Darwin’s Finch – Galapagos Finch
April 29, 2010 § Leave a Comment
Have you ever wondered about how man became the dominate species in the world? We’re not the biggest, the fastest, the strongest or the hardest working creature on the planet. What separates us from other creatures is both our intelligence and our ability to use tools. Man’s use of tools dates back to prehistoric ages when we used stones and clubs throughout history. Over the years we have developed new tools making our lives easier and making it possible to dominate our environment.
For many years it was thought that man was the only creature that used tools, through research it was observed that other animals also use tools. Sticks and stones have been observed being used for various purposes. Other than humans, primates are known to make the widest use of tools and the Woodpecker Finch that collects up to 50% of their diet by using a tool to collect their food. These finches are second only to man, in their reliance of tools in order to obtain food. The Woodpecker Finch uses sticks, twigs and cactus spines to make up for its short tongue and gather insects from plants and trees.
The Woodpecker Finch is just one of 14 species known as Darwin Finch named after Charles Darwin. Darwin collected these finches during his visit to the Galapagos. Brownish Grey in color these noisy birds were unimpressive at first – Darwin thought them to be blackbirds or grosbeaks. Upon returning to England, Darwin presented the birds along with other animals he collected during his voyage to the Geological Society of London it was there that an ornithologist, discovered that Darwin had discovered an entirely new group of birds and 12 different species. It was this discovery, which directly led to his theory of evolution and the transmutation of species.
“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”
Since the days of Darwin this group of birds continues to intrigue scientists. The term “Darwin Finch” was coined in the 1900’s and made popular by David Lack who spent 3 months in the Galapagos studying the birds and wrote a book about his studies. Yet the real experts on the Darwin Finch are Peter and Rosemary Grant who spent 30 years studying the birds and wrote the Pulitzer Prize winning book The Beak of the Finch. Winners of the prestigious Balzan prize for popular biology their citation reads…
“Peter and Rosemary Grant are distinguished for their remarkable long-term studies demonstrating evolution in action in Galápagos finches. They have demonstrated how very rapid changes in body and beak size in response to changes in the food supply are driven by natural selection. They have also elucidated the mechanisms by which new species arise and how genetic diversity is maintained in natural populations. The work of the Grants has had a seminal influence in the fields of population biology, evolution and ecology.”
Through these studies we have come to learn there are 14 species of Darwin Finch 13 in the Galapagos Islands plus one living at Cocos Island. These birds are members of the tanager family rather than a true finch. Each species is approximately the same size 10 – 20 cm making them difficult to tell apart. The primary difference between the finches is their beak size and shape which mutated to adapt to their diet ranging from seeds, insects, flowers, leaves and the blood of sea birds. For example, finches which eat insects will have a thin extended beak to poke into holes in the ground and extract the grubs. Finches that eat flowers and seeds have a claw like beaks can grind down their food and thus give them a selective advantage in circumstances in parts of the islands where seeds are the only real food available.
Typically the Darwin Finch are divided into (4) groups representing each genus: ground finches (Geospiza) are made up of 4 species seeding eating ground finches each with a crushing bill plus one cactus dwelling finch with a probing bill. There is the insect eating warbler finch (Certhidea) with its probing bill and the Cocos Finch (Pinaroloxias). As well as the more diversified group of tree finches (amarhynchus) consisting of the fruit eating vegetarian tree finch with its parrot like bill, the small and large tree finch both dine on insects and have a grasping bill. The Woodpecker finch we discussed earlier with its probing bill. Found only on the Island of Cocos along the coast of Costa Rica, the Cocos finch which eats both fruits and insects and is the most plentiful bird on the island this is in direct contrast to the Mangrove Finch which can be found in two mangrove areas on the western coast of Isabela and is critically endangered.
Though these remarkable birds have adapted to life in the Galapagos Islands for thousands of years, it is the introduction of new species by man that has devastated the Mangrove Finch. The mangrove finch closely resembles the Woodpecker Finch only these birds do not use tools. Historically the Mangrove Finch could be found in the mangrove areas on the east of Ferndandina and on the west, south and north of Isabela. However, recent surveys have determined the bird is now extinct on Fernandina and there is thought to be approximately 70 remaining on Isabela.
The plight of the Mangrove Finch is due to two parasites a pox virus which creates lesions on the birds unfeather parts and a blood sucking parasite known as the Philornis downsi. Accidently introduced to the Galapagos thought by imported fruits, the larvae of the fly emerge at night to feed both internally and externally on the blood and flesh of developing nestlings. The presence of this parasite is causing significant (16 – 95%) mortality rate in Darwin Finch and devastating both the Medium Tree Finch and Mangrove Finch both of which are now considered critically endangered.
The national park has made great strides in the conservation and preservation of endemic species from their tortoise rearing and breeding program for giant tortoises, the restoration of land iguanas to the eradication of goats and other introduced species on many of the islands.
However the P. downsi creates a whole new issue. When eradicating goats on Isabela, Pinta and Santiago the national park used radio collars to track the goats leading them to other goats in the heard. Yet using a radio collars to track flies is impossibility. Whereas goats produce on average 2 – 3 kids after a 150 day gestational period. The P. downsi produces hundreds of off springs in a matter of days – the ramifications of which are staggering.
Since its introduction, the parasite has spread to 12 of the 13 islands and can be found in 64-100% of the nests. The Darwin Station is searching for a solution to this problem that affects all of the Darwin Finch as well as the other land birds in Galapagos.
In order to protect the Mangrove Finch from extinction, the national park has been working on a captive breeding program both for the finch as well as for the P. downsi. Their hopes are to breed the finch in a safe environment. While in studying the P. downsi it is in hopes to create a sterile version of the parasite which can be introduced into the population to eradicate it. Additionally the park is working to eradicate of rats (another predator) in the habitat of the Mangrove Finch. They have established a monitoring program and through these resources and education the park and scientists are hopeful they can save the Mangrove Finch from extinction and continue to preserve the endemic species of the Galapagos Islands.
Learn more about Darwin Finches and other Galapagos Birds
Learn more about the scientific work to find a solution to this problem Where Darwin Watched Beaks, WSU looks at Antibodies