Threskiornis molucca (Cuvier, 1829)

Species Identity

This species, the Australian white ibis, is a fairly large ibis.

Body Length and Head Features

It measures around 65–75 cm (26–30 in) in total length, and has a completely bald black head and neck, plus a long black downcurved beak.

Beak Sexual Dimorphism

Males have a beak longer than 16.7 cm (6.6 in), while females have a beak shorter than this measurement.

Weight Sexual Dimorphism

The species shows sexual dimorphism in size: males are slightly heavier, weighing between 1.7–2.5 kg (3.7–5.5 lb), while females weigh 1.4–1.9 kg (3.1–4.2 lb).

Weight Comparison with Related Species

For comparison, the American white ibis usually reaches a weight of just 1 kg (2.2 lb).

Body Plumage Coloration

The bird's body plumage is white, though it can become stained brown.

Secondary Plume Features

Inner secondary plumes are displayed as lacy black feathers that look like a tail.

Breeding Season Tail Coloration

The upper tail turns yellow during the breeding season.

Limb and Underwing Features

The legs and feet are dark, and red skin is visible on the underside of the wing.

Immature and Juvenile Traits

Immature birds have shorter bills, and juvenile birds have feathers covering their head and neck.

Vocalization

The Australian white ibis's call is a long croak.

Maturity and Lifespan

It reaches sexual maturity at three years of age, and can live up to 28 years old.

Distribution Range

The Australian white ibis is widespread across eastern, northern, and south-western Australia.

Habitat

It lives in marshy wetlands, often near open grasslands, and has become common in city parks and rubbish dumps across urban areas of the Australian east coast, including Wollongong, Sydney, Perth, the Gold Coast, Brisbane, and Townsville.

Historical Urban Rarity

Historically, the species was rare in urban areas.

Urban Colonization Timeline

The first records of birds visiting urban areas came after drought pushed populations eastwards in the late 1970s, and there were no recorded breeding events in Sydney until the 1980s.

Historical Breeding Site

The Macquarie Marshes in north-western New South Wales was once one of this ibis's main breeding areas, with 11,000 nests recorded there in 1998.

Recent Breeding Site Status

However, no breeding events have been recorded at this site since 2000.

Absence Range

The species does not occur in Tasmania.

Population Boom Periods

Populations of the Australian white ibis, especially in urban areas, have boomed multiple times: in the 1970s, the early 2000s, and around 2010.

Population Monitoring Status

There is no national monitoring program for the species, so there are no official total population counts.