Anhinga melanogaster

Geographic Range

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 oriental
  • native native

Habitat

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.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial

• Other Habitat Features
• riparian riparian
• estuarine estuarine

Physical Description

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.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

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 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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• oviparous 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 altricial
• male parental care male parental care
• female 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

Lifespan/Longevity

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.

Behavior

Oriental darters spend most of their time roosting or swimming. Since their feathers are not completely waterproof, they absorb water and are less buoyant, allowing for faster swimming and diving. Darters swim with their wings extended and paddle with their webbed feet. After swimming, darters sit on branches in the sun and spread their wings to preen and allow them to dry. On, or close to the ground, they are rather ungainly.

Darters may sit on top of the water, or actively swim. While swimming, only their heads and necks are exposed, with the remainder of their body submerged. They may abruptly dive from on top of the water, or from a tree branch.

In flight, A. melanogaster is very similar to cormorants . They are powerful flyers and can soar for very long distances without flapping their wings.

• Key Behaviors
• arboreal arboreal
• flies
• natatorial natatorial
• motile motile
• sedentary sedentary
• social social
• colonial colonial

Home Range

Anhinga melanogaster lives in large colonies of up to several hundred individuals. These colonies roost close together in wooded areas, or bamboo groves. The exact size of these areas is unknown, as most evidence is anecdotal. Often times, darters live near and build nests alongside colonies of cormorants and herons . Cormorants and darters also hunt and rest in each other's company. Ordinarily, A. melanogaster does not migrate; however, those living in more extreme areas will migrate to other areas.

Communication and Perception

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 visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

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.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore

• Animal Foods
• amphibians
• reptiles
• fish
• insects
• mollusks
• aquatic crustaceans
• echinoderms

• Plant Foods
• leaves
• seeds, grains, and nuts

Predation

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.

Ecosystem Roles

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.

Economic Importance for Humans: Positive

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 food
• body parts are source of valuable material

Economic Importance for Humans: Negative

It is unknown if A. melanogaster negatively affects humans .

Conservation Status

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.

Additional Links

Encyclopedia of Life

Contributors

Jason Ning (author), The College of New Jersey, Matthew Wund (editor), The College of New Jersey, Leila Siciliano Martina (editor), Texas State University.

References

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Barson, M., B. Marshall. 2004. First record of Contracaecum spp. ( Nematoda : Anisakidae ) in fish-eating birds from Zimbabwe. Journal of the South African Veterinary Association , 75 (2): 74-78. Accessed November 12, 2012 at http://jsava.co.za/index.php/jsava/article/viewFile/456/440 .

Birdlife International, 2012. " Anhinga melanogaster " (On-line). IUCN Redlist of Threatened Species. Version 2012.1. Accessed October 12, 2012 at http://www.iucnredlist.org/details/106003662/0 .

Birdlife International, 2008. "Oriental Darter Anhinga melanogaster " (On-line). Birdlife International. Accessed October 12, 2012 at http://www.birdlife.org/datazone/speciesfactsheet.php?id=3662 .

Blanford, W. 1898. Plotus melanogaster . The Indian Darter or Snake-bird. Pp. 344-345 in The Fauna of British India, Including Ceylon and Burma , Vol. 4, 1 Edition. London: Taylor and Francis. Accessed October 23, 2012 at http://archive.org/stream/birdsindia04oaterich#page/344/mode/1up .

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Gupta, R. 1964. Schwartzitrema anhingi sp. nov. from the Indian Darter, Anhinga melanogaster Pennant, with a remark on the taxonomic position of the genus Schwartzitrema (Vigueras, 1940) Vigueras, 1941 ( Trematoda : Strigeidae ). Revista de Biología Tropical , 12 (1): 75-79. Accessed November 12, 2012 at http://www.biologiatropical.ucr.ac.cr/attachments/volumes/vol12-1/09-Gupta-Schwartzitrema.pdf .

Keswal, 1886. Notes on the Waters of Western India. The Journal of the Bombay Natural History Society , 1: 97-123. Accessed October 23, 2012 at http://archive.org/stream/journalofbombayn01bomb#page/96/mode/2up .

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Sharpe, R., W. Ogilvie Grant. 1898. Catalogue of the Plataleae, Herodiones, Steganopodes, Pygopodes, Alcae, an Impennes in the Collection of the British Museum . London: Longmans & Co.. Accessed October 23, 2012 at http://archive.org/stream/catalogueofbirds26brit#page/414/mode/1up .

Sinclair, W. 1899. Plumage of the Snake-Bird ( Plotus melanogaster ). The Journal of the Bombay Natural History Society , 12: 784. Accessed October 23, 2012 at http://archive.org/stream/journalofbombayn121900bomb#page/784/mode/1up .

Whistler, H. 1949. Popular Handbook of Indian Birds . London: Gurney and Jackson. Accessed October 23, 2012 at http://archive.org/stream/popularhandbooko033226mbp#page/n542/mode/1up .

WoRMS, 2011. " Anhinga melanogaster Pennant, 1769" (On-line). WoRMS World Register of Marine Species. Accessed October 12, 2012 at http://www.marinespecies.org/aphia.php?p=taxdetails&id=212610 .

Zoological Society of London, 1882. Proceedings of the general meetings for scientific business of the Zoological Society of London for the year 1882. Zoological Society of London: 208-212. Accessed October 23, 2012 at http://archive.org/stream/proceedingsofgen82busi#page/208/mode/2up .

2012. " Anhinga melanogaster " (On-line). Life in the Suburbs. Accessed October 12, 2012 at http://keys.lucidcentral.org/key-server/data/03050501-000c-4503-8203-0a030507090d/media/Html/Anhinga_melanogaster.htm .

2012. "AnAge entry for Anhinga melanogaster " (On-line). AnAge: The Animal Ageing and Longevity Database. Accessed October 12, 2012 at http://genomics.senescence.info/species/entry.php?species=Anhinga_melanogaster .