South Island Oystercatcher

The South Island oystercatcher, or tōrea as it is known in Māori, is a striking bird with a pied appearance. This large wader boasts a bold contrast of black and white plumage, complemented by a long red-orange bill and red legs. It is a species that commands attention, measuring 46 cm in length, with a wingspan of 80–86 cm, and weighing around 550 grams.

Identification Tips

To distinguish the South Island oystercatcher from its relatives, look for the white lower back and more extensive white on the wing. The demarcation line between black and white on the breast is set further forward compared to the variable oystercatcher. When compared to the Australian pied oystercatcher, note the South Island species' longer bill, shorter legs, and the pointed, rather than square, forward demarcation line of white on the back.

Habitat

This bird is endemic to New Zealand, breeding inland on the South Island. Its breeding grounds include diverse landscapes such as braided river systems, open paddocks, cultivated land, lake beaches, subalpine tundra, and herb fields.

Distribution

After breeding, most of the South Island oystercatcher population migrates to estuaries and harbors on the North Island. While primarily found in New Zealand, it has been occasionally spotted as a vagrant on Norfolk Island, Lord Howe Island, and the eastern coast of mainland Australia.

Behaviour

The South Island oystercatcher is known for its foraging habits, mostly feeding on mollusks and worms. It is particularly fond of the New Zealand cockle, with an individual bird consuming an estimated 200,000 cockles annually.

Song & Calls

This bird communicates with a variety of calls, including piping sounds used both socially and aggressively. It also emits a piercing alarm call and a quieter call during flight.

Breeding

Nesting occurs in sand scrapes on farmland or gravel banks within braided rivers. The typical clutch consists of two to three brown eggs, blotched with dark and pale brown. Both parents share the duty of incubation, which lasts 24–28 days. The young are precocial and nidifugous, taking to the wing 6 weeks after hatching.

Parasites

The South Island oystercatcher plays host to the flatworm Curtuteria australis. This parasite's life cycle involves infecting cockles, which are then consumed by the oystercatchers. The birds excrete the eggs, which are ingested by whelks, completing the cycle.

Conservation Status

Once in decline due to hunting, the South Island oystercatcher's numbers have been on the rise since receiving legal protection in 1940. As of 2002, the population was estimated at 110,000, and the species is currently classified as Least Concern.