Distribution

Breeding Range

Figure 1 . Widely distributed breeder in North America. Nests on open sandy beaches, sandbars, unvegetated islands, and a variety of deposited materials along the coasts of oceans, bays, inland rivers, large lakes and reservoirs, as well as in alkali wetlands of the Great Plains. Has recently (at least since 1951) begun breeding on flat gravel rooftops in certain coastal areas, particularly where natural habitats have been disturbed or lost. May change breeding locations frequently in response to changing environmental conditions. Breeding range described below is based on recent surveys as cited. Breeding colonies have existed at many other locations in the past.

Coastal U.S. Breeds locally at coastal sites from s. Maine south to s. Florida, and along both shores of Chesapeake Bay north to Baltimore and Queen Annes Cos., MD (Robbins 1996); also along extreme s. Delaware Bay. Breeds locally along Gulf Coast from s. Florida west to s. Texas (Portnoy 1977, Blacklock et al. 1978, Toups and Jackson 1987, Spendelow and Patton 1988, Robertson and Woolfenden 1992), and locally along Pacific Coast from San Francisco Bay in California south to Mexican border (Small 1994, B. Massey pers. comm.).

Inland U.S. Breeds locally from Missouri, Ohio, and Mississippi Rivers west throughout Great Plains to e. Montana, e. Colorado, and e. New Mexico. Breeds locally along Missouri River in extreme e. Montana (Bergeron et al. 1992); from Burleigh Co., ND (Stewart 1975), south to Sully Co., SD; from Charles Mix Co. south to Union Co., SD; in Pottawattamie Co., IA (Peterson 1995, Jackson et al. 1996), and in Nebraska upriver from confluence with Platte River near Omaha (E. Wilson pers. comm.). Not on Missouri River in Missouri (J. Wilson pers. comm.). Breeds along Ohio River in Carlisle, Hickman, Fulton, and Livingston Cos., KY (Palmer-Ball 1996). Breeds along Mississippi River from Alexander Co., IL (Bohlen 1989), and Cape Girardeau Co., MO (Robbins and Easterla 1992), south through Tennessee and Arkansas to East Carroll, Madison, and Tensas Parishes, in n. Louisiana, and from Saint James Parish east to Orleans Parish in s. Louisiana (S. Cardiff pers. comm.).

Other inland breeding areas include the following. In Colorado: Adobe Creek and Nee Noshe Reservoirs, Kiowa Co., and Horse Creek Reservoir, Otero Co. (Andrews and Righter 1992). In S. Dakota: along Cheyenne River in Meade Co. (Peterson 1995). In Nebraska: Platte River throughout from Lincoln Co. eastward, on Lake McConaughy of North Platte River, Loup River from Nance Co. to confluence with Platte, Elkhorn River throughout, and Niobrara River in Keyapaha and Boyd Cos. (Johnsgard 1979, E. Wilson pers. comm.). In Kansas: Quivira National Wildlife Refuge (Stafford Co.) and on Cimarron River in Meade Co.; none documented on Arkansas River or Missouri River in Kansas (Thompson and Ely 1989, EMK, LAH, K. Brunson pers. comm.). In Oklahoma: Arkansas River downstream from Ponca City, Salt Fork of Arkansas River at Great Salt Plains Lake only, Cimarron River throughout, s. Canadian River from Eufala Lake westward to Texas, and Red River from Arkansas west to at least Highway 44 south of Lawton, OK, and Optima Lake in Texas Co., OK (Baumgartner and Baumgartner 1992, Hill 1993a, M. Howery pers. comm.)., In Texas: Canadian River (contiguous with s. Canadian River in Oklahoma) in Hemphill and Roberts Cos.; Red River adjacent to Oklahoma and Prairie Dog Town Fork in Childress Co.; upper drainage of Brazos River between Wichita Falls and Abilene; Trinity River drainage form Dallas scattered downstream; and Rio Grande drainage at Falcon Reservoir (Zapata Co.), Lake Casa Blanca (Webb Co.), and Amistad Reservoir (Val Verde Co.) (Sidle et al 1988, K. Benson pers. comm., BCT). In New Mexico: Bitter Lake National Wildlife Refuge, Chaves Co. (Hubbard 1978). In Arkansas: locally along Arkansas River (Conway, Desha, Johnson, Perry, and Sebastian Cos.; James and Neal 1986). In Louisiana: along Red River in Caddo, Bossier, and Red River Parishes (S. Cardiff pers. comm.). In S. Carolina: possible breeding at Lake Moultrie, Berkeley Co. in May–Jun 1991 (McNair and Post 1993). Considered an increasing inland breeder (frequently on rooftops) in Florida, but sites not specified (Robertson and Woolfenden 1992).

Middle America. In Mexico, breeds locally at coastal sites along both coasts of Baja, locally along Pacific Coast from Sonora south to at least Oaxaca, along Atlantic Coast in n. Tamaulipas, and along coast of n. and e. Yucatán Peninsula. Also breeds in Belize and w. Honduras (Howell and Webb 1995).

Caribbean. Breeds locally throughout the region, including Bahamas, Cuba, Jamaica, Hispaniola, Puerto Rico, and locally in Lesser Antilles south to Grenada (except Redonda, Montserrat, St. Lucia, St. Vincent, and Barbados; Evans 1990).

South America. Breeds on islands off coast of Venezuela, including Aruba, Curaçao, Bonaire, Los Roques, Margarita, and probably Aves Is., and other islands. Recorded breeding at Morrocoy, Falcón, on coast of Venezuela in 1976 (Voous 1983). Status in Trinidad uncertain.

Winter (Or Marine) Range

Winters primarily in marine coastal areas. Rarely winters as far north as Gulf Coast in U.S.; regularly winters throughout Pacific coast of s. Mexico, and along eastern coasts of Mexico, Central and South America, south to n. Argentina and s. Brazil. Largely absent from Caribbean and Netherlands Antilles breeding areas in winter; unknown where s. Caribbean breeders winter but flocks of Least Terns have been seen in winter in offshore waters of Venezuela (Voous 1983, Raffaele 1989). Small numbers seen in Jan in Colima, Mexico, including some banded in s. California; not found during focused search of Pacific coast of Costa Rica during Jan (JLA and B. Massey unpubl. data). Recorded on Suriname coast in every month but Dec (Spaans 1978). Rarely occurs as far south as Buenos Aires, Argentina (Meyer de Schauensee 1970, Schulenberg et al. 1987). Many remain in wintering areas through their first year (Haverschmidt 1968). In Colima, Mexico, during early Apr, about 60% of Least Terns at known wintering area were first-year birds (JLA). Limited band recoveries make it impossible to define winter areas for Atlantic and Gulf coastal versus interior populations. Banded Least Terns from temperate North America appear to pass through the s. Caribbean to wintering sites on South America coast (Thompson 1982, Voous 1983).

Almost no records outside Americas, because of similarity to and recent separation from Little Tern, but a small tern with characters of Least Tern was reported in East Sussex, England, during 1982–1993 (Chandler and Wilds 1994).

Dramatic fluctuations are documented in populations and distribution of colony sites across species’ breeding range—e.g., New York (Weil 1932), Georgia (Tomkins 1959), California (Massey 1974), Mississippi (Jackson and Jackson 1985). Breeding distribution in 1990s is largely similar to historic geographic extent of breeding range a century earlier, but colony distribution within that area is much more fragmented, especially for interior and California populations (Massey 1974, Sidle et al. 1988). Historic breeder in Bermuda but now only vagrant there (Amos 1991).

None given by Brodkorb (1967), Olson (1985), or Feduccia (1996).