These small land birds of the Galapagos Islands were named after Darwin by ornithologist Percy Roycroft Lowe in 1936 in his publication "The finches of the Galapagos in relation to Darwin's conception of species", Ibis (6): 310–321. Here is found the first reference to “Darwin’s finches”, and so they have been known ever since.
They are a group of 14 species in four genera; all found on the Galapagos Islands with the exception of the Cocos finch on Cocos Island ( an island belonging to Costa Rica).
Large Cactus Finch, Geospiza conirostris
Sharp-beaked Ground Finch, Geospiza difficilis
Vampire Finch, Geospiza difficilis septentrionalis
Medium Ground Finch, Geospiza fortis
Small Ground Finch, Geospiza fuliginosa
Large Ground Finch, Geospiza magnirostris
Common Cactus Finch, Geospiza scandens
Vegetarian Finch, Camarhynchus crassirostris - sometimes separated in Platyspiza
Large Tree Finch, Camarhynchus psittacula
Medium Tree Finch, Camarhynchus pauper
Small Tree Finch, Camarhynchus parvulus
Woodpecker Finch, Camarhynchus pallidus - sometimes separated in Cactospiza
Mangrove Finch, Camarhynchus heliobates
Warbler Finch, Certhidea olivacea
Cocos Island Finch, Pinaroloxias inornata
The original ancestors of Darwin's finches have been identified as a group of South American birds known as seed-eaters. Mitochondrial DNA sequence variation has pinpointed the most likely closest living relatives of Darwin's finches as members of what are known as the grassquit genus Tiaris (Sato et al. 2001). The difference in mitochondrial DNA between Darwin's finches and the Tiaris species suggests the ancestors arrived on the Galapagos two to three million years ago. Somehow they managed to cross open ocean for 1,000 km (600mls) and successfully establish a breeding colony. There has been some debate in the past on whether Cocos Island could have been the jump-off point for the finches to reach Galapagos. Here, a solitary species of finch resides today, but molecular genetic data has eliminated that possibility; the data demonstrated a phylogenetic origin of the Cocos finch after an initial evolutionary split among Darwin's finches on the Galapagos (Petren et al. 1999, Sato et al. 1999). This evidence indicates that ancestral finches first colonized the Galapagos, after which the populations began to diverge, only later producing what is known today as the Cocos finch. Two scenarios are plausible: the Cocos finch (Pinaroloxias) could potentially have arisen from an ancestral warbler finch (Certhidea fusca) that colonized Cocos Island; or the Cocos finch may have appeared on the Galapagos Islands, with the species colonizing Cocos island later, eventually becoming extinct on the Galapagos. The black plumage and song of the Cocos finch so closely resembles that of the Galapagos Islands finches, that the second possibility is greatly favored by many.
In 1963, Robert Bowman compared the different beak sizes and shapes of Darwin’s finches to the different types of pliers found in a workman’s toolbag. From needle-nosed pliers to heavy-duty linesman pliers, this analogy is useful for the layman to understand how the differing beak shapes allow for a high degree of specialization in foraging techniques which in turn allows for a division of resources and separation of niches.
Darwin’s finches are found throughout the archipelago, from the low, arid coastlines up to the highest crater rims above 1,700m (5, 600ft). They are found in all the ecosystems in Galapagos, from mangrove estuaries and cactus forest to the Miconia and tree fern zones. As Darwin himself wrote “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.” (Voyage of the Beagle, 1839)
Rosemary and Peter Grant have spent most of their professional lives deeply involved with the study of Darwin’s finches. They have opened up innumerable fields of inquiry into evolutionary processes through their in-depth observations and meticulous field work with the finches of Galapagos. They realized very early on, in the 1970’s, that the small islands of Galapagos with their resident populations of small land birds were the ideal location to study natural selection in action, in the here and now. Up until then, changes in natural populations were thought to occur at a glacier’s pace, impossible to measure within a human lifetime. The Grants and the finches have shown that natural selection is at work every moment of every day, and can be measured and analyzed, evolutionary trends seen and observed. The Island of Daphne Major cannot be mentioned in relation to finches without also mentioning the years the Grants and their graduate students have spent on shore measuring, banding, toiling and sweating. After decades of research, there is probably no better-studied population of living birds than the Darwin’s finches of Galapagos.
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