Campbell Island Teal (Anas nesiotis)
Justification This species qualifies as Critical as it has a tiny breeding population. Population trends are unknown but assumed stable. If translocations successfully establish a second population, and overall numbers increase, it could be downlisted to Endangered.
Identification 48 cm. Small, flightless, dark brown duck. Brown eclipse male, female, juvenile. Mottled dark brown breast. Prominent white eye-patch. Breeding male has glossy green head. Very narrow white collar, flank patch. Voice Soft, high-pitched wheezy whistles and popping (male), low quacks and growls (female).
Taxonomy Genetic work has shown very high genetic variation within the original Brown Teal A. aucklandica taxon (treated as Vulnerable in 1994), and it has been split into three species: A. aucklandica, A. chlorotis and A. nesiotis. All are threatened.
Population estimate 49
Population trend stable
Range estimate 1 km2
Country endemic? Yes
Range & Population Anas nesiotis is endemic to New Zealand where it has been confined to Dent Island, an offshore islet of Campbell Island, for many decades. It was first collected in 1886 from the sea near Campbell (just 3 km away from Dent and likely to have been a stronghold for the species), but was not discovered on Dent until 1975. In 1990, a survey of Dent estimated a population of 60-100 birds. It is likely that no more than 25 breeding pairs are present. In March 1999, 12 captive-bred birds were released on Codfish Island, and appear to have established
Ecology It lives under thick, chest-high tussock (there are no pools or running water on Dent). It has been sighted over most of the island, but is probably more common below 100 m, and in damp areas. It has not been observed feeding on the island, but in captivity it feeds on amphipods, weevils, earthworms, seaweed and other insects. No nests, eggs or chicks have been found in the wild. In captivity, females sometimes lay two clutches of between one and four eggs.
Threats The accidental introduction of mammals to Dent could cause the extirpation of the species from its last natural refuge. Brown rat Rattus norvegicus on Campbell (one of the most dense field populations in the world) may have caused its disappearance from this island. Severe weather events and the introduction of avian disease are also possible threats.
Action In 1998, 35 individuals were held in captivity originating from seven males and three females caught in 1984 and 1990. The temporary Codfish Island population will be further supplemented with captive-raised birds until 2000-2001, at which point the success of the transfers will be reviewed. Plans are advanced to eradicate R. norvegicus from Campbell. Following successful eradication, birds will be reintroduced to Campbell from the temporary Codfish Island population.
