
n check-list, the Galápagos species are incertae sedis, of uncertain place (Remsen et al. 2007).
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of passerine
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
birds. It is still not clear which bird family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
they belong to, but they are not related to the true finches. They were first collected by Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
on the Galápagos Islands
Galápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...
during the second voyage of the Beagle
Second voyage of HMS Beagle
The 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...
. Thirteen are found on the Galápagos Islands and one on Cocos Island
Cocos Island
Cocos Island is an uninhabited island located off the shore of Costa Rica . It constitutes the 11th district of Puntarenas Canton of the province of Puntarenas. It is one of the National Parks of Costa Rica...
.
The term Darwin's Finches was first applied by Percy Lowe
Percy Lowe
Percy Roycroft Lowe was an English surgeon and ornithologist.Lowe was born at Stamford, Lincolnshire and studied medicine at Jesus College, Cambridge. He served as a civil surgeon in the Second Boer War, and it was whilst in South Africa that he became interested in ornithology...
in 1936, and popularised in 1947 by David Lack
David Lack
David Lambert Lack FRS, was a British evolutionary biologist who made contributions to ornithology, ecology and ethology. His book on the finches of the Galapagos Islands was a landmark work.- Early life :...
in his book Darwin's Finches. The birds vary in size from 10 to 20 cm and weigh between 8 and 38 grams. The smallest is the Warbler Finch
Warbler Finch
The Warbler Finch is a species of bird, one of Darwin's finches in the tanager family Thraupidae. Sometimes classified in the family Emberizidae, more recent studies have shown it to belong in the tanager family. It is the only member of the genus Certhidea...
and the largest is the Vegetarian Finch
Vegetarian Finch
The Vegetarian Finch is a species of bird in the Darwin's finch group of the bunting family Emberizidae. It is monotypic within the genus Platyspiza, which is, however, often subsumed into Camarhynchus. It is endemic to the Galapagos Islands...
. 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-colored.
Darwin's theory
During the survey voyage ofSecond voyage of HMS Beagle
The 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...
HMS Beagle
HMS Beagle
HMS Beagle was a Cherokee-class 10-gun brig-sloop of the Royal Navy. She was launched on 11 May 1820 from the Woolwich Dockyard on the River Thames, at a cost of £7,803. In July of that year she took part in a fleet review celebrating the coronation of King George IV of the United Kingdom in which...
, Darwin had no idea of the significance of the birds of the Galápagos. He had learned how to preserve bird specimens while at the University of Edinburgh
University of Edinburgh
The University of Edinburgh, founded in 1583, is a public research university located in Edinburgh, the capital of Scotland, and a UNESCO World Heritage Site. The university is deeply embedded in the fabric of the city, with many of the buildings in the historic Old Town belonging to the university...
and had been keen on shooting, but he had no expertise in ornithology
Ornithology
Ornithology is a branch of zoology that concerns the study of birds. Several aspects of ornithology differ from related disciplines, due partly to the high visibility and the aesthetic appeal of birds...
and by this stage of the voyage concentrated mainly on geology. In Galápagos he mostly left bird shooting to his servant Syms Covington
Syms Covington
Syms Covington was a fiddler and cabin boy on HMS Beagle who became an assistant to Charles Darwin and was appointed as his personal servant in 1833, continuing in Darwin's service after the voyage until 1839. Originally named Simon Covington, he was born in Bedford, Bedfordshire, England, the...
. Nonetheless, these birds were to play an important part in the inception of Darwin's theory
Inception of Darwin's theory
The inception of Darwin's theory occurred during an intensively busy period which began when Charles Darwin returned from the survey voyage of the Beagle, with his reputation as a fossil collector and geologist already established...
of evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
by natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
.
On the Galápagos Islands
Galápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...
and afterward, Darwin thought in terms of "centres of creation" and rejected ideas of transmutation of species
Transmutation of species
Transmutation of species was a term used by Jean Baptiste Lamarck in 1809 for his theory that described the altering of one species into another, and the term is often used to describe 19th century evolutionary ideas that preceded Charles Darwin's theory of natural selection...
. From Henslow
John Stevens Henslow
John Stevens Henslow was an English clergyman, botanist and geologist. He is best remembered as friend and mentor to his pupil Charles Darwin.- Early life :...
's teaching he was interested in geographical distribution of species, particularly links between species on oceanic islands and on nearby continents. On Chatham Island
San Cristóbal Island
San Cristóbal is the easternmost island in the Galápagos archipelago, and one of the oldest geologically.Its Spanish name "San Cristóbal" comes from the patron saint of seafarers, St. Christopher...
he recorded that a mockingbird
Mockingbird
Mockingbirds are a group of New World passerine birds from the Mimidae family. They are best known for the habit of some species mimicking the songs of other birds and the sounds of insects and amphibians, often loudly and in rapid succession. There are about 17 species in three genera...
was similar to those he had seen in Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
, and after finding a different one on Charles Island
Floreana Island
Floreana Island is an island of the Galápagos Islands. It was named after Juan José Flores, the first president of Ecuador, during whose administration the government of Ecuador took possession of the archipelago, having previously been called 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
Tahiti
Tahiti is the largest island in the Windward group of French Polynesia, located in the archipelago of the Society Islands in the southern Pacific Ocean. It is the economic, cultural and political centre of French Polynesia. The island was formed from volcanic activity and is high and mountainous...
Darwin noted that all the mockingbirds on Charles Island were of one species, those from Albemarle
Isabela Island (Ecuador)
Isabela Island is the largest island of the Galápagos with an area of , and length of nearly 4 times larger than Santa Cruz, the next largest of the islands. This island was named in honor of Queen Isabella of Spain, who sponsored the voyage of Columbus. . By the English, it was named Albemarle...
of another, and those from James
Santiago Island (Galápagos)
Santiago Island is an island of the Galápagos Islands. It is also known as San Salvador, named after the first island discovered by Columbus in the Caribbean Sea , or as James Island. The island, which consists of two overlapping volcanoes, has an area of 585 km² and a maximum altitude of...
and Chatham Islands of a third species. As they sailed home about nine months later this, together with other facts including what he'd heard about Galápagos tortoise
Galápagos tortoise
The Galápagos tortoise or Galápagos giant tortoise is the largest living species of tortoise, reaching weights of over and lengths of over . With life spans in the wild of over 100 years, it is one of the longest-lived vertebrates...
s, made him wonder about the stability of species.
Following his return from the voyage, Darwin presented the finches to the Geological Society of London
Geological Society of London
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"...
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
John Gould
John Gould was an English ornithologist and bird artist. The Gould League in Australia was named after him. His identification of the birds now nicknamed "Darwin's finches" played a role in the inception of Darwin's theory of evolution by natural selection...
, 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
Galápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...
which Darwin had thought were blackbirds
Icterid
The Icterids are a group of small to medium-sized, often colorful passerine birds restricted to the New World. Most species have black as a predominant plumage color, often enlivened by yellow, orange or red. The family is extremely varied in size, shape, behavior and coloration...
, "gross-beaks
Grosbeak
Grosbeak is a form taxon containing several species of seed-eating passerine birds with large beaks. Although they all belong to the superfamily Passeroidea, they are not a natural group but rather a polyphyletic assemblage of distantly related songbirds....
" and finch
Finch
The true finches are passerine birds in the family Fringillidae. They are predominantly seed-eating songbirds. Most are native to the Northern Hemisphere, but one subfamily is endemic to the Neotropics, one to the Hawaiian Islands, and one subfamily – monotypic at genus level – is found...
es 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.
Darwin had been in Cambridge
Cambridge
The city of Cambridge is a university town and the administrative centre of the county of Cambridgeshire, England. It lies in East Anglia about north of London. Cambridge is at the heart of the high-technology centre known as Silicon Fen – a play on Silicon Valley and the fens surrounding the...
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
Wren
The wrens are passerine birds in the mainly New World family Troglodytidae. There are approximately 80 species of true wrens in approximately 20 genera....
" was another closely allied species of finch. The mockingbird
Mockingbird
Mockingbirds are a group of New World passerine birds from the Mimidae family. They are best known for the habit of some species mimicking the songs of other birds and the sounds of insects and amphibians, often loudly and in rapid succession. There are about 17 species in three genera...
s Darwin had labelled by island were separate species rather than just varieties. Gould found more species than Darwin had anticipated, 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 America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
n 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
Robert FitzRoy
Vice-Admiral Robert FitzRoy RN achieved lasting fame as the captain of HMS Beagle during Charles Darwin's famous voyage, and as a pioneering meteorologist who made accurate weather forecasting a reality...
, FitzRoy’s steward Harry Fuller and Darwin's servant Covington
Syms Covington
Syms Covington was a fiddler and cabin boy on HMS Beagle who became an assistant to Charles Darwin and was appointed as his personal servant in 1833, continuing in Darwin's service after the voyage until 1839. Originally named Simon Covington, he was born in Bedford, Bedfordshire, England, the...
, who had labelled them by island. From these, Darwin tried to reconstruct the locations where he had collected his own specimens. The conclusions supported his idea of the transmutation of species.
Text from the Voyage of the Beagle
At the time he rewrote his diary for publication as Journal and Remarks (later The Voyage of the BeagleThe Voyage of the Beagle
The Voyage of the Beagle is a title commonly given to the book written by Charles Darwin and published in 1839 as his Journal and Remarks, bringing him considerable fame and respect...
), he described Gould's findings on the number of birds, noting that "Although the species are thus peculiar to the archipelago, yet nearly all in their general structure, habits, colour of feathers, and even tone of voice, are strictly American". In the first edition of The Voyage of the Beagle
The Voyage of the Beagle
The Voyage of the Beagle is a title commonly given to the book written by Charles Darwin and published in 1839 as his Journal and Remarks, bringing him considerable fame and respect...
Darwin said 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".
In 1839 Darwin conceived of his theory of natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
, and by the time of the second edition in 1845 Darwin had brought together his theory. He now added two closing sentences: "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".
Text from the Origin of Species
Darwin discussed the divergence of species of birds in the Galápagos more explicitly in his chapter on geographical distribution in On the Origin of Species:Polymorphism in Darwin's finches
Whereas DarwinCharles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
spent just five weeks in the Galápagos, and David Lack
David Lack
David Lambert Lack FRS, was a British evolutionary biologist who made contributions to ornithology, ecology and ethology. His book on the finches of the Galapagos Islands was a landmark work.- Early life :...
spent three months, Peter and Rosemary Grant
Peter and Rosemary Grant
Peter Raymond Grant and Barbara Rosemary Grant, a married couple, are both British evolutionary biologists at Princeton University; each holds the position of Emeritus Professor. They are noted for their work concerning Darwin's finches on the Galápagos Island named Daphne Major...
and their colleagues have made research trips to the Galápagos for about thirty years, particularly studying Darwin's finches. Here we look briefly at the case of the large cactus finch Geospiza conirostris on Isla Genovesa (formerly Tower Island) which is formed from a shield volcano, and is home to a variety of birds. These birds, like all well-studied groups, show various kinds of morphism
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
.
Males are dimorphic in song type: songs A and B are quite distinct. Also, males with song A have shorter bills than B males. This is also a clear difference. With these beaks males are able to feed differently on their favourite cactus, the prickly pear Opuntia
Opuntia
Opuntia, also known as nopales or paddle cactus , is a genus in the cactus family, Cactaceae.Currently, only prickly pears are included in this genus of about 200 species distributed throughout most of the Americas. Chollas are now separated into the genus Cylindropuntia, which some still consider...
. Those with long beaks are able to punch holes in the cactus fruit and eat the fleshy aril
Aril
An aril is any specialized outgrowth from the funiculus that covers or is attached to the seed. It is sometimes applied to any appendage or thickening of the seed coat in flowering plants, such as the edible parts of the mangosteen and pomegranate fruit, the mace of the nutmeg seed, or the...
pulp which surrounds the seeds, whereas those with shorter beaks tear apart the cactus base and eat the pulp and any insect larvae and pupae (both groups eat flowers and buds). This dimorphism clearly maximises their feeding opportunities during the non-breeding season when food is scarce.
If the population is panmixic
Panmixia
Panmixia means random mating.A panmictic population is one where all individuals are potential partners. This assumes that there are no mating restrictions, neither genetic or behavioural, upon the population, and that therefore all recombination is possible...
, then Geospiza conirostris exhibits a balanced genetic polymorphism and not, as originally supposed, a case of nascent sympatric speciation
Sympatric speciation
Sympatric speciation is the process through which new species evolve from a single ancestral species while inhabiting the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap or are even identical, so that...
. The selection maintaining the polymorphism maximises the species' niche
Ecological niche
In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...
by expanding its feeding opportunity. The genetics of this situation cannot be clarified in the absence of a detailed breeding program, but two loci with linkage disequilibrium
Linkage disequilibrium
In population genetics, linkage disequilibrium is the non-random association of alleles at two or more loci, not necessarily on the same chromosome. It is also referred to as to as gametic phase disequilibrium , or simply gametic disequilibrium...
is a possibility.
Another interesting dimorphism is for the bills of young finches, which are either 'pink' or 'yellow'. All species of Darwin's finches exhibit this morphism, which lasts for two months. No interpretation of this phenomenon is known.
Family
For some decades taxonomists have placed these birds in the family EmberizidaeEmberizidae
The Emberizidae are a large family of passerine birds. They are seed-eating birds with a distinctively shaped bill.In Europe, most species are called buntings. In North America, most of the species in this family are known as sparrows, but these birds are not closely related to the sparrows, the...
with the New World sparrows and Old World buntings (Sulloway 1982). However, the Sibley-Ahlquist taxonomy
Sibley-Ahlquist taxonomy
The Sibley-Ahlquist taxonomy is a bird taxonomy proposed by Charles Sibley and Jon Edward Ahlquist. It is based on DNA-DNA hybridization studies conducted in the late 1970s and throughout the 1980s....
puts Darwin's finches with the tanager
Tanager
The tanagers comprise the bird family Thraupidae, in the order Passeriformes. The family has an American distribution.There were traditionally about 240 species of tanagers, but the taxonomic treatment of this family's members is currently in a state of flux...
s (Monroe and Sibley 1993), and at least one recent work follows that example (Burns and Skutch 2003). The American Ornithologists' Union
American Ornithologists' Union
The American Ornithologists' Union is an ornithological organization in the USA. Unlike the National Audubon Society, its members are primarily professional ornithologists rather than amateur birders...
, in its North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n 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 America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
n check-list, the Galápagos species are incertae sedis, of uncertain place (Remsen et al. 2007).
Species
- Genus GeospizaGeospizaGeospiza is a genus of bird in the Thraupidae family; all species of Geospiza are endemic to the Galápagos Islands; together with related genera they are collectively known as Darwin's finches...
- Large Cactus Finch, Geospiza conirostris
- Sharp-beaked Ground Finch, Geospiza difficilis
- Vampire FinchVampire FinchThe Vampire Finch is a small bird native to the Galápagos Islands. It is a very distinct subspecies of the Sharp-beaked Ground Finch endemic to Wolf and Darwin Islands....
, Geospiza difficilis septentrionalis
- Vampire Finch
- Medium Ground Finch, Geospiza fortis
- Small Ground Finch, Geospiza fuliginosa
- Large Ground Finch, Geospiza magnirostris
- Darwin's Large Ground Finch, Geospiza magnirostris magnirostris – possibly extinct (1957?)
- Common Cactus Finch, Geospiza scandens
- Genus CamarhynchusCamarhynchusCamarhynchus is a genus of bird in the Thraupidae family; all species of Camarhynchus are endemic to the Galápagos Islands, and together with related genera they are collectively known as Darwin's finches...
- Vegetarian FinchVegetarian FinchThe Vegetarian Finch is a species of bird in the Darwin's finch group of the bunting family Emberizidae. It is monotypic within the genus Platyspiza, which is, however, often subsumed into Camarhynchus. It is endemic to the Galapagos Islands...
, Camarhynchus crassirostris – sometimes separated in Platyspiza - Large Tree Finch, Camarhynchus psittacula
- Medium Tree Finch, Camarhynchus pauper
- Small Tree Finch, Camarhynchus parvulus
- Woodpecker FinchWoodpecker FinchThe Woodpecker Finch, Camarhynchus pallidus, is a species of bird in the Darwin's finch group of the tanager family Thraupidae. Woodpecker Finches occur widely in the Galapagos Islands, from sea level to high elevations....
, Camarhynchus pallidus – sometimes separated in Cactospiza - Mangrove FinchMangrove FinchThe Mangrove Finch, Camarhynchus heliobates, is a species of bird in the Darwin's finch group of the tanager family Thraupidae. It is endemic to the Galápagos Islands. It was found on the islands of Fernandina and Isabela, but recent surveys have failed to record the species on Fernandina...
, Camarhynchus heliobates
- Vegetarian Finch
- Genus Certhidea
- Warbler FinchWarbler FinchThe Warbler Finch is a species of bird, one of Darwin's finches in the tanager family Thraupidae. Sometimes classified in the family Emberizidae, more recent studies have shown it to belong in the tanager family. It is the only member of the genus Certhidea...
, Certhidea olivacea
- Warbler Finch
- Genus Pinaroloxias
- Cocos Island FinchCocos Island FinchThe 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. Sometimes classified in the family Emberizidae, more recent studies have shown it to belong in the tanager family...
, Pinaroloxias inornata
- Cocos Island Finch
Molecular basis of beak evolution
Developmental research in 2004 found that bone morphogenetic protein 4 (BMP4), and its differential expression during development, resulted in variation of beak size and shape among finches. BMP4 acts in the developing embryo to lay down skeletal features, including the beak. The same group showed that the different beak shapes of Darwin's finches develop are also influenced by slightly different timing and spatial expression of a gene called calmodulin (CaM). Calmodulin acts in a similar way to BMP4, affecting some of the features of beak growth. The authors suggest that changes in the temporal and spatial expression of these two factors are possible developmental controls of beak morphology.External links
- Grant, K.T. and Estes, G. B. 2009. "Darwin in Galapagos: Footsteps to a New World" Princeton University Press, Princeton. http://www.darwiningalapagos.com
- Sulloway, F.J. (1982): "Darwin and his finches: the evolution of a legend". J. Hist. Biol. 15: p. 1–53
- Different bills and song melodies
- Genetics and the Origin of Birds Species, Grant and Grant in PNAS
- Sato et al. Phylogeny of Darwin's finches as revealed by mtDNA sequences in PNAS
- Galápagos Online. Darwin's Finches.
- Galapagos Online. List of birds of the Galapagos Islands.
- Darwin's Finches Evolve Before Scientists' Eyes: new developments reported 13 July 2006
- Fink F.A.Q. Darwin's finches inspired the naming of the FinkFinkThe Fink project is an effort to port and package open-source Unix programs to Mac OS X. Fink uses dpkg and APT , as well as its own frontend program, fink ....
project, a collaborative initiative for porting open source software to the Darwin platform to enable its use and evolution in the Apple Mac OS X environment. "Fink" is the German name for "finch." - Aug 2006 Nature Article that shows how modulation of a certain gene during development can account for the differences seen in beak shape.
- Speciation Kimball's Biology Pages