Of all the birds in the Galapagos, none were as important to Darwin's thinking, or to the on-going study of evolution than the mockingbirds and finches. While intrigued by the finches, Darwin was especially struck by the 4 species of very similar mockingbirds. He wondered why there were multiple species in the Galapagos, when any one could have easily filled the niche of any other on such closely spaced islands. Of the four, only three can readily be seen by visitors - the Galapagos mockingbird, the Chatham mockingbird, and the Hood mockinbird. The fourth, the Charles mockingbird is extinct on its main island, Floreana, but is still present on the small islets adjacent to Floreana.