A prominent wing patch and the long slender neck are features shared with the common Indian spot-billed duck.

[5] Confusion with male red-crested pochards stems mainly from observations of swimming birds, as the latter species also has a conspicuous red head (although the color is actually very different from the pink-headed duck).

Young birds had a nearly whitish head without a trace of pink and a mellow two note call wugh-ah has been attributed to the species.

[11] Allan Octavian Hume and Stuart Baker noted that the stronghold of the species was north of the Ganges and west of the Brahmaputra, mainly in Maldah, Purnea, Madhubani and Purulia districts of present-day Bihar.

Hume collected a specimen in Manipur which he noted was very rare, hiding among dense reeds in Loktak Lake.

The populations (possibly) undertook local seasonal movements, resulting in scattered historic records as far as Punjab, Maharashtra and Andhra Pradesh.

Mary Impey maintained a menagerie in Calcutta and commissioned Indian artists such as Bhawani Das from Patna to illustrate animals in the collection.

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.

[25] A study of its tracheal anatomy by Alfred Henry Garrod in 1875[26] suggested that it had a "slight fusiform dilatation" in the anterior syringeal region.

[11] 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.

It was always rare,[35][36] and the last confirmed sighting, by C. M. Inglis, was from Bhagownie, Darbhangha District, in June 1935, with reports from India persisting until the early 1960s.

[39] In 1988, Rory Nugent, an American birder, and Shankar Barua of Delhi, reported spotting the elusive bird on the banks of the Brahmaputra.

The pair started their quest for the bird at Saikhoa ghat on the north-eastern end of the river on the Indian side of the border.

Reports of pink-headed ducks after the 1960s have been received from the largely unexplored Mali Hka and Chindwin Myit drainages in Northern Myanmar.

Another, more dubious report stated that shortly after a failed expedition in the area by Birdlife International ended, a local hunter caught a live male and a female or juvenile pink-headed duck, and contacted Myanmar's Biodiversity and Nature Conservation Association to sell it to them for a fee.

The hunter also said that there were large, impassable ponds in the wetland's center that may still hold pink-headed ducks, but these could only be accessed with a drone, which are banned in the region.

It is not known why it was always considered rare, but the rarity is believed to be genuine (and not an artefact of insufficient fieldwork) as its erstwhile habitat was frequently scoured by hunters in Colonial times.