The New Zealand merganser (Mergus australis) (Māori: Miuweka),^[3] also known as Auckland merganser or Auckland Islands merganser, was a typical merganser which is now extinct.

Quick Facts New Zealand merganser Temporal range: Late Holocene, Conservation status ...

New Zealand merganser Temporal range: Late Holocene
Stuffed specimen from 1902
Conservation status
Extinct (c.1902)  (IUCN 3.1)[1]
Extinct (c.1902) (NZ TCS)[2]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Anseriformes
Family:	Anatidae
Genus:	Mergus
Species:	†M. australis
Binomial name
†Mergus australis Hombron & Jacquinot, 1841

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This duck was similar in size to the red-breasted merganser (Mergus serrator). The adult male had a dark reddish-brown head, crest and neck, with bluish black mantle and tail and slate grey wings.^[4] The female was slightly smaller with a shorter crest.

This bird's Māori name was miuweka.^[2] It was first collected when a French expedition led by the explorer Jules Dumont d'Urville on the ships L'Astrolabe and La Zelee visited the Auckland Islands in 1840. Its decline was caused by a combination of hunting and predation by introduced mammals.^[5] The bird was not flightless, but rather hard to flush; it preferred to hide between rocks when pursued. The last sighting was of a pair shot on January 9, 1902. It was not found in a 1909 search, and a thorough 1972/1973 exploration of possible habitat concluded that it was long extinct.^[6]

Subsequent fossil discoveries suggest that this merganser was previously resident in the South Island, and on Stewart Island/Rakiura in New Zealand. Fossils of a subspecies or closely related species have also been found on the Chatham Islands. There exists a short remark mentioning "a merganser" found on Campbell Island,^[7] but this may just as well refer to the semi-marine Campbell teal which is otherwise missing in McCormick's notes: he only mentions the Pacific black duck ("a New Zealand species of duck").^[8]