What is "tadorninae"

The Tadorninae is the shelduck-sheldgoose subfamily of the Anatidae, the biological family that includes the ducks and most duck-like waterfowl such as the geese and swans.

This group is largely tropical or Southern Hemisphere in distribution, with only two species, the common shelduck and the ruddy shelduck breeding in northern temperate regions, though the crested shelduck (presumed extinct) was also a northern species.

Most of these species have a distinctive plumage, but there is no pattern as to whether the sexes are alike, even within a single genus.