Bird of the Month: Caspian Tern
By Hugh Jennings
PC: Micl Thompson (Caspian Tern)
Scientific Name: Sterna caspia
Length 21 in
Wingspan 50 in
Weight 1.4 lb
AOU Band code CATE
The Caspian Tern (CATE) is about 21” long with a wingspan of 50” and weight of 1.4 lb (660g). The genus name Sterna (STIR-nah) is Latin stemming from Anglo-Saxon stearn , tern. The species name caspia is Latin of Caspian Sea where a specimen was collected for which the species was named by Pallas in 1770. This is the largest of the terns. The CATE nests on five continents. In North America, it is common along both coasts and locally inland, mainly around large bodies of water. In Washington state, non-breeders are abundant summer residents in coastal bay in inland marine waters.
It is a fairly common summer resident in Eastern Washington on a few major lakes and the Columbia River. They are often seen flying constantly 20 to 50 feet above the water, with bill pointing downward, looking for fish. It catches fish by diving completely underwater, but also may pick fish off the water surface. It may steal fish from other seabirds.
Its summer plumage: large, crested, black cap and big blood-red bill (sometimes the bill is slightly darker at the tip). The bird is overall gray above and light below. The plumage in winter is like the summer, but the cap is splotchy and gray. Juveniles are like winter adults, but bill is orange and upper parts lightly marked with dark bars and V’s. The adult calls include a low, harsh scream “kwok” and “cahar”. The Caspian Tern first breeds at about 3 years. This tern nests singly or in colonies. The nest being a depression in the ground lined with grasses and seaweed, located on sandy beaches. There are usually 2-3 eggs which are pinkish with darker markings. Incubation is 20-22 days. The young may leave the nest a few days after hatching. If colony is not disturbed, the young may stay at the nest until ready to fly. Both parents bring food to the young. The age at first flight is 28-35 days. The young terns are noted for their long adolescence, with the young dependent on their parents for many months. Even in late winter many adult Caspian Terns are trailed by a begging youngster from the previous nesting season. During migration, the terns fly high with bill pointing forward. It is the least sociable of all terns and travels singly or in small groups. Inland breeders move to the coast and fly south for winter, some wintering south to West Indies and northern South America.