Rodrigues solitaires grew to the size of swans, and demonstrated pronounced sexual dimorphism. Males were much larger than females and measured up to in length and in weight, contrasting with and for females. Its plumage was grey and brown; the female was paler than the male. It had a black band at the base of its slightly hooked beak, and its neck and legs were long. Both sexes were highly territorial, with large bony knobs on their wings that were used in combat. The Rodrigues solitaire laid a single egg that was incubated in turn by both sexes. Gizzard stones helped digest its food, which included fruit and seeds.