Global Heating Threatens the `I`iwi (Vestiaria coccinea), Currently a Common Bird of Upper Elevation Forests in Hawaii

Abstract

The `I`iwi is one of 17 surviving Hawaiian honeycreepers (Fringillidae: Drepanidinae) of 37 species known historically and 55 extant prior to human arrival on Hawaii (Pratt 2009). Its closest relative is the extinct Hawaii Mamo (Drepanis pacifica) (Pratt 2005). Disease and habitat loss are primary reasons for the decline of Hawaiian honeycreepers and other native forest birds. Extinctions continue to this day, with the most recent being the Poo-uli (Melamprosops phaeosoma) in 2004. The `I`iwi, a scarlet bird with black wings and tail, and a long curved, salmon-colored bill, is generally placed in the monotypic genus Vestiaria. It is a largely nectarivorous species that occurs commonly in closed canopy, high-stature native forests above 1500 m elevation (Fancy and Ralph 1998). `I`iwi breed and winter primarily in mesic and wet forests dominated by native 'ヨhi'a (Metrosideros polymorpha) and koa (Acacia koa) trees (Scott et al. 1986). They often travel widely in search of ‘ヨhi‘a flowers and are important ‘ヨhi‘a pollinators (Mitchel et al. 2005). The birds respond to seasonal flowering patterns, often moving to lower elevations where they are exposed to deadly disease (Pratt 2005). The `I`iwi uses its long bill to extract nectar from decurved corollas of Hawaiian lobelioids, which have become far less common on Hawaii over the past century (Smith et al. 1995). Female `I`iwi typically lay two eggs, and they alone are thought to incubate eggs and brood young (Mitchel et al. 2005). But males provision females with food off the nest. Breeding takes place predominantly from February to June, and is usually associated with peak flowering of 'ヨhi'a (Fancy and Ralph 1998). For native Hawaiians, the `I`iwi and other forest birds have a spiritual nexus. Feathered objects represented gods, ancestors, and divine lineage (Amante-Helweg and Conant 2009). Red feathers of clothing, such as cloaks, capes, and helmets, were predominantly from `I`iwi. Once a familiar sight on all main Hawaiian Islands, the `I`iwi remains an icon of Hawaii’s native forests. Today `I`iwi occur in higher elevation habitats largely free of avian disease, to which the species is highly susceptible. With climate change, these refugia may be lost entirely as pathogens and vectors advance upslope in response to higher ambient temperatures. This prognosis points to the needs for swift remedial action by responsible U.S. federal and State of Hawaii authorities to prevent the `I`iwi from joining the tragically long list of extinct or feared extinct Hawaiian birds (Banko and Banko 2009).