Scaups started declining in the late 1800s until they were fully protected in 1934, and their population is now increasing thanks to predator control and new habitat.

The New Zealand scaup was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae.

[3] Gmelin based his description of the "New-Zealand duck" that had been described in 1785 by the English ornithologist John Latham in his A General Synopsis of Birds.

[4] The naturalist Joseph Banks had provided Latham with a water-colour drawing of the duck by Georg Forster who had accompanied James Cook on his second voyage to the Pacific Ocean.

[8] The New Zealand scaup is a small, round-bodied diving duck that have dark plumage, but both sexes are easily distinguished.

They have black legs and webbed feet for swimming, and they spend a lot of time underwater, where they can also travel considerable distances.

[11] Despite being widespread, they have a patchy distribution, and most scaups are on suitable habitat areas in Northland, the upper Waikato, Rotorua, Taupō, Hawke's Bay, West Coast, North Canterbury, and the Southern Alps.

[12] Unlike other members of this genus, the scaup is not migratory, although it does move to open water from high country lakes if they become frozen in winter.

[12] Average and maximum lifespan, age at first breeding, and survival rate of fledglings is not known because few New Zealand scaups have been banded.

[12] During the late 1800s and early 1900s, New Zealand scaup populations declined due to habitat destruction, introduction of predators and duck hunting.