[1] It was first scientifically described by Tommaso Salvadori as a full species in the genus Anas, named after its collector, the French zoologist Emile Oustalet.

[citation needed] After Salvadori, most taxonomists, such as Dean Amadon and Ernst Mayr, considered it a subspecies of the mallard.

[3] If Yamashina's hypothesis is correct, the Mariana mallard would have presumably evolved into near species status in only about ten thousand years.

[5] A species of flightless duck is known from a prehistoric bone found on Rota in 1994; it was apparently not closely related to the Mariana mallard.

Two intergrading color morphs were found in males, called the "platyrhynchos" and the "superciliosa" type after the species they resembled more.

Only the former had a distinct nuptial (breeding) plumage: the head was green as in mallard drakes, but less glossy, with some buff feathers on the sides, a dark brown eyestripe and a faint whitish ring at the base of the neck.

The bill was black at the base and olive at the tip, the feet reddish orange with darker webs and the iris brown.

The birds were rather reclusive, preferring sheltered habitat with plenty of wetland and water plants – fern thickets (Acrostichum aureum) and reed beds (Scirpus, Cyperus and Phragmites),[9][10] where they also nested.

Usually, pairs or small flocks were encountered, but in the key habitats larger groups of dozens and rarely up to 50–60 individuals could be found.

The courtship behavior, which in the strongly sexually dimorphic mallard is focused more on presentation of visual cues than in the monomorphic Pacific black duck (although it is generally similar in both species), was never recorded.

As Lake Susupe offered the most plentiful and least accessible habitat, although it too suffered from pollution by sugar mill wastes, the Saipan population lingered on for a few more years.

The pair was brought to Pohakuloa Training Area, Hawaii, and later to SeaWorld San Diego, where it was attempted to have them reproduce in captivity.