Australian Bittern
- Scientific name:
- Botaurus poiciloptilus
- Family:
- Ardeidae
- Order:
- Ciconiiformes
Description
The Australasian Bittern is a heavy-set, partially nocturnal heron with upperparts that are patterned dark brown, buff and black, and underparts that
are streaked brown and buff. The eyebrow and throat are pale, and the side of the neck is dark brown. The bill is brown and the legs are greenish.
The Australasian Bittern is also called the Australian Bittern or the Brown Bittern.
Population information
In Australia, the population is now estimated to number not more than 1,000 mature individuals.
Most Australasian Bitterns are in the Murray-Darling basin and adjacent coastal areas. In Western Australia, the population was estimated to
contain up to 100 pairs in 1980, but it is now much reduced, with the largest concentration in the Albany and
Lake Muir wetlands.
It has fairly specific habitat
preferences, preferring shallow, vegetated freshwater or brackish swamps where there is a mixture
of short and tall emergent sedges and rushes. It has been recorded in rice paddies in the Murray Darling basin, but it is not thought to use such
habitat for breeding.
In Australia, the main threats are wetland drainage for agriculture, as well as changes brought about by high levels of grazing and
salinisation of swamps. Loss of these habitats may explain its decline in Western and South Australia. The Murray-Darling basin, a former
stronghold of the species, has suffered consecutive droughts in recent years and over-extraction of water is an on-going problem. In
Australia, introduced red foxes are thought to take eggs and juveniles.
Activity
Australasian Bitterns forage mainly at night on a wide range of small animals, including birds, mammals, fish, frogs, yabbies, snails, insects
and spiders. Like other herons, these birds use several techniques to capture prey, including: standing and waiting, slow stalking, and active
pursuit. Wing and leg movements are used to confuse or attract prey items.
The Australasian Bittern has a regular season but will also breed during inland flooding. The nest is a shallow structure of dry or green reeds,
within a clump of reeds in water or a swamp and is built on a platform of bent-over reeds. Several females will nest within one male's territory.
The bird can be very difficult to detect due to its camouflage-coloured plumage (its streaked and scalloped feathers blend in perfectly with
background reedy vegetation); birds will also freeze if approached, and on windy days may even sway to match the movement of the vegetation.
The Australasian bittern has a very distinctive booming call, which can be heard over large distances.
