Habitat

Usually nests on islands, sometimes on barrier beaches or promontories attached to mainland, or salt marshes; occasionally freshwater marshes. Prefers sites with sand, gravel, shell, or cobble substrates and with scattered vegetation or other protected places where chicks can shelter. Hence, usually on sites washed over by winter storms or floods, or affected by other factors that prevent development of woody vegetation. At most sites, nesting areas <5 m above high water mark and <100 m from water’s edge.

Along Atlantic Coast, mostly on rocky islands from Labrador to New Hampshire, sandy islands or barrier beaches from Massachusetts to S. Carolina, or salt marshes from New Hampshire to Virginia (Andrews 1990). In Great Lakes, formerly nested on rocky or gravelly islands or shoals; now frequently on artificial sites (see Breeding: nest site, below). Elsewhere in interior North America, mostly on small treeless (rocky or gravelly) islands in lakes. Widespread on rivers in Europe (Glutz von Blotzheim and Bauer 1982, Becker and Sudmann 1998), but few river sites reported in North America (Fimreite 1974, Stelfox and Brewster 1979, Smith 1996, C. S. Houston). Interior distribution includes both open (prairie) and forested habitats. In Texas, formerly nested on islands in salt lagoons (Pemberton 1922). In Bermuda, nests on small, undercut islets of fragmented limestone with little or no vegetation (D. B. Wingate). In s. Caribbean, nests on small reef islands with little or no cover, or on small islets in inland bays and lagoons (Voous 1957, LeCroy 1976, van Halewyn 1985).

No information on spring migrants. Staging birds in Massachusetts in Aug–Sep concentrate around outer Cape Cod, feeding in inlets and probably offshore, resting and roosting on remote, undisturbed beaches and sand flats near tidal inlets (Trull et al. 1999). Scarce >10 km offshore along Atlantic Coast of U.S., but recorded in small numbers (<1 bird/km², May–Oct) out to edge of continental shelf from Georges Bank to Georgia (Powers et al. 1980, Haney and Stone 1988). No evidence that birds migrating across w. North Atlantic feed in open ocean. In British Columbia, frequent open ocean as well as bays and estuaries; often rest on kelp beds, floating driftwood, or log booms (Campbell et al. 1990).

Little information. In Trinidad, Guyana, and Suriname, frequent turbid waters inshore; accompany and perch on fishing boats inshore and offshore across continental shelf (up to 200 km from shore); rest by day on beaches, boats, rigging, and platforms; roost on outer mudflats or on boats (Blokpoel et al. 1982, 1984; Erwin et al. 1986). In e. and s. Brazil, recorded mainly at nocturnal roosts on barrier beaches, apparently feeding offshore (Harrington et al. 1986; Hays et al. 1997, 1999). In Peru, however, recorded feeding on ocean beaches (Blokpoel et al. 1989).

For habitats in Europe, Asia, and Australia, see Glutz von Blotzheim and Bauer 1982, Cramp 1985, Il’icev and Zubakin 1990, Higgins and Davies 1996 .