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Caspian Tern is the largest of terns in Kazakhstan. It is 6-7 times heavier than Common Tern. In comparison to Gulls it is larger than Black-headed and Common Gulls and some lesser than Caspian Gull. The adult Caspian Terns in breeding plumage have black crown and nape; feathers of nape are long and form small crest. Back is bluish-grey, uppertail and tail feathers are lighter than back, almost white. Bill is large, red; legs are black with orange soles. Eyes are dark-brown. In winter plumage adult birds have white crown with black longitudinal streaks; fore-head have black spots too. Juvenile birds have white crown with brownish longitudinal streaks and spots. feathers on the back are grey with buffy edges and brownish little arrow-shaped spots. Tail feathers have brownish terminal spots and buffy tips. Bill is orange, legs are black. Sizes: wing 380 – 400 mm, tarsus 40 -47 mm, bill 60 – 75 mm. Weight: 500 – 700 grams.

Biology

Caspian Tern is common, in places rare breeding migrant. It inhabits marine islands, large salty lakes and fresh reservoirs with islands and with fish in these or in nearby lakes. It appears by small flocks in the end April - mid-May. Caspain Tern breeds in dense colonies on sandy, cockle-shell or pebbly islands with scarce vegetation or without them. Some colonies numbered up to several hundred pairs. It nests often with large Gulls, other Terns and waders. Nest is shallow (4-7 cm) hole without lining or with some dry grass; nests placed on 0.8-4.0 m each of other. Clutches of 1-3 eggs founded in May - mid-July. Both parents incubate for 20-22 days and feed juveniles, which begin to fly at the age some more than one month. Flying juveniles recorded in end June - early August. Repeated nesting after washing away of colonies on low islands by the strong gales is not rare. Caspian Terns very actively defend their colonies; loudly crying birds attack each predator closing to their nests. Even such predators as Caspian Gulls and Crows can't close to colony of Caspian Terns. Caspian Tern eats mostly fish. In addition to fishes it eats cancers and sometimes eggs and chicks. After the beginning of juveniles flying the Caspian Terns live in wanders. They don't form large flights but wander alone or in small groups up to 5-7 birds. Wanders are very wide; wandering birds were recorded not only to south from the breeding areas but in each course, including north direction, sometimes in very far distance. Autumn migrations begins in August, majority of birds leaves breeding areas up to end of August, linger singles recorded in mid-September - early October.

References

"Птицы Казахстана" том 2. Алма-Ата, 1962. Э.И.Гаврилов. "Фауна и распространение птиц Казахстана". Алматы, 1999. Gavrilov E. I., Gavrilov A. E. "The Birds of Kazakhstan". Almaty, 2005.