The term perching ducks is used colloquially to mean any species of ducks distinguished by their readiness to perch high in trees. Until the late 20th century, perching ducks meant Cairinini, a tribe of ducks in the duck, goose and swan family Anatidae, grouped together on the basis of their readiness to perch high in trees. It has been subsequently shown that the grouping is paraphyletic and their apparent similarity results from convergent evolution, with the different members more closely related to various other ducks than to each other. Perching duck species include: Plectropterinae Tadorninae Anatinae Species that were formally in the Cairinini tribe, and do not have an identified current subfamily include: