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Whiskered Tern

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[edit] Taxonomy

Whiskered Tern is a seabird of the tern family Sternidae belonging to genus Chlidonias. There are 3 geographical races. Namely, C. h. hybridus found in warmer parts of Europe and Asia. C. h. delalandii is found in east and south Africa, and the paler C. h. javanicus from Java to Australia.


Class: Aves

Order: Charadriiformes

Family: Sternidae

Genus: Chlidonias

Species: Chlidonias hybridus

Subspecies: Chlidonias hybridus hybridus

Subspecies: Chlidonias hybridus delalandii

Subspecies: Chlidonias hybridus javanicus


[edit] Distribution

This species breeds in highly disjunct (separated) populations across southern Europe and Asia, in south-eastern Africa and Madagascar, and in Australia. It occurs as a migrant, vagrant or winter visitor throughout Europe, Africa and Australia.


[edit] Physical Characteristics

Whiskered Tern is long and bulky. Wings are relatively broad and bill rather strong. Tail shows a deep notch and legs are slightly longer than in other terns. Wings are well projected behind the tail. The Whiskered Tern is a small, marsh tern with a slightly forked tail. The Whiskered Tern in breeding plumage has a black crown and white cheeks and sides of neck. The upperparts, upperwings and tail are medium grey, the underparts dark grey to slate grey and the undertail is white with the underwings mainly white. The eye is brown and the bill and legs are red. The sexes are similar. Non-breeding Whiskered Terns are similar to breeding adults except the underparts are white, the forehead is white and the dark crown is streaked white. The lores (area between bill and eyes) and ear coverts are black while the bill and legs are also blackish.

Young birds have a pale grey back, rump and upper wings, heavily mottled medium-brownish grey, especially along leading edge of inner wing, and the tail is pale grey, edged black. The Whiskered Tern is also known as the Marsh Tern or Black-fronted Tern. In summer plumage their black cap and white cheeks makes them look more like Common Terns than Black Terns but they have the short, broad wings and tails typical of 'marsh terns' and their underparts are such a deep grey that the white cheeks stand out boldly. In juvenile plumage, they have a dark mantle recalling the saddle effect which is a key feature of White-winged Black Terns. In a Whiskered Tern, however, this saddle is paler, browner and is noticeably interrupted by pale scaly markings. Also, the rump is not as conspicuously white as on a White-winged Black Tern and the wings of a Whiskered Tern are a more uniform grey. These features are also helpful in winter plumage when the crown goes mostly white, leaving a definite dark horizontal line going back from the eye.

Whiskered Tern gives a raucous "kersh" when flying high in the sky. This call resembles a nail's squeaking on a table. Other calls include a "kek" often repeated.


[edit] Habitat

The Whiskered Tern prefers shallow terrestrial freshwater wetlands, freshwater swamps, brackish and saline lakes, floodwaters, sewage farms, irrigated croplands and large dams.

[edit] Diet

Whiskered Terns eat mainly small fish, amphibians, crustaceans, insects and their larvae. There are three main methods of feeding, plunging, dipping and hawking. Plunging involves a hover then dive, with wings raised, from 2 m - 4 m above water. They may also hover and dive to take insects in paddocks. Dipping means that they fly low over water, skimming the surface to take insects from on or just below it. Hawking is taking insects (up to 40mm long) on the wing; Whiskered Terns may hawk over dry plains.


[edit] Behavior

Whiskered Tern is migratory. They fly continuously above water, very excited for capturing preys in the middle of the buzz of insects' clouds. When they select a prey, they soar while rushing forward in a rapid dive, with motionless wings, catching it immediately.

When reproduction is finished, they gather at dusk in large roosts where several thousands of birds run up. At dawn, they fly again to feeding areas where they spend more of half day, moving continuously.


[edit] Breeding

The breeding season of the Whiskered Tern is erratic. They breed in loose colonies in large, often temporary, inland swamps and marshes. The nest is a rough raft of vegetation, either floating or moored. The sexes share nest-building, incubation and care of the young. A single brood is usually raised in a season. Whiskered Tern builds a floating platform which is an amount of aquatic vegetation. Nest is built above this platform by both parents. It is made with grass and reeds, floating on water. Female lays 3 to 5 greenish eggs spotted with dark brown, of 39mm in size. Incubation lasts about 14 to 18 days, shared by both adults. Laying takes place from April to June. Chicks, raised by both parents, leave the nest at about 12 to 14 days after hatching, and fly at about three weeks of age. Whiskered Tern reaches its sexual maturity at 2 years.


[edit] Threat

Whiskered Terns populations strongly vary due to natural features. They are mainly threatened by habitat destruction, due to wetlands drainage and canalizing of rivers, water eutrophication, disappearance of submerged vegetation and tourism and aquatics sports disturbances.


[edit] References

  • The Clements Checklist of Birds of the World: James F. Clements, Jared Diamond, John W. Fitzpatrick.
  • Wetlands International Waterbird Population Estimates - Fourth Edition.
  • Ali, S. & Ripley, D. (1964-74 ) Handbook of the Birds of India & Pakistan (Vols. 1-10). Bombay: OUP
  • Grimmet, R Inskipp, T., & Inskipp, C. (1998) Birds of the Indian Subcontinent. UK: A&C Black.
  • Inskipp, T. et al. (1996) An Annotated Checklist of the Birds of the Oriental Region. Sandy, UK: OBC.
  • Kazmierczak, K. & van Perlo, B. (2000) A Field-Guide to the Birds of the Indian Subcontinent. UK: Pica Press
  • BirdLife International (2004).
  • IUCN Red List of Threatened Species. IUCN 2006
  • Bridge, E. S.; Jones, A. W. & Baker, A. J. (2005): A phylogenetic framework for the terns (Sternini) inferred from mtDNA sequences: implications for taxonomy and plumage evolution. Molecular Phylogenetics and Evolution
  • Harrison, Peter (1988): Seabirds (2nd edition). Christopher Helm, London
  • Peterson, R.T., Mountfort, G. & Hollom, P.A.D. (1993) Collins Field Guide- Birds of Britain and Europe.