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R.F.C.G. News

News update April 2009

HOW 14 FINCH SPECIES AND ONE MAN CHANGED THE WORLD'S THINKING

Published by the Rare Finch Conservation Group

2009 marks the bicentenary of the birth of Charles Darwin on 11 February, and the 150th anniversary on 24 November of the publication of his epoch-marking work " On the Origin of Species by means of Natural Selection ." These events are being celebrated around the world with innumerable museum exhibitions ,conventions ,television documentaries and even a full length movie.

It is apposite for the Rare Finch Conservation Group to align itself with these worldwide tributes to one of the world's greatest thinkers of all time, and to this scientific discovery that has developed into evolutionary biology, ranging astronomically wider and deeper with the advent of ever increasingly sophisticated technological means, undreamed of in Darwin's day.

The revolutionary theory of evolution was developed by Darwin from data gathered during his 5 year voyage around the world on HMS Beagle as a naturalist on a surveying expedition ( 1831-1836 ). The main clue came from the collection of 14 species of finches in which the males are predominantly black with more or less white, grey or brown areas streaked in darker tones apparent on their lower parts, while the females are dully coloured greyish brown birds much paler underneath and with heavy darker streaks throughout.

Their most amazing feature is the difference in their beaks, clearly suiting them to food gathering in their specific isolated habitats in the remote Galapagos Islands, 500 miles west of Ecuador, where many other strange forms of life are found e.g giant tortoises,
( GALAPOS is the Spanish name for a tortoise ). For example one species the Cactus ground-finch ( Geospiza scandens ) has a long decurved beak designed for feeding off flowers of the prickly pear, while another ,the Woodpecker-finch ( Camarhynchus pallidus ) has a stout straight beak modified in the direction of a woodpecker , but with which it uniquely holds a rigid cactus spine 3 to 5 cm long lengthwise to poke into the crack in the bark of a tree, then dropping it to seize the insect as it emerges .On the other hand a species feeding on hard seeds, such as the Large ground-finch ( Geospiza magnirostris ) has a very heavy conical beak .

Early in 1837 the birds collected by Darwin were sent to the Zoological Society in London for expert evaluation, and the greatest ornithologist of the day , John Gould , identified 13 species from the Galapagos, 11 of which were new to science. Gould's identification of these species as finches ,although they occupied ecological niches filled by other types of birds elsewhere in the world e.g woodpeckers, and in some instances resembled aspects of those types ,was remarkable. Gould worked further and found that the specimens of the Galapagos mocking birds collected by Darwin showed great enough differences to be categorized in 3 distinct species, each of which was confined to a separate island, as was proved through Darwin's careful noting of where each specimen had been found . It is thought probable that it was during discussions between these two great men on the above and many further instances, that for Darwin the penny began to drop that these species were not ready-made by God to the perfect design required for life in their particular environments, but that they were forms of a common ancestral stock gradually modified by isolation in their harsh and diverse habitats through the processes of natural selection and the survival of the fittest.

Darwin hesitated for a further 12 years , making quite sure and not wanting to offend the sensibilities of Christians , especially his wife , before publishing his controversial theory. In its wake came fame and infamy . It met a good deal of mindless prejudice and no insult was deemed too harsh to be hurled at " the man who killed the Creator ." Yet 150 years on few indeed would be foolhardy enough to contradict the essence of Darwin's view .

For anyone interested in what are known as " Darwin's finches."( some 14 species in 3 genera ) the RFCG can recommend the book by David Lack " Darwin's Finches -an essay on the general biological theory of evolution"(Harper&Brothers,New York.1947) or refer to the websites at the end of this article .

David Lack saw the 14 species of Darwin's finches as an ideal group for the study of territorial behavior in birds and traveled to the Galapagos in 1938/39 to conduct ecological studies on them at first hand in their natural habitats. The result was a very thorough scientific treatise, the writing of which was interrupted by the War, and it was only published in 1947 . It was found that the taxonomic problems of speciation needed experimentation in crossbreeding the different species, for which several of the species were taken into captivity. The test of species formation is whether, when two forms meet they interbreed and merge ,or whether they keep distinct through sterility of the offspring. The level of the diversity between any two species can thus be determined by the degree of sterility found in their hybrid offspring. Therefore experimental hybrid breeding of the Galapagos finches under controlled conditions could furnish a far better understanding of their speciation. Lack had hoped to take the finches to England to complete the study ,but ultimately it was deemed best for the birds to take them first on the far shorter journey to California ,where the California Academy of Sciences in San Francisco ,an institution which had long made a special study of the Galapagos fauna and flora offered to house them .

Until the special buildings could be erected an amateur aviculturist of great skill , E.C Kinsey ,took charge of them in his private aviaries succeeding in getting them into very good condition .Ultimately at the California Academy of Sciences several species bred successfully with their own kind , but no results were achieved with crossing the species by the time Lack published his book . Since then the taking of birds into controlled environments in the interests of science has been made increasingly difficult despite improved technology in transport and diets etc. As far as we are aware no further attempts at propagating Darwin's finches and experimenting in crossbreeding the various species has been attempted under controlled conditions .

The time of Darwin predates what is today known as " Aviculture"( the keeping and breeding of birds - analogous to " Horticulture" for gardening) . If he had been around today he certainly would have been interested in this pursuit and probably actively involved in it ,for at his home in Downe, Kent he kept, bred and meticulously studied the most popular bird of his day ,the domestic pigeon. He used his first hand experiences with the massive diversity of the different breeds - Tumblers, Carriers, Runts, Pouters, Fantails, Trumpeters etc. to challenge the then accepted theory of the " Immutability of the Species ." and became convinced (correctly) that they were all descended from a single species ,the Rock Pigeon ( Calumba livia )

Fortunately at the time of the publication of Threatened Birds of the World by Bird Life International in 2000 only 2 of the 14 Darwin's finches were listed as struggling to survive . The Medium Tree Finch ( Camarhynchus pauper ) with a population 1000-2,499 was categorized as "Vulnerable " and the Mangrove Finch ( Camarhynchus heliobates ) with a population below 110 as Critical .

Listed as reasons for their decline are introduced predators such as rats, cats, dogs ,pigs and cattle, extensive habitat destruction and degradation for agriculture ,free ranging domestic live stock ,the arrival of a wasp ( poliste versicolor ) in the early 1900's and many parasite insect larvae

In view of the avicultural expertise available today and the extent to which these finches proved amenable to breeding in aviaries as far back as the 1940's, some form of intervention and the building up of viable stocks maintained under controlled conditions would seem wise. It is sad to think that despite all the advances in technology and expertise in aviculture since Darwin's day, such a move would be likely to be met in some quarters with quite as much mindless prejudice and obstruction as was encountered by Darwin in 1859 !

For more information on Charles Darwin and the Darwin finches the Rare Finch Conservation Group recommends that readers visit:

http://en.wikipedia.org/wiki/Darwin's_finches

http://www.biology-online.org/2/11_natural_selection.htm

http://www.pbs.org/wgbh/evolution/library/01/6/l_016_02.html

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Speciation.html

http://www.travel-travel-travel.com/out/archives/16/DARWINS_FINCHES.htm

http://www.darwinfoundation.org/files/species/pdf/finches-en.pdf

The attached watercolour portrait of Charles Darwin at the age of 31 was done by George Richmond in 1840


 

 

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