Abstract

First collected by Charles Darwin in the Galapagos Archipelago, the Geospizinae, or “Darwin’s finches, ” have rightly been celebrated as a classic instance of the workings of evolution through natural selection. Among birds, Darwin’s finches are rivaled only by the Hawaiian honey-creepers (Drepanididae) as a microcosmic exemplification of the princi-ple of adaptive evolutionary radiation. Although the Drepanididae have undergone more evolution and adaptive radiation than the Geospizlnae, the latter are in some ways more valuable to ornithologists. “Their special interest today, ” writes David Lack, “is in providing the best example, in birds, of an adaptive radiation into different ecological niches that is sufficiently recent, geologically speaking, for intermediate and transitional forms to have survived ” (1964: 178). The Galapagos Archipelago, where Darwin spent five weeks collect-ing these finches during the voyage of Q.M.S. Beagle (1831-1836), comprises sixteen principal islands located on the equator some six