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Anhinga

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For the bird genus Anhinga, see Darter.

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 a'ñinga in the Brazilian Tupi language and means "devil bird" or "snake bird".[3] The origin of the name is apparent when swimming: only the 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.

Anhinga
Temporal range: Pleistocene–present
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Male in Costa Rica
Female in Florida

Secure  (NatureServe)[2]
Scientific classification Edit this classification
Domain: Eukaryota
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 Linnaeus, 1766

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

Distribution and migration

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Members of the Anhinga genus live in warm, shallow waters and swamplands worldwide.[4] The American anhinga has been subdivided into two subspecies, A. a. anhinga and A. a. leucogaster, based on their respective location. A. a. anhinga can be found mainly east of the Andes in South America, east to the islands of Trinidad and Tobago. A. a. leucogaster can be found in the southern United States, Mexico, Cuba, and the Caribbean island of Grenada.[5] A fossil species, Anhinga walterbolesi, has been described from the Late Oligocene to Early Miocene of Australia.

Only birds living in the extreme north or south of their respective ranges will migrate based on temperature and available sunlight; anhinga will travel closer towards the equator during winter, but this range is "determined by the amount of sunshine to warm the chilled birds".[4] Although not part of their traditional range, American anhinga have been found as far north as the states of Pennsylvania,[6] Wisconsin,[7] and New York.[8]

Kettles of anhinga often migrate with other species of birds, and have been described as resembling "black paper gliders".[9]

Description

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The anhinga is a large bird, measuring 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.[10][11] The A. a. anhinga subspecies is larger than A. a. leucogaster and has broader buffy tail tips.[5] 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).[11][12][13] The bill is relatively long (about twice the length of the head), sharply pointed, and yellow, and the webbed feet are yellow as well.[7][14][10][12]

The male is a glossy black-green with the wings, base of wings, and tail a glossy black-blue.[14] The tip of the tail is white.[15] The back of the head and the neck have elongated feathers that have been described as gray[16] or light purple-white.[14] The upper back of the body and wings are spotted or streaked with white.[16]

The female anhinga is similar to the male except for its pale gray-buff[17] or light brown[18] head, neck, and upper chest. The lower chest or breast is a chestnut color, and the back is browner than the male's.[19]

 
Skeleton, showing the unusual eighth cervical vertebra.

The hatchling starts bald but gains tan down within a few days of hatching. Within two weeks, the tan down is replaced by white down. Three weeks after hatching, the first juvenile feathers appear. Juveniles are mostly brown until they first breed, usually after the second or third winter.[4]

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 the cormorant's. The bill of the anhinga is pointed, while the bill of the cormorant has a hook-tip.[20]

Like other species in the genus, anhingas have a noticeable "kink" midway up their necks. This is due to the peculiar morphology of the eighth cervical vertebra.[21]

Behavior

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Anhinga swim by kicking their webbed feet to pursue their prey, fish or amphibians, underwater, which they spear by rapidly outstretching their bent neck. They come up to the surface to consume and swallow prey.[22] Unlike ducks, ospreys and pelicans, which coat their feathers with oils from the uropygial gland, the anhinga does not have this ability; anhinga lack waterproof feathers on their bodies, causing them to be saturated upon immersion into water, while the flight feathers are slightly less wettable. Thus, their habit of basking in the sun with outstretched wings is crucial. Their dense bones, wetted plumage, and neutral buoyancy when in water allows them to fully submerge and hunt for underwater prey.[23][24]

The anhinga cannot fly for any extended distance with soaked feathers; if they attempt to fly while wet, notable difficulty is experienced, the birds flapping vigorously while "running" on the water’'s surface for a short distance (often escaping a perceived threat). Like cormorants, anhingas perch and rest on fallen trees, logs or rocks near the water's edge with wings spread and feathers fanned-open in a semicircular shape, facing away from the sun, in order to dry themselves and absorb the sun's heat.[25] Anhingas also lose body heat relatively fast, and their posture helps them absorb solar radiation from the sun to counteract this.[25] Because an anhinga in the drying position resembles a male turkey, it has been colloquially referred to as the 'water turkey' or 'swamp turkey'.

Diet

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Eating a cichlid. In Florida.

Anhingas feed on moderately sized wetland fishes,[11] amphibians,[26] aquatic invertebrates and insects.[27] In Alabama, the anhinga's diet consists of fishes (such as mullet, sunfish, black bass, catfish, suckers, and chain pickerel), crayfish, crabs, shrimp, aquatic insects, tadpoles, water snakes and small terrapins.[28] In Florida, sunfishes and bass, killifishes, and live-bearing fishes are primarily eaten by the anhingas.[29] Other fish eaten include pupfish and percids.[27]

Anhingas stalk fish underwater, mainly where there is some vegetation. Once they locate their prey, they partly open their bill and stab the fish swiftly. For larger fish, they use both their jaws; for small fish they may use only the lower jaw.[11] If the fish is too large to forage, the anhinga stabs it repeatedly and then lets it go.[30] The anhingas bring their capture to the surface of the water, toss it backward and engulf it head-first.[29]

Conservation status

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The US protects the anhinga under the Migratory Bird Treaty Act of 1918.[31] 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]

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    Male drying its feathers and warming its body, Florida, US
  •  
    Showing snake-like neck and pointed beak
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    In flight, South Carolina, US
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    Juvenile in Uarini, Amazonas, Brazil
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    Juveniles with white plumage
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    Female in Florida, US
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    Anhinga on Harris Lake in Leesburg, Florida.

References

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  1. ^ a b BirdLife International (2016). "Anhinga anhinga". IUCN Red List of Threatened Species. 2016: e.T22696702A93581588. doi:10.2305/IUCN.UK.2016-3.RLTS.T22696702A93581588.en. Retrieved 13 November 2021.
  2. ^ "Anhinga anhinga". NatureServe Explorer. Retrieved 17 April 2024.
  3. ^ Ferreira, A. B. H. (1986). Novo Dicionário da Língua Portuguesa. Second edition. Rio de Janeiro: Nova Fronteira. p. 123.
  4. ^ a b c Nellis, David W. (2001). Common Coastal Birds of Florida and the Caribbean. Pineapple Press, Inc. p. 110. ISBN 978-1-56164-191-8.
  5. ^ a b Blake, Emmet Reid (1953). Birds of Mexico: a guide for field identification. University of Chicago Press. pp. 151–152. ISBN 0-226-05641-4.
  6. ^ McWilliams, Gerald M.; Brauning, Daniel W. (1999). Birds of Pennsylvania. Cornell University Press. p. 43. ISBN 978-0-8014-3643-7.
  7. ^ a b 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.
  8. ^ "The 'Devil Bird' Lands in New York, With More Likely to Come", The New York Times, 4 May 2023
  9. ^ 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.
  10. ^ a b 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.
  11. ^ a b c d "Anhinga". All About Birds. Cornell Lab of Ornithology.
  12. ^ a b 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.
  13. ^ Hennemann, III, Willard W. (December 1985). "Energetics, Behavior and the Zoogeography of Anhingas and Double-Crested Cormorants". Ornis Scandinavica. 16 (4). Wiley: 319–323. doi:10.2307/3676697. JSTOR 3676697.
  14. ^ a b c Audubon, John James (1843). The Birds of America. J.B. Chevalier. pp. 443–457.
  15. ^ Wood, Tom; Williamson, Sheri L.; Glassberg, Jeffrey (2005). Birds of North America. Sterling Publishing Company, Inc. p. 50. ISBN 1-4027-2821-2.
  16. ^ a b Chapman, Frank M. (1904). Handbook of Birds of Eastern North America (PDF). Harvard University. p. 93. doi:10.5962/bhl.title.34046.
  17. ^ Burton, Maurice; Burton, Robert (2002). International Wildlife Encyclopedia. Marshall Cavendish. pp. 646. ISBN 0-7614-7271-1.
  18. ^ Gregware, Bill; Gregware, Carol (1997). Guide to the Lake Okeechobee Area. Pineapple Press Inc. p. 54. ISBN 1-56164-129-4.
  19. ^ Fjeldså, Jon; Krabbe, Niels; Jørgensen, Povl; Byskov, Jens Ole (1990). Birds of the High Andes. Apollo Books. p. 74. ISBN 87-88757-16-1.
  20. ^ Peterson, Roger Tory (1998). A Field Guide to the Birds of Texas. Houghton Mifflin Harcourt. p. 130. ISBN 0-395-92138-4.
  21. ^ Garrod, A. H. (1876). "1. Notes on the Anatomy of Plotus anhinga". Proceedings of the Zoological Society of London. 44 (1): 335–345. doi:10.1111/j.1096-3642.1876.tb02572.x. ISSN 1469-7998.
  22. ^ Frederick, P. C. and D. Siegel-Causey (2000). Anhinga (Anhinga anhinga), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. Pg 4-5 DOI: 10.2173/bna.522
  23. ^ "Anhinga - Introduction". Birds of North America Online. Archived from the original on 2018-06-05. Retrieved 2018-12-08 – via website: birdsna.org.
  24. ^ Rijke, Arie M.; Jesser, William A.; Mahoney, Sheila A. (1989). "Plumage wettability of the African darter Anhinga melanogaster compared with the double-crested cormorant Phalacrocorax auritus". Ostrich. 60 (3): 128–132. Bibcode:1989Ostri..60..128R. doi:10.1080/00306525.1989.9633739. ISSN 0030-6525.
  25. ^ a b Hennemann, Willard W. "Energetics and Spread-Winged Behavior of Anhingas in Florida" The Condor84, no. 1 (1982): 91-96. JSTOR 1367827
  26. ^ "The Online Guide to the Animals of Trinidad and Tobago - Anhinga anhinga (Anhinga or Snake-bird)" (PDF).
  27. ^ a b Kearns, Laura. "ADW: Anhinga anhinga: INFORMATION". Animaldiversity.org. Retrieved 2022-08-08.
  28. ^ Imhof, Thomas, A (1962). Alabama Birds. University of Alabama Press. ISBN 978-0-8173-1701-0.{{cite book}}: CS1 maint: multiple names: authors list (link)
  29. ^ a b Owre, Oscar, T (1967). "Adaptations for locomotion and feeding in the Anhinga and the Double-crested cormorant" (PDF). Ornithological Monographs (6). American Ornithologists Union: 126–127. doi:10.2307/40166666. ISBN 978-0-9436-1006-1. JSTOR 40166666.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  30. ^ Wellenstein, Charlie (1986). "Prey Handling by Anhingas". Florida Field Naturalist. 14: 74-75- via SORA
  31. ^ 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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