Mandarin duck

Name and taxonomy

The scientific name of the mandarin duck is Aix galericulata. Aristotle used the Greek word aix for a diving bird that nobody has identified. The second half of the name comes from a Latin word for a wig or a cap. It probably refers to the crest that both sexes carry.

The German traveller Engelbert Kaempfer wrote about the bird in 1727. He gave the Japanese name kinmodsui and said he could hardly believe the colours. The English naturalist George Edwards figured it in 1747 as the Chinese teal. He drew a living bird kept at Richmond by the merchant Matthew Decker. Carl Linnaeus named it Anas galericulata in 1758. Friedrich Boie set up the genus Aix in 1828, and the duck sits there today.

The species is monotypic, so no subspecies are recognised. Chinese speakers call it yuanyang, Korean speakers use a carved pair at weddings, and Japanese speakers say oshidori. The English name probably points at the officials of imperial China and their bright robes.

Evolution and relatives

Only two species belong to the genus Aix. The other is the wood duck of North America. Both birds perch in trees and lay their eggs in hollow trunks. The two females look so much alike that birdwatchers confuse them. The mandarin is a little smaller than its American cousin.

The mandarin duck carries 84 chromosomes, and every one of them is acrocentric. Other ducks usually carry 80, and many of those are submetacentric. That difference makes crossing with other ducks very hard, and it may rule it out. Hybrids with six other duck species have been reported, but none has been confirmed. A fossil bone from West Runton in England was once given to this species. Later work reassigned it to an unnamed member of the duck subfamily.

Appearance

An adult is 41 to 49 cm long with a wingspan of 65 to 75 cm. Weight runs from 0.428 to 0.693 kg. The body is shorter than that of most dabbling ducks. A newly hatched duckling weighs about 41 grams.

The drake has a small red bill and a broad white crescent above the eye. His face is reddish, with long feathers that look like whiskers. Two white bars cross the purple breast, and the flanks are a warm ruddy brown. Two orange sail feathers stand upright at the back. Each sail is a modified secondary flight feather with a widened inner vane. Both sexes have a crest, and the purple crest of the drake is the stronger one.

The female is greyish brown, with a thin white eye-ring and a white stripe behind the eye. She is paler below, carries a small white flank stripe and has a pale bill tip. Both sexes flash a blue-green speculum on the wing in flight. After the breeding season the drake moults into eclipse plumage and looks like the female. An eclipse drake still shows a bright yellow-orange or red bill and loses the crest. Ducklings resemble young wood ducks, and their eye-stripe stops at the eye.

Habitat and range

The native range covers East and Northeast Asia. Birds breed in southeast Siberia, the Korean peninsula, Japan and eastern China. The favoured ground is a river or lake edge with thick shrubs and standing timber. Most pairs stay in the lowlands, though some breed in valleys as high as 1,500 m. Asian birds migrate, and they winter in lowland eastern China and southern Japan.

Winter birds add marshes, flooded fields and open rivers to their range. Fresh water suits them best, but some winter in coastal lagoons and estuaries. The species is recorded in 93 countries on GBIF, which counts escapes as well as wild birds.

Escapes from waterfowl collections built a feral population in Great Britain during the twentieth century. About 7,000 now live there. Small numbers breed in Ireland, mostly in the parks of Dublin. The largest mainland European group lives around Berlin. In the United States there are birds at Black Mountain in North Carolina and several hundred in Sonoma County, California. European birds use more open ground than Asian ones, including lake edges, water meadows and farmland near woods.

Diet and feeding

The mandarin duck feeds by dabbling at the surface or by walking on land. Plants and seeds make up most of what it eats. Acorns and beech mast are the staples, and rice and other grain matter too. The bird adds snails, insects and small fish through the year.

The diet shifts with the season. Autumn and winter birds live mainly on acorns and grain. Spring birds turn to insects, snails, fish and water plants. Summer birds take small worms, small fish, frogs, molluscs and small snakes. Feeding happens near dawn and near dusk. By day the ducks rest in trees or on the ground. Like other perching ducks, the mandarin can break down a swallowed acorn in its gizzard.

Behaviour and social life

The mandarin duck is shy for a duck. It looks for cover under trees, and an overhanging willow is a favourite spot. Flocks are smaller than those of most other ducks. Birds that live near people can grow much bolder.

This is a perching duck, so it settles on branches without trouble. Like other perching ducks, it grips the bark with sharp claws. Pairs form at the start of winter and may hold together for several seasons.

Birds in the Far East migrate every year. Most of the British birds stay in one place. Some British birds still make long journeys. Animal Diversity Web reports flights of 500 miles inside 24 hours.

Communication and senses

The mandarin duck appears to signal with plumage more than with sound. A displaying drake raises his crest and lifts the orange sails clear of the back. Courtship includes mock drinking and a shaking movement. The white crescent over the eye and the white breast bars probably show up at a distance. The blue-green wing patch shows only in flight, and it may help a flock stay together.

Sight leads the search for a nest hole, and the female inspects each site herself. The drake follows her from tree to tree. The most important call of the year is probably the one after hatching. The female drops to the ground and calls up to the nest. The ducklings answer by leaving the hole one after another. A drake in eclipse plumage loses his crest, so his signals probably fade with the colours.

Reproduction and life cycle

Pairs form early in the winter, well before the nesting season. A bond may last for many seasons. The female chooses the nest hole, and the male joins her on the search. Nests sit in cavities in trees near shallow lakes, marshes or ponds. A hole can be as much as thirty feet above the ground. The female lines it with down from her own breast.

A single clutch of nine to twelve white oval eggs is laid in April or May. The eggs go down at daily intervals. The female alone sits on them, for 28 to 30 days. The drake may guard her, but he leaves before the eggs hatch. Every egg hatches inside the same few hours.

The mother flies down and calls, and each duckling climbs out and drops. The young land unhurt and follow her to the nearest water. They can fly after 40 to 45 days and then join a new flock. Ringing gives a maximum wild age of 10.4 years. AnAge suggests that figure is low, and anecdotes reach 20 years.

Female mandarin ducks often lay in the nest of another bird. At the Zuojia Nature Reserve in northeast China, 46.1% of the ducks did so. A shortage of nest holes makes the habit more common. The laying female saves the cost of sitting and cuts her own risk from predators. Extra eggs did not lower the hatching success of the host's own clutch.

Predators and threats

Predators differ from one part of the range to another. Mink, raccoon dogs, otters and polecats all take mandarin ducks. Eurasian eagle-owls hunt them from the air. Grass snakes reach eggs and small young. A nest high in a trunk is safer than one on the ground, which is probably why the habit spread.

The heaviest pressure comes from logging, which removes the old trees the birds need. Hunters cannot tell a mandarin from another duck in flight, so many are shot by mistake. Nobody hunts the species for meat, because it tastes bad. Poachers still take birds for their looks. Heavy export and forest clearance cut Russia and China below 1,000 pairs each by the 1980s.

Population and conservation

The IUCN lists the mandarin duck as Least Concern. Japan was thought to hold about 5,000 pairs when the mainland numbers crashed. A survey in 2009 put the Chinese total at 12,000 to 14,000 birds. Animal Diversity Web suggests the whole Asian population may sit under 20,000. China now protects the species by law.

The bird has a long record of local decline. Settlers were let into the Tung Ling forest in 1911, and clearance followed. By 1928 few good breeding areas were left there. Taiwan rates the duck as Vulnerable on its own red list. Russia includes it in the national Red Book.

The feral British flock of about 7,000 is probably a large share of the world total. Birdwatchers record the species often, and iNaturalist holds 27,023 observations. Protecting old riverside woodland is probably the practical measure in the native range.

Relationship with humans

People have shipped mandarin ducks west since 1745. Britain took the largest share. European aviculturists breed the species in numbers. Zoos and waterfowl collections keep it for its colours. Breeders have selected pale silver birds and white birds.

Escaped birds started the British population, and they now breed without help. The duck appears to have done no harm to native British wildfowl. It does not fight other ducks for habitat, and it filled a gap that was empty. Britain does not treat it as an invasive species. As the range spreads it may meet the common goldeneye, which also nests in trees.

In culture and myth

Chinese tradition calls the bird yuanyang. The first syllable names the drake and the second names the duck. Chinese lore holds that a pair stays together for life, unlike other ducks. The pair therefore stands for married love and loyalty, and painters use it often. A proverb about two mandarin ducks in the water describes a devoted couple. Chinese weddings use the symbol to wish the couple a settled life.

The two sexes look so unlike that Cantonese speakers took the word for other purposes. Yuen-yeung can mean an odd pair, or two unlike things of one kind. A drink of coffee mixed with tea carries the name, and so does a kind of fried rice. The bird also flew on the flag of Weihaiwei while Britain ruled the territory.

Korean tradition reads the pair as peace, faithfulness and many children. Carved wooden ducks are given as a wedding present and kept afterwards. Japanese speakers call the bird oshidori. The phrase oshidori fufu describes a couple who are devoted to each other. The Japanese Crown Prince wears a sokutai patterned with the bird.