Measurements
Both Sexes
- Length
- 18.5–21.3 in
47–54 cm - Wingspan
- 47.2–53.1 in
120–135 cm - Weight
- 18.7–27.6 oz
530–782 g
Other Names
- Sterne Caspienne (French)
- Charrán caspia, Pagaza Piquirroja (Spanish)
Cool Facts
- 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.
- The Caspian Tern aggressively defends its breeding colony. It 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 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.
- 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.
Habitat
Shore-line
- Breeds in wide variety of habitats along water, such as salt marshes, barrier islands, dredge spoil islands, freshwater lake islands, and river islands.
- During migration and winter found along coastlines, large rivers and lakes. Roosts on islands and isolated spits.
Food
Fish
Almost entirely fish; occasionally crayfish and insects.
Nesting
Nesting Facts
- Egg Description
- Buff, sparingly marked with dark spots and sometimes large irregular blotches.
- Condition at Hatching
- Eyes open. Covered with down and able to leave nest (usually after several days).
Nest Description
A scrape in ground. Lined often with dried vegetation, small pebbles, broken shells or other debris. May have elaborate rim of sticks. Nesting colonies occur on island beaches, often near colonies of other bird species.
Nest Placement
Ground
Behavior
Aerial Dive
Flies over water with bill pointing down; plunges into water to catch fish.
Conservation
Least Concern
Numbers increasing across North America: using man-made dredge spoil islands and dikes for breeding. Declining in Europe. It is listed as rare or vulnerable in some areas because of the scattered nature of breeding colonies. Beach nesting areas vulnerable to disturbance and predation.
Credits
- Cuthbert, F. J., and L. R. Wires. 1999. Caspian Tern (Sterna caspia). In The Birds of North America, No. 403 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.