Finch populations had not evolved over time . Geospiza magnirostris (the large ground finch), 2. They are generally found in the low mountains and foothills. Humans artificially selected finches based on their desired beak type. This reflects the fact that the two species feed on the same type and size of insect. This reflects the fact that the two species feed on the same type and size of insect. Where found with the Large Tree-Finch (C. psittacula) the Small Tree-Finch is more common and has a wider habitat breadth, while the Large Tree-Finch tends to be found in areas with larger and older trees. 30 seconds . This small bird features a very thin, curved beak. Finch populations had not evolved over time . Present-day species express a full toolbox: large and powerful lineman's pliers for Geospiza ground finches that must crack large, hard seeds; small and versatile needle-nose pliers for Certhidea warbler finches that glean insects from vegetation; and many models in between ( Bowman 1963 ). In contrast to the sharp-beaked ground finches, birds with large robust beaks, such as the large tree finch, Camarhynchus psittacula, do not probe Opuntia flowers or poke at eggs. Food appears to be a mix of seeds, fruit and insects. SURVEY . SURVEY . It has a curved beak that is short. The range of beak sizes of the Medium Tree-finch on Floreana and the Large Tree-finch, Camarhynchus psittacula, on Isabela is roughly the same. One of Charles Darwin's famous 14 finches — the island-dwelling bird species that helped inspire the theory of evolution — the medium tree finch is found only on Floreana, one of the nine major islands comprising the Galápagos archipelago. References. Student Handout . The beak of the Medium Tree-finch is intermediate in size between the Small Tree-finch and Large Tree-finch. Instead, the beak of this finch is a tool for tearing bark and crushing twigs and small branches—a beak modified for a different end. What did the beak type of finches on different islands tell Darwin? The range of beak sizes of the Medium Tree-finch on Floreana and the Large Tree-finch, Camarhynchus psittacula, on Isabela is roughly the same. Finch populations evolved over time to favor beaks based on food type. Darwin’s Finches are named after the great biologist Charles Darwin, the explorer who discovered the theory of evolution on the Galapagos Isles during a voyage in 1835. This type of Darwin Galapagos finch is small, per its name. Darwin's finches, inhabiting the Galapagos archipelago and Cocos island, constitute an iconic model for studies of speciation and adaptive evolution. Food appears to be a mix of seeds, fruit and insects. Tags: Question 18 . It is a large finch, approximately 15 centimeters in length. Name: Medium Tree Finch Family: Thraupidae Scientific Name: Camarhynchus pauper Length: 13 cm Weight: 16 g Category: Darwin Finches Number of Species: 13 Endemic Species: 13 Darwin Finches, or Galapagos Finches, are small land birds with generally dull black, brown or olive, often streaky, plumage; short tails; and short, rounded wings. Humans artificially selected finches based on their desired beak type. The finch beaks had no relationship to the available food on the islands.