[1] Scissor-billed koa finch fossils have been found on Maui and Kauai.

[1] The scissor-billed koa finch was a granivore, that, like the other members of its genus, had a bill adapted to eat the hard seeds and pods of legumes.

Pollen and fossil evidence indicates that Ka palupalu o Kanaloa (Kanaloa kahoolawensis) and koaiʻa (Acacia koaia) were probably important food sources, and it may have eaten caterpillars and ʻaʻaliʻi (Dodonaea viscosa) berries.

[2] The koa finches seem to have been driven to extinction by habitat destruction, and not by climatic variation nor mosquito-vectored diseases.

Koa finches were likely driven out of lowland habitat before or shortly after the time of western contact in 1778.