Tuesday, 12 August 2014

Caspian tern

Hydroprogne caspia

Photo by Vladimirs Suščinskis (Ornitofaunistika)

Common name:
Caspian tern (en); gaivina-grande (pt); sterne caspienne (fr); pagaza piquirroja (es); raubseeschwalbe (de)

Order Charadriiformes
Family Sternidae

This species has a cosmopolitan but scattered distribution, breeding in the Baltic sea, in eastern Europe and central Asia from the southern Ukraine to western Mongolia, along the coast of China, in West Africa, around the eastern Mediterranean, in Pakistan, in Sri Lanka, in Madagascar and the coasts of southern Africa, in Australia and New Zealand, in the great lakes of North America, in the western United States and along the coast of Texas. Outside the breeding season they also spread along most of the coasts and inland wetlands of Central America, Africa and India.

The largest tern in the world, the Caspian tern is 48-56 cm long and has a wingspan of 127-140 cm. They weigh 580-780 g.

These birds are found in various coastal and inland wetlands, including coastal waters and estuaries, bays, harbours, coastal lagoons, saltmarshes, lakes, inland seas, large rivers, creeks, reservoirs and sewage ponds. They breed in sandy beaches, sand dunes, rocky coasts, sheltered reefs and islands with sparse vegetation and flat or gently sloping margins surrounded by clear, shallow, undisturbed waters.

They feed mainly on small and medium-sized fish, as well as the eggs and young of other birds, carrion, aquatic invertebrates such as crayfish, flying insects and earthworms.

Caspian terns can breed all year round, varying among different parts of their range. They breed most often in large colonies, often together with other terns, although they can also breed in smaller colonies or even in isolated pairs. Each pair nests on a shallow depression in sand or gravel, or sometimes on flat stone, where the female lays 2-3 buff-coloured eggs with dark spots and blotches. The eggs are incubated for 22-28 days and the chicks are able to leave the nest after a few days, but are fed by both parents until they fledge 35-45 days after hatching.

IUCN status - LC (Least Concern)
This species has a very large breeding range and the global population is estimated at 240.000-420.000 individuals. The overall population trend is increasing, although some populations are decreasing, stable, or have unknown trend. Population in North America have increased by 38% per decade over the last 4 decades.

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