The Mandarin duck, scientifically known as Aix galericulata, is a perching duck species that is native to the East Palearctic region. It is a medium-sized bird, measuring between 41–49 cm (16–19 in) in length and having a wingspan of 65–75 cm (26–30 in). This species is closely related to the North American wood duck and is the only other member of the genus Aix. The name "Aix" is derived from an Ancient Greek word used by Aristotle to describe an unknown diving bird, while "galericulata" means a wig in Latin, stemming from "galerum," meaning cap or bonnet. Outside of its natural habitat, the Mandarin duck has established a large introduced population in the British Isles and Western Europe, as well as smaller populations in North America.
Mandarin ducks are known for their shy nature and prefer to stay hidden under trees such as overhanging willows, forming smaller flocks. However, they may become bolder around humans due to repeated interactions and taming.
In their natural habitats, mandarin ducks breed near bodies of water such as shallow lakes, marshes, or ponds surrounded by dense woodland. During the springtime, they build nests in cavities of trees close to the water and lay a single clutch of 9 to 12 eggs in April or May. While the male may defend the brooding female and eggs during incubation, he does not participate in incubating the eggs and leaves before they hatch. Once the ducklings have emerged from the eggs, their mother will coax them out of the tree and lead them to a nearby body of water.
Mandarins feed by dabbling or foraging on land. They mostly consume plants and seeds, particularly beech mast. They also supplement their diet with snails, insects, and small fish. The species' diet varies with the seasons, with acorns and grains being the main food source in the fall and winter, insects, snails, fish, and aquatic plants in the spring, and dew worms, small fish, frogs, mollusks, and small snakes in the summer. They typically feed at dawn or dusk, perching in trees or on the ground during the day.
The male mandarin duck is easily recognizable by its unique markings. It has a striking red bill, a large white crescent above the eye, and a reddish face with distinctive "whiskers". Its breast is a vibrant shade of purple with two white vertical bars and its flanks are a rich ruddy color. The male also sports two distinctive orange feathers at the back which resemble boat sails. On the other hand, the female mandarin duck is similar in appearance to the female wood duck, with a white eye-ring and stripe running from the eye, but is paler in color below and has a small white flank stripe and a pale tip on its bill.
Following the breeding season, the male mandarin duck goes through a molt, entering into an eclipse plumage stage. During this stage, it resembles the female, but can be distinguished by its bright yellow-orange or red bill, lack of a crest, and a less noticeable eye-stripe.
Mandarin ducklings closely resemble wood ducklings and mallard ducklings in appearance. However, they can be differentiated from mallard ducklings by the eye-stripe, which stops at the eye in mandarin and wood ducklings, while it extends all the way to the bill in mallard ducklings.
The occurrence of different mutations of the mandarin duck has been observed in captive populations. The white mandarin duck is the most frequently observed variation. The exact origins of this mutation are uncertain, but it is believed that interbreeding between closely related birds and selective breeding practices have led to the manifestation of recessive gene combinations, resulting in genetic conditions like leucism.