mtDNA cytochrome b and NADH dehydrogenase subunit 2 sequence data indicate that the dabbling and diving ducks are fairly distant from each other, the outward similarities being due to convergent evolution.

[2] Alternatively, the diving ducks are placed as a subfamily Aythyinae in the family Anatidae which would encompass all duck-like birds except the whistling-ducks.

These are gregarious ducks, mainly found on fresh water or on estuaries, though the greater scaup becomes marine during the northern winter.

[1][2] The probably extinct pink-headed duck, previously treated separately in Rhodonessa, has been suggested to belong into Netta,[1][4] but this approach has been questioned.

[6] The molecular analysis also suggests that the white-winged duck should be placed into a monotypic genus Asarcornis which is fairly close to Aythya and might belong into this subfamily.