Grey Grasswren (Bulloo) (Amytornis barbatus barbatus)

Advice to the Minister for the Environment and Heritage from the Threatened Species Scientific Committee (TSSC) on Amendments to the list of Threatened Species under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)
14 February 2005

1. Scientific name, common name (where appropriate), major taxon group.

Amytornis barbatus barbatus (Grey Grasswren (Bulloo))

Two subspecies of Grey Grasswren are recognised, the Bulloo subspecies (Amytornis barbatus barbatus) and the Lake Eyre Basin subspecies (Amytornis barbatus diamantina). Amytornis barbatus barbatus (Grey Grasswren (Bulloo)) is confined to the Bulloo River drainage system in south-western Queensland and north-western NSW. Amytornis barbatus diamantina occurs from the lower reaches of Coopers Creek in Queensland, down the Diamantina River (Goyder's Lagoon) in South Australia.

2. Description

The Grey Grasswren (Bulloo) is a small elusive bird which lives exclusively in swampy floodplains along the Bulloo River which runs through arid inland Australia. A striking grey, white and black striped bird, it is well camouflaged in the tall Lignum and Canegrass vegetation where it lives. The Grey Grasswren (Bulloo) is thought to be a relatively sedentary bird. Its diet consists of seeds and insects.

3. National context

The Grey Grasswren (Bulloo) is endemic to the arid channel country of inland Australia occurring on the swamp floodplain of the Bulloo River north east of Tibooburra, NSW. Its known distribution straddles the north west NSW and south west Queensland border. The subspecies is considered to be a specialist living in swamps dominated by Lignum (Muehlenbeckia cunninghamii) and Canegrass (Eragrostis australasica). The Grey Grasswren (Bulloo) occurs solely on a small number of leasehold properties.

Neither the Grey Grasswren (Amytornis barbatus) nor the Grey Grasswren (Bulloo) (Amytornis barbatus barbatus) are currently listed under the EPBC Act. The Grey Grasswren (Bulloo) (Amytornis barbatus barbatus) is currently listed as endangered under the NSW Threatened Species Conservation Act 1995. The Grey Grasswren (Amytornis barbatus) is listed as rare under both the Queensland Nature Conservation Act 1992 and the South Australian National Parks and Wildlife Act 1972.

A draft recovery plan for the species, Amytornis barbatus, has been completed by the NSW Department of Environment and Conservation. This plan covers the NSW distribution of Amytornis barbatus barbatus.

EPBC Act criteria.

TSSC judges Amytornis barbatus barbatus to be eligible for listing as vulnerable under the EPBC Act. The justification against the criteria is as follows:

Criterion 1 - It has undergone, is suspected to have undergone or is likely to undergo in the immediate future a very severe, severe or substantial reduction in numbers.

The population size of the Grey Grasswren (Bulloo) is not well known. Garnett and Crowley (2000) estimated there were 10,000 breeding Grey Grasswrens (Bulloo) but stated that this estimate was not considered reliable and gives no evidence to support this figure.

There are a number of threats operating on this subspecies' habitat (see below). As a result of these, it is likely to have undergone a reduction in numbers and may continue to do so due to habitat degradation. However, there are no data to quantify the extent of the decline in numbers.

There is no quantitative data available against this criterion. Therefore, the species is not eligible for listing under this criterion.

Criterion 2 - Its geographic distribution is precarious for the survival of the species and is very restricted, restricted or limited.

The Grey Grasswren (Bulloo) has a restricted distribution and is only known from a small number of sites within the Bulloo River drainage basin. Research indicates that the subspecies is also subject to extreme fluctuations in area of occupancy during times of drought.

The Grey Grasswren (Bulloo) is estimated to have an extent of occurrence of less than 500 km2 and an area of occupancy of 100 km2 based on known sites. Its distribution is highly fragmented often separated by dunes and clear areas which would prevent movement between suitable habitat. This subspecies has been reasonably well surveyed during the Birds Australia 1977-1981 Atlas and the 1998- Present Atlas and specific studies.

The Grey Grasswren (Bulloo) population appears to exhibit extreme fluctuations in area of occupancy in response to drought. A banding study (Hardy 2002) found a seven fold increase in the capture rate of this subspecies at the study site during dry years. This increase was attributed to the birds congregating in the refuge of the denser Lignum stands. During times of drought, the tendency of the birds to concentrate in lignum swamp may make them more vulnerable to catastrophic events such as a major fire which may destroy or degrade their habitat.

There are a number of factors which may contribute to habitat degradation including inappropriate fire regimes, grazing by rabbits, trampling by cattle, and rooting (digging) by feral pigs, all of which are exacerbated during dry years (McAllan and Cooper 1995, and Hardy 2002).

There are a number of other potential threats. Predation by foxes and cats is thought to occur but the extent of this threat is not known. Invasive and noxious weeds (e.g. parthenium and mesquite) also have the potential to spread downstream from the upper catchment areas of the Bulloo River and affect habitat for the subspecies.

The geographic distribution of the Grey Grasswren is restricted and is precarious for the survival of the species due to a range of threats operating in its preferred habitat and the tendency of the birds to congregate during drought in lignum swamp. Therefore, the species is eligible for listing as vulnerable under this criterion.

Criterion 3 - The estimated total number of mature individuals is limited to a particular degree and: (a) evidence suggests that the number will continue to decline at a particular rate; or (b) the number is likely to continue to decline and its geographic distribution is precarious for its survival.

Although the population size of the Grey Grasswren (Bulloo) is not well known and estimates of population size are considered unreliable, the subspecies has a limited geographic distribution that is precarious for its survival and threats operating on its habitat are likely to be causing a decline in numbers.

However, there is no quantitative data available against this criterion. Therefore, the species is not eligible for listing under this criterion.

Criterion 4 - The estimated total number of mature individuals is extremely low, very low or low.

There is no quantitative data available against this criterion. Therefore, the species is not eligible for listing under this criterion.

Criterion 5 - Probability of extinction in the wild

There is no quantitative data available against this criterion. Therefore, the species is not eligible for listing under this criterion.

5. Conclusion

The geographic distribution of the Grey Grasswren (Bulloo) is precarious for its survival. The subspecies has a restricted distribution within the Bulloo River drainage basin. The subspecies is subject to extreme fluctuations in area of occupancy in response to drought conditions. There are a number of threatening processes operating in the species' habitat. The species is eligible for listing as vulnerable under criterion 2.

6. Recommendation

TSSC recommends that the list referred to in section 178 of the EPBC Act be amended by including in the list in the vulnerable category:

Amytornis barbatus barbatus (Grey Grasswren (Bulloo))

Publications used to assess the nomination

Garnett, S.T., & G.M. Crowley. 2000. The Action Plan for Australian Birds 2000. Environment Australia, Canberra.

Hardy, J. W. (2002) A Banding Study of the Grey Grasswren Amytornis barbatus barbatus in the Caryapundy Swamp of South-western Queensland. Corella 26(4):106-109.

McAllan, I.A.W. and Cooper, R.M. (1995) The Distribution of Grey Grasswren in New South Wales. Australian Birds 28(3):65-70

NSW National Parks and Wildlife Service (2003) Grey Grasswren (Amytornis barbatus) Draft Recovery Plan. NSW National Parks and Wildlife Service, Hurstville.

Higgins, P.J., Peter, J.M. and Steele, W.K. (2001) Handbook of Australian, New Zealand and Antarctic Birds. Volume 5: Tyrant Flycatchers to Chats. Oxford University Press, Melbourne.

Conservation Advice

The Grey Grasswren (Bulloo) is a small elusive bird endemic to the arid channel country of inland Australia occurring in the Lignum and Canegrass swamps of the floodplain of the Bulloo River in north west NSW and south west Queensland (NHT regions - Desert Channels, South West (Qld), and Western NSW). The subspecies occurs solely on a small number of privately managed cattle properties. The key threat to this subspecies is the decline in area, extent and quality of its habitat predominantly through grazing by stock and feral animals.

The priority recovery and threat abatement actions required for this species are:

  • To notify the relevant land management agencies of the listing and encourage them to liaise with one another and local landholders to develop specific management strategies to conserve the Grey Grasswren (Bulloo).

These may include:

  • management of feral herbivore species such as rabbits, goats, pigs and horses to reduce total grazing pressure; and
  • development of a fire management plan to identify appropriate fire regimes for hazard reduction and pasture promotion and the management of wild fires.
  • This list does not encompass all actions that may be of benefit to this species, but highlights those that are considered to be of the highest priority at the time of listing.

    The NSW Department of Environment and Conservation has a draft Recovery in place for Amytornis barbatus (Grey Grasswren) within NSW which sets out specific management actions and guidelines for the conservation of this species including the Bulloo subspecies.

    Priority for the development of recovery plan: Medium.