Tadorna

The shelducks, most species of which are found in the genus Tadorna (except for the Radjah shelduck, which is now found in its own monotypic genus Radjah), are a group of large birds in the tribe Tadornini of the Anatidae, the biological family that includes the ducks and most duck-like waterfowl such as the geese and swans. Shelducks are a group of large, often semiterrestrial waterfowl, traditionally seen as intermediate between geese and ducks, but now known to be significantly more closely related to ducks than to geese or swans, forming a clade that is sister to all other ducks. They are medium-sized (from 55–70 cm) Old World waterfowl. The sexes are slightly differently coloured in most species, and all have a characteristic upperwing pattern in flight, with the secondary remiges forming an iridescent green speculum, the primaries black, and the coverts (forewing) white. Their diet consists of small shore animals (winkles, crabs, etc.), as well as grasses and other plants. They were originally known as "sheldrakes", which remained the most common name until the late 19th century, with 'sheld' meaning variegated. Other archaic names include bergander, burrow-duck, and vulpanser, the last meaning "fox goose". The word "sheldrake" is still sometimes used to refer to a male shelduck. The genus Tadorna was introduced by German zoologist Friedrich Boie in 1822. The type species is the common shelduck.