The Australasian Bittern is a large bird, standing approximately one metre tall with a body length about 75 cm.

Males (875-2085g) are heavier than females (571-1135g). They are a mostly mottled brown colour (and have been commonly known as Brown Bitterns), they are generally darker on their back, with a pale buff coloured underside heavily streaked with brown and have a white throat with dark brown streaks down the side.

They are listed as critically endangered due to their declining numbers, and their total population is thought to be around 2000 individuals. They occur in south east Australia, South West WA, Tasmania, New Zealand and New Caledonia.

They are generally a shy, cryptic inhabitant of well vegetated wetlands and waterways, more often heard than seen, they usually occur singly or in pairs, and will usually be seen in or very near to reedbeds or stands of rushes/reeds.

They will often stand motionless, with neck and bill pointed skyward, swaying with the reeds, and slowly lower their head into the vegetation. When flushed they will usually fly slowly with a lumbered appearance a short distance before dropping down into a patch of vegetation where they will disappear from view or adopt the bill skyward pose.