(Notes come from Silversea's publication.) The nickname “Darwin’s Finches” was attributed to these finches because they played such an important role in Darwin’s thoughts that eventually led to his development of the theory of evolution by means of natural selection.
Darwin was interested in the diversity of the species and how quickly they seemed to have evolved from a common ancestor and adapted to different food types on each island. These adaptations are mainly manifested in the shape and size of their beaks.
Despite all their fame, these birds are not particularly beautiful or striking, although they do have a melodious lilting song. They all look pretty much alike (size, plumage, behavior). They are small, sparrow-sized land birds with drab black and brown or olive feathers. They have short round wings and short tails which are cocked to one side.
Although commonly seen, they are hard to tell apart without close observation. The major difference remains with size and shape of their beaks. It is believed that all 14 species derived from a single species similar to the Blue-back Grassquit commonly found along the Pacific Coast of South America.