Approximately 94 percent of scaup wings can be correctly assigned to species using wing length, provided the age-sex class of each wing is known. The following points will identify greater scaup in each age class: adult males > 213 mm., adult females > 206 mm., immature males > 209 mm and immature females > 203 mm. Wings in each age class that are shorter than these measurements are, in most cases, lesser scaup.
Because the two species are similar, the following discussion pertains to both. Scaup differ from most other species of the same genus in that they rarely molt tertial coverts during the hunting season (October-January). Other characteristics useful for age-sex identification do not vary greatly, and once a person has learned to recognize them, wings of scaup are relatively easy to classify. Although characteristics that separate ages and sexes are similar for both species, they are not identical, and each is presented in a separate table.