The wood duck or Carolina duck (Aix sponsa) is a partially migratory species of perching duck found in North America. The male is one of the most colorful North American waterfowls. Linnaeus based his account on the "summer duck" from Carolina that had been described and illustrated by the English naturalist Mark Catesby in the first volume of his The Natural History of Carolina, Florida and the Bahama Islands that was published between 1729 and 1731. Linnaeus specified the type locality as North America but this has been restricted to Carolina following Catesby. The wood duck is now placed together with the mandarin duck in the genus Aix that was introduced in 1828 by the German naturalist Friedrich Boie. The species is monotypic: no subspecies are recognised. The genus name is an Ancient Greek word for an unidentified diving bird mentioned by Aristotle. The specific epithet sponsa is Latin meaning "bride" (from meaning "pledge").

Description

The wood duck is a medium-sized perching duck. A typical adult is from in length with a wingspan of between . The wood duck's weight ranges from . This is about three-quarters the length of an adult mallard. It shares its genus with the Asian mandarin duck (Aix galericulata).

The male's call is a rising whistle, jeeeeee; the females utter a drawn-out, rising squeal, do weep do weep, when flushed, and a sharp cr-r-ek, cr-e-ek for an alarm call.

Given its native distribution, the species is also a potential natural vagrant to Western Europe and there have been records in areas such as Cornwall, Scotland and the Isles of Scilly, which some observers consider may relate to wild birds; however, given the wood duck's popularity in captivity, it would be extremely difficult to prove their provenance.

Behavior

Reproduction

Their breeding habitat is wooded swamps, shallow lakes, marshes, ponds and creeks in the eastern United States, the west coast of the United States, some adjacent parts of southern Canada, and the west coast of Mexico. They get their name from being one of the only species of ducks who perch and nest in trees. In recent decades, the breeding range has expanded towards the Great Plains. Currently most breeding occurs in the Mississippi alluvial valley. They usually nest in cavities in trees close to water, although they will take advantage of nesting boxes in wetland locations. Other species may compete with them for nesting cavities, such as birds of prey, as well as mammals such as grey squirrels, and these animals may also occupy nest boxes meant for wood ducks. Wood ducks may end up nesting up to a mile away from their water source as a result. Females line their nests with feathers and other soft materials, and the elevation provides some protection from predators such as raccoons, owls, and hawks. Females typically lay seven to fifteen eggs which are incubated for an average of thirty days.

The day after they hatch, the precocial ducklings climb to the opening of the nest cavity and jump down from the nest tree to the ground. The morning after hatching, the hen will leave the nest to feed and make sure it is safe for her chicks. When she decides it is safe, she uses a maternal call to call the chicks out. Chicks can jump from as high as 50 feet, surviving by landing either in water, or on top of soft material such as leaf litter.

Vocalization

The wood duck has distinctive vocalizations that play an important role in communication, particularly during mating season. The male's primary call is a rising whistle, described as "jeeeeee," while females produce several distinct calls including a drawn-out, rising squeal "do weep do weep" when flushed, and a sharp "cr-r-ek, cr-e-ek" as an alarm call.

Conservation

thumb|Male at a nest box in Louisiana

The population of the wood duck was in serious decline in the late 19th century as a result of severe habitat loss and market hunting for both meat and plumage for the ladies' hat market in Europe. By the beginning of the 20th century, wood ducks had become rare, almost disappearing in many areas. In response to the Migratory Bird Treaty, established in 1916, and enactment of the U.S. Migratory Bird Treaty Act of 1918, wood ducks finally began to repopulate. By enforcing existing hunting regulations and protecting woodland and marsh habitat, wood duck populations began to rebound starting in the 1920s. The erection of nesting boxes starting in the 1930s further assisted wood duck conservation.

Landowners as well as park and refuge managers can encourage wood ducks by building wood duck nest boxes near lakes, ponds, and streams. Fulda, Minnesota, has adopted the wood duck as an unofficial mascot, and a large number of nest boxes can be found in the area.

Expanding North American beaver (Castor canadensis) populations throughout the wood duck's range have also helped the population rebound as beavers create an ideal forested wetland habitat for wood ducks.

In 2013, the Royal Canadian Mint created two coins to commemorate the wood duck. The two coins are each part of a three coin set to help promote Ducks Unlimited Canada as well as celebrate its 75th anniversary.