- Stocky diving duck.
- No white in wings.
- Male all black with swollen yellow or orange knob at base of bill.
- Female blackish with large whitish face patch.
Male DescriptionBlack with metallic gloss. Side and flank feathers long and pointed. Eyelids yellow. Swollen orange-yellow knob on base of upper bill, divided by black along middle of upper surface.
Female DescriptionSooty brownish. Dark cap contrasting sharply with pale grayish brown feathers on rest of head. Sides and flanks paler with indistinct barring. Bill not swollen or only slightly, may have hint of yellow.
Immature DescriptionSimilar to adult female but with white belly.