Grey Duck (Anas supercilliosa) is the New Zealand name for the Pacific Black Duck. It is our native, mallard sized member of the genus, Anas. Our smaller teals, Grey Teal (Anas gracilis), Brown Teal (Anas chlorotis), Auckland Island Teal (Anas aucklandica) and Campbell Island Teal (Anas nesiotis) all belong to the same genus but the Grey Duck hybridises with the introduced Mallard (Anas platyrhyncos) which has led to it being classified nationally critical.

I had always noticed that the birds in Australia seemed darker with much clearer facial lines and put this down to Gloger’s rule which suggests that within a species , those in warmer, more humid areas have darker plumage than those living in cooler, drier areas. I had especially noticed this with White-faced Heron where the Queensland birds had darker more intensely coloured plumage than their New Zealand relatives. With the Grey Duck / Pacific Black Duck, I still think that this is a contributing factor but suspect that the highly hybridised New Zealand population makes it hard for us to see a true Grey Duck in New Zealand. Reviewing my photographic archives the one image that I recalled as being a good example of a Grey Duck still shows some speckling of it’s facial stripes and greenish rather than leaden grey bill,  suggesting possible Mallard genes. Other features that can give away Mallard influence are any orange colouration on the legs, blue speculum or anterior pale bar on speculum. 

For more information on ducks in New Zealand see NZBirdsOnline. Entries for Grey Teal, Auckland Island Teal, Blue Duck and Mallard all use photos of mine as the species image. Follow these links for Grey Duck, Brown Teal, Campbell Island Teal and Scaup.