Greater koa finch below. It had a thick black bill which allowed it to break open seed pods that were found in the trees. In historical times, its range was largely confined to the Kona District of the island of Hawaii, although it was observed in the Kīlauea area in 1895. It was much more widespread prior to the arrival of humans in Hawaii, and related species lived on other islands. In Kona, it co-occurred with the closely related lesser koa finch ("Rhodocanthis flaviceps"), and the Kona grosbeak. The lesser and greater koa finches were once thought by scientists to be the minimum
Koa wilt mortality rate over several years due to Koa wilt. It is also a legume, giving it the ability to form symbiosis with nitrogen fixing bacteria, which has led to efforts to use koa in agroecological systems with crops such as coffee and cacao. Ecologically, koa is an important species because it is one of the few native trees that remains dominant in alien mixed forests on the Hawaiian Islands. Invasive species make up the majority of the State's current plant population. Koa trees also are important because provide a habitat for many native bird species. Historically, there were once two