Observations on breeding success and flocking of Australian Sarus Cranes Grus antigone gillae and Brolgas G. rubicunda in the Gulf Plains bioregion, north-western Queensland, Australia

Known breeding sites of the Australian Sarus Crane Grus antigone gillae are concentrated in the Gulf Plains bioregion of north-western Queensland, where this species is sympatric with the Brolga G. rubicunda. Breeding success in cranes may be highly variable and roadside surveys in the Gulf Plains on 11 days in April–June 2014 showed that breeding success (number of young as a proportion of the number of pairs) was low, at 28% for Brolgas and 21% for Australian Sarus Cranes. This might have resulted from excessive flooding after heavy cyclonic rains during the height of nest initiation in February. At the 90 roadside sites occupied by only one species, Australian Sarus Cranes showed a significant preference for wooded habitats, whereas Brolgas were more likely to prefer open habitats and were the only occupants of saline areas. Both species were present at two grassland (open) sites and three moist woodland sites. Opportunistic observations showed that flocking (aggregations of ≥10 birds, including families) was well established on one cattle station (Miranda Downs), where both species foraged on a recently harvested hay paddock with readily accessible artificial water sources. Other foraging and wetland sites on this property were also shared by both species, suggesting that close association between them occurs more often, and earlier after the breeding season, than previously thought.