White tern
| White tern | |
|---|---|
| |
| Nominate Gygis alba alba on Ascension Island | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Charadriiformes |
| Family: | Laridae |
| Genus: | Gygis |
| Species: | G. alba
|
| Binomial name | |
| Gygis alba (Sparrman, 1786)
| |
| |
The white tern or common white tern (Gygis alba) is a small seabird found across the tropical oceans of the world.[2] It is sometimes known as the fairy tern, although this name is potentially confusing as it is also the common name of Sternula nereis. Other names for the species include angel tern and white noddy in English, and manu-o-Kū in Hawaiian. In the Cook Islands, it is known as the kakaia.
Taxonomy
[edit]The white tern was first formally described by the Swedish naturalist Anders Sparrman in 1786 under the binomial name Sterna alba.[3] The genus Gygis was introduced by the German zoologist Johann Georg Wagler in 1832.[4] The name Gygis is from the Ancient Greek guges for a mythical bird and the specific alba is Latin for "white".[5]
Molecular phylogenetic studies have shown that the white tern is more closely related to the noddies (Anous) than it is to the other terns.[6][7] This implies that "white noddy" would be a more appropriate English name;[8] this has been taken up by at least one major text.[9]
The white tern has four accepted subspecies:[8][10][11]
- G. a. alba (Sparrman, 1786) — islands of the south tropical Atlantic Ocean including Fernando de Noronha, Trindade, Martin Vas Rocks, Ascension and Saint Helena islands. Larger, 25–30 cm; bill slender, slightly downcurved, all-black; legs dark grey.
- G. a. candida (J. F. Gmelin, 1789) — Indian Ocean islands (Seychelles, Mascarene Islands, and southern Maldives) east to the central Pacific Ocean but excluding range of G. a. leucopes and G. a. microrhyncha in the more southeastern parts of the central Pacific. Larger, 25–30 cm; bill stout, black with a dark blue-grey base, and slightly uptilted at the gonydeal angle; legs dark grey.
- G. a. leucopes Holyoak & Thibault, 1976 — Henderson and Pitcairn Islands. Similar to G. a. candida but with pale grey legs.
- G. a. microrhyncha H. Saunders, 1876 (Little white tern) — Line Islands, Marquesas Islands, Phoenix Islands and Kiribati. Smaller, 23–25 cm, with a slender black bill slightly uptilted at the gonydeal angle; legs pale grey to pinkish.
The little white tern, usually considered a subspecies G. a. microrhyncha of the white tern, is treated as a separate species Gygis microrhyncha by some authors,[12] but not by either the IOC World Bird List or the Clements Checklist of Birds of the World.[8]
One study has gone further and suggested that there may be three species of Gygis, with Gygis alba in the Atlantic Ocean, Gygis candida in the Indian and western to central Pacific Oceans, and Gygis microrhyncha in the southeast-central Pacific.[11] This study also proposed that G. candida is gradually extending its range southeastwards, and may in the future result in the extinction of G. microrhyncha by replacing it.[11]
Description
[edit]The white tern is 23–30 cm (9.1–11.8 in) long with a wingspan of 76–87 cm (30–34 in).[10] It has pure white plumage, except for a dark streak along the shafts of the outer primary feathers in G. a. candida), a black eye accentuated by a narrow ring of black feathers round the eye, and a long black to bluish-black bill. The tail is shallowly forked, but like in the noddies, with the longest feathers the second-from outermost, not the outermost as in other terns. The legs are dark grey, to paler grey in G. a. leucopes and G. a. microrhyncha.[10][13] The juvenile is white mottled with grey or greyish-brown. Nesting on coral islands, usually on trees with small branches but also on rocky ledges and on man-made structures, the white tern feeds on small fish which it catches by plunge diving.
Distribution and habitat
[edit]The white tern ranges widely across tropical regions of South Atlantic Ocean, the Pacific Ocean from the coasts of Chile and Colombia to New Zealand and along the eastern and southern coasts of Asia from China to India, South Maldives, the islands of the Indian Ocean, and the coast of South Africa.[1] Occasional vagrants have been found in Japan, Madagascar, Mexico, and on some islands north of the Equator in the Atlantic Ocean. It is a pelagic and epipelagic bird, living along the coast and moving into wooded areas during the breeding season.
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Gygis alba egg - MHNT -
G. a. candida, Tench Island, Bismarck Archipelago, Papua New Guinea -
G. a. candida chick, Midway Island, Hawaii -
G. a. candida parents near their chick, Cousin Island, Seychelles -
G. a. candida juvenile showing the mottled plumage, Cousin Island, Seychelles -
G. a. candida with a fish -
G. a. microrhyncha, Kiribati -
G. a. candida in flight, Rarotonga, Cook Islands
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_in_flight_Rarotonga_2.jpg)
Behaviour
[edit]This species is notable for laying its egg on bare thin branches in a small fork or depression without a nest. This behaviour is unusual for terns, which generally nest on the ground, and even the related tree-nesting black noddy constructs a nest. It is thought that the reason for the absence of nests is the reduction in nest parasites, which in some colonial seabirds can cause the abandonment of an entire colony.[14] In spite of these benefits there are costs associated with tree nesting, as the eggs and chicks are vulnerable to becoming dislodged by heavy winds. For this reason the white tern is also quick to relay should it lose the egg. The newly hatched chicks have well-developed feet with which to hang on to their precarious nesting site. It is a long-lived bird, having been recorded living for 42 years.[15]
Predators
[edit]Giant tortoises have been observed to hunt the bird on Fregate Island in the Seychelles.[16]
Relationship with humans
[edit]The white tern, manu-o-Kū, was named Honolulu, Hawaiʻi's official bird on April 2, 2007.
New Zealand's Department of Conservation classifies the white tern as Nationally Critical, with populations having been largely decimated by the introduction of feral cats and rats on Raoul Island, the terns' only breeding site in the country.[17] As of 2016, the white tern population in New Zealand was reported to be increasing following the eradication of introduced predators in 2002.[17][18] Globally, the white tern has a large range that is home to several large colonies, and both recognised species are listed as Least Concern by the IUCN Red List.
References
[edit]- ^ a b BirdLife International (2018). "Gygis alba". IUCN Red List of Threatened Species. 2018: e.T22694821A132576063. doi:10.2305/IUCN.UK.2018-2.RLTS.T22694821A132576063.en. Retrieved 12 November 2021.
- ^ "Common White Tern (Gygis alba) - BirdLife species factsheet". datazone.birdlife.org. Retrieved 2021-05-04.
- ^ Sparrman, Anders (1786–1789). Museum Carlsonianum, in quo novas et selectas aves, coloribus ad vivum brevique descriptiones illustratas (in Latin). Vol. fasc. 1. Holmiae: Ex Typographia Regia. Plate 11.
- ^ Wagler, Johann Georg (1832). "Neue Cippen und Gattugen der Caugthiere und Vögel". Isis von Oken (in German and Latin). Column 1223.
- ^ Jobling, James A. (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. pp. 37, 182. ISBN 978-1-4081-2501-4.
- ^ Baker, A.J.; Pereira, S.L.; Paton, T.A. (2007). "Phylogenetic relationships and divergence times of Charadriiformes genera: multigene evidence for the Cretaceous origin of at least 14 clades of shorebirds". Biology Letters. 3 (2): 205–209. doi:10.1098/rsbl.2006.0606. PMC 2375939. PMID 17284401. Baker, Allan J; Pereira, Sérgio L; Paton, Tara A (2008). "Erratum: Phylogenetic relationships and divergence times of Charadriiformes genera: multigene evidence for the Cretaceous origin of at least 14 clades of shorebirds". Biology Letters. 4: 762–763. doi:10.1098/rsbl.2006.0606erratum.
- ^ Černý, David; Natale, Rossy (2022). "Comprehensive taxon sampling and vetted fossils help clarify the time tree of shorebirds (Aves, Charadriiformes)" (PDF). Molecular Phylogenetics and Evolution. 177: 107620. doi:10.1016/j.ympev.2022.107620. Retrieved 2025-02-27.
- ^ a b c "Noddies, skimmers, gulls, terns, skuas, auks – IOC World Bird List". IOC World Bird List – Version 14.2. 2025-02-20. Retrieved 2025-02-27.
- ^ Howell, Steve N. G.; Zufelt, Kirk (2019-08-20). Oceanic Birds of the World. Princeton, New Jersey: Princeton University Press. p. 322–337. ISBN 978-0-691-17501-0.
- ^ a b c Gochfeld, M.; Burger, J.; Christie, D.A.; Kirwan, G.M. "Common White Tern (Gygis alba)". In del Hoyo, J.; Elliott, A.; Sargatal, J.; Christie, D.A.; de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions. Retrieved 16 April 2017.
- ^ a b c Pratt, H. Douglas (22 June 2020). "Species limits and English names in the genus Gygis (Laridae)". Bulletin of the British Ornithologists' Club. 140 (2): 195–208. doi:10.25226/bboc.v140i2.2020.a10.
- ^ del Hoyo, J; Collar, N.J.; Christie, D.A.; Elliott, A.; Fishpool, L.D.C. (2014). HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Barcelona, Spain and Cambridge, UK.: Lynx Edicions BirdLife International.
- ^ Niethammer, K. R., and L. B. Patrick-Castilaw. 1998. White Tern (Gygis alba). in The Birds of North America, No. 371 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. doi:10.2173/bna.371
- ^ Houston, D.C. (1978). "Why do fairy terns Gygis alba not build nests?". Ibis. 121 (1): 102–104. doi:10.1111/j.1474-919X.1979.tb05023.x.
- ^ Hawaii’s Comprehensive Wildlife Conservation Strategy, 1 October 2005
- ^ Zora, Anna; Gerlach, Justin (2021-08-23). "Giant tortoises hunt and consume birds". Current Biology. 31 (16): R989 – R990. Bibcode:2021CBio...31.R989Z. doi:10.1016/j.cub.2021.06.088. ISSN 0960-9822. PMID 34428417.
- ^ a b Island invasives : eradication and management : proceedings of the International Conference on Island Invasives. C. R. Veitch, Michael N. Clout, D. R. Towns, International Union for Conservation of Nature and Natural Resources. Species Survival Commission, Centre for Biodiversity & Biosecurity. Gland, Switzerland: IUCN. 2011. ISBN 978-2-8317-1291-8. OCLC 770307954.
{{cite book}}: CS1 maint: others (link) - ^ Robertson, Hugh A. (2017). Conservation status of New Zealand birds, 2016. Karen Baird, J. E. Dowding, Graeme Elliott, Rod Hitchmough, Colin Miskelly, Nikki McArthur. Wellington, New Zealand. ISBN 978-1-988514-23-9. OCLC 993614035.
{{cite book}}: CS1 maint: location missing publisher (link)
Further reading
[edit]- Yeung, N.W.; Carlon, D.B.; Conant, S. (2009). "Testing subspecies hypothesis with molecular markers and morphometrics in the Pacific white tern complex". Biological Journal of the Linnean Society. 98 (3): 586–595. doi:10.1111/j.1095-8312.2009.01299.x.
External links
[edit]- White tern videos, photos & sounds on the Internet Bird Collection
