Taxonomic and Systematics
The Pink-headed Duck was described by John Latham in 1790 under the genus Anas. In describing the species, it is possible that he made of use of a painting in the collection of Lady Impey, wife of Sir Elijah Impey who was Chief Justice of court in Calcutta from 1774 to 1783. Mary Impey maintained a menagerie in Calcutta and commissioned Indian artists such as Bhawani Das from Patna to illustrate animals in the collection. Lady Impey moved to England after the death of her husband and sold these paintings at an auction in 1810. Some of these paintings were acquired by the 13th Earl of Derby.
The genus Rhodonessa was originally created for this species alone. Jean Delacour and Ernst Mayr, in their 1945 revision of the family Anatidae considered it a somewhat abnormal member of the Anatini (or river-ducks) group because the hind toe is slightly lobed, display behaviour and the tendency to feed at the surface. The birds were observed in European aviaries and although they never bred, the males displayed often and this involved puffing the neck feathers, lowering the neck to rest on the back and then stretching up the neck while producing a wheezy whistle like a Mallard. A study of its tracheal anatomy by Alfred Henry Garrod in 1875 suggested that it had a "slight fusiform dilatation" in the anterior syringeal region. The "bulba ossea" at the lower part of the male syrinx is peculiar in being swollen. The colour pattern has also been considered unique, lacking any of the metallic colours on the secondaries that are characteristic of the Anatini. The other unique feature being the somewhat large and nearly spherical shape of the eggs. All of these features supporting the retention of the species in a separate genus. Such mid-tracheal swellings were found only in Mergini and Aythyini and is extremely rare in the genus Anas. This tracheal bulla is rounded in Anas but angular with fenestrae in Netta and Aythya. Johnsgard considered Marmaronetta and Rhodonessa as intermediate in form. Based on the available morphological and behavioural evidence, especially the structure of the humerus and the structure of tracheal rings, Sidney Dillon Ripley suggested that it was undoubtedly in the Aythyini.
A study found that Rhodonessa was closely allied to the Red-crested Pochard (Netta rufina) suggesting that the two species be placed in the same genus. Rhodonessa was described prior to Netta which would then make Rhodonessa rufina the name of choice, however these changes have not been widely accepted.
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