Anhinga

For the bird genus Anhinga, see Darter.
Anhinga
Male in Costa Rica
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Suliformes
Family: Anhingidae
Genus: Anhinga
Species: A. anhinga
Binomial name
Anhinga anhinga
(Linnaeus, 1766)
Subspecies

A. a. anhinga
A. a. leucogaster

Range of A. anhinga      Breeding range     Resident range
Synonyms

Plotus anhinga

The anhinga (/ænˈhɪŋɡə/; Anhinga anhinga), sometimes called snakebird, darter, American darter, or water turkey, is a water bird of the warmer parts of the Americas. The word anhinga comes from the Brazilian Tupi language and means devil bird or snake bird. When swimming the origin of the name snakebird is apparent: only the colored neck appears above water so the bird looks like a snake ready to strike. They do not have external nares (nostrils) and breathe solely through their epiglottis.

The anhinga is placed in the darter family, Anhingidae, and is closely related to Indian (Anhinga melanogaster), African (A. rufa), and Australian (A. novaehollandiae) darters. Like other darters, the anhinga hunts by spearing fishes and other small prey using its sharp, slender beak.

Distribution and migration

Anhinga species are found all over the world in warm shallow waters.[2] The American anhinga has been subdivided into two subspecies, A. a. anhinga and A. a. leucogaster, based on their location. A. a. anhinga can be found mainly east of the Andes in South America and also the islands of Trinidad and Tobago. A. a. leucogaster can be found in the southern United States, Mexico, Cuba, and Grenada.[3] A fossil species Anhinga walterbolesi has been described from the Late Oligocene to Early Miocene of Australia.

Only birds that live in the extreme north and south of their range migrate and do so based on temperature and available sunlight. Anhingas will migrate towards the equator during winter but this range is "determined by the amount of sunshine to warm the chilled birds".[2] Although not in their usual range, anhingas have been found as far north as the states of Pennsylvania[4] and Wisconsin[5] in the United States.

Kettles of anhingas often migrate with other birds and have been described as resembling black paper gliders.[6]

Description

The A. anhinga species is a large bird and measures approximately 89 cm (35 in) in length, with a range of 75–95 cm (30–37 in), with a 1.14 m (3.7 ft) wingspan.[7][8] The A. a. anhinga subspecies is larger than A. a. leucogaster and has "broader buffy tail lips".[3] They weigh on average around 1.22 kg (2.7 lb), with a range of 1.04–1.35 kg (2.3–3.0 lb).[8][9][10] The bill is relatively long[5] (about twice the length of the head[11]), sharply pointed[7] and yellow as are the webbed[9] feet.

Most of the male anhinga's body is a glossy black green with the wings, base of wings, and tail being a glossy black blue.[11] The tip of the tail has white feathers.[12] The back of the head and the neck have elongated feathers that have been described as gray[13] or light purple-white.[11] The upper back of the body and wings is spotted or streaked with white.[13]

The female anhinga is similar to the male except that it has a pale gray-buff[14] or light brown[15] head, neck, and upper chest. The lower chest or breast is a chestnut color and as compared to the male, the female has a more brown back.[16]

The hatchling starts out bald but gains tan down within a few days of hatching. Within two weeks the tan down has been replaced by white down. Three weeks after hatching, the first juvenile feathers appear. Juveniles are mostly brown until first breeding after the second or third winter.[2]

This bird is often mistaken for the double-crested cormorant due to its similar size and shape, although the two species can be differentiated by their tails and bills. The tail of the anhinga is wider and much longer than that of the cormorant. The bill of the anhinga is pointed, while the bill of the cormorant has a hook-tip.[17]

Behavior

In order to dive and search for underwater prey, including fish and amphibians, the anhinga does not have waterproof feathers, (unlike ducks, which coat their feathers with oil from their uropygial gland). Because the anhinga is thus barely buoyant, it can stay below the surface more easily and for longer periods of time.

If it attempts to fly while its wings are wet, the anhinga has difficulty, flapping vigorously while "running" on the water. As do cormorants when drying their feathers, the anhinga will stand with wings spread and feathers fanned open in a semicircular shape, resembling a male meleagrine, which led to the anhinga being referred to colloquially as the "water turkey."

Anhinga will often search for food in small groups.

Conservation status

The anhinga is protected in the US under the Migratory Bird Treaty Act of 1918.[18] The number of individual anhingas has not been estimated but they are considered to be of least concern because of the frequency of their occurrence in their 15,000,000 km2 (5,800,000 sq mi) global range.[1]

References

  1. 1 2 BirdLife International (2012). "Anhinga anhinga". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
  2. 1 2 3 Nellis, David W. (2001). Common Coastal Birds of Florida and the Caribbean. Pineapple Press, Inc. p. 110. ISBN 978-1-56164-191-8.
  3. 1 2 Blake, Emmet Reid (1953). Birds of Mexico: a guide for field identification. University of Chicago Press. pp. 151–152. ISBN 0-226-05641-4.
  4. ↑ McWilliams, Gerald M.; Brauning, Daniel W. (1999). Birds of Pennsylvania. Cornell University Press. p. 43. ISBN 978-0-8014-3643-7.
  5. 1 2 Robbins, Samuel D. (1991). Wisconsin Birdlife: Population and Distribution Past and Present. University of Wisconsin Press. pp. 127–128. ISBN 978-0-299-10260-9.
  6. ↑ Eubanks, Ted L.; Behrstock, Robert A.; Weeks, Ron J. (2006). Birdlife of Houston, Galveston, and the Upper Texas Coast. Texas A&M University Press. p. 70. ISBN 978-1-58544-510-3.
  7. 1 2 Sibley, David Allen (2003). The Sibley Field Guide to Birds of Eastern North America. New York: Alfred A. Knopf. p. 45. ISBN 0-679-45120-X.
  8. 1 2 "Anhinga". All About Birds. Cornell Lab of Ornithology.
  9. 1 2 Maehr, David S.; Kale, H.W.; Kale, II, Herbert W. (2005). Florida's Birds: A Field Guide and Reference. Pineapple Press Inc. pp. 33, 38. ISBN 1-56164-335-1.
  10. ↑ Hennemann, III, Willard W. (December 1985). "Energetics, Behavior and the Zoogeography of Anhingas and Double-Crested Cormorants". Ornis Scandinavica. Wiley. 16 (4): 319–323. JSTOR 3676697.
  11. 1 2 3 Audubon, John James (1843). The Birds of America. J.B. Chevalier. pp. 443–457.
  12. ↑ Wood, Tom; Williamson, Sheri L.; Glassberg, Jeffrey (2005). Birds of North America. Sterling Publishing Company, Inc. p. 50. ISBN 1-4027-2821-2.
  13. 1 2 Chapman, Frank M. Handbook of Birds of Eastern North America (PDF). Harvard University. p. 93. doi:10.5962/bhl.title.34046.
  14. ↑ Burton, Maurice; Burton, Robert (2002). International Wildlife Encyclopedia. Marshall Cavendish. p. 646. ISBN 0-7614-7271-1.
  15. ↑ Gregware, Bill; Gregware, Carol (1997). Guide to the Lake Okeechobee Area. Pineapple Press Inc. p. 54. ISBN 1-56164-129-4.
  16. ↑ Fjeldså, Jon; Krabbe, Niels; Jørgensen, Povl; Byskov, Jens Ole (1990). Birds of the High Andes. Apollo Books. p. 74. ISBN 87-88757-16-1.
  17. ↑ Peterson, Roger Tory (1998). A Field Guide to the Birds of Texas. Houghton Mifflin Harcourt. p. 130. ISBN 0-395-92138-4.
  18. ↑ U.S. Fish and Wildlife Service (1995). "Birds Protected by the Migratory Bird Treaty Act". Archived from the original on 8 May 2008. Retrieved 15 September 2008.

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