Botaurus poiciloptilus — Details

Australasian Bittern learn more about names for this taxon

Overview

Distribution

Range Description

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Botaurus poiciloptilus occurs in the wetlands of southern Australia, New Zealand and New Caledonia (to France). In Australia the population is now estimated to number not more than 1,000 mature individuals15. Consecutive atlas censuses in Australia have shown a marked decrease in reporting rate; the species was recorded in 260 10-minute grid squares in 1977-1981, 142 grid squares in 1998-2003, and just 61 in 2003-200816. The declining reporting rate was particularly pronounced in the Riverina (63%), Tasmania (>90%), and south-west Australia (>90%). This decline in reporting rate is thought to represent a genuine population decline over the period. In Australia, most birds are in the Murray-Darling basin and adjacent coastal areas. In Western Australia, the population was estimated to contain up to 100 pairs in 19807, but it is now much reduced, with the largest concentration in the Albany and Lake Muir wetlands. There have been no confirmed records from the Swan Coastal Plain since 1992 and surveys conducted in 2007 and 2008 found that half the wetlands that supported the species in 1980 now retained no suitable habitat17. There are now only occasional records from Queensland5 and there appears to have been no great influx to remnant wetlands after the recent drought, as might have been expected if they were more common inland. In South Australia, breeding is confined to the south-east, however, loss of suitable habitat at Bool Lagoon, arguably the key site in Australia for this species, and other wetlands in the area due to changes in regional drainage, has probably had a large impact in last 10-20 years13. It is now known from just one site, Hirds Swamp, in Victoria18. In Tasmania the species is now recorded from only handful of sites and several of the major lakes that it once occupied have been dry for some years. In New Zealand, the estimated population was between 580-725 individuals in 19806; numbers may be greater, given the lack of targeted survey work, and the large size of suitable swamps9. In New Caledonia and Uvea, there have been just two recent records of single calling males, and the population is not thought to exceed 50 individuals1,3.
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Ecology

Habitat

Habitat and Ecology

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Habitat and Ecology
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 rushes4. It has been recorded in paddies in the Murray Darling basin, but it is not thought to use such habitats for breeding18. It usually lays four eggs. It feeds, mostly at night, on fish, eels, frogs, freshwater crayfish and aquatic insects6. The population seems to increase rapidly in good years and decline rapidly in poor ones12.

Systems
  • Freshwater
  • Marine
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Botaurus poiciloptilus

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Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Species: 3
Species With Barcodes: 1

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Conservation

Conservation Status

IUCN Red List Assessment

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Red List Category
EN
Endangered

Red List Criteria
C1

Version
3.1

Year Assessed
2009

Assessor/s
BirdLife International

Reviewer/s
Garnett, S., Butchart, S., Bird, J.

Contributor/s
Herman, K., O'Donnell, C., Blyth, J., Tzaros, C., Bell, B., Garnett, S., Holmes, T., Miskelly, C., Loyn, R., Wakefield, B., Watson, D., Burbidge, A., Jaensch, R., Barré, N., O'Connor, J., Sherley, G., Ford, H., Christidis, L.

Justification
This species is listed as Endangered because it has a very small and rapidly declining population owing to loss and degradation of its wetland habitats. Urgent action is a priority to halt declines in Australia.

History
  • 2008
    Endangered
  • 2006
    Endangered
  • 2004
    Endangered
  • 2000
    Vulnerable
  • 1996
    Endangered
  • 1994
    Endangered
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Population

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Population
In New Zealand, the estimated population was between 580-725 individuals in 1980 (Heather and Robertson, 1997). The population on New Caledonia is not thought to exceed 50 individuals. Following apparently rapid declines, the Australian population is now thought to number fewer than 1,000 mature individuals (R. Loyn in litt. 2008).

Population Trend
Decreasing
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Threats

Threats

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Major Threats
In Australia and New Zealand, the main threats are wetland drainage for agriculture, as well as changes brought about by high levels of grazing and salinisation of swamps2,4,5. In Australia, the species appears able to adapt to the availability of ephemeral wetlands, but is likely to be particularly sensitive to the destruction of drought refugia. Loss of these habitats may explain its decline in Western and South Australia5. The Murray-Darling basin, a former stronghold of the species, has suffered consecutive droughts in recent years and over-extraction of water is an ongoing problem14,15. Shooting and flying into powerlines are additional contributory causes2, but hunting pressure is very low11.
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Management

Conservation Actions

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Conservation Actions
Conservation Actions Underway
In Australia, Bool Lagoon and Lake Muir are managed specifically for the species5. In Australia, recent initiatives by the Threatened Bird Network to survey Painted Snipe Rostratula benghalensis australis will contribute to the information on the distribution of this species10, 18.

Conservation Actions Proposed
Complete field surveys to determine current global distribution, status and key sites for conservation1,5,8. Develop methods for assessing population trends5. In New Zealand, determine factors that may be limiting populations8. In New Caledonia, obtain legal protection of representative, low altitude habitats1. Protect remaining sites against drainage or salinisation. Rehabilitate former breeding sites5.

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Wikipedia

Australasian Bittern

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The Australasian Bittern (Botaurus poiciloptilus), also known as the Brown Bittern, is found in south-western and south-eastern Australia, Tasmania, New Zealand, New Caledonia and Ouvea. Populations in Australia and New Zealand have declined in the 20th century.

It is a large bittern, patterned and streaked brown, buff and black, with a pale throat. It is a cryptic and partly nocturnal species that inhabits densely vegetated wetlands. It feeds on aquatic animals such as frogs, eels and freshwater crustaceans. It is a solitary nester on the ground in dense wetland vegetation on trampled reeds and other plants. It has a distinctive booming voice and may be heard more often than seen.

The principal cause of past and ongoing decline is thought to be wetland drainage and degradation. In Australia it is thought to be particularly sensitive to the destruction of drought refugia.

Conservation status

The Australasian Bittern is listed as Endangered on the Environment Protection and Biodiversity Conservation Act 1999. The Australasian Bittern is listed as threatened on the Victorian Flora and Fauna Guarantee Act 1988.[2] Under this Act, an Action Statement for the recovery and future management of this species has not been prepared.[3] On the 2007 advisory list of threatened vertebrate fauna in Victoria, this species is listed as endangered.[4]

Gallery

  • Painting by John Gould.

  • In the grass, Leeton, NSW, Australia.

References

  1. ^ BirdLife International (2008). Botaurus poiciloptilus. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 4 February 2009. Database entry includes range map and justification for why the species is listed as endangered.
  2. ^ Department of Sustainability and Environment, Victoria
  3. ^ Department of Sustainability and Environment, Victoria
  4. ^ Victorian Department of Sustainability and Environment (2007). Advisory List of Threatened Vertebrate Fauna in Victoria - 2007. East Melbourne, Victoria: Department of Sustainability and Environment. p. 15. ISBN 978-1-74208-039-0. 
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