Definition of spirit duck in English:

spirit duck

noun

historical, rare
  • The bufflehead, Bucephala albeola, a North American diving duck which can submerge quickly and reappear a distance away; (occasionally also) any of various other waterfowl having this ability.

Origin

Late 18th century; earliest use found in Thomas Pennant (1726–1798), naturalist, traveller, and writer.