Populations under particular pressure

The actions described in this Recovery Plan are designed to provide ongoing protection for Australasian Bitterns throughout their Australian range. The meta-population structure of the species is largely unknown. Australasian Bitterns persist as at least two isolated, subpopulations in eastern and south western Australia. In recent decades, numbers in the previous strong-holds in the Murray–Darling Basin have declined, perhaps permanently due to pressure on water resources and thus now only rare inundation of floodplains. The Western Australian subpopulation has become more restricted with few records away from the south and south-east coasts and Lake Muir wetlands, which is part of the Muir-Byenup System Ramsar wetland (Pickering 2013). There have been few confirmed records from the Swan Coastal Plain since 1992 and surveys in 2007 and 2008 found that half the wetlands that supported the species in 1980 now retained no suitable habitat (Pickering and Gole 2008; Pickering 2013; DBCA 2018). Breeding in South Australia is confirmed from the Bool Lagoon, and the coast from Adelaide to Victorian border. There are few recent Queensland records (Barrett et al. 2003).

All subpopulations covered by this plan have restricted distributions and small population sizes, which present significant challenges for their recovery and exert strong pressures on their survival in the wild. Given these challenges, all subpopulations of Australasian Bittern covered by this plan require strong protective measures.

In Western Australia, the Department of Biodiversity, Conservation and Attractions have approved a state recovery plan for Australasian Bittern (DBCA 2018). The population is estimated to be between 50–100 individuals. Actions relating to the Western Australian subpopulation should consider both the national and state recovery plans in parallel when implementing research and management actions.