Distribution

Breeding Range

Figure 1 . Breeds at scattered locations throughout North America. Largest area of fairly contiguous breeding occurs on freshwater lakes and marshes from se. Alberta (Lac Saint Ann, Lac la Biche, and Cold Lake regions south to Verdigris Lake and Pakowki Lake, and probably northwest to Winagami Lake and Fairview; Gerrard and Whitfield 1971, Semenchuk 1992), east across southern half of Saskatchewan, except southwest corner where breeding suspected but unverified (Gerrard and Whitfield 1971, Smith 1996); sw. Manitoba north to Lake Winnipeg (Koonz and Rakowski 1985); eastern half of N. Dakota (Stewart 1975); ne. South Dakota south to at least Sully and Deuel Cos. (Peterson 1995); w. and s.-central Minnesota, east to at least Clearwater, Anoka, and Jackson Cos. (Janssen 1987); and n.-central Iowa within region bounded by Osceola, Dickinson, Pocahontas, Hamilton, and Cerro Gordo Cos. (Dinsmore 1996).

In w. North America, also breeds in extreme se. British Columbia at Creston (Goossen et al. 1982); s.-central Washington (Grant Co. and south and west along Columbia River to Klickitat Co.; Smith et al. 1997); ne. (Morrow Co.) and s. (east of Cascades in Klamath, Lake, Harney, and sw. Deschutes Cos.) Oregon (Gilligan et al. 1994); ne. (Siskiyou, Modoc, Lassen, and Plumas Cos., south, east of Cascades, to Mono Co.), w.-central (around San Francisco Bay, mid-Central Valley, and San Joaquin Valley), south-coastal (locally at least in Monterey, Orange, and San Diego Cos.), and se. (irregularly at Salton Sea) California (Small 1994); n. Baja California Norte (Laguna Figueroa; Howell and Webb 1995); n. and w.-central Nevada (T. Floyd pers. comm.); s. Idaho (Snake River region; Burleigh 1972, Stephens and Sturts 1998); n. Utah (Behle 1981); scattered locations throughout Montana (Montana Bird Distribution Committee 1996) and Wyoming (Oakleaf et al. 1992); central Colorado (Jackson and Alamosa Cos.; Nelson 1998); s.-central South Dakota (Bennett Co.) and w. Nebraska (Cherry, Sheridan, and Garden Cos.; Johnsgard 1979, Peterson 1995, Sharpe et al. 2001); and central Kansas (Barton Co.; Thompson and Ely 1989).

In Great Lakes region, e. Wisconsin (Wisconsin Breeding Bird Atlas [BBA] unpubl.); extreme ne. Illinois (at least formerly in Lake Co.; Bohlen 1989); e. Michigan (Mackinac and Chippewa Cos. of Upper Peninsula, and around Saginaw Bay, and St. Clair, Macomb and Monroe Cos. in Lower Peninsula; Scharf 1991); and extreme s. Ontario (along St. Clair River and Lake Erie, Lambert, Kent, and Haldimand-Norfolk Cos.; Peck and James 1983, McNicholl 1987).

Along Atlantic Coast in Massachusetts (Plum I.; single breeding record in 1991; Veit and Petersen 1993); s. New York (Long I. occasionally; Connor 1988); New Jersey (Cape May, Atlantic, Ocean, and Salem Cos.; Walsh et al. 1999); Delaware (at least Sussex Co.; Hess et al. 2000); Maryland (Dorchester, Somerset, and Worcester Cos.; Brinker 1996); Virginia (Accomack, Northhampton, and Mathews Cos.; Virginia BBA unpubl.); N. Carolina (along Pamlico and Core Sounds; Potter et al. 1980); and S. Carolina (Bull’s Bay; Post and Gauthreaux 1989).

Also along Gulf Coast of Tamaulipas, Mexico (along northern coast and possibly also in interior along Presa Marte R. Gómez; Howell and Webb 1995); Texas (Oberholser 1974); sw. (Cameron Parish) and se. (Terrebonne to St. Bernard Par-ishes) Louisiana (Wiedenfeld and Swan 2000); and s. (Mobile Co.) Alabama (Portnoy 1981).

In summer, nonbreeding immatures found throughout winter range.

Winter Range

Figure 1 . In U.S., winters in California (along Pacific Coast, San Francisco Bay area, Salton Sea); from extreme s. New Jersey, Atlantic Coast of Delaware and Maryland, and lower Chesapeake Bay south to s. Georgia; throughout Florida; along the Gulf Coast west to s. Texas; and at inland locations throughout s.-central and e. Texas, extreme s. Arkansas, Louisiana, Mississippi, and Alabama; locally to e. Oklahoma, and rarely to n. Arkansas (Christmas Bird Count data).

In Middle America, winters throughout Baja California, along the Pacific slope from Sonora, Mexico, to El Salvador; in the interior of Mexico from Durango and San Luis Potosí to w. Chiapas; along the Atlantic slope of Mexico from e. Coahuila and w. Tamaulipas to Tabasco; and along the Gulf Coast of the Yucatán Peninsula; apparently no verified records for Belize but recorded along Gulf Coast of Honduras (Howell and Webb 1995). Winter records extend south to Costa Rica (Golfo de Nicoya, Tempisque basin), where considered “rare or casual winter resident” (Stiles and Skutch 1989), and Panama where “only recently reported” (total of 6 reports as of 1989; Ridgely and Gwynne 1989).

Frequently winters in small numbers in Bermuda (Amos 1991). Rare winter resident in the Bahamas, Cuba, and the Cayman Is.; very rare on Hispaniola, Puerto Rico, and the Virgin Is. (Raffaele et al. 1998).

Other Records

Casual in ne. British Columbia (Campbell et al. 1990). Vagrant on Jamaica and the Lesser Antilles, where recorded from Antigua, Montserrat, and St. Vincent (Raffaele et al. 1998). Origin of specimen said to have been taken in Jun on Yukon delta, Alaska, questioned (Gibson and Kessel 1997). Also recorded in s. Atlantic about 400 km east of Pernambuco, Brazil (Blake 1977; presumably source of frequent erroneous inclusion of Brazil in winter range).

Not known to breed outside U.S. and Canada, unlike other North American terns. Strays documented to Iceland and British Isles (Olsen and Larsson 1995) and the Netherlands (Ovaa 1987); now occurs almost annually in British Isles during fall and winter (Alström and Colston 1991).

Ephemeral nature of nesting habitat blurs distinction between changes in breeding distribution and long-term fluctuations.

On Pacific Coast, first recorded nesting in San Francisco Bay area, CA, in 1948—1 colony of about 100 pairs; in 1989, about 2,500 pairs nesting in 8 colonies (Shuford et al. 1989). First breeding at San Diego Bay, CA, recorded in 1962; first record for Baja California, Mexico, in 1990 (Palacios and Alfaro 1991, Massey and Palacios 1994). First breeding in se. British Columbia about 1976 (Goossen et al. 1982).

On Atlantic Coast, first Delaware confirmed nesting in 1985, but may have been established there by 1950 (Hess et al. 2000). Confirmed breeding for N. Carolina in 1971 (Fussell 1974) and for S. Carolina in 1987 (doubtful record of “former” breeding in 1904; Post and Gauthreaux 1989).

For locations in interior North America, established (or reestablished) breeding in s. Ontario in 1976 (Peck 1976). First breeding record in Indiana in 1957 at marsh in Lake Co., but no record after 1962 when marsh filled in (Mumford and Keller 1984).

Single specimen from late Pleistocene at Fossil Lake, OR (Am. Ornithol. Union 1957, Brodkorb 1967).