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The White-faced duck

9 February 2015

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The white-faced duck Dendrocygna viduata is one of the whistling ducks and was first named scientifically as Anas viduata by Linnaeus in 1766 based on a specimen from Cartagena in Colombia. The name viduata is Latin for having a mask and reflects the striking white-masked face of this duck which occurs throughout much of Africa, the Comoro Islands and tropical America. In South Africa it is widespread in the north-eastern regions, occurring as far south as the Free State but with a scattered and irregular occurrence further south.

This type of duck stands upright on long legs, is up to 48 cm tall and weighs up to 700 g, with the sexes looking alike. When swimming, it floats high in the water. The chin, throat and front half of the head are striking white, often with a variable black, rusty or brown stripe separating the white chin from the white throat. The rear of the head and the upper neck are black, while the breast and lower neck are chestnut in colour. The back is dark grey, often with a chestnut median streak. The sides of the breast and flanks are narrowly and vertically barred black and white. The bill is blackish with a blue-grey bar near the tip. The eyes are brown and the legs and feet are bluish-grey. Immature ducks look like the adults but are more dull in colour. These ducks are known as whistling ducks because they are highly vocal and normally give a repeated three-syllable whistle although the alarm whistle only consists of a single repeated note.

In its movements the white-faced duck is usually fairly sedentary and it only moves around locally but it can move as far as 1125 km. It moults in permanent wetlands, lives on inland water bodies with short vegetation and readily occupies man-made water bodies. The white-faced duck only forms colonies when breeding and lives as pairs or family groups along the shores of a water body where it forages for up to 50 per cent of the day. The rest of the time is spent in loafing, sleeping and preening. It feeds in summer from dawn to dusk and does so both in shallow water and on land, dabbling the head and neck under water when feeding there. On land it strips seeds from plants or picks the seeds up from the ground. In the winter, foraging also occurs at night. It is largely a herbivore but may eat invertebrates when it is breeding or moulting. On water it often eats the shoots of the wavy-leaved pondweed Potamogeton crispus and water lily Nymphaea sp, the seeds of sedges and the mullets of the string-of-stars Heliotropium indicum. It will eat maize kernels and various grass seeds but its total diet includes a wide variety of plants.

The white-faced duck is a monogamous breeder with a possible long-term pair bond and solitary nesting. The nests are spaced more than 75 m apart and mating involves display flights by the male. Mating usually occurs from November to April with a peak in January and February. Copulation occurs in the water and is followed by a step-dance display where both sexes tread water vigorously for a few seconds with the heads and breasts held well clear of the water. The nest is built by both sexes and is usually only a scrape of 160 to 180 mm in the ground to form a bowl of 140 mm diameter and 150 mm deep. This bowl is lined with dry grass or other vegetation but not down. The nests are well concealed in dense, tall grasses or sedges, with the surrounding vegetation being pulled over the nest for concealment. The nests are usually close to the water but can be up to 3 km away from it. Grassy islands that are surrounded by shallow water are preferred nesting sites.

From seven to 13 eggs are laid at 24-hour intervals. The eggs are oval to rounded, creamy-white with a pink tinge when fresh, smooth but chalky. Incubation starts at the completion of the clutch, lasts for 26 to 30 days and is done mostly by the male, but the sexes switch incubating in die morning and evening. A newly hatched chick has a crown and the upper parts and wings are olive-brown while it is creamy-yellow below. It weighs 16 to 27 g when it hatches. A young duck flies for the first time when it is 77 to 83 days old and moults to obtain some of the white face when it is 90 days old. By 180 days of age the adult plumage is complete. The ducklings start foraging on water for food when they are 14 days old.

 

Reference:

Hockey, P A R, W R J Dean and P G Ryan (Eds) 2005. Roberts – birds of southern Africa, seventh edition. Cape Town: The Trustees of the John Voelcker Bird Book Fund, pp 85 - 87.

 

article by Prof J du P Bothma

 

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