What breed of duck was introduced to the British Isles from the far east?

The mandarin duck (Aix galericulata) is a perching duck species found in East Asia. It is medium-sized, at 41–49 cm (16–19 in) long with a 65–75 cm (26–30 in) wingspan. It is closely related to the North American wood duck, the only other member of the genus Aix. Aix is an Ancient Greek word used by Aristotle to refer to an unknown diving bird, and galericulata is the Latin for a wig, derived from galerum, a cap or bonnet.

The species was once widespread in East Asia, but large-scale exports and the destruction of its forest habitat have reduced populations in eastern Russia and in China to below 1,000 pairs in each country; Japan, however, is thought to still hold some 5,000 pairs. The Asian populations are migratory, overwintering in lowland eastern China and southern Japan.

Specimens frequently escape from collections, and in the 20th century a large feral population was established in Great Britain; more recently small numbers have bred in Ireland, concentrated in the parks of Dublin. There are now about 7,000 in Britain, and other populations on the European continent, the largest in the region of Berlin. Isolated populations exist in the United States. The town of Black Mountain, North Carolina has a limited population, and there is a free-flying feral population of several hundred mandarins in Sonoma County, California. This population is the result of several mandarin ducks escaping from captivity, then going on to reproduce in the wild.