NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. The Grey Grasswren is a cryptic ground-dwelling passerine bird that occupies swamps and areas of inundation in north-western NSW.
2. The Grey Grasswren was first described in 1968 and has two recognised subspecies, both confined to the swampfields of the lower Eromanga (Lake Eyre) basin (Schodde and Mason, 1999). Amytornis barbartus diamantina Schodde & Christidis, 1987 is found along the Cooper and Diamantina drainage systems both in Queensland and South Australia. The other form, Amytornis barbatus barbatus is confined to the Bulloo River drainage system in south-western Queensland and north-western NSW where the area of occurrence is estimated to be less than 100km2 (Garnett and Crowley 2000).
3. The Grey Grasswren has been recorded in NSW from only nine locations in the Caryapundy Swamp north of the Bulloo Overflow, adjacent to the Queensland border (Favaloro and McEvey 1968, Robinson 1973, Blakers et al. 1984, Cooper and McAllan 1995, McAllan and Cooper 1995). The habitat used by Grey Grasswrens is dominated by lignum Muehlenbeckia florulenta, canegrass Eragrostis australasica and old man saltbush Atriplex nummularia but habitat use may be quite specific within these broad vegetation type, depending on levels of floodwater (McAllan and Cooper 1995).
4. A long term population study on the Grey Grasswren sub-species in south-western Queensland found that the number of captures varied seven fold during the course of the study with high capture numbers correlating with drought conditions. During dry periods the grasswrens congregate in the high quality habitat of tall, dense lignum at the northern end of its range and then disperse into other marginal habitats to the south when there is flooding (Hardy 2002, I. McAllan, pers. comm.).
5. The principal threat to the Grey Grasswren comes from alteration and destruction of habitat by grazing stock and rabbits. Cattle grazing, particularly in dry years, damages both lignum and canegrass. Rabbits eat the bark of lignum with the resulting ring-barking causing thinning of the lignum clumps (Hardy 2002). Feral pigs also damage lignum by their habit of extensive rooting. Feral cats are numerous in the grasswren habitat but there is no direct evidence of predation (Hardy 2002).
6. Grey Grasswrens have not been recorded in any conservation areas in NSW.
7. In view of the above the Scientific Committee is of the opinion that the Australian subspecies of the Grey Grasswren, Amytornis barbatus barbatus Favaloro & McEvey, 1968, is likely to become extinct in nature in New South Wales unless the circumstances and factors threatening its survival or evolutionary development cease to operate.
Associate Professor Paul Adam
Chairperson
Scientific Committee
Proposed Gazettal date: 25/06/04
Exhibition period: 25/06/04 - 06/08/04
References:
Blakers M, Davies SJJF, Reilly PN (1984) 'The Atlas of Australian Birds.' (Melbourne: Melbourne University Press).
Cooper RM, McAllan IAW (1995) 'The Birds of Western New South Wales: a Preliminary Atlas.' (Albury, NSW: NSW Bird Atlassers).
Favaloro NJ, McEvey A (1968) A new species of Australian Grass-wren. Memoirs of the National Museum of Victoria 28, 1-9.
Garnett S, Crowley G (2000) 'Action Plan for Australian Birds.' (Environment Australia: Canberra).
Hardy JW (2002) A banding study of the Grey Grasswren Amytornis barbatus barbatus in the Caryapundy Swamp of south-western Queensland. Corella 26, 106-109.
McAllan IAW, Cooper RM (1995) The distribution of the Grey Grasswren in New South Wales. Australian Birds 28, 65-70.
Robinson L (1973) The Grey Grass-Wren. Australian Bird Watcher 4, 251-256.
Schodde R, Christidis L (1987) Genetic differentiation and subspeciation in the Grey Grasswren Amytornis barbatus (Maluridae). Emu 87, 188-192.
Schodde R, Mason I (1999) 'The Directory of Australian Birds: Passerines.' (CSIRO: Melbourne)