| Eastern spot-billed duck | |
|---|---|
 | |
| Swimming in Japan | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Anseriformes |
| Family: | Anatidae |
| Genus: | Anas |
| Species: | A. zonorhyncha |
| Binomial name | |
| Anas zonorhyncha R. Swinhoe, 1866 | |
Theeastern spot-billed duck orChinese spot-billed duck (Anas zonorhyncha) is a species ofdabbling duck that breeds inEast and Southeast Asia. This species was formerly considered a subspecies of theIndian spot-billed duck and both were referred to as the spot-billed duck (A. poecilorhyncha). The name is derived from the yellow spot on the bill.
The eastern spot-billed duck wasdescribed by the English biologistRobert Swinhoe in 1866 under its currentbinomial nameAnas zonorhyncha.[2][3] The name of the genusAnas is the Latin word for a duck. The specific epithetzonorhyncha is derived from the classical Greek wordszōnē meaning "band" or "girdle" andrhunkhos meaning "bill".[4]
Historically, the eastern spot-billed duck was usually considered as asubspecies of the Indian spot-billed duck (A. poecilorhyncha). The American ornithologistBradley Livezey in a morphological study of thedabbling ducks published in 1991 proposed that the eastern spot-billed duck should be promoted to species status.[5] Subsequently, fieldwork conducted at Hong Kong in southern China found that although both the eastern spot-billed duck and the Indian spot-billed duck (subspeciesA. poecilorhyncha haringtoni) bred in the region at the same time, mixed pairs were only very rarely observed.[6] Base on this observation, theAmerican Ornithologists' Union recognised the eastern spot-billed duck as a separate species in 2008.[7] Most taxonomists now treat the eastern spot-billed duck as a separate species.[8][9][10] There is also some degree of hybridization with the mallard in the wild in eastern Russia with a tendency for a greater ratio of male eastern spot-billed ducks to mate with female mallards than the other way round.[11]
This duck is around the same size as amallard and has a scaly patterned body with a bluespeculum. At rest the long neck and the bill with the yellow tip are distinctive. It measures 55–63 cm (22–25 in) in length and 83–95 cm (33–37 in) across the wings, with a body mass of 790–1,500 g (1.74–3.31 lb).[12][13] These are mainly grey ducks with a paler head and neck and a blackbill tipped bright yellow. The wings are whitish with black flight feathers below, and from above show a white-bordered green. The male does not have an eclipse plumage. Juveniles are browner and duller than adults. The legs and feet are bright orange.[14] Both the male and female havecalls similar to themallard, with females producing a loud quack, and males a deeper, quieter sound.
The eastern spot-billed duck is darker and browner than the Indian spot-billed duck; its bodyplumage is more similar to thePacific black duck. It lacks the red bill spot, and has a blue speculum.[14][15]
Both males and females undergo a complete postnuptial moult, dropping all their wing feathers simultaneously.[14]
The eastern spot-billed duck ismigratory, wintering in southern China and possibly Southeast Asia. It is quite gregarious outside the breeding season and forms small flocks. The populations in Japan and the Russian Far East have expanded their range northwards by more than 500 km since the early 20th century, possibly in reaction toglobal warming.[11]
It is a bird of freshwaterlakes andmarshes in fairly open country and feeds by dabbling for plant food mainly in the evening or at night. The breeding season varies with rainfall and water condition but normally between April and July.[8] It nests on the ground in vegetation near water. The clutch is usually 7–9 eggs.[8] Incubation begins after the last egg is laid (allowing the chicks to hatch simultaneously) and the young hatch after about 24 days. The chicks are black with a yellow back and resemble those of mallards but with a wider eyestripe.[14]
