The Australasian Bittern is a large heron relative that hides among dense reeds and rushes. When alarmed, it points its neck and bill upward and freezes among the plants.
It is heavy-set, with dark brown, buff, and black patterning above and brown and buff streaks below.
It is usually solitary and forages mainly at night in wetlands for small animals, including birds, mammals, fish, frogs, crustaceans, and insects. In Australia it usually breeds from October to February, but may also breed during inland floods.
It nests on plant platforms near water level within reedbeds. Clutches contain three to six eggs, usually four or five; the female alone incubates for 25 days, starting with the first egg.
Females are much smaller than males but have the same plumage. Individual coloration varies from pale to dark, with reddish birds also occurring.
Juveniles resemble adults but are paler and yellower, with rufous underpart streaking. Their eyes are yellow and facial skin pale green to yellow-green.
An extinction-risk assessment has not been added yet.