Threskiornis spinicollis

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Family

Threskiornithidae

Genus

Threskiornis

Species

spinicollis

Common Names

Straw-necked Ibis, Dryweather Bird, Farmer's Friend, Letterbird

Distinguishing Features

This large bird of 60-70cm is distinguished by its extremely long, downcurved bill. It has a dark, baldhead and a long neck. It earns its name from the straw-like feathers that grow from the base of its neck in the breeding season. The feathers on its back and wings are black with an iridescent green, bronze and purple sheen. The tail and rump are white, as are the underparts and a large panel of feathers on the underside of the wings. The legs are strong, long and red-coloured.

Survey Techniques

Call and visual identification.

Species Call

A long, harsh croak or rapid croaks.

Similar Species

The Australian White Ibis (Threskiornis molucca) is a similarly sized bird with the same baldhead, long bill and strong legs, however its plumage is almost all white.

Distribution

This species is found across most of Australia, except for the most arid areas. It is uncommon in Tasmania and on Norfolk and Lord Howe Islands. Some birds are also found in Indonesia and southern Papua New Guinea.

Country of Origin

Australia

Conservation (Pet/Pest) Status - Regional

Numbers increased dramatically from 1990 to 1998 and since then have steadily declined to the low previous levels. Bird numbers peak in the region over April and May (COG).

Conservation (Pet/Pest) Status - National

Secure, not listed under the EPBC Act 1999. It is especially common in the irrigated Murray Darling Basin and around inland watered-regions. Farmers particularly value them, as they feed on pest insects.

LSCCES Population

Seven sightings of this species were made in Turner, including at the David Street Wetland.

Associated vegetation community

The Straw-necked Ibis is particularly fond of areas with lush green pastures and irrigated playing fields. They will also inhabit areas around wetlands and will move through dry grasslands if there is a plentiful food supply such as grasshoppers.

Limiting Resources

This species needs to be close to easily accessable water. They will only breed when water levels around wetlands are high.

Breeding

In this region of Australia, the breeding season runs from July to December, or in response to very good rainfall. The birds breed in large colonies, often with other Ibis species or the Great Egret (Ardea alba ). Both sexes build large, platform nests into dense wetland or mangrove vegetation such as reeds, cumbungi or lignum. They line their trampled nest with grass and crowd nests together, often forming one giant nesting platform. The damp nest quickly stains the 3-5 oval-shaped, white eggs a darker colour. The eggs hatch after 20-25 days incubation and the young birds are ready to leave the nest after 35-40 days.

Behaviour

This species is very social and the birds are usually sighted in fairly large groups. The birds travel frequently in flocks, holding a 'V' formation and soaring at a great height. Flocks often perch on large dead trees. The birds feed by pecking at the ground and usually drink at dusk. During the nesting season they make complex displays for one another. They regurgitate food for their young to eat, who sometimes wrap their wing around their parent's neck, pleading for a feed.

Functional Group

Insectivore

Food Species

The Straw-necked Ibis feeds mostly on ground-dwelling invertebrates sich as grasshopers (Schistocerca emarginata) and locusts (Chortoicetes terminfera). It will also eat some frogs and small reptiles and mammals.

Predators

The eggs and young birds of this species may be vulnerable to attack from Black Rats (Rattus Rattus) and Swamp Harriers (Circus aeruginosus).

Interesting Fact

The straw-coloured quills on this species neck are raised in displays of courtship and aggression. During courtship they also develop a red patch of skin on each side of the breast that fades after they find a partner.