Arguably the best way to differentiate this species from the similarly-plumaged, but larger Greater Scaup is by head shape. Lesser Scaup have a steep forehead and the highest point on the head is at the back of the crown. The transition from hindcrown to nape is more angular (somewhat like Ring-necked Duck). Greaters exhibit a more rounded head with no obvious transition from nape to crown, and the highest point on the head of a Greater is at the front of the crown. Male: The head, neck, and breast are black, as are the vent and undertail region. The back and sides are white with fine gray barring on the back, fading to a dingy white on the sides. In good light, the head can show both purple and green iridescence. Formerly, it was believed that the color of this iridescence was useful in separating Lesser and Greater Scaup, but this is not a reliable field mark. The bill is slaty-blue with a narrow black nail at the tip. The eye is bright yellow. In Summer and early Fall adult males assume a cryptic female-like appearance, but are more gray than brown on the flanks and lack white around the base of the bill. Female: The head is chocolate brown with a white patch near the base of the dark gray bill. Upperparts are brown overall, darker on the back, and mottled with gray on the sides. The belly is white. Immatures resemble females, but the pale area around the base of the bill is more restricted and usually cream-colored or off-white. In flight, both sexes show a strong white bar along the trailing edge of the secondaries, abruptly changing to gray at the base of the primaries.

Adult male Lesser Scaup are told from male Ring-necked Ducks by their paler flanks and and backs and a less patterned bill. Ring-neckeds also have dark (near black) backs that contrast noticeably with the paler sides and their head shape is more squared off and peaked at the hindcrown. Female Lessers lack the white eye-ring and do not show the contrast between the crown and face that is shown by a female Ring-necked Duck.

Length: 38 (cm) Wingspan: 61 (cm)

Voice:

A hoarse, crow-like aarrr, and a descending two-syllable Ah-ow.

Habitat:

Nests along seasonal and shallow wetlands. In winter and during migration, uses bodies of water ranging from small ponds up to large lakes, reservoirs and rivers. Prefers freshwater or brackish estuaries; less likely on open saltwater.

Behavior:

Able to walk on land more easily than other diving ducks. During breeding season, when fat reserves are low, able to take flight directly from water or land. In autumn migration, when fat reserves are high, requires a running takeoff.

Feeding:

Dives, primarily for aquatic invertebrates. Also takes seeds and other aquatic plant material.