The Chatham Islands Brown Duck is only known from subfossil remains found on the Chatham Islands, that have not yet been described, it may have been a subspecies of the New Zealand Brown Duck (Anas chlorotisGray) (see depiction below) or even a distinct species.

The taxon was apparently already wiped out by the Moriori, the first human settlers on the Chatham Islands. [1]

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References:

[1] Trevor H. Worthy, Richard N. Holdaway: The Lost World of the Moa, Prehistoric Life of New Zealand. Indiana University Press, Bloomington 2002

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New Zealand Brown Duck (Anas chlorotis) (the two birds on the left) together with Auckland Teal (Anas aucklandica Gray)

Depiction from: ‘John C. Phillips: A Natural History of the Ducks. Boston; Houghton Mifflin Company; 1922-1926’

(public domain)

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edited: 10.11.2021