Evolution and systematics

Hawaiian honeycreepers are a splendid living textbook and gazetteer of adaptive radiation, or the evolution of many species, with varied characteristics, from one.

Establishing the relationships among the many genera and species of honeycreepers is ongoing and far from settled. As of 2002, ornithologists consider all honeycreeper species to be monophyletic, i.e., sharing one common ancestral species, probably a cardueline finch species from North America, a small flock of which reached the Hawaiian Islands sometime between 3 and 5 million years ago. Although the Hawaiian honeycreepers are as of 2002 often listed taxonomically as subfamily Drepanidinae within the family Fringillidae, the finches, for the purposes of this account they are treated as a separate family—the Drepanididae.

Once established in Hawaii, the founder species evolved and radiated explosively, filling empty ecological niches and producing a fantastically varied toolbox of bill forms for dealing with virtually every sort of food. Researchers have found fossils of honeycreepers as old as 120,000 years. Fossil ages in Hawaii are limited by the nature of the islands, which are volcanic and relatively transient in geological time.

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