About Aix sponsa (Linnaeus, 1758)
This species, the wood duck, has the scientific name Aix sponsa (Linnaeus, 1758). It is a medium-sized perching duck. A typical adult measures 47 to 54 cm (19 to 21 in) in length, with a wingspan of 66 to 73 cm (26 to 29 in), and weighs 454 to 862 grams (16.0 to 30.4 oz). The adult wood duck is roughly three-quarters the length of an adult mallard. It shares its genus with the Asian mandarin duck (Aix galericulata).
Adult males have striking multicolored iridescent plumage, red eyes, and a distinct white flare running down the neck. Females are less colorful, with a white eye-ring and a whitish throat. All adult wood ducks have crested heads. The speculum is iridescent blue-green, with a white border along its trailing edge. Males produce a rising whistle call transcribed as jeeeeee. When flushed, females give a drawn-out, rising squeal transcribed as do weep do weep, and they use a sharp cr-r-ek, cr-e-ek call as an alarm.
In parts of the species' southern range, wood ducks are year-round residents, while northern populations migrate south for winter. They overwinter in the southern United States near the Atlantic Coast. 75% of wood ducks in the Pacific Flyway are non-migratory. Because of their attractive plumage, wood ducks are popular in waterfowl collections, and they are frequently recorded in Great Britain as escaped captives. Temporary established populations have existed in Surrey in the past, but these are not considered self-sustaining, unlike populations of the closely related mandarin duck. Along with the mandarin duck, the wood duck is classified as an invasive species in England and Wales, and releasing it into the wild is illegal. Based on its native distribution, the species is also a potential natural vagrant to Western Europe, and there are records from areas including Cornwall, Scotland, and the Isles of Scilly; some observers think these records may refer to wild birds, but proving the origin of recorded birds is extremely difficult due to the species' widespread popularity in captivity.
Wood ducks feed by dabbling, which means feeding from the water surface instead of diving underwater, or by grazing on land. They are omnivores: they mainly eat berries, acorns, and seeds, but also consume insects. They can crush acorns inside their gizzard after swallowing them.
