Ducks are unusual in that males of many species acquire brightly pigmented plumages in autumn rather than in spring. This has led to confusion in defining molts and plumages, using both traditional European terminology and that proposed by Humphrey and Parkes (1959). To investigate molt patterns in waterfowl relative to molt and plumage nomenclature, 2,227 specimens of ducks and geese were examined. Both the “first prebasic” (“post-juvenile” using traditional European terminology) and the “definitive prebasic” (“adult post-breeding”) body molts in most ducks, the latter producing the cryptic spring (female) and summer (male) plumages preceding the wing molt, are considerably more variable and less extensive than reported. By contrast, the “definitive prealternate” (“adult pre-breeding”) body molt of most ducks, which follows the wing molt and produces the brightly colored plumages of males, is complete or virtually so. Based upon presumed homologies with the molts of geese, the wing molt and ensuing complete body molt of ducks are better considered the prebasic rather than the prealternate molt and, thus, the bright feathering of male ducks should be considered the basic plumage. The incomplete and ephemeral cryptic plumages, attained by some ducks in spring and summer, may have evolved more recently in species that benefit from camouflage at this time, and should be considered alternate plumages. The molts and plumages of the adult Ruddy Duck (Oxyura jamaicensis) appear to be homologous with those of other Anatine ducks, with a slight temporal shift in the hormonal cycles that control pigment deposition (as opposed to differences in molt patterns) explaining the differences in plumage-coloration patterns in males. Because feather pigment-deposition patterns are controlled by various factors related to seasonal and reproductive phenomena, which differ considerably both among and within taxa, plumage color should not be a critical factor in attempts to define homologous molts and plumages.