African Darter

Anhinga rufa - The African Darter

The African darter, also known as the snakebird or, slanghals in Afrikaans, is a water-bird that is common throughout sub-Saharan African. It has earned the name snakebird for the way that it swims – it keeps its entire body very low in the water, with only the neck and the head sticking out, giving it the appearance of a swimming snake.

Did you know? When it flies, the African darter will thrust its head forward slightly and fan its tail. It will frequently soar high above its colony.

The male darter's body is almost completely glossy black with the exception of the white streaking on the face and body, and the colouration of the neck, which has a warm chestnut hue. The female (like the juvenile birds) is browner than the male with less noticeable white streaks. Both of them have gold-coloured eyes with brown bills. The male's bill is slightly larger than the female's. This bill is used to impale fish and is, as a result, strong and sharply pointed.

Size

Range weight: 1 – 1.35 kg
Range length: 81 – 97 cm
Range wingspan: 115 – 128 cm.

Habitat

As a water-bird, the African darter can be found around fresh and brackish waters that are surrounded by (or close to) fresh vegetation. Shallow lakes and slow-flowing rivers that are flanked by trees, mangroves and reeds are ideal. They will also be found around swamps, lagoons, and reservoirs, but will avoid marine habitats, generally speaking. They need trees or bushes for their roosting.

Distribution

These birds are common right from just below the Sahara Desert all the way down to South Africa. In some places, their population is patchy, but they are found in abundant numbers in southern Africa. It is common in South Africa, Namibia, Zimbabwe, Botswana and Mozambique.

In South Africa, it can be spotted on Thesen Island in Knysna on the Garden Route, Gillooly's Farm in Johannesburg, Midmar Dam Nature Reserve near Pietermaritzburg, and the Blyde River Canyon in Mpumalanga.

Diet

The African darter's diet consists mainly of fish, which it hunts in its watery habitat. It dives down, spears the fish with its beak, rises to the surface, tosses the fish into the air and then catches it with its bill and swallows it head-first. However, it is also known to eat the amphibians, reptiles and invertebrates that it finds too. This darter is a solitary feeder.

Behaviour

The African darter is able to dive for long periods of time in search of a meal. It swims with its entire body under the water, which allows it a more surprising ambush, as it does not create a massive disturbance to the water when it dives or surfaces.

It nests with up to 100 egrets, herons, cormorants and other darters, but remains an extremely territorial bird that will become aggressive with other males if it sees the need.

They are often found perched on stumps above the water, on jetties or on bare branches. If surprised or threatened, it dives vertically into the water for protection. On exiting the water, it will spread its wings to allow them to be dried by the sun and air. This is because it does not have the oil ducts of other birds and is, therefore, not waterproof.

Communication

This darter is mainly quiet but does make a croak sound while nesting. This is not a soft, delicate sound; but a harsh, jarring one.

Reproduction

The breeding season is determined mainly by the rainfall, but can occur all year round. They are seasonally monogamous birds (sticking to one mate for one breeding season). The female is responsible for building the nest, which she makes from sticks and other vegetation that the male has brought to her. They choose the fork of tree branches or reed beds that are above or next to water for their nests, as these are relatively inaccessible or well hidden from predators. The female lays 3 to 5 eggs, which are a pale green colour.

The pair takes turns to incubate the eggs until they hatch, up to a month later. When they hatch, the chicks are incapable of doing anything for themselves, and are completely dependent on their parents for food, warmth and protection. They are covered in a soft, white down for the first two days. They are fed and brooded by both parents until they fledge, which is at about 5 weeks of age. After that, they have 2 more weeks of parental care before embarking on an independent life. They will start to breed at around 2 years of age.

Incubation

Incubation lasts 25 to 30 days.

Life Expectancy

The African darter is known to live for up to 16 years.

Threats

The African darter's population numbers are very healthy. However, the birds and their eggs may be the prey of choice for crocodiles, birds of prey and crows. Humans have also been known to collect the eggs for consumption. In some parts of southern Africa, it is incorrectly believed that these birds are threatening trout (and other recreational fish) populations. In these places, humans actively pursue them to kill them. Pollution, urbanisation and nest disturbance are also threatening factors in some countries.

References

Oiseaux Birds; BirdLife International; Handbook of the Birds of the World, vol. 1: Ostrich to Ducks; Cormorants, darters, and pelicans of the world; Biodiversity Explorer.