Akialoa

Hemignathus is a Hawaiian honeycreeper genus in the finch family, Fringillidae. These birds are endemic to the Hawaiian Islands.

Many of its species became extinct during the 19th and 20th centuries due to a combination of habitat destruction, introduced predators, and most importantly mosquito-borne diseases. Some others became extinct in prehistoric times, when Polynesian settlers deforested the lowlands for agriculture.

They have a wide variety of bill shapes and sized; if the genus is broadly defined this diversity is probably the largest of all bird genera living or extinct.

Systematics
The genus Hemignathus is sometimes split into four distinct genera. While it is probably desirable to move at least some species to their own genera, many authorities are reluctant to do so at present due to the lack of comprehensive studies. That half of the taxa are extinct does not make such studies easier.

(Sub)Genus Hemignathus sensu stricto - pointed or long and downcurved bills, insectivores or nectarivores.
 * Common ʻAmakihi or Hawaiʻi ʻAmakihi, Hemignathus virens
 * Oʻahu ʻAmakihi, Hemignathus flavus or Hemignathus chloris
 * Kauaʻi ʻAmakihi, Hemignathus kauaiensis
 * Greater ʻAmakihi, Hemignathus sagittirostris - extinct (1901)
 * Giant Nukupu‘u, Hemignathus vorpalis - prehistoric
 * Nukupuʻu, Hemignathus lucidus - probably extinct (late 1990s?)
 * Maui Nukupuʻu Hemignathus (lucidus) affinis - probably extinct (late 1990s?)
 * Oʻahu Nukupuʻu Hemignathus (lucidus) lucides - extinct (1837)
 * Kauaʻi Nukupuʻu Hemignathus (lucidus) hanapepe - probably extinct (late 1990s?)

(Sub)Genus Magumma - slim pointed bill, insectivore (Sub)Genus Akialoa - long and downcurved bills, primarily nectarivores (Sub)Genus Heterorhynchus - long and downcurved upper and short and stout lower bill, probes for insects
 * ʻAnianiau, Hemignathus parvus or Magumma parva
 * Lesser ʻAkialoa or Hawai'i 'Akialoa, Hemignathus obscurus - extinct (1940)
 * Greater ʻAkialoa, Hemignathus ellisianus  or Akialoa ellisianus - extinct (1969)
 * Oʻahu ʻAkialoa Hemignathus (ellisianus)ellisianus  or Akialoa (ellisiana) ellisiana - extinct (1940)
 * Maui Nui ʻAkialoa or Lanaʻi ʻAkialoa, Hemignathus (ellisianus) lanaiensis or Akialoa (ellisiana) lanaiensis - extinct (1892)
 * Kauaʻi ʻAkialoa, Hemignathus (ellisianus) stejnegeri or Akialoa (ellisiana) stejnegeri - extinct (1969)
 * Hoopoe-billed ʻAkialoa, Hemignathus upupirostris or Akialoa upupirostris - prehistoric
 * Giant ʻAkialoa, Hemignathus sp. or Akialoa sp. - prehistoric
 * ʻAkiapolaʻau, Hemignathus munroi or Heterorhynchus wilsoni