Australian Ibis Threskiornis molucca Scientific name definitions

63–76 cm; 1400–2500 g, female lighter; wingspan 110–125 cm. Male generally larger, with longer bill, as in most ibises. Narrow pinkish transversal  nuchal tracts . Bill thinner and legs less intensely black than congeners; in breeding plumage easily separated from T. aethiopicus by extensive feathering up neck , with ornamental plumes on foreneck; black tips to primaries only . Non breeding adult has tertials dull grey, less lacy, and lacks neck plumes; bare skin of underwing pink instead of red. Immature  totally feathered on head and neck  , variably dark; tertials greyish brown, not lacy. Race <em>pygmaeus</em> significantly smaller.

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Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Inland wetlands , especially shallow swamps with abundant vegetation , and floodplains; sheltered marine habitats, especially tidal mudflats, mangrove swamps, salt pans and coastal lagoons; also grasslands, cultivation, open areas and recently burnt land, often far from wetlands. Reservoirs, farm ponds and sewage works widely used; also uses large gardens, rubbish dumps, abattoirs and other humanized areas. Breeds in reedbeds, shrubs or trees in wide variety of wetlands, occasionally in urban areas.

Most adults sedentary, although throughout range some irregular, nomadic movements occur, sometimes over long distances, and usually related to availability of water. Population of SW Australia partially migratory, apparently moving N in winter, returning S in summer. Young birds disperse widely. Irregular visitor to Tasmania and vagrant to New Zealand. Some movement recorded between NE Australia and New Guinea, and flocks of up to 500 birds have been recorded crossing Torres Strait.

Diet very variable, depending on habitat. Main prey includes frogs, fish (Gambusia, Perca, Arenigobius, Clinus), freshwater crayfish (Cherax), mussels, crabs, shrimps, earthworms, crickets, grasshoppers and beetles; occasionally snakes and mice; also feeds on carrion. Usually forages in flocks of up to 40 birds, occasionally up to 200; on occasions solitary. Forages by walking slowly , probing in soft substrate or pecking at surface.

Mainly vocal around breeding colonies. Calls include drawn-out nasal goose-like barks at different pitches, also grunts and squeals. In flight, a croaking bark at intervals. Young begging for food utter continuous high-pitched squeals.

Season very variable according to prevailing water conditions. Usually forms colonies of up to 20,000 pairs, sometimes with other Ciconiiformes; occasionally in single pairs. Nest  is compact cup of sticks  and twigs, lined with leaves and other soft materials; where breeds in swamps, nest built of reeds. 1–4 eggs  , with clutches of 5–6 eggs  recorded, but possibly laid by 2 females; incubation 20–23 days; chicks have blackish brown down on head  and neck, white on body; leave nest at 30–48 days. Success varies annually: in study of 2025 breeding attempts, 51% failed; 1·73 young fledged  per successful nest.

Not globally threatened (Least Concern). Common in Australia, frequently forming large gatherings. The largest colonies are in S New South Wales and Victoria, occasionally with over 20,000 pairs. Both the population size and its range in Australia have apparently increased since European colonization. Conversion of woodland for farming has increased available foraging grounds. In particular, its unspecific dietary and habitat requirements mean that it adapts well to artificial habitats and even nests in cities. The population of the Sydney area, New South Wales, is substantially reliant on landfill rubbish dumps for food (3 Smith, A.C.M. and Munro, U. (2010). Seasonal population dynamics of the Australian White Ibis (Threskiornis molucca) in urban environments. Emu. 110(2): 132–136. Close ). Its numbers have increased to the point that it is regarded an urban pest along the east coast of Australia since the birds may pose a threat to aircraft safety, scavenge food at waste-management sites, cafés and parks, and compete with other native species for food and habitat; accordingly their colonies are sometimes subject to egg removal and egg oiling as control measures (4 Martin, J. M., French, K. and Major, R. E. (2007). The pest status of Australian white ibis (Threskiornis molucca) in urban situations and the effectiveness of egg-oil in reproductive control. Wildlife Research. 34(4): 319–324. Close ).

It is a sparse and very uncommon breeder in W and N New Guinea, locally common visitor to S; up to 37,000 birds recorded in Bensbach area, Papua New Guinea. Ground and air surveys suggested a minimum 45,000 birds in SE Irian Jaya in 1983, where colonies of c. 10,000 birds discovered at Wasur/Rawa Biru Reserve in 1988, but these suffer some disturbance from hunting. In Wallacea molucca is apparently resident and not uncommon on Seram, and recorded on other islands, but its status there is uncertain (5 Coates, B. J., and K. D. Bishop (1997). A Guide to the Birds of Wallacea: Sulawesi, The Moluccas and Lesser Sunda Islands, Indonesia. Dove Publications, Alderley, Queensland, Australia. Close ); it is known only as a vagrant in Timor Leste (6 Trainor, C. R. (2011). The waterbirds and coastal seabirds of Timor-Leste: new site records clarifying residence status, distribution and taxonomy. Forktail 27:63–72. Close ).