Data Zone
Taxonomic source(s)
Christidis, L. and Boles, W.E. 2008. Systematics and Taxonomy of Australian Birds. CSIRO Publishing, Collingwood, Australia.
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
Turbott, E.G. 1990. Checklist of the Birds of New Zealand. Ornithological Society of New Zealand, Wellington.
| Critically Endangered | Endangered | Vulnerable |
|---|---|---|
| - | - | C2a(i) |
| Year | Category | Criteria |
|---|---|---|
| 2022 | Vulnerable | C2a(i) |
| 2016 | Endangered | C1 |
| 2013 | Endangered | C1 |
| 2012 | Endangered | C1 |
| 2009 | Endangered | C1 |
| 2008 | Endangered | |
| 2006 | Endangered | |
| 2004 | Endangered | |
| 2000 | Vulnerable | |
| 1996 | Endangered | |
| 1994 | Endangered | |
| 1988 | Lower Risk/Least Concern |
| Migratory status | not a migrant | Forest dependency | does not normally occur in forest |
| Land-mass type |
Australia |
Average mass | - |
| Estimate | Data quality | |
|---|---|---|
| Extent of Occurrence (breeding/resident) | 10,200,000 km2 | medium |
| Number of locations | 11-100 | - |
| Severely fragmented? | no | - |
| Estimate | Data quality | Derivation | Year of estimate | |
|---|---|---|---|---|
| Population size | 1000-2499 mature individuals | poor | estimated | 2020 |
| Population trend | decreasing | poor | inferred | - |
| Generation length | 4.9 years | - | - | - |
| Number of subpopulations | 4 | - | - | - |
| Percentage of mature individuals in largest subpopulation | 1-89% | - | - | - |
Population justification: In 2009–2010, there were estimated to be 3–16 Australasian Bitterns on natural wetlands in Queensland, 82–162 in New South Wales, 86–248 in Victoria, 12–100 in Tasmania, 26–116 in South Australia and 38–154 in Western Australia (Garnett et al. 2011). The Western Australia population is now considered to comprise fewer than 100 individuals (WA Recovery Team unpublished, in Herring et al. 2021), while Tasmania is now thought to support 20–80 birds (E. Znidersic unpublished, in Herring et al. 2021). Previously overlooked, c.500–1,000 are estimated to use rice fields in the Riverina, depending on the area sown, while the Barmah-Millewa wetland complex is considered Australia’s most important site, with up to 73 booming males (Herring et al. 2019). In total c.950 of the eastern mainland birds are thought to occur in the Murray–Darling Basin, of which approximately half move to the coast in winter where another 200 live year-round (M. Herring unpublished, in Herring et al. 2021). Overall the Australian population is estimated to number 750-1,800 mature individuals, with a best estimate of 1,300. In New Zealand, the population was estimated at 580–725 birds in 2000 (Heather and Robertson 2000) which is now thought to be too high given recent declines at key wetlands including Whangamarino (O’Donnell and Robertson 2016). Additionally, recent research suggests that individuals may have been double counted in the past due to birds travelling long distances to find different wetland habitats (Ornithological Society of New Zealand 2019). The most recent estimate of the New Zealand population is 125 pairs (Robertson et al. 2021), equivalent to 250 mature individuals. Overall the global population is estimated at c.1,600 mature individuals and best placed in the band 1,000-2,499 mature individuals, equating to 1,500-3,749 individuals in total and rounded here to 1,500-4,000.
Trend justification: Based on published data, declines in the Australian population have been occurring for decades and have been associated with loss of key breeding habitats (Commonwealth of Australia 2019). In the past, the reporting rate in national Atlas surveys decreased from being recorded in 260 10-minute grid squares in 1977-1981, to 142 squares in 1998-2003, and 61 in 2003-2008 (Birds Australia 2010, Garnett et al. 2011). The reporting rate declined by >90% in Tasmania and Western Australia, and by 63% in the Riverina. The long-term rate of decline was overall estimated to exceed 20% over two generations, and the area of occupancy in Australia is thought to have declined by 70% between 1977 and 2008 (Commonwealth of Australia 2019). However, currently there is no evidence for a population decline exceeding 20% in two generations, and although a continuing decline is inferred, the rate is not known (Herring et al. 2021). Riverina's rice fields support c.60% of the national population and declines are thought to be continuing here given reduced water allocations associated with drought, the trend towards cotton and other alternative irrigation water uses that do not support bitterns, and a shift away from “early permanent water” rice crops, which are favoured by bitterns (Commonwealth of Australia 2019). In New Zealand (c.15% of the global population) the species is thought to be rapidly declining at a rate equivalent to 50-70% within three generations (Robertson et al. 2021).
| Country/Territory | Presence | Origin | Resident | Breeding visitor | Non-breeding visitor | Passage migrant |
|---|---|---|---|---|---|---|
| Australia | extant | native | yes | |||
| New Caledonia (to France) | extant | native | yes | |||
| New Zealand | extant | native | yes |
| Habitat (level 1) | Habitat (level 2) | Importance | Occurrence |
|---|---|---|---|
| Artificial/Terrestrial | Arable Land | major | resident |
| Marine Intertidal | Salt Marshes (Emergent Grasses) | major | resident |
| Wetlands (inland) | Bogs, Marshes, Swamps, Fens, Peatlands | major | resident |
| Altitude | 0 - 800 m | Occasional altitudinal limits |
| Threat (level 1) | Threat (level 2) | Impact and Stresses | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Agriculture & aquaculture | Annual & perennial non-timber crops - Agro-industry farming | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Slow, Significant Declines | Low Impact: 5 | ||||||
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| Biological resource use | Hunting & trapping terrestrial animals - Intentional use (species is the target) | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Negligible declines | Low Impact: 4 | ||||||
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| Climate change & severe weather | Droughts | Timing | Scope | Severity | Impact | ||||
| Ongoing | Whole (>90%) | Slow, Significant Declines | Medium Impact: 7 | ||||||
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| Human intrusions & disturbance | Recreational activities | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Negligible declines | Low Impact: 4 | ||||||
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| Invasive and other problematic species, genes & diseases | Invasive non-native/alien species/diseases - Capra hircus | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Negligible declines | Low Impact: 4 | ||||||
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| Invasive and other problematic species, genes & diseases | Invasive non-native/alien species/diseases - Equus caballus | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Negligible declines | Low Impact: 4 | ||||||
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| Invasive and other problematic species, genes & diseases | Invasive non-native/alien species/diseases - Felis catus | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Negligible declines | Low Impact: 4 | ||||||
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| Invasive and other problematic species, genes & diseases | Invasive non-native/alien species/diseases - Named species | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Negligible declines | Low Impact: 4 | ||||||
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| Invasive and other problematic species, genes & diseases | Invasive non-native/alien species/diseases - Sus scrofa | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Negligible declines | Low Impact: 4 | ||||||
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| Invasive and other problematic species, genes & diseases | Invasive non-native/alien species/diseases - Vulpes vulpes | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Negligible declines | Low Impact: 4 | ||||||
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| Natural system modifications | Dams & water management/use - Abstraction of ground water (agricultural use) | Timing | Scope | Severity | Impact | ||||
| Ongoing | Majority (50-90%) | Slow, Significant Declines | Medium Impact: 6 | ||||||
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| Natural system modifications | Fire & fire suppression - Increase in fire frequency/intensity | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Negligible declines | Low Impact: 4 | ||||||
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| Natural system modifications | Other ecosystem modifications | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Slow, Significant Declines | Low Impact: 5 | ||||||
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| Transportation & service corridors | Utility & service lines | Timing | Scope | Severity | Impact | ||||
| Ongoing | Minority (<50%) | Negligible declines | Low Impact: 4 | ||||||
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| Purpose | Scale |
|---|---|
| Sport hunting/specimen collecting | subsistence, national |
Recommended citation
BirdLife International (2024) Species factsheet: Australasian Bittern Botaurus poiciloptilus. Downloaded from
https://datazone.birdlife.org/species/factsheet/australasian-bittern-botaurus-poiciloptilus on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/11/2024.