Caspian Tern

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Image:Caspian tern.JPG

Common Name: Caspian Tern
Scientific Name: Hydroprogne caspia

Size: 23.6 inches (48-56 cm); 127-140 cm wingspan

Habitat: Worldwide; breeding habitat is large lakes and ocean coasts in North America (including the Great Lakes), and locally in Europe (mainly around the Baltic Sea and Black Sea), Asia, Africa, and Australasia (Australia and New Zealand). North American birds migrate to southern coasts, the West Indies and northernmost South America. European and Asian birds spend the non-breeding season in the Old World tropics. African and Australasian birds are resident or disperse over short distances.

Status: Least Concern. Global Population: 240,000 - 420,000 mature individuals. The overall population trend is increasing, although some populations are decreasing, stable, or have unknown trends. The largest breeding colony in North America is off the coast of Oregon. Increasing numbers of terns at this site have caused problems with young salmon releases, some of them endangered species. Efforts are being made to move the colony to other areas, away from the fish stocking programs. Caspian Terns are protected under the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) and the Migratory Bird of 1918 in the United States.

Diet: Fish; occasionally eat large insects, the young and eggs of other birds and rodents. They may fly up to 60 km from the breeding colony to catch fish at freshwater lakes or at sea by hovering high over the water and then falling into plunging dives.

Breeding: Male and female look alike. Adult birds have black legs, and a long thick red-orange bill with a small black tip. They have a white head with a black cap and white neck, belly and tail. The upper wings and back are pale grey while the under wings are pale with dark primary feathers. In flight, the tail is less forked than other terns and wing tips black on the underside. In winter, the black cap is still present (unlike many other terns), but with some white streaking on the forehead.

Breeding is in spring and summer, with one to three pale blue green eggs, with heavy brown spotting, being laid. They nest either together in colonies, or singly in mixed colonies of other tern and gull species. The nest is on the ground among gravel and sand, or sometimes on vegetation; incubation lasts for 26–28 days. The chicks are variable in plumage pattern, from pale creamy to darker grey-brown; this variation assists adults in recognizing their own chicks when returning to the colony from feeding trips. Fledging occurs after 35–45 days. Young Caspian Terns appear to have a difficult time learning to catch fish efficiently. They stay with their parents for long periods of time, and are fed by them even on the wintering grounds. Many young terns do not return to the nesting grounds for several years, remaining instead on the wintering areas.

Cool Facts: It is the world's largest tern and was recently reclassified from the Sterna family to Hydroprogne family. This tern is sometimes confused with the Common Tern. The Caspian Tern is much larger, has blackish feet and a less defined black tip stripe as well as a less forked tail.

Terns aggressively defend their breeding colonies. They will pursue, attack, and chase potential predatory birds, and can cause bloody wounds on the heads of people who invade the colony. The entire colony will take flight, however, when a Bald Eagle flies overhead, exposing the chicks to predation from gulls.

The oldest known wild Caspian Tern lived to be more than 26 years old. Average life span of Great Lakes Caspian Terns is estimated to be 12 years.

In New Zealand, it is also known by the Maori name Taranui.


Found in Songbird ReMix Seabirds Volume 2

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