Oriental darter  (Anhinga melanogaster)

The Oriental darter is classified as Near Threatened (NT) on the IUCN Red List (1).

The Oriental darter (Anhinga melanogaster) is a large, dark waterbird with a very long, slender neck, a long tail and a thin, straight bill (2) (4) (5). Highly adapted to swimming and diving, the Oriental darter typically swims low in the water with only its long, snake-like neck and head exposed (2) (3) (5), giving this species its alternative name of ‘snakebird’ (3).

The adult Oriental darter has a dark blackish-brown head and hind neck, while the sides and front of the neck are chestnut with a white stripe (2) (3) (4) (5). The throat is mottled black and white (2). The rest of the body and tail are largely black with a green-brown tinge, while the wing feathers are for the most part black with a central white stripe (2) (4). There is some variation in the colouration of Oriental darters from different areas and in different seasons (4).

The male and female Oriental darter are similar in appearance (2), but breeding males may have a reddish-brown instead of black-brown to chestnut head and neck, while the white stripes on the wing feathers are more pronounced than in the female (4). The juvenile Oriental darter has a grey head and neck with no white streak, and the rest of the body is browner than in the adult (4) (5).

This species is much like a cormorant (Phalacrocorax spp.) in appearance, but differs in the straight, dagger-like shape of its bill, as well as in its longer, more slender neck (2) (3) (4). The Oriental darter’s bill is greenish or yellowish, its eyes are yellow, and its legs are grey-brown or blackish (2) (4). The tail of this species is stiff and fan-like (3).

Although generally silent, the Oriental darter sometimes gives croaks or squeals (5), a frog-like ‘kek-kek’ or a rapid ‘chigi’ (3).

Four subspecies of the Oriental darter have previously been recognised: Anhinga melanogaster melanogaster, Anhinga melanogaster rufa, Anhinga melanogaster vulsini and Anhinga melanogaster novaehollandiae (6). However, these are now generally split into three distinct species: the Oriental darter (Anhinga melanogaster), African darter (Anhinga rufa) and Australian darter (Anhinga novaehollandiae) (2) (6) (7).

The Oriental darter is found across Asia, from Pakistan, India, Nepal and Sri Lanka, east through Bangladesh, Myanmar, Lao People’s Democratic Republic, Thailand, Cambodia and Vietnam, and south through Peninsular Malaysia to Singapore, Indonesia and Brunei (7).

In the past, this species was fairly widespread in Thailand. However, current evidence suggests that there is little or no breeding activity of this species there and that it has become extremely rare (7).

The Oriental darter is usually found in shallow inland wetlands, including lakes, rivers, swamps, reservoirs, marshes, lagoons and ponds (2) (3) (5) (7).

The Oriental darter usually feeds by diving around floating weeds or in standing water, typically with a depth of around 0.9 to 1.7 metres. It generally hunts in the early morning, late morning and afternoon, feeding mainly on small fish in the Cyprinidae family (8). Other prey species include cichlid fish (Cichlidae species), insects, snakes, tadpoles and crustaceans (4).

A skilled diver, the Oriental darter swims underwater and spears prey with its bill (2) (5), before using the bill to hold or pick apart the prey, which it then throws into the air and swallows (8). After eating, the Oriental darter typically sits on stumps or dead trees up to 30 metres in height and holds its wings open to dry them (2) (3) (5) (8).

Breeding in the Oriental darter usually occurs between May and August (2) (3). Although usually solitary, this species breeds in small colonies, often alongside other waterbirds such as herons (2) (3)(5). The Oriental darter constructs a loose, unlined stick nest in a tree, usually close to water (2) (3), with colonies building around five nests per tree on average (4).

The Oriental darter usually lays three or four eggs, which are pale greenish-blue (3).

The main threats to the Oriental darter are habitat loss, hunting, pollution, and disturbance at its feeding grounds and breeding colonies. Its foraging areas are being degraded and nesting trees have been felled, and its eggs and nestlings are collected in some areas (7).

The Oriental darter population is currently estimated at around 4,000 individuals in total, but is undergoing a decline (7).

In Thailand, the Oriental darter is protected under the Wildlife Preservation and Protection Act and is listed as ‘critically endangered’ on the Wildlife in Thailand List (8). It also occurs in a number of protected areas across its range (7).

Recommended conservation measures for the Oriental darter include surveys to discover new colonies, as well as regular monitoring of known colonies throughout its range. Complete and permanent protection is needed for all the Oriental darter’s breeding colonies, and campaigns have been established among local people to help prevent hunting and to encourage a sense of local pride in this unusual waterbird (7).

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more about the Oriental darter and its conservation:

• BirdLife International - Oriental darter:
  http://www.birdlife.org/datazone/speciesfactsheet.php?id=3662&m=0