Darwin’s Finches


10/11/04



The Galapagos Islands are located off the coast of Ecuador. The 20 islands in this archipelago are over 4 million years old. Darwin traveled to the islands in 1835. He discovered many species that were crucial to his theory about evolution. He found 14 different species of finches. There are many reasons on how these finches evolved.


The Nazca plate, where the Galapagos Islands are, is eventually moving southeast towards the South American plate. As the two plates collapse, they make volcanic eruptions. Since the crustal plate is in constant motion, new islands are made. The new islands are formed further from the continents and the farthest island is the youngest islands of the Galapagos Islands.


Recently, former Galapagos Islands, now submerged, have been discovered between the island Isla San Cristobal and the mainland. Thus several million years ago, the finches migrated from the mainland to the Galapagos Islands, which are now submerged, and spread out.


It seems unlikely that 14 different species of finches could evolve onto the islands. It all started with 1 species of finch. This species reproduced with variations and mutations. The mutated form of the species traveled to different islands and adapted to the environment. The mutated species reproduced and the mutated generation flew to a new island and adapted. This kept on happening until a full 14 species were formed. Species are probably still forming today.


They are able to live on the islands because there are no predators or competition. This is good because they can be more spread out so the can’t be seen from a bird’s eye view. The finches are also able to live on the islands at the same time because they have all adapted to their habitat. The most important adaptation is the beaks. Beak types differ in size and shape depending on the kind of food the finch eats.


There are a lot of similarities and differences between the different species of finches. All the species are about the size of a sparrow and their feathers are gray, brown, black, or olive. They have short rounded wings and rounded tails. Males tend to mature to a blackish color while females mature to a grayish color. One exception is that male Vegetarian and Tree Finches never turn completely black. Only their head, neck, and upper breast turn black. The Warbler, Woodpecker, and Mangrove Finches all have an olive like color.