Linguists derive the Hawaiian language word ʻiʻiwi from Proto-Nuclear-Polynesian *kiwi, which in central Polynesia refers to the bristle-thighed curlew (Numenius tahitiensis), a migratory bird.

The adult ʻiʻiwi is mostly scarlet, with black wings and tail and a long, curved, salmon-colored bill used primarily for drinking nectar.

The contrast of the red and black plumage with surrounding green foliage makes the ʻiʻiwi one of Hawaiʻi's most easily seen native birds.

[4] The ʻiʻiwiʻs peculiar song consists of a couple of whistles, the sound of balls dropping in water, the rubbing of balloons together, and the squeaking of a rusty hinge.

Starting in 1902 the lobelioid population declined dramatically, and the ʻiʻiwi shifted to nectar from the blossoms of ʻōhiʻa lehua (Metrosideros polymorpha) trees.

[6]In the early winter in January to June, the birds pair off and mate as the ʻōhiʻa plants reach their flowering maximum.

The female lays two to three eggs in a small cup shaped nest made from tree fibers, petals, and down feathers.

[9] Overall, ninety percent of the ʻiʻiwi population is confined to a narrow band of forest on East Maui and the windward slopes of the island of Hawaii, between 4,265 and 6,234 feet (1,300 and 1,900 meters) in elevation.

It has also been noted that birds on Mauna Kea, Hawaiʻi Island, likely make daily trips from lower elevations to feed on nectar.

Many disease-susceptible endemic birds, including ʻiʻiwi and kiwikiu, became rare to absent at lower elevations, even in relatively intact native forest.

[12] There is a movement to begin an official eradication of mosquitos in Hawaii, as there are no native species on the islands, and their removal would not hurt the food web.

[20] ʻIʻiwi habitat has been reduced and fragmented through various types of land development, including clearing native forest for food crops and grazing.

[23] There has been extensive death of these trees in untouched part of the forest, which has further contributed to the problem of the 'I'iwi having to leave higher elevations to find food and being exposed to malaria.

Conservation groups are diligently working to reduce the risk of spreading a disease called Rapid ˋŌhiˋa Death (ROD).