Caspian Tern
Sterna caspia

Overview

Key Features:

In summer the black cap above the bright red bill is very distinctive.

Similar Species:

Elegant Tern (Sterna elegans)

Primary Common Name:

Caspian Tern

General Grouping:

Seabirds and shorebirds

Geographic Range:

World-wide

Sterna caspia has a worldwide range, present on every continent except for Antarctica.

Habitats:

bay (rocky shore), bay (sandy shore), estuary

Notes:

Sterna caspia occupies coastal waters, lakes, rivers, fresh and salt water wetlands, especially estuaries, coastal bays and beaches. They prefer protected waters to open ocean. Sterna caspia breeds in a variety of habitats along the water, including salt marshes, barrier islands, dredge spoil islands, freshwater lake islands and river islands. They usually nest on low sand or gravel with sparse vegetation.

Abundance:

Relative Abundance:

Sterna caspia is very common from mid-March into October, with more birds present in the south than in the north of California. They cling to the coast and are seldom encountered more than a short distance off shore.

Species Description:

General:

Sterna caspia is the largest tern and is one of the most widespread tern species in the world. Its large coral red bill makes it also one of the most easily identified terns throughout its worldwide range.

Distinctive Features:

Sterna caspia has a black cap, white body and large, thick and brilliant red with dark tip bill. It has silvery gray back and wings with white underparts, rump and tail. The legs and feet are black and the tail is short and slightly notched.

The summer breeding adult has a black cap and the bill is bright red. In contrast the winter nonbreeding adult has a blackish cap that is streaked white and the bill is red with a black tip. The immature Sterna caspia looks like the winter adult but has dark scalloping on back and an orange bill.

Sterna caspia can be distinguished from the Royal Tern, Sterna maxima by its much thicker bill, less deeply forked tail and the lack of a fully white forehead. Sterna caspia is heavier and larger in all regards than Sterna maxima or the Elegant Tern, Sterna elegans and has bolder black underwing tips. The bill of Sterna caspia is also much redder than the other two smaller species. The call of Sterna caspia adults is harsh, while juveniles have a distinctive whistling call.

Size:

Sterna caspia can grow to a size of 53 cm with a wingspan of 127 cm.

Natural History:

General:

Sterna caspia is in the Gull and Tern Family, Family Sternidae. This tern is less gregarious than other terns and if often found solitary or in pairs and generally nests in smaller colonies. They can, however, be quite aggressive, especially when catching fish. Sterna caspia will also aggressively defend its breeding colony by pursuing, attacking and chasing potential predatory birds. Their broad wings allow them to soar by flapping with strong, slow wing-beats. Young Sterna caspia stay with their parents for a long periods of time and appear to have a difficult time learning to catch fish efficiently. The average life span of Sterna caspia is about 12 years with the oldest known wild individual living to be more than 26 years old.

Predator(s):

Eggs on nesting beaches are vulnerable to predation. The major predator to Sterna caspia chicks is the Herring Gull Larus argentatus. Other predators include fox Vulpes vulpes and coyotes Canis latrans.

Prey:

Sterna caspia feeds mostly on fish, especially those that swim near the surface of the water. They occasionally eat crayfish, insects and the young and eggs of other birds.

Feeding Behavior:

Carnivore

Notes:

Sterna caspia dives for fish. It will hover high over the water and then point its bill down, plunging into the water and catching fish.

Seasonal Behavior

January - December

Migration:

Some Sterna caspia are medium-distance migrants, while others travel greater distances.

Overall during the summer they breed in scattered locations across North America, including along the Pacific Coast, in central Canada, around the Great Lakes, in west-central United States, along the Gulf Coast, and along the Atlantic Coast. They can also be found breeding in Eurasia, Africa, Australia, and New Zealand. During the breeding season, Sterna caspia is found on islands and isolated spits.

During the winter it can be found along the Pacific Coast from southern California southward to Guatemala, and along the Atlantic and Gulf coasts from North Carolina westward to Texas, Mexico, and southward to Honduras. It can also be found wintering in the West Indies, Panama, and northern South America, as well as Africa, Mediterranean, Indian Ocean and India. During these winter months, Sterna caspia is found along coastlines, large rivers and lakes.

June - August

Reproduction:

Sterna caspia begins breeding at the age of three years. They nest in colonies in areas with no vegetation, such as beaches, and are often on islands. The nest is located on the ground and can range from a scrape in the sand to a depression lined with a sturdy rim of vegetation, sticks, pebbles, mollusk and crustacean shells and other debris. Both parents help build the nest and both incubate the 1 to 3 eggs for about three weeks. Within a few days of hatching, the young may leave the nest, but they stay nearby. Alternatively, they may remain at the nest until they are ready to fly. The young Sterna caspia first fly about a month after hatching, but may stay with and be fed by both parents for many more months.

References

Related Information

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