Australasian Bitterns occupy shallow, vegetated freshwater or brackish swamps, favouring those dominated by sedges, rushes and/or reeds from 0.5 – 3.5 metres in height (Marchant and Higgins 1990), as well as rice fields (Herring et al. 2019), where they feed on fish, eels, frogs, freshwater crayfish and aquatic insects (Heather and Robertson 1997, Menkhorst 2012). They are also known to prey on small mammals (Gitsham 2018), and on occasion they can feed away from waterbodies such as in grassland or crop stubble, particularly during rodent plagues (A. Silcocks unpublished, in Herring et al. 2021). The population seems to increase rapidly in good years and decline rapidly in poor ones (S. Garnett in litt. 2003). The species can disperse widely, including seasonal movements of 400-600 km from inland rice fields to coastal wetlands; during periods of drought; and to ephemeral wetlands during and after periods of rainfall (Garnett et al. 2011, Bitterns in Rice Project 2020).

Botaurus poiciloptilus occurs in the wetlands of southern Australia, New Zealand and New Caledonia. In Australia they occur in south-eastern mainland Australia from south-east Queensland to south-eastern South Australia as well as Tasmania (Marchant and Higgins 1990). In south-western Australia, they occur in nine wetland complexes from Perth to Esperance (DBCA 2018). Previously, they occurred between Moora and Cape Arid. Half the wetlands on the Swan Coastal Plain that supported the species in 1980 are no longer suitable (Pickering and Gole 2008). In south-eastern Australia, including Tasmania, fewer than 30 natural wetlands are now thought to support breeding in most years, or support more than one booming male, with the number substantially lower in drought years. A further 50–1,130 km² of suitable breeding habitat occurs in rice fields of the New South Wales Riverina, especially those receiving early permanent water, with the area sown to rice varying by over an order of magnitude according to water availability. Satellite tagged birds disperse from the Riverina to coastal wetlands in South Australia, Victoria and New South Wales (Herring et al. 2019). Australasian Bitterns also occur in New Zealand (Marchant and Higgins 1990) and have occasionally been recorded in New Caledonia (Spaggiari et al. 2007) although these records are unconfirmed and the species may be extinct here (G. Dutson in litt. 2020, A. Silcocks in litt. 2022).

Conservation Actions Underway
In Australia, Bool Lagoon and Lake Muir are managed specifically for the species (Garnett and Crowley 2000). BirdLife Australia started a Bittern Project in 2007. Most natural breeding wetlands are conserved or restoration has commenced. The species is listed as threatened under appropriate legislation, including as a National Threatened Species Strategy priority. Major conservation program run with rice farmers. Environmental water delivery at key sites incorporates Australasian Bittern requirements. WA Recovery Team established.

Conservation Actions Proposed
Complete field surveys to determine its current global distribution, status and key sites for conservation (N Barré in litt. 1999, C. O'Donnell in litt. 1999, Garnett and Crowley 2000). Develop methods for assessing population trends (Garnett and Crowley 2000). In Australia, establish a national monitoring program, incorporating known sites and strategically targeting potential habitat on private property. Determine ecological requirements at drought refuge sites.  Assess population impacts of fire and predators, particularly foxes and cats. Map known and potential habitat and determine habitat management guidelines for increasing Australasian Bittern density and breeding success. Compare genetic diversity of western, eastern and Tasmanian populations. Rehabilitate selected former breeding wetlands (Garnett et al. 2011). Encourage cultivation of bittern-friendly rice in the Riverina. Ensure water made available for known Australasian Bittern drought refuges. In partnership with land managers, restore Australasian Bittern habitat at selected sites across its range. Manage water levels, water quality, predators, fire and vegetation structure to maximise density and breeding success. In New Zealand, ensure that wetland habitats are protected and mammalian predators are managed (O'Donnell and Robertson 2016). Develop a national recovery plan for New Zealand (O'Donnell and Robertson 2016).