Australian Bustard (Ardeotis australis)
- Family: Otididae (Bustards)
- Class: Birds
DESCRIPTION
Bustards, which weigh 14 kg, are the heaviest flying birds in Australia, and amongst the heaviest in the world. These huge birds stand 120 cm tall, with a wingspan of around 2 m. Because of their great weight, bustards much prefer to walk, though it is a spectacular sight when they do fly. They have a pale grey neck and belly, and freckled brown wings and tail. Male bustards have a black crown, while the females have a brown crown.
DISTRIBUTION
These birds were once very common across much of mainland Australia, often occurring in immense flocks. For example, in 1897 a flock of 1000 bustards was seen near Hay, NSW. However, the species has suffered a massive historical decline, and now they have all but disappeared from south-eastern Australia.
HABITAT
Australian bustards are found in tussock grassland, Triodia hummock grassland, grassy woodland, and low shrublands. They will also use denser habitat that has been opened up by recent fire. They lay usually one egg, directly on the ground, typically along a boundary between open grasslands and more protective shrubland or woodlands. They appear to move nomadically in response to local variations in the supply of their preferred diet of insects, small vertebrates, seeds and fruit.
THREATS
Key threatening processes include habitat alteration due to human harvesting, altered fire regimes (they need a mixture of open ground for grazing and thick vegetation to hide their young; and some of their fruit/seeds are from fire-sensitive plants), cattle grazing, and invasion by woody weeds. Furthermore, they lay their eggs directly on the ground, so are vulnerable to predation by introduced predators such as cats, foxes and dingoes, and trampling by cattle.
GENERAL INFORMATION
Bustards are unique among Australia’s birds in that they exhibit what is known as an ‘exploded lek’ mating system. Leks are tight aggregations of males that come together to display in specific areas, in order to attract females. A lek arena is regarded as ‘exploded’ if males are well spaced from one another (that is from 100 to 1000 m apart). Usually, among lekking species, it is the larger, more elaborate males that are most successful at attracting mates. This has important implications for harvesting bustards, because if bigger birds are preferred for harvest, then the breeding performance of the population as a whole may suffer. Furthermore, as leks are located in traditional arenas, damage to the habitat encompassing the lek arena may prohibit birds from displaying and breeding.