New Zealand has mallard ducks (Anas platyrhynchos), which were introduced in the late 1800s, and it has grey ducks (Anas superciliosa), which are native and, because of the introduction of the mallard, have a conservation status of “Nationally Critical”. The reason is interbreeding, and today it’s hard to say how many truly pure grey ducks exist. What we have is a mish-mash of grey/mallard hybrids, with all sorts of weird patterning variations. Both male and female grey ducks look like the mallard females, with their dark brown feathers edged with cream. Greys have the dark eyestripe shown in this photo, and, in fact, some greys have a much stronger eyestripe. Other features distinguishing the two species are the patch on the wing, which is green in the grey duck and blue with white top and bottom edges in the mallard, and the leg colour, which is orange in mallards and dark grey-green in greys. These features vary by degree of hybridisation, so you can get a grey duck with orange feet because of a mallard ancestor, or a mallard female with a bit of eyestripe because of a grey duck ancestor.
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