Grey-crowned babbler (eastern subspecies) (Pomatostomus temporalis temporalis) - vulnerable species listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Grey-crowned Babbler (eastern subspecies), Pomatostomus temporalis temporalis (Vigors and Horsfield, 1827), as a VULNERABLE SPECIES on Schedule 2 of the Act. Listing of Vulnerable Species is provided for by Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee found that:

1. The eastern form of the Grey-crowned Babbler Pomatostomus temporalis temporalis, formerly ranged throughout eastern Australia from South Australia, through Victoria and broadly through NSW and central Queensland up into southern New Guinea. The Grey-crowned Babbler is now extinct in South Australia, coastal Victoria and the ACT. In NSW, the Grey-crowned Babbler occurs on the western slopes and plains but was less common at the higher altitudes of the tablelands. Isolated populations are known from coastal woodlands on the North Coast, in the Hunter Valley and from the South Coast near Nowra (Blakers et al. 1984, Schodde & Mason 1999).

2. Grey-crowned Babblers occupy open woodlands dominated by mature eucalypts, with regenerating trees, tall shrubs, and an intact ground cover of grass and forbs. The species builds conspicuous dome-shaped nests and breeds co-operatively in sedentary family groups of 2-13 birds (Davidson and Robinson 1992). Grey-crowned Babblers are insectivorous and forage in leaf litter and on bark of trees.

3. The Grey-crowned Babbler has declined in numbers and disappeared from large parts of its range. The species is extinct in the Orange area (Heron 1973) and possibly also from around Bathurst, where A. Fisher (pers.comm.) has made no record of the species in a study of almost 300 sites. Recent surveys (A. Overs, unpubl.) show a decline in the number of family groups that remain in the southern portion of its range, such that approximately five groups remain in Boorowa Shire, less than 10 around Wagga Wagga, and less than 30 groups in the shires of Young, Junee and Harden. A survey of 96 woodland sites in Holbrook Shire revealed only four groups (S. Collard, unpubl.). Further, the species has apparently disappeared from the Shires of Gundagai, Gunning, Yass and Yarrowlumla.

4. There are probably no Grey-crowned Babblers left on the New England Tableland (H. Ford, pers. comm.) and they are now very uncommon in the Hunter Valley with most family groups reduced to two or four members (P. Cowper, pers. comm.)

5. In southern NSW, the size of Grey-crowned Babbler family groups is also reduced. In a three year study of 15 family groups near West Wyalong, the mean number of birds in each group was four (A. Overs, unpubl.). Such groups are much smaller than those recorded further north near Peak Hill, where groups averaged 8-13 birds (A. Overs, unpubl.). The impact of reduced family groups on breeding success is unknown, although it is likely to be detrimental.

6. The Grey-crowned Babbler is threatened by clearance and the fragmentation of habitat including removal of dead timber. The species occupies woodlands on fertile soils of plains and undulating terrain. Therefore, Grey-crowned Babbler habitat has been disproportionately cleared for agriculture. Isolation of populations in scattered remnants is exacerbated by the apparent reluctance of birds to traverse tracts of cleared land. As reduced family groups, these isolated small populations are vulnerable to extinction via stochastic events and to loss of genetic viability in the long term.

7. Habitat degradation threatens Grey-crowned Babblers, particularly as a result of weed invasion and grazing by stock. In addition, it is likely that increased abundance of competitors, such as Noisy Miners, and nest predators, including the Pied Currawong and Australian Raven (Major et al. 1996) threaten Babbler foraging efficiency and breeding success.

8. In view of the above points, the Scientific Committee is of the opinion that the Grey-crowned Babbler (eastern subspecies) Pomatostomus temporalis temporalis, is likely to become endangered unless the circumstances and factors threatening its survival or evolutionary development cease to operate, and is therefore eligible for listing as a vulnerable species.

Proposed Gazettal date: 26/10/01
Exhibition period: 26/10/01 - 30/11/01

References

Blakers, M., Davies, S.J.J.F. and Reilly, P.N. (1984). 'The Atlas of Australian Birds'. Melbourne University Press: Melbourne.

Davidson, I. and Robinson, D. (1992). 'Grey-crowned Babbler, Pomatostomus temporalis: Action Statement No. 34.' Department of Conservation and environment: Victoria.

Heron, S.J. (1973). Birds of the Orange district, NSW. Emu 73, 1-8.

Major, R., Gowing, G. and Kendal, C. (1996). Nest predaton in Australian urban environments and the role of the Pied Currawong, Strepera graculina. Australian Journal of Ecology 21, 399-409.

Schodde, R. and Mason, I.J. (1999) 'The Directory of Australian Birds: Passerines'. CSIRO:Melbourne.