Members of this genus were granivores, with bills adapted to the seeds and pods of legumes.

[3] The combination of a giant bill with brightly colored plumage (yellow for R. flaviceps, orange for R. palmeri) gave the males a very striking appearance.

The two prehistoric species, R. forfex and R. litotes, were denizens of more lowland tropical dry forests and shrublands on Kauaʻi, Maui, and Oʻahu.

It is speculated that koaiʻa (Acacia koaia) was an important food source for both species, as their range did not overlap with that of koa.

pods and ʻaʻaliʻi (Dodonaea viscosa) berries were probably also eaten in addition to the occasional caterpillar.