[order] CICONIIFORMES | [family] Threskiornithidae | [latin] Threskiornis spinicollis | [authority] Jameson, 1835 | [UK] Straw-necked Ibis | [FR] Ibis d’Australie | [DE] Stachelibis | [ES] Ibis Tornasol | [NL] Strohalsibis
Threskiornis is a genus of , wading birds of the family Threskiornithidae. They occur in the warmer parts of the Old World in southern Asia, Australasia and sub-Saharan Africa. They are colonial breeders, which build a stick nest in a tree or bush and lay 2-4 eggs. They occur in marshy wetlands and feed on various fish, frogs, crustaceans and insects. Adult Threskiornis ibises are typically 75cm long and have white body plumage. The bald head, neck and legs are black. The bill is thick and curved. Sexes are similar, but juveniles have whiter necks duller plumage. The Straw-necked Ibis differs from the other species in having dark upperparts, and is some times placed in the separate genus Carphibis (Jameson, 1835)as Carphibis spinicollis.
The straw-necked ibis gets its name from the straw-like feathers that are on the neck and breast area. It has a black, bald head and long bill used for probing into the mud. A portion of its neck and all of its underbody are white; the rest of the body is a dark iridescent color. Long legs help it move through grasses and marshy areas. The toes are webbed at the base.
Australasia : widespread. The straw-necked ibis is endemic in continental Australia, but it has occurred as a vagrant in Tasmania, southern New Guinea and Indonesia, and on Norfolk and Lord Howe Islands.
It often occurs in mixed flocks with the sacred ibis, but it prefers grassland and pastoral country rather than wetlands, which are the favored habitat of the sacred ibis. It usually occurs in very large flocks.
Nesting occurs in large dense traditional colonies, often in the company of sacred ibis and other water birds. Breeding behavior is strongly influenced by local flooding. The largest colonies may number tens or even hundreds of thousands of birds. Nests are often so close together that the sites become trampled to a common platform as the season progresses. Sometimes two broods are raised in succession. The usual clutch is 2-3 eggs, which hatch in 20 – 25 days. Chicks fledge after about 35 days.
The ibis feeds by using its beak to probe through soft mud in shallow holes, and under plants and roots for crawfish, snails, worms, small crustaceans, or whatever else it feels as it probes along.
copyright: Nick Talbot
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be fluctuating, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Partially migratory: some birds sedentary; others make seasonal or irregular movements as water conditions vary. Seasonal migration recorded from SE and N Australia, and from coast and inland wetlands in CE Australia; also across Torres Strait between NE Australia and S New Guinea. Vagrant to Norfolk I and Lord Howe I. usually flies in line or in V-formation; at great heights during long distance movements.