Yellow-billed duck

The yellow-billed duck (Anas undulata) is also known as the “African yellowbill”. It is found in many countries of southern and eastern Africa, where it is relatively common, and it is therefore in the “least concern” category on the IUCN Red List of endangered species.

There are two sub-species, Anas undulata undulata being the southern yellow-billed duck and Anas undulata ruepelli the northern yellow-billed duck. However, the range of “undulata undulata” extends as far north as Kenya. There are slight differences in appearance between the two sub-species.

Appearance

The yellow-billed duck is related to the mallard and is similar in size and shape, the average length being about 55 centimetres (21.5 inches). The feathers of the wings and body are dark brown to black, with each feather having a white border. There is a green speculum patch (on the upper secondary wings), lined with white, that is seen when the bird is in flight. In the northern sub-species the speculum is blue. The head is black and the bill a brighter yellow in the northern sub-species than the southern. There is a black marking on the upper part of the bill and at the tip. Males and females look alike.

Habitat

The yellow-billed duck inhabits mainly freshwater locations but can also tolerate moderate salt levels in brackish lagoons and river estuaries. It prefers slow-moving or still water, such as is found in flooded grasslands, seasonal lakes and artificial reservoirs. In Kenya it is found mainly in upland areas, only breeding at locations above 1500 metres (5000 feet).

It is a sedentary species over much of its range, but southern yellow-billed ducks tend to move to follow the availability of seasonal wetlands.

Behaviour

The yellow-billed duck is largely nocturnal, hiding itself away during the day.

Outside the breeding season it can be seen in very large flocks, but during the breeding season, which coincides with the rainy season, it is generally found only in pairs or small groups.

Female yellow-billed ducks quack, whereas males whistle.

Feeding

The yellow-billed duck feeds both on plants and animals, the latter including insects, larvae, molluscs and crustaceans.

Breeding

The breeding season coincides with the rainy season, which varies in length and timing depending on location.

Pairs form after displays that include fighting, preening, aerobatics and swimming. However, the pair bond is short and the male has usually left before the chicks hatch.

The nest is constructed on the ground, by the female, and consists of a shallow scrape lined with fine grassy material. It is concealed in thick vegetation which may only be reachable via a tunnel through the grass. However, it will never be more than 20 metres (65 feet) from open water.

The clutch can be anything from two to ten eggs, laid one a day, and the female incubates them alone for up to 30 days. When she needs to leave the nest to feed she will cover the eggs with plant material.

When the chicks hatch they are fed by the mother duck for three weeks and are protected by her for some time afterwards. Fledging is at around 70 days, but the chicks will stay near the nest for as much as another six weeks before they become fully independent.

Conservation

The yellow-billed duck is not regarded as being in need of special conservation measures as its population in the wild is large and stable. There are places where pollution poses an environmental threat, and there are risks to the long-term stability of the species, especially in the south, through cross-breeding with mallards and other species.

The yellow-billed duck can be seen outside Africa at wetland reserves such as Slimbridge in Gloucestershire, England, where many species of duck are kept in a protected environment.

© John Welford