The Chatham oystercatcher or Chatham Island oystercatcher (Haematopus chathamensis) is a species of oystercatcher. It is a wading bird endemic to the Chatham Islands, New Zealand. This species is rated by the IUCN as endangered, and has a current population of 310 to 325 birds (2004 census). The main threat is from introduced predators.
The Chatham oystercatcher has distinctive black and white plumage and a long, thick orange-red beak. The head, neck, breast, back, wings and tail are black. The lower underparts are white with an unclear demarcation on the breast. The irises are yellow and the eyes have orange orbital rings. The short, thick legs are pink. Adults are about 48 centimetres (19 in) in length.
The Chatham oystercatcher is only found on the Chatham Islands, an archipelago about 680 kilometres (420 mi) south east of New Zealand. Each of the four main islands has small breeding populations
The Chatham oystercatcher feeds on molluscs and marine worms, digging them out of the sand with its beak and hammering the shells to open them. The nest is built on the beach on sandy or rocky shores and consists of a simple scrape. Sometimes it is built among low vegetation and may be rather more elaborate. Two or three eggs are usually laid. Juvenile birds become mature at about three years of age and the lifespan is about eight years. The success rate of each pair averages 0.44 fledglings per breeding season.
The IUCN rates the Chatham oystercatcher as "Endangered". In 2006 the total population on the four Chatham Islands was estimated to be 310 to 360 individuals of which fewer than 250 were mature individuals. The population is believed to be stable. The main threats faced by this bird are predation, particularly by feral cats on eggs and chicks, and the cattle and sheep which roam onto the beaches and may trample the nests. The flightless weka (Gallirallus australis) is also a nest predator.