Male Lesser Scaups, also known as bluebills, are striking birds with a combination of black and white plumage, while females are predominantly brown. Males have a black head, breast, and tail, with white flanks and a grayish back. Their heads can show iridescent purple or green hues in good light. Females are brown with a white patch at the base of their bill. Both sexes have a white stripe on the trailing edge of their wings.

Male Lesser Scaup:
• Head: Iridescent purple or green sheen (sometimes appearing black), with a subtle peaked shape at the back.
• Breast and Tail: Black.
• Flanks: White.
• Back: Lined gray, often appearing white with gray barring.
• Bill: Bluish-gray with a small black tip.
• Eyes: Yellow.
• Other: White wing stripe visible in flight.

Female Lesser Scaup:
• Body: Brown, with lighter sides and a white belly.
• Head: Dark brown with a white patch at the base of the bill.
• Bill: Dark gray with a white band around the base.
• Other: White wing stripe visible in flight.

Overall:
• Lesser Scaups are medium-sized diving ducks, slightly smaller than Greater Scaups.
• They are found in large flocks during migration and winter, often on lakes, reservoirs, and estuaries.
• They are diving ducks, primarily feeding on aquatic invertebrates and plants.