The behavioural ecology and conservation of a mulga-dependent, cooperatively-breeding Australian passerine: the Hall's babbler (Pomotostomus halli)

A project undertaken at the School of Biological, Earth and Environmental Sciences, The University of New South Wales, and supervised by Richard Kingsford and Dean Portelli

Habitat loss and degradation is perhaps the most consistent threat to the survival of wild animal populations worldwide. Consequently, to implement effective conservation strategies for threatened species, detailed knowledge of their habitat requirements is needed. Furthermore, for highly social species, knowledge of the social organisation and breeding ecology is equally important as their complex sociality may increase extinction risk.

In Australia, much effort has been devoted to the conservation of avifauna in eucalypt and mallee communities, which have both been extensively cleared for agriculture. Communities dominated by mulga (Acacia aneura) in eastern Australia have also been extensively cleared and degraded by pastoral activities over the last two centuries; however, the birds of this community have been poorly studied and their conservation status is poorly understood. However, several species appear to be dependent upon mulga and other acacia-dominated communities and thus like many woodland- and mallee-dependent species have the potential to be of conservation concern. One such species is Hall’s babbler (Pomatostomus halli), for which very little is known, preventing an accurate assessment of its conservation status.

Only two short-term studies have been undertaken on Hall’s babbler since it was formally described as a new species as recently as 1964. From these and other anecdotal sources the species appears to be a habitat specialist, predominantly occurring in the tall acacia shrublands of semi-arid and arid eastern Australia, which are often dominated by mulga. The species has been recorded living in groups of up to 15 individuals and is known to breed cooperatively like the four other species of Australo-Papuan babblers. Beyond this rather general information, very little is known about the biology, social organization, and habitat requirements of Hall’s babbler, yet this information is highly desirable as the species is classified as vulnerable in New South Wales under the Threatened Species Conservation Act 1995.

While little is known of the biology of Hall’s babbler, previous research on two of its congeners, the grey-crowned (P. temporalis) and white-browed (P. superciliosus) babblers provides a framework from which to develop a research project investigating the behavioural ecology of Hall’s babbler. Our research will address two broad questions concerning the behavioural ecology of Hall’s babbler:

1. What is the social organisation of Hall’s babbler, particularly its cooperative breeding behaviour, and how does it compare to that of other Australo-Papuan babbler species?
2. What are the key habitat requirements of Hall’s babbler across its range?

The information gathered from this research will provide natural resource managers with the necessary information to implement effective conservation actions for the species. Furthermore, this research will be the first comprehensive study of the behavioural ecology of a bird restricted to arid and semi-arid acacia communities and as such it is hoped that this research will draw attention to the conservation of biodiversity associated with these communities.

Captions to Figures

Figure 1. Adult Hall's babbler (Photo: D. Portelli).

Figure 2. Close-up of adult Hall's babbler with distinctive plumage and down-curved probing bill (Photo: D. Portelli).

Figure 3. Three 13-day-old chicks temporarily removed from the nest for banding (Photo: D. Portelli).

Figure 4. Typical Hall's babbler habitat, dominated by mulga (Acacia aneura), at Bowra, SW Queensland (Photo: D. Portelli).

Figure 5. Colour-banded Hall’s Babbler. Each babbler in the study population is banded with an individually-unique combination of three colour bands permitting identification of individuals with binoculars.

Figure 6. A recently fledged Hall’s Babbler.