Darters are most known for their fishing strategies. Oriental darters are no exception and may capture their prey one of several ways. They may dive from their perch, or dive from the surface, to slowly stalk or chase fish. Others wait for fish to rise to the surface, or swim past. At this point, they will attempt to shoot their neck out, to spear the fish. This sudden movement is possible due to the bend in their neck, at the 7th through 9th vertebrae. Once their prey is impaled, darters rise to the surface and throw the fish up in the air, swallowing it headfirst. Darters may also swallow the fish whole while underwater, instead of spearing. Afterwards, darters usually exit the water and dry their wings.
Anhinga melanogaster usually eats fish, but has been found to eat insects, aquatic reptiles (turtles, snakes) and amphibians (frogs, newts), shrimp, mollusks, sponges, and various plant grasses and seeds in small quantities. However, the presence of these plant materials in their stomachs may have been accidental.
Animal Foods: amphibians; reptiles; fish; insects; mollusks; aquatic crustaceans; echinoderms
Plant Foods: leaves; seeds, grains, and nuts
Primary Diet: carnivore (Piscivore )
Parental care usually precludes predation of the young. Scientific literature has not detailed the identity of these predators. It is also unknown if adult darters have any natural predators.
Anhinga melanogaster is a long necked bird, similar in size and shape to cormorants. On average, A. melanogaster is between 850 and 900 mm in length. It possesses a long, straight bill, long neck, long tail (202 to 240 mm long), and webbed feet. The wings of A. melanogaster are generally 331 to 357 mm in length. Typically, adult males are slightly larger than females. Oriental darters' feathers are semi-permeable to water, which aids in swimming.
Anhinga melanogaster also possesses a bend in the 7th, 8th, and 9th vertebrae, which allows for a sudden shooting movement of their neck to capture fish. It is for this behavior that darters earned their name.
Adult male and female A. melanogaster are alike in coloration; juveniles, however, have different coloration. Their crown and rear neck is brown and the back of their head is blackish. Their bill is long and yellow and serrated along each edge. The underside of their neck is white; there is also a white line along each side of their head. Their back and long tail is black. Their tail is composed of 12 feathers. Their wings, however, have black feathers interspersed with white feathers. Their legs are black; their feet have four digits and are webbed.
The crown and rear neck of juveniles is a more pale brown. The underside of their neck is white, but the white lines on the lateral sides of their neck are absent. Darters' white wing feathers are a more yellow-white in juveniles.
Anhinga melanogaster molts and may lose so many feathers that they may be unable to fly for several days. They often have a "crinkled" appearance during this period.
Range length: 850 to 920 mm.
Average length: 900 mm.
Range wingspan: 331 to 357 mm.
Sexual Dimorphism: male larger
Other Physical Features: endothermic ; bilateral symmetry
The average lifespan of A. melanogaster is 9 years in the wild. The oldest known individual died in captivity at the age of 16 years.
Range lifespan
Status: captivity: 16 (high) years.
Average lifespan
Status: wild: 9 years.
Anhinga melanogaster typically lives in trees or bamboo thickets, near watery environments and roosts in large communities. These watery environments often include deep estuaries, lakes, ponds, streams, rivers, or marshes. The water in these environments need only be deep enough for diving and swimming.
Average elevation: 0 m.
Habitat Regions: temperate ; tropical ; terrestrial
Other Habitat Features: riparian ; estuarine
Anhinga melanogaster (also known as Oriental darters or snake-birds) is native to the Indian subcontinent. Anhinga melanogaster can be found as far west as Pakistan and as far north as the Indian-Nepalese border. Indian darters typically live in India, Laos, Myanmar, Cambodia, Sri Lanka, Singapore, Thailand, Malaysia and also in the island countries of the Philippines, and Indonesia.
Biogeographic Regions: oriental (Native )
Anhinga melanogaster is a host to several different parasitic roundworms including Schwartzitrema anhinga, Contracaecum rudolphii, Contracaecum carlislei, Contracaecum microcephalum, and Contracaecum tricuspis. Studies found these nematodes present in darters' gastrointestinal tracts; however, they listed the host as Anhinga melanogaster and did not differentiate between Oriental darters and African darters subspecies. Although Anhinga melanogaster is a piscivore, their impact on fish populations and the environment in general, is unknown.
Commensal/Parasitic Species:
Anhinga melanogaster is hunted for sport and for their plumage. Hunters often only shoot those with good plumage and not those undergoing molting. Humans also collect A. melanogaster eggs and nestlings for food.
Positive Impacts: food ; body parts are source of valuable material
It is unknown if A. melanogaster negatively affects humans.
Anhinga melanogaster is listed as a near threatened species by the IUCN. They are currently threatened by habitat loss (through draining bodies of water, cutting down trees, and intrusion of breeding and feeding areas), as well as egg collection, hunting, and pollution. Pollution may be due to chemical runoff or algal blooms in their habitat. One innovative solution enacted in 2002 at Prek Toal on Tonle Sap Lake in Cambodia, involved hiring former egg hunters as guards for the colonies. As guards, they protected and monitored darters populations. From 2002 to 2011, nest numbers increased from 241 to over 6,000. Proposed conservation actions include discovering, monitoring, and protecting new colonies, as well as public awareness campaigns. It is hoped that the public can be persuaded to be proud of darters (as well as other large waterfowl) to reduce hunting and poaching.
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Oriental darters communicate with one another, primarily via calls. Their distinctive call is a hoarse croak-like "kah-kah-kah", with hissing and clicking. Darters' voices are similar to cormorants' voices, but they are slightly lower. While breeding, mates call out to each other and will communicate via wing flapping displays. When approached, or surprised by humans, they will often crane their necks and flap their wings, possibly as a warning to others in the vicinity.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Anhinga melanogaster is serially monogamous and typically breeds in colonies. Males attract and greet mates with displays, including wing flapping. Mates build nests of twigs, approximately 40 to 50 cm in diameter and line them with leaves. These nests are typically in trees overhanging water and may be reused from year to year. Both male and female mates defend the nest and young by hopping, hissing, and snapping if threatened. Mates communicate with each other through calls, as well as wing flapping displays.
Mating System: monogamous
The breeding season of A. melanogaster can last for several months, up to all year, depending on the monsoon season's effects on water levels in the region. Oriental darters usually lay when water levels are high and fish are abundant. For example, their breeding season is from July to August in Northern India and Burma and from January to February in Madras and Sri Lanka.
After mating, eggs are laid and incubated by both the male and female for 25 to 30 days before hatching. The eggs usually hatch asynchronously. These eggs are oval in shape and covered in a greenish-white coating (which may turn brown due to incubation). Underneath this coating, the egg is a pale greenish blue.
Adolescents leave the nest and live independently at around 50 days of age. Sexual maturity occurs at about 2 years of age.
Breeding interval: Anhinga melanogaster breeds once per breeding season.
Breeding season: The breeding season is dependent on region and weather.
Range eggs per season: 2 to 6.
Average eggs per season: 3.
Range time to hatching: 25 to 30 days.
Average time to hatching: 28 days.
Average fledging age: 50 minutes.
Average age at sexual or reproductive maturity (female): 2 years.
Average age at sexual or reproductive maturity (male): 2 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; oviparous
Once hatched, the altricial young are cared for by both parents. For the first several weeks, the young are fed regurgitated food as many as 6 to 9 times per day by the parents.
Parental Investment: altricial ; male parental care ; female parental care ; pre-hatching/birth (Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
Accidental visitor.
The Oriental darter (Anhinga melanogaster) is a water bird of tropical South Asia and Southeast Asia. It has a long and slender neck with a straight, pointed bill and, like the cormorant, it hunts for fish while its body is submerged in water. It spears a fish underwater, bringing it above the surface, tossing and juggling it before swallowing the fish head first. The body remains submerged as it swims, and the slender neck alone is visible above the water, which accounts for the colloquial name of snakebird. Like the cormorants, it has wettable feathers and it is often found perched on a rock or branch with its wings held open to dry.
The Oriental darter is like all other anhingas, a cormorant-like species that has a very long neck. The structure of the neck is as in other species of darter with strongly developed muscles about a kink in the neck at the 8th and 9th vertebrae that allows it to be flexed and darted forward with rapid force to stab fish underwater. The edges of the commissures of the mandible tips have minute inward pointing serrations that hold impaled fish.[4][5]
The adult plumage above is black and the wing coverts and tertials having silvery streaks along the shaft. The crown and neck are brown shading to black towards the back of the neck. The underparts are blackish brown. A pale line over the eye and throat and a line running along the sides of the neck gives it a striped appearance. The iris is white with a yellow ring (brighter yellow in breeding birds) around it. The tip of the upper mandible is dark while the base is pale brown bill while the lower mandible is yellowish. The legs and webbing on the foot are yellow in immatures and non-breeding birds while breeding birds have darker grey tarsi and toes with yellow webbing.[6] The sexes are not easily distinguishable but males tend to have black speckles that coalesce on the white throat.[7] Adult females have a shorter bill and tend to have the black at the base of neck and chest separated from the hind neck by a wide buff band that ends at the shoulder. This pattern however is also found in immatures whose neck is lighter and lack the long pointed scapulars.[8] In flight the long and slender neck, wide wing and wedge shaped tail make it distinctive.[9][10] Young birds have a pale brown neck and appear whitish on the underside and lack the white streak along the side of the neck. The inner secondaries or tertials and the central tail feathers appear wavy or corrugated.[11] The tail is long and made up of twelve stiff feathers which are dragged along the ground when the bird attempts to walk or hop on land.[12]
The Oriental darter is a member of the darter family, Anhingidae, and is closely related to American (Anhinga anhinga), African (Anhinga rufa, with vulsini of Madagascar as a subspecies), and Australasian (Anhinga novaehollandiae) darters. These were for sometime treated as subspecies of Anhinga melanogaster.[13] The Oriental darter differs in appearance from American darters most recognisably by its white lateral neck stripe.[6]
The Oriental darter is found mainly in freshwater lakes and streams. They usually forage singly, with the entire body submerged, swimming slowly forward using their webbed feet while the head and neck is moved jerkily above the water. It darts its neck to impale 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 which share the habit of spreading out their wings to dry when perched on a waterside rock or tree. They sometimes soar on thermals during the warm part of the day but will alternate flapping and gliding in normal flight.[14]
They nest in mixed species heronries where they build a stick platform on the nest tree which is usually surrounded by water. Several pairs may nest close to each other.[15] The branch is flattened by the birds prior to the placement of the sticks that form the nest platform. The nest sites are defended from other birds with posturing and thrusts of the neck. The breeding season is June to August (during the rainy season) in northern India, April–May in southwestern India and in winter in southeastern India (during the northeast monsoon).[16] The usual clutch consists of three to six spindle shaped bluish-green eggs with a white chalky covering that gets soiled over time. Both parents incubate the eggs, beginning after the first egg is laid which leads to asynchronous hatching of the young. The newly hatched chicks are bare and covered with some down on the head. As they grow, they become covered in white down. The chicks feed by thrusting their heads down the throat of their parents.[14]
Adults go through a synchronous moult of their flight feathers after the breeding season, resulting in the loss of flying ability for a brief period. When disturbed from their perches during this period, they dive into the water below and attempt to escape underwater.[14] This escape behaviour is also employed by chicks at the nest.[17][18] They are very silent except at the nest where they produce grunts and croaks and a disyllabic chigi-chigi-chigi. Chicks are noisy when begging for food.[14] Adults roost communally in trees close to or over water.[19]
Chicks, especially those more than half grown are sometimes preyed on by raptors such as Pallas's fish eagle (Haliaetus leucoryphus).[14] The long scapular feathers were once popular for use in decorating hats.[20] A number of parasites have been recorded from adult birds including Schwartzitrema anhingi (Trematoda),[21] Petasiger nicolli,[22] Mesorchis pendulus,[23] and Echinorhynchotaenia tritesticulata (Cestoda:Dilepididae).[24]
In some parts of northeastern India, darters were (or are) used by tribals to capture fish from streams.[14] A ring is tied around the neck to prevent them from swallowing the prey just as is done with cormorant fishing in parts of Southeast Asia.[25]
The Oriental darter (Anhinga melanogaster) is a water bird of tropical South Asia and Southeast Asia. It has a long and slender neck with a straight, pointed bill and, like the cormorant, it hunts for fish while its body is submerged in water. It spears a fish underwater, bringing it above the surface, tossing and juggling it before swallowing the fish head first. The body remains submerged as it swims, and the slender neck alone is visible above the water, which accounts for the colloquial name of snakebird. Like the cormorants, it has wettable feathers and it is often found perched on a rock or branch with its wings held open to dry.
