The Australasian Bittern is a large, stocky, thick-necked, heron-like bird. The species grows to a length of 66-76 cm and has a wingspan of 1050-1180 cm. The average male weighs approximately 1400 g and the average female weighs approximately 900 g. The upper-parts of the body are brown and dark brown to black, mottled and buff, in complex patterns that aid the bird’s concealment in swamp vegetation. The under-parts of the body are streaked and scalloped, brown and buff. The species has a prominent black-brown stripe running down the side of the neck, the eyebrow is pale, and the chin and upper throat are white. The bill is straight, pointed and straw yellow to buff in colour with a dark grey ridge. The legs and feet are pale green to olive and the eyes are orange-brown or yellow. Darker and paler variants of the plumage have been observed in adults. Juveniles are generally paler than adults and have heavier buff flecking on the back.
Australasian Bittern |
Status: Endangered on the EPBC Act list
Government evidence of impact of climate change:
Australian Government, Conservation Advice, Botaurus poiciloptilus
Habitat degradation due to factors such as reduced water quality; invasion by weeds; impacts from grazing animals and reduced water flows due to a changing climate are also impacting on Australasian Bittern survival and breeding success.
Climate change Changes in Suspected There is strong evidence that rising temperatures caused by water Current increased greenhouse gases is leading to reduced rainfall across availability southeast and southwest Australia; and to increased evaporation; leading to large declines in surface water runoff (CSIRO 2010).
For example; Phragmites is plant becoming more common across wetlands in South Australia (J. species; van Weenen 2018. pers comm); which may impact on the quality (including of foraging habitat and hence occupancy and breeding success of native the Australasian Bittern at these sites. species and introduced weeds) Inappropriate Possible Frequent or intense burning of wetland areas may reduce the fire regimes Current dense vegetation that forms the core habitat of the Australasian Bittern; potentially resulting in reduced nesting success.
Australian Government, Listing Advice, Botaurus poiciloptilus
In addition; current climate modelling indicates that annual temperatures appear to be increasing and rainfall decreasing across Australia where this species is found; placing further stress on this species (CSIRO; 2010).