Population of Spot-Billed Duck
Spot-Billed Duck has three populations, treated here as subspecies, the Indian spot-billed duck ( Poecilorhyncha poecilorhyncha), Eastern spot-billed duck ( Poecilorhyncha zonorhyncha), and Burmese spot-billed duck (Poecilorhyncha haringtoni). Some authors elevate the eastern population as a species, Anas zonorhyncha. The name is derived from the yellow and red spot on the bill.
Structure of Spot-Billed Duck
Spot-Billed Duck is around the same size as a mallard and has a scaly patterned body with a green speculum and a band of white tertials that is prominent in flight. At rest the white stripe stands out and the long neck and the bill with yellow tip and orange red spots at the base are distinctive in the nominate subspecies.
Measurement of Spot-Billed Duck
Spot-Billed Duck measures 55-63 cm in length and 83–95 cm across the wings, with a body mass of 790-1,500 g (1.74-3.31 lb). These are mainly grey ducks with a paler head and neck and a black bill tipped bright yellow. The wings are whitish with black flight feathers below, and from above show a white-bordered green. The male has a red spot on the base of the bill, which is absent or inconspicuous in the smaller but otherwise similar female. The male does not have an eclipse plumage. Juveniles are browner and duller than adults. The legs and feet are bright orange.
Types of Spot-Billed Duck
Spot-billed ducks are of many types. The eastern spot-billed duck is darker and browner; its body plumage is more similar to the Pacific black duck. It lacks the red bill spot, and has a blue speculum.
Wings of Spot-Billed Duck
The males and females of Spot-Billed Ducks undergo a complete postnuptial moult, dropping all their wing feathers simultaneously.
Concentration of Spot-Billed Duck
Spot-Billed Ducks are residing in the southern part of its range from Pakistan and India to southern Japan, but the northern subspecies, the eastern spot-billed duck (A. p. zonorhyncha), is migratory, wintering in Southeast Asia. Some individuals of the nominate population may also move. A bird ringed at Bharatpur District in Rajasthan on 5th December 1969 was recovered near Novosibirsk in August 1970. It is quite gregarious outside the breeding season and forms small flocks. The northernmost populations have expanded their range northwards by more than 500 km since the early 20th century, possibly in reaction to global warming.
Residence of Spot-Billed Duck
Spot-Billed Ducks are residing in the freshwater lakes and marshes 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 and is from July to September in northern India and November to December in southern India.
Nestlings of Spot-Billed Duck
Spot-Billed Duck nests on the ground in vegetation near water, and lays 8-14 eggs. Incubation begins after the last egg is laid 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. The phylogenetic placement of this species is highly debated. The eastern spotbill is often considered a distinct phylogenetic species by many taxonomists. And while molecular analyses and biogeography indicate that most species of the mallard group in the genus Anas form two distinct clades, hybridization between all of these species is a regular phenomenon and hybrids are usually fully fertile. The present species is known to produce fertile hybrids with the Pacific black duck and the Philippine duck in captivity, and naturally hybridizes with the mallard as their ranges now overlap in the Primorsky Krai due to the Spot-billed ducks northward expansion.
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