Caspian Tern (Hydroprogne caspia)

From CopperWiki

As large as a big gull, the Caspian Tern is the largest tern in the world. Its large coral red bill makes it one of the most easily identified terns throughout the world. Terns are seabirds from the Sternidae family, previously considered a subfamily (Sterninae) of the Laridaegull family.

Earlier Caspian tern was placed in typical Tern genus Sterna but after 2005 pioneering work by Bridge, Jones and Baker on a phylogenetic framework for the terns inferred from mtDNA sequences; they were placed in Hydroprogne genus.

[edit] Distribution

Caspian tern found in North America, northeast Europe (Baltic), Africa, Madagascar, Central and South Asia and Australia. They mainly inhabit the coasts but some are found inland like in New Zealand. Eurasian birds spend their winter in the Old World tropics. Their breeding habitat is large lakes and ocean coasts in North America including the Great Lakes and locally across much of Europe, Asia, Africa, Australia and New Zealand. In India, Caspian Tern breed in some parts of Gujarat.

[edit] Physical Characteristics

Gull-like in appearance, the Caspian Tern is one of the largest terns in the world. It has pale gray upperparts, and a white throat, breast, flanks, rump and tail. The all-black cap on the mature adults extends forward to below the eye. The large size and massive red bill are usually enough to allow easy identification. Males and females are of like plumage, though the males average slightly larger. This species is generally 47 to 54 cm long, with a wingspan of approximately 127 cm. The Caspian Tern has a dark red, stout, rather massive bill, with a dark gray colored tip. The bill on juvenile birds is more orange-red and their upperparts are paler than on the adults.

The vocalization of this species is described as a deep, harsh, heron-like scream "aaayayaum". Several other vocalizations are described as the contact, alarm, gakkering, fish (advertising), and female begging calls. Call a raspy "kowk." Juvenile begging call a high pitched whistling; heard frequently during migration and in winter.

Habitat

Caspian Terns prefer islands within large lakes or reservoirs, where sandy or stony beaches are used for nesting. The species has also been noted to utilize rivers. They breed on sand, shell or rocky islands, occasionally on salt marshes. They winter along coasts and on large inland lakes and reservoirs.

[edit] Diet

The diet of the Caspian Tern consists mostly of fish, but is supplemented with aquatic invertebrates, especially crustaceans. Caspian Terns will occasionally pirate food from other birds. Chicks are fed a steady diet of fish. Caspian tern can take larger fish than most other terns. They forage on freshwater lakes, inland seas, and coastal estuaries.

[edit] Behavior

Caspian Terns feed by hovering over the water, and diving for fish schooling near the surface. Crustaceans may be taken in the same fashion, and pirating may also yield supplemental food. This large tern protects its colonies vigorously, fiercely attacking potential predators with the bill and feet. It is not as gregarious as other terns, and its flight is quite gull-like. The Caspian Tern is monogamous, and nest in small to large colonies on sand or gravel beaches, or occasionally in marshes. The courtship of the Caspian Tern is highly complex and variable, and includes aerial chasing of females by males. Both members of the pair construct the nest by making a shallow depression in the ground, and lining it with seaweed, moss, algae, or fine grass. The nest may be concealed among rocks or driftwood.

[edit] Breeding

The Caspian Tern is monogamous, and nest in small to large colonies on sand or gravel beaches, or occasionally in marshes. They are Colonial nesting birds. Nesting may occur in association with other species, occasionally with Cormorant and gull (Larus) species. Their nesting begins by late May or early June. The nest, built by both sexes, is usually a shallow, sparsely lined, or unlined hollow. Clutch size of the smooth, non-glossy sub-elliptical eggs is usually 2 to 3. The eggs sometimes have a finely textured surface, and are light buff in coloration and are generally evenly marked with specks or small blotches of black, brown, olive, and pale gray. Incubation, by both sexes, lasts for 20 to 22 days. Both parents tend young, which leave the nest in a few days, and first fly at 4 to 5 weeks. Parental care (feeding) may extend up to 5 to 7 months after fledging; their parents feed them for the longest period of time for any tern, up to 7 months post-fledging. They nest singly or usually in colonies of up to several thousand pairs.

[edit] Threat

Predation is one of the largest mortality factors at a colony. In the past, tern eggs were even collected for food by humans

[edit] When rare species eat endangered ones

In the mid 1980s, observers noted Caspian terns breeding on Rice Island in the Columbia River. Studies in the late 1990s revealed that salmon smolts made up 74 percent of the birds' diet. The birds caught 10.2 million of these young salmon, representing 11 percent of those swimming down the Columbia. In an attempt to lower the toll, biologists tried to persuade the colony to move to East Sand Island, closer to the mouth of the Columbia. The new location offered more species of fish as alternative food.

[edit] See Also

• Black-headed Gull (Larus ridibundus)
• Crab Plover (Dromas ardeola
• Great Black-headed Gull (Larus ichthyaetus)

[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.
• [1]