Greater Koa Finch
(Rhodacanthis palmeri)

The bird was about ten inches (23 centimeters) long when fully grown. It was the largest known honey-creeper, although its typical weight is unknown. The bird is sexually dimorphic; the male was brilliant scarlet-orange on head, neck, and breast, with lighter orange on its bottom, and olive brown with orange touches on back, wings, and tail; however, the female was brownish olive, and somewhat lighter below. It had a thick black bill which allowed it to break open seed pods that were found in the trees. It was confined in all of its range, its range was on the Big Island of (Hawaii, in which it lived mostly in the Kona District. Neighboring species of this bird included, the closely related lesser koa finch (Rhodocanthis flaviceps), and the Kona grosbeak. Perkins had mistook the call of this bird to be the song of the Kona Grosbeak. The Lesser and Greater Koa Finches were once thought by scientistys to be the minimun and maximum growth of a single spercies of Koa Finch.
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Greater Koa Finch - Wikipedia, the free encyclopedia

This was the largest of the Hawaiian finches, and was about 9 inches long. It was found only on Hawaii Island, in the koa forests of the Kona District at elevations above 4000 feet. The males had a bright orange head, and a greenish-brown body, while the females were a dull green all over. Their distinctive feature was a gray, heavy-pointed beak used to feed on the hard seed pods of the koa tree.

The Greater Koa-Finch was last seen in 1894 and is considered extinct. The causes for its disappearance are still unknown, as its high-elevation habitat is still relatively intact, and it is above the range of mosquito-borne diseases.
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Native Birds of Hawai`i



Lesser Koa-Finch
(Rhodacanthis flaviceps)

Rhodacanthis flaviceps) is a species of finch in the Fringillidae family. One of the earliest of all the recorded lost species is the Lesser-Koa Finch. The Lesser Koa Finch has different coloring depending on gender and age. The only specimens caught was a family group with member of different ages and genders, perfect for studying. The males were gold yellow and were olive green on the bottom. The females were almost undistinguishable from its larger relative, other than the fact that it was darker in color. The juveniles are slightly mottled on the bellies and are similar to the females. It is small as its name proclaims, only five inches in size. It has its life centered around the Koa where it gets its nectar and fruit from.
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Lesser Koa Finch - Wikipedia, the free encyclopedia

The tragic end of the Lesser Koa-finch was recorded by the collectors who shot the last remaining bird. The following is from "Birds of Hawaii" by George Munro. "September 30, 1891. Palmer killed another (Koa-finch) a much smaller bird with golden head and neck and light yellow breast .".
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http://www.oahunaturetours.com/oahukoafinch.html