The Australasian bittern (Botaurus poiciloptilus), also known as the brown bittern or matuku hūrepo, and also nicknamed the "bunyip bird", is a large bird in the heron family Ardeidae. A secretive bird with a distinctive booming call, it is more often heard than seen. Australasian bitterns are endangered in both Australia and New Zealand.
The bird has a deep brown upper surface, mauled with buff on wing coverts; face and eyebrow buff, with dark brown stripe running from bill to erectile plumes at sides of neck. Under surface buff, striped with brown. The face skin is a dull green as are the legs and feet, it possesses a dark brown bill, yellow eyes, and the base of the lower mandible is green-yellow.