Introduced Avian Diseases, Climate Change, and the Future of Hawaiian Honeycreepers

The Hawaiian archipelago is isolated in the central Pacific and consists of 7 large islands and a chain of low coral atolls and small rocky islets that extend in a long arc from Hawaii Island in the southeast to Kure Atoll in the northwest. The archipelago is the most isolated island system in the world, separated from the nearest continental landmass by more than 2000 miles of ocean.1 The islands range in elevation from just above sea level for atolls in the Northwestern Hawaiian Islands to peaks that exceed 4000 m on Hawaii Island. The interaction of extreme topographic relief, trade winds, and local climatic patterns creates a wide diversity of habitats, ranging from alpine deserts on the highest peaks to montane rain forests with precipitation exceeding 7600 mm per year. The endemic passerine avifauna of the Hawaiian Islands, particularly the endemic Hawaiian hon eycreepers (subfamily Drepanidinae) is often heralded as an outstanding example of adaptive radiation, equal to Darwin's finches from the Galapagos Islands in terms of diversity of bill types and number of species that descended from a common founder.2 From an initial colonization by only a few individuals of a single ancestral cardueline finch, this group radiated throughout the diverse habitats on the islands, specializing on a variety of food resources that included nectar, fruits, and insects. Based on recent studies of subfossils, the diversity of this group may have reached 20 genera with more than 50 species prior to human contact with the islands.3 Remarkably, a new genus and species of honeycreeper, the po'ouli {Melamprosops phaeosoma), was described in the 1970s from remote rain forests on Maui.4 Today, the endemic Hawaiian avifauna faces one of the highest rates of extinction in the world.