The bird has a generally subdued coloration, with fine linear patterns of black, grey and brown.
Its remiges however have vividly colored middle webs, which with wings fully spread show bright eyespots in red, yellow, and black.
These are shown to other sunbitterns in courtship and threat displays, or used to startle potential predators.
Male and female adult sunbitterns can be differentiated by small differences in the feather patterns of the throat and head.
Like some other birds, the sunbittern has powder down.

The sunbittern has a long and pointed bill that is black above, and a short hallux as in shorebirds and rails.
In the South American subspecies found in lowlands east of the Andes, the upperparts are mainly brown, and the legs and lower mandible are orange-yellow.
The two other subspecies are greyer above, and their legs and bill are sometimes redder.
The bird has a generally subdued coloration, with fine linear patterns of black, grey and brown. Its remiges however have vividly colored middle webs, which with wings fully spread show bright eyespots in red, yellow, and black. These are shown to other sunbitterns in courtship and threat displays, or used to startle potential predators. Male and female adult sunbitterns can be differentiated by small differences in the feather patterns of the throat and head. Like some other birds, the sunbittern has powder down.
The sunbittern has a long and pointed bill that is black above, and a short hallux as in shorebirds and rails. In the South American subspecies found in lowlands east of the Andes, the upperparts are mainly brown, and the legs and lower mandible are orange-yellow. The two other subspecies are greyer above, and their legs and bill are sometimes redder.
Sunbittern