Shelduck

The shelducks, genus Tadorna, are a group of large birds in the Tadorninae subfamily of the Anatidae, the biological family that includes the ducks and most duck-like waterfowl such as the geese and swans.
The shelducks are a group of larger often semi-terrestrial waterfowl, which can be seen as intermediate between geese (Anserinae) and ducks. They are mid-sized (some 50-60 cm) Old World waterfowl. The sexes are colored slightly different in most species, and all have a characteristic upperwing coloration in flight: the tertiary remiges form a green speculum, the secondaries and primaries are black, and the coverts (forewing) are white. Their diet consists of small shore animals (winkles, crabs etc.) as well as grasses and other plants.
They were originally known as "sheldrakes", this remained the most common name until the late 19th century. The word is still sometimes used to refer to a male shelduck and can also occasionally refer to the Canvasback (Aythya valisineria) of North America.