Elegant Tern Thalasseus elegans 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: Study of the mitochondrial DNA of terns, along with their plumage characteristics, have suggested that the heretofore broadly defined genus Sterna is paraphyletic. Reclassification of this genus now places Elegant Tern in the genus Thalasseus. See the 47th Supplement to the AOU Check-list of North American Birds for details. Future revisions of this account will account for this change.

This medium-sized tern with a long, shaggy crest, a pink flush on its belly feathers, and a distinctive bill, has the most restricted breeding distribution of any tern in North America (see Figure 1). It nests in isolated mainland or insular colonies, among larger, more aggressive larids—primarily Heermann's Gulls (Larus heermanni) and Caspian Terns (Hydroprogne caspia). Historically, at least a dozen breeding colonies existed, but commercial egging and the introduction of mammalian predators appear to have eliminated most of them. Only 5 nesting colonies remain, and 90–97% of the world's Elegant Tern population breeds on Isla Rasa, Mexico. Such limited distribution makes the species highly vulnerable and a “Species of Special Concern” in California.

After breeding, Elegant Terns disperse north and south along the coast from their nesting colonies. In southern California, breeding success and dispersal patterns appear related to oceanographic conditions, particularly El Niño–Southern Oscillation events, which affect the distribution of key prey, the northern anchovy (Engraulis mordax). A strongly social bird, this tern nests in tight groups and, when feeding in a flock, calls frequently. Individuals generally lay a single egg but have 2 brood patches. After hatching, the chick remains in the nest scrape only a few days; then, like young of other crested terns, it joins creches—large groups of chicks in which each individual is fed by its own parents. Because foraging skills are difficult to learn in this species, postfledging parental care lasts at least 5–6 months.

Compared to most other terns, the Elegant Tern has been little studied, and most work has been concentrated at 2 California colonies. Schaffner's (Schaffner 1982 Schaffner, F. C. (1982). Aspects of the reproductive ecology of the Elegant Tern (Sterna elegans) at San Diego Bay. Master's Thesis, San Diego State Univ., San Diego. Close ) research was especially comprehensive and covered reproductive biology, individual recognition, diet, and general natural history. Kirven (Kirven 1969 Kirven, M. (1969). The breeding biology of Caspian Terns (Hydroprogne caspia) and Elegant Terns (Thalasseus elegans) at San Diego Bay. Master's Thesis, San Diego State College, San Diego. Close ) reported general breeding biology, while Evans (Evans 1973a Evans, M. U. (1973a). The reproductive ethology of the Caspian Tern (Hydroprogne caspia) breeding at San Diego Bay. Master's Thesis, California State Univ., San Diego. Close ) focused on breeding behavior. Extensive data on prey selection and diet are reported in Tordesillas 1992 Tordesillas, B. (1992). Dieta del gallito de mar elegante (Sterna elegans) durante la temporada de reproducción de 1985 y 1986 en Isla Rasa, B.C. (Aves: Laridae). M.S. Thesis, Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Mexico, D.F. Close , Loeffler 1996 Loeffler, W. E. (1996). Dietary overlap and its implications for coexistence in a recently established assemblage of nesting seabirds at the Bolsa Chica Ecological Reserve. Master's Thesis, California State Univ., Fullerton. Close , and Horn et al. 1996b Horn, M. H., P. A. Cole and W. E. Loeffler. (1996b). Prey resource base of the tern and skimmer colonies at Bolsa Chica Ecological Reserve, Orange County, and the Western Salt Works, South San Diego Bay. Carlsbad, CA: U.S. Fish and Wildl. Serv. Close .