Knob billed Duck eBird African Comb Duck Sarkidiornis melanotos Borrow others' nests Comb Duck, or Knob billed Duck males have a large growth, or comb, on the top of their black beak. During breeding season, the male's Sarkidiornis melanotos African comb duck in Forth Worth Zoo Photos and pictures of: knob billed duck (Sarkidiornis melanotos), Sabi Sands, Greater Kruger National Park, South Africa The Africa Image Library Knob billed Duck (Subspecies Sarkidiornis melanotos melanotos) iNaturalist