Australasian Bittern

The Australasian bittern, known scientifically as Botaurus poiciloptilus, and colloquially as the brown bittern or matuku hūrepo, is a member of the heron family Ardeidae. This large bird, sometimes referred to as the "bunyip bird," is a master of concealment, its presence often betrayed only by its distinctive booming call.

Identification Tips

Adult Australasian bitterns range in length from 650 to 750 mm, with males being notably larger than females. Their upper surfaces are a deep brown, mottled with buff on the wing coverts. The face and eyebrow are buff, accented by a dark brown stripe extending from the bill to the erectile plumes at the sides of the neck. The underparts are buff, striped with brown. The skin of the face, legs, and feet is a dull green, complemented by a dark brown bill and yellow eyes. The base of the lower mandible is a green-yellow hue.

Habitat

The Australasian bittern is a cryptic and partly nocturnal species that inhabits densely vegetated wetlands.

Distribution

This species can be found in south-western and south-eastern Australia, Tasmania, New Zealand, New Caledonia, and Ouvea. Populations have experienced a decline in the 20th century.

Behaviour

Australasian bitterns feed on a variety of aquatic animals, including frogs, eels, and freshwater crustaceans. They are solitary nesters, laying their eggs on the ground amidst dense wetland vegetation, often on trampled reeds. Males are known for their conspicuous breeding calls, which are used as a reliable method for monitoring the species.

Conservation status

The Australasian bittern is currently listed as Vulnerable. The primary threats to its survival are wetland drainage and degradation, with Australian populations being particularly sensitive to the destruction of drought refugia. It is protected under various conservation acts and is the focus of important bird area designations in Australia.

Important Bird Areas

BirdLife International has identified several sites in Australia as critical for the conservation of the Australasian bittern, including wetlands in New South Wales, Tasmania, Victoria, South Australia, and Western Australia.

Similar Species

The Australasian bittern is one of four similarly plumaged species within the genus Botaurus. However, its distinctive call and habitat preferences help distinguish it from its congeners.

Diet and Feeding

The diet of the Australasian bittern consists mainly of aquatic animals such as frogs, eels, and freshwater crustaceans, which it hunts within its wetland habitat.

Breeding

Breeding males are known for their conspicuous calls, which are most effectively detected one hour before sunrise in the austral spring, particularly on moonlit nights without cloud cover or rain. They nest solitarily on the ground in dense wetland vegetation.