Populations are declining, mostly due to loss of habitat and pollution, and the International Union for Conservation of Nature has rated the bird's status as "endangered".

Other generic synonyms used in the past include Erismatura, Cerconectes, Gymnura, Undina, Bythonessa, Plectrura, and Pervicauda.

Its scientific name comes from the Greek Oxyura (from oxus, "sharp", and oura, "tail") and leucocephala (from leukos, "white" and kephalos, "head".

However, some studies have found that they do display morphological differences, with western populations being larger in size, having darker ventral coloration, and males having more yellow feathers on their back.

[4] Adult males have a grey and reddish body, a blue bill and a largely white head with a black cap and neck.

[5] Individuals are fairly frequently reported well north of their breeding range, but as with many wildfowl, the status of these extralimital records is clouded by the possibility of escapes from collections.

Most of this decline is due to habitat loss and hunting, but interbreeding of the Spanish population with the introduced ruddy duck (Oxyura jamaicensis) is a more recent threat.