Caspian Tern Hydroprogne caspia Scientific name definitions

Editor's Note: Due to a recent taxonomic revision, this species account is still being edited and may contain content from an earlier version of the account.

Editor’s Note (November 2017): Maps, rich media, and text have been updated to reflect a taxonomic change for this species. This account is being revised and may contain content from an earlier version of the account.

The largest tern, the Caspian Tern is distinguished by its massive coral red bill, hoarse vocalizations, and similarities to large Larus gulls in flight. Bent (1 Bent, A. C. (1921). Life histories of North American gulls and terns. United States National Museum Bulletin 113. Close ) described it as “king of all the terns . . . the dominant ruling spirit in the colonies . . . the largest, strongest and fiercest of the terns.” Its broad, expansive wings allow it to soar and wheel dramatically like a gull, and its slow wing beats power a graceful flight that is strong and swift. Its loud raucous call is heard frequently in breeding colonies, especially when nesting birds are approached by intruders.

With the exception of Antarctica, the Caspian Tern occurs on all continents, breeding and/or wintering along coastlines and inland along rivers, lakes, and marshes. In North America, it breeds at scattered localities along the Pacific, Atlantic, and Gulf Coasts, and inland in the western interior, Prairie Provinces of Canada, and along the Great Lakes. It generally nests in colonies. Flat rocky islands, beaches, and sandy shores, sparsely vegetated and littered with driftwood, are typical breeding habitat for this species. Its nests range from mere scrapes in sand or gravel to clam shell or vegetation lined depressions with elaborately built-up rims that contain mollusk shells or crayfish appendages. Changing water levels often lower nesting success, as does competition with gulls and harassment by predators and humans. Birds desert colonies readily if disturbed early in the breeding season.

Caspian Terns from North America winter along the southern portions of the Atlantic and Pacific Coasts and the Gulf Coast, as far south as Colombia and Venezuela.

This species lives almost entirely on fish, capturing them in shallow surface waters near breeding and wintering sites. When fishing, flies with bill pointing downward; spotting a fish, it hovers, flexes its wings and plunge-dives, usually submerging completely.

Populations of this tern have increased in most parts of its North American range, owing to protection of the species and its traditional nesting sites, and to human alterations in habitat. In Europe and Africa, however, it has declined and is now extinct or rare in parts of its former range (2 Cramp, S. (1985). The Birds of the Western Palearctic. Volume 4. Terns to Woodpeckers. Oxford University Press, Oxford, UK. Close ).

In North America, the Caspian Tern has been studied mainly during the breeding season in freshwater and marine habitats. Information on phenology, nesting, parental behavior, mate and site fidelity, habitat, and diet is available from studies conducted in the Great Lakes and on the Pacific and Gulf Coasts (3 Baltz, D. M., G. V. Morejohn and B. S. Antrim. (1979). Size selective predation and food habits of two California terns. Western Birds 10:17-24. Close , 4 Quinn, J. S. (1980). Feeding rates, parental investment and brood reduction in the Caspian Tern. Master's Thesis, Brock Univ., St. Catharines, Ontario. Close , 5 Clapp, R. B., D. Morgan-Jacobs and R. C. Banks. (1983c). Marine birds of the southeastern United States and Gulf of Mexico, Part 3. Charadriiformes. Washington, D.C.: U.S. Fish Wildl. Serv., Office of Biol. Serv. Close , 6 Cuthbert, F. J. (1985a). Intraseasonal movement between colony sites by Caspian Terns in the Great Lakes. Wilson Bulletin 97:502-510. Close , 7 Cuthbert, F. J. (1988). Reproductive success and colony-site tenacity in Caspian Terns. Auk 105:339-344. Close , 8 Ewins, P. J., D. V. Weseloh, R. J. Norstrom, K. Legierse, J. H. Auman and J. P. Ludwig. (1994b). Caspian Terns on the Great Lakes: organochlorine contamination, reproduction, diet, and population changes, 1972-1991. Canadian Wildlife Service Occasional Paper 85. Close ). Band recovery data have illuminated movement patterns and overwintering sites for Great Lakes and Pacific Coast populations (9 Ludwig, F. E. (1942). Migration of Caspian Terns banded in the Great Lakes area. Bird-Banding 13:1-9. Close , 10 Ludwig, J. P. (1965b). Biology and structure of the Caspian Tern (Hydroprogne caspia) population of th Great Lakes from 1896-1964. Bird-Banding 36:217-233. Close , 11 Gill, Jr., R. and L. R. Mewaldt. (1979). Dispersal and migratory patterns of San Francisco Bay produced herons, egrets and terns. North American Bird Bander 4:4-13. Close , 12 Gill, Jr., R. and L. R. Mewaldt. (1983). Pacific coast Caspian Terns: Dynamics of an expanding population. Auk 100:369-381. Close ).