he Oriental Darter or Indian TDarter (Anhinga melanogas- ter) is a water bird of tropical South Asia and Southeast Asia. In Cambodia, the bird lives around the Tonlé Sap Lake. It has a long and slender neck with a straight, pointed bill and like a cormorant, it hunts for fish while it hunts with its body submerged in water.
It spears fish underwater, brings it to the surface and tosses it into the air before swallowing. The body remains submerged as it swims and the slender neck alone is visible above the water leading to its other name of snakebird. Like the cormorants, it has wettable feathers and it is often found perched on a rock or branch Oriental Darter (Anhinga melanogaster) with its wings held open to dry. TAXONOMY DESCRIPTION The Oriental Darter is a member of the darter family, Anhingidae, and is closely related The Oriental Darter is like all other anhingas, to American (Anhinga anhinga), African (Anhinga rufa, with vulsini of Madagascar as a a cormorant-like species that has a very long subspecies), and Australasian (Anhinga novaehollandiae) Darters. These are sometimes all neck. The structure of the neck is as in other treated as subspecies of Anhinga melanogaster. The Oriental Darter differs in appearance species of darter with strongly developed from American darters most recognizably by its white lateral neck stripe. muscles about a kink in the neck at the 8th and 9th vertebrae that allows it to be flexed BEHAVIOR AND ECOLOGY and darted forward with rapid force to stab fish The Oriental Darter is found mainly in freshwater lakes and streams. They usually forage underwater. The edges of the commissures of singly, with the entire body submerged, swimming slowly forward using their webbed feet the mandible tips have minute inward pointing while the head and neck is moved jerkily above the water. It darts its neck to impale fish serrations that hold impaled fish. and then brings them out of water, tossing them into the air before swallowing the fish head first. They may sometimes be found along with cormorants that share the habit of The adult plumage above is black and the spreading out their wings to dry when perched on a waterside rock or tree. They sometimes wing coverts and tertials having silvery soar on thermals during the warm part of the day but will alternate flapping and gliding in streaks along the shaft. The crown and neck normal flight. are brown shading to black towards the back of the neck. The underparts are blackish They nest in mixed species heronries where they build a stick platform on the nest tree which brown. A pale line over the eye and throat is usually surrounded by water. Several pairs may nest close to each other. The branch and a line running along the sides of the is flattened by the birds prior to the placement of the sticks that form the nest platform. neck gives it a striped appearance. The iris The nest sites are defended from other birds with posturing and thrusts of the neck. The is white with a yellow ring around it. The tip breeding season is June to August (during the rainy season) in northern India, April–May in of the upper mandible is dark while the base southwestern India and in winter in southeastern India (during the northeast monsoon). The is pale brown bill while the lower mandible is usual clutch consists of 3 to 6 spindle shaped bluish-green eggs with a white chalky covering yellowish. The legs and webbing on the foot that gets soiled over time. Both parents incubate the eggs, beginning after the first egg is laid are yellow in immatures and dark grey in older which leads to asynchronous hatching of the young. The newly hatched chicks are bare and birds. The sexes are not easily distinguishable covered with some down on the head. As they grow, they become covered in white down. but males tend to have black speckles that The chicks feed by thrusting their heads into the throat of their parents. coalesce on the white throat. Adult females have a shorter bill and tend to have the black Adults go through a synchronous moult of their flight feathers after the breeding season at the base of neck and chest separated from resulting in the loss of flying ability for a brief period of time. When disturbed from their the hind neck by a wide buff band that ends perches during this period, they dive into the water below and attempt to escape underwater. at the shoulder. This pattern however is also This escape behavior is also employed by chicks at the nest. They are very silent except at found in immatures whose neck is lighter and the nest where they produce grunts and croaks and a disyllabic chigi-chigi-chigi. Chicks are lack the long pointed scapulars. In flight, the noisy when begging for food. Adults roost communally in trees close to or over water. slender and long neck, wide wing and wedge shaped tail make it distinctive. Young birds Chicks, especially those more than half grown are sometimes preyed on by raptors such as have a pale brown neck and appear whitish on Pallas’s Fish Eagle (Haliaetus leucoryphus). The long scapular feathers were once popular the underside and lack the white streak along for use in decorating hats. A number of parasites have been recorded from adult birds the side of the neck. The inner secondaries including Schwartzitrema anhingi (Trematoda), Petasiger nicolli, Mesorchis pendulus, and or tertials and the central tail feathers appear Echinorhynchotaenia tritesticulata (Cestoda: Dilepididae). wavy or corrugated. The tail is long and made up of twelve stiff feathers which are dragged In some parts of northeastern India, darters were (or are) used by tribals to capture fish from along the ground when the bird attempts to streams. A ring is tied around the neck to prevent them from swallowing the prey just as is walk or hop on land. done with cormorant fishing in parts of Southeast Asia.■
L’Écho du Cambodge n° 169 janvier 2015 Page 09