The species was already very rare when it was first discovered, being found in only about 10 square kilometres (3.9 sq mi), and was last collected in 1894.

[3] The Kona grosbeak was a frugivore, with a large beak adapted to break through the hard endocarp of dried naio (Myoporum sandwicense) fruits.

It may have also taken green naio fruit and leaves, as well as softer bracts such as that of the ʻieʻie (Freycinetia arborea) of which it served as a pollinator.

[3] The ornithologist Scott Barchard Wilson was one of the few people to observe Kona grosbeaks in the wild.

It is a dull, sluggish, solitary bird and very silent-its whole existence may be summed up in the words “to eat.” Its food consists of the seeds of the fruit of the aaka (Myoporum sandwicense) (bastard sandal-tree, and probably in other seasons of those of the sandalwood tree), and as these are very minute, its whole time seems to be taken up in cracking the extremely hard shells of this fruit, for which its extraordinarily powerful beak and heavy head have been developed.