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Home , Ardeotis, Australian bustard, Chlamydotis

203 AUSTRALIAN Field Ornithology 2008, 25, 203–206 Male–male Conflict and Breeding of the Australian australis in Rehabilitated Mine Land in Arnhem Land, Northern Territory

CHRISTOPHER J. BRADY School of Science and Primary Industries, Charles Darwin University, Darwin, Northern Territory 0909 Present address: CSIRO Science Education Centre, PMB 44, Winnellie, Northern Territory 0822 (Email: [email protected])

Summary Observations were made of Australian Ardeotis australis over 2 years (1998– 2000) at the Gove bauxite mine-site in north-eastern Arnhem Land, Northern Territory. The was observed in ten out of the 12 survey months, and four males held individual mating territories in recently cleared or young rehabilitated areas, where they displayed. An aerial combat involving two males is described for the first time, and anecdotal evidence of successful breeding is presented. Clearing for mining, and subsequent rehabilitation, have created novel habitats, which has evidently allowed an expansion of the breeding range of this species.

Introduction The Ardeotis australis is a widespread though generally scarce species in the Northern Territory (Ziembicki 2003), where it is listed as Vulnerable (Territory Parks & Wildlife Conservation Act 2001). It is a of open country, preferring grasslands, low shrublands, savanna woodlands and other structurally similar habitats such as croplands, golf-courses and airfields (Downes & Speedie 1982; Grice et al. 1986). Like other members of its family (Otididae), Australian Bustards exhibit an ‘exploded’ or ‘dispersed’ lek mating system (del Hoyo et al. 1996). As in all lek systems, males aggregate in display arenas that are visited by females for the purpose of mating, but in the ‘exploded’ system of bustards the males’ display arenas are well spaced apart and aggregations may not be detectable until they are mapped over a large area (Ziembicki 2003).

Study area and methods Opportunistic observations of Bustards were made during a 2-year study of the avifauna of rehabilitated areas at the Gove bauxite mine near Yirrkala in north-eastern Arnhem Land, Northern Territory (Figure 1). I undertook bird research on the mine-site for 18 days every second month between October 1998 and October 2000 (total 234 days). Mining has created novel habitats on the Gove Peninsula, with open areas associated with mine faces and wide haul roads, as well as a range of early successional vegetation communities from open grassland to low open forest in rehabilitated areas. The original vegetation of the mining leases, like that of the areas still surrounding them, was open woodland dominated by Darwin Stringybark Eucalyptus tetrodonta. All observations of Australian Bustards were made on roads or recently mined areas, which were bare of vegetation or in the early stages of rehabilitation. AUSTRALIAN 204 BRADY Field Ornithology

Figure 1. Locality of mining lease on the Gove Peninsula, north-eastern Arnhem Land, Northern Territory.

Results and discussion Bustards were recorded in all survey months except October 1999 and October 2000. They may have moved away from the mine-site in October, the end of the dry season, to take advantage of recently burnt habitat. Burning by traditional owners was observed between August and October each year. Although numbers fluctuated, I estimate that there were never more than five individual Bustards in the area. Most observations were of males, generally as single individuals. A lek was observed to be in operation on the mineral lease. The mining process at Gove resulted in several simultaneously active mine faces separated by 0.75–1.5 km. Four such open mine faces were utilised by males for display, the open ground increasing visibility for observation by potential mates. As described previously by other authors (e.g. Caldwell 1919; Fitzherbert 1978), the display involved inflating a white-feathered breast-sac, to such an extent that it almost touched the ground, cocking the tail-feathers over the back, and pointing the wings towards the ground. The bird then swung the sac from side to side while making a loud roaring call (Plate 29). On the morning of 7 April 1999 a violent clash was observed between two males in a display area. One male had been regularly observed displaying on open ground in the week leading up to the clash. Around 0830 h a second male was observed flying into the area where the resident male was displaying. The intruder landed and approached within 30 m of the resident. The intruder and the resident stood facing each other for less than a minute before the resident male began to walk towards the intruder. The intruder began walking away and the resident took pursuit. The walked slowly along the mine haul road maintaining a distance VOL. 25 (4) DECEMBER 2008 Australian Bustard in Rehabiltated Mine Land, NT 205

Male Australian Bustard with breast- sac extended during display Plate 29 Photo: K. Fitzherbert

of 30–50 m. This continued for ~15 minutes, by which time they had moved >1 km. At this time the intruder turned to face the resident. The birds then flew at each other. At a height of ~25 m they thrust out their chests and collided (chest on chest). On landing, the intruder began walking at a faster pace, then turned, and took off, flying back in the direction from whence he came. The resident returned to his normal display area. Although male Australian Bustards are known to aggressively defend territories against rival males during the mating season, to my knowledge, the mid-air battle described here has not previously been reported. Downes (1967) observed a displaying male chasing another large male that flew across his territory. Caldwell (1919) watched birds circling each other with plumes extended and calling between fighting bouts, which he described as vicious. Fitzherbert (1978) also recorded a Bustard chasing another with its wings spread, tail cocked and fanned, neck outstretched, and head pointed forward, whilst the loser retreated, maintaining an erect posture despite running at high speed. The aerial combat that I observed is more common in smaller species of bustards (e.g. Schulz 1986; de Swardt 1992; del Hoyo et al. 1996). In contrast, aggressive encounters are mostly limited to terrestrial movement in the larger Kori Ardeotis kori (Lichtenberg & Hallager 2008), Houbara undulata (Launay & Paillat 1990) and Great Indian Bustards Ardeotis nigriceps (Ali & Rahamani 1982). Lichtenberg & Hallager (2008) suggested that body size may be important in determining the frequency of aerial combat, with aerial combat too energetically costly for large bustards. An aerial clash similar to the one reported here has been reported for the large , where after an extended confrontation involving walking parallel and shaking the breast-sac repeatedly, two males faced each other, jumped from the ground at the same instant and clashed breasts and legs against each other (Joshua et al. 2005). Because of energy constraints, such AUSTRALIAN 206 BRADY Field Ornithology aerial clashes between large bustards may occur only in rare cases where more usual territorial conflict behaviours have not resulted in a winner. Although I did not directly observe any nests or young in the area, mine staff reported a nest, with one egg, on the ground, and a female with a single much smaller Bustard (D. Ellis pers. comm.). These observations were made in woodland ~1 km from the nearest display area. Storr (1977) claimed that the species bred as far north as the Roper River in the east (~300 km south of the study area), and that its occurrence farther north was as a dry-season visitor only. It was not recorded breeding in the Top End, north of 15°S, during surveys for either of the Australian Bird Atlases (Blakers et al. 1984; Barrett et al. 2002), although it is known to breed in the Douglas/Daly region ~130 km south of Darwin (M. Ziembicki, R. Noske & P. McGrath, pers. comm.).

Acknowledgements I am indebted to Alcan Pty Ltd for providing the funding of which this research was a part. Dave Ellis, Dieter Hinz and other mine staff provided local historical information on Bustards. I also thank Richard Noske, Mark Ziembicki, Colin Trainor and David Watson for comments on drafts of this manuscript.

References Ali, S. & Rahmani, A.R. (1982), Annual Report on Ecology of Certain Endangered Species of Wildlife and their Habitats. The Great Indian Bustard, Bombay Natural History Society, Bombay. Barrett, G., Silcocks, A., Barry, S. & Poulter, R. (2002), The New Atlas of Australian Birds, Birds , Melbourne. Blakers, M., Davies, S.J.J.F. & Reilly, P.N. (1984), The Atlas of Australian Birds, Melbourne University Press, Melbourne. Caldwell, E.R. (1919), ‘Stray feathers’, Emu 18, 207–209. del Hoyo, J., Elliott, A. & Sargatal, J. (Eds) (1996), Handbook of the Birds of the World, vol. 3, Lynx Edicions, Barcelona. de Swardt, D.H. (1992), ‘A behaviour study of the Black Korhaan afraoides, Navors nas Mus’, Bloemfontein 8, 237–258. Downes, M.C. (1967), Reptiles, Fish and Wildlife, Northern Territory Expedition, 1965–67, Northern Territory Fish and Wildlife Division, Darwin. Downes, M.C. & Speedie, C. (1982), Classification of Bustard Habitat in the Northern Territory, Report to Conservation Commission of the Northern Territory, Darwin. Fitzherbert, K. (1978), Observations on Breeding and Display in a Colony of Captive Australian Bustards Ardeotis australis, Bsc Hons thesis, Monash University, Melbourne. Grice, D., Caughley, G. & Short, J. (1986), ‘Density and distribution of the Australian Bustard, Ardeotis australis’, Biological Conservation 35, 259–267. Joshua, J., Gokula, V. & Sunderraj, S.F.W. (2005), ‘Territorial fighting behaviour of Great Indian Bustard’, Journal of the Bombay Natural History Society 102, 114–115. Launay, F. & Paillat, P. (1990), ‘A behavioural repertoire of the adult (Chlamydotis undulata macqueenii)’, Revue d’Ecologie 45, 65–87. Lichtenberg, E.M. & Hallager, S. (2008), ‘A description of commonly observed behaviours for the (Ardeotis kori)’, Journal of Ethology 26, 17–34. Schulz, H. (1986), ‘Agonistic behaviour, territorial behaviour and courtship display of the (Tetrax tetrax)’, Journal für Ornithologie 127, 125–204. Storr, G.M. (1977), Birds of the Northern Territory, Western Australian Museum Special Publication 7, Western Australian Museum, Perth. Ziembicki, M. (2003), Australian Bustard Ardeotis australis, Threatened Species of the Northern Territory, Information Sheet, Northern Territory Government, Darwin.

Received 26 June 2007 