Habitat

Breeds in wide variety of habitats, ranging from coastal estuarine, salt marsh, and barrier islands along Pacific, Atlantic and Gulf Coasts, to James Bay beaches and freshwater islands in Great Lakes and other inland sites. In western interior, often nests on islands in rivers and salt lakes (D. Paul pers. comm., C. Trost pers. comm.). Nests found among driftwood and debris on low, flat, sandy or rocky islands, often small; on shell banks and beaches; and on sandy, muddy, or pebbly shores sparsely vegetated (see Breeding: nest site, below). Although diverse, breeding habitat is specific: open, fairly flat islands or similar environments, because eggs and young are vulnerable to ground predators (see Behavior: predation, below; Ludwig 1991). On Pacific and Gulf Coasts, often nests on sparsely vegetated natural and dredge-material islands and salt dikes; largest colonies now associated with artificial habitats (Gill and Mewaldt 1983, Quinn 1990, Stadtlander et al. 1993, Rodgers et al. 1996; see Conservation and management: management, below). Average temperature for Pacific Coast is 15–20°C (Penland 1976, Schew et al. 1994). In Great Lakes, nests on pristine habitat on open pebble, gravel, or sandy beach islands, where average temperature is 5–20°C (Cuthbert 1981, Ludwig 1991).

Occurs along coastlines, large rivers, and large inland freshwater lakes (Ludwig 1965, Lowery 1974, DeGraaf and Rappole 1995). Of migrant North American terns, this species is one of the most likely to be seen inland along watercourses or in large marshes; scarcity of records along coasts of Central America suggests direct overwater flight to wintering areas off n. Colombia (Clapp et al. 1983). On Pacific Coast, frequents freshwater lakes and estuaries (Garrett and Dunn 1981, Gilligan et al. 1994). On Atlantic Coast, uses outer barrier islands, beaches, impoundments, and managed wetlands during migration and winter.

Much the same as in migration. Generally found along beaches and on isolated spits, often roosting with other larids, though sometimes alone (Burleigh 1958, Clapp et al. 1983, Blokpoel et al. 1984, DeGraaf and Rappole 1995). In Louisiana, fishes along freshwater canals and prefers marshes over front beaches (Lowery 1974). In San Diego Co., CA, found at nearly all fresh and brackish bodies of water (Ohlendorf et al. 1985). Avoids regions where mean average ocean surface temperature falls below 13°C (Root 1988), nor is it frequently found at sea beyond inshore zone (Cramp 1985).