Refers specifically to the mandarin duck (Aix galericulata). Often used in the context of marital harmony because these ducks are believed to mate for life.
A pair of mandarin ducks were swimming in the pond.
Etymology
The kanji 鴛 and 鴦 each refer to the male and female mandarin duck respectively, and together they form the word for the species. The reading えんおう is the on'yomi of these characters.
