Habitat

Favored habitats vary considerably in east along Atlantic and Gulf coasts and in Florida, but generally prefers shallow estuarine sites for feeding including salt-marsh pools, tidal channels, shallow bays, and mangroves (see Food habits: feeding, below). In N. Carolina, 84% of breeding individuals flew to tidal foraging habitat (Custer and Osborn 1978a). Reliance on estuarine wetlands linked to predictability of foraging habitat (Powell 1987, Frederick et al. 1992).

Breeds in mixed-species colonies on relatively isolated, mainly estuarine sites. Colonies in New Jersey typically located in thick vegetation on barrier, dredge-spoil, and salt-marsh islands and in white cedar (Chamaecyparis thyoides) swamps (Palmer 1962, Burger 1978b; see Breeding: nest site, below). Dredge-spoil islands are particularly important along Atlantic and Gulf coasts because of their abundance and location near inlets where food resources are stable and abundant (Parnell and Soots 1978). In Louisiana and Florida, breeds in red mangroves (Rhizophora mangle) and tropical buttonwoods (Conocarpus spp.; Palmer 1962, Ryder 1978). Often nests on freshwater lakes and swamps in Florida (Jenni 1969). Breeders most numerous but least successful in estuarine compared to freshwater and marine habitats in s. Florida (Frederick et al. 1992). In Texas, has nested on dry coastal islands in prickly pear cactus (Opuntia spp.; Palmer 1962).

In Midwest, preferred habitats include marshes in Ohio (shores of Lake Erie; Peterjohn and Rice 1991), swamps and flooded fields in Mississippi lowlands of Missouri (Robbins and Easterla 1992), stands of trees around reservoirs in S. Dakota (Peterson 1995), and river bottomlands in Illinois (Bohlen 1989).

In the West, preferred habitats include: willows along large rivers in Nevada (Alcorn 1988); reservoirs, grassy marshes, and wet meadows in the Great Basin, Colorado, and Wyoming (Ryser 1985, Andrews and Righter 1992, Oakleaf et al. 1992); inland lakes and canals in the Harney Basin in Oregon (Gilligan et al. 1994); irrigation channels, estuarine habitats, marshes, and river courses in California (Garrett and Dunn 1981). In San Francisco Bay, CA, most individuals breed on islands in mixed-species colonies (Kelly et al. 1993).

See Migration: timing and routes, above.

Throughout the Caribbean, prefers mangroves for nesting and roosting (Voous 1983, Evans 1990, Raffaele et al. 1998) although some individuals also found on salt-water lagoons, freshwater swamps, grassy ponds, and temporary pools (Bradley and Rey-Millet 1985, Raffaele et al. 1998). Beaches, shallow reef areas, flooded rice fields, and wet grassy meadows are preferred foraging areas (Voous 1983; X. Ruiz, Univ. of Barcelona, unpubl. data; O. Garrido and A. Kirkconnell unpubl. data; see Food habits: feeding, below).

In Central America, absent from highlands, casual at 1,280 m in Lagunas de Volcan in Panama (Wetmore 1965). Found mainly in lowlands in freshwater swamps and lakes (Thurber et al. 1987), lagoons, and coastal areas including tidal flats throughout (Stiles and Skutch 1989). Many references indicate preference for large rivers and river mouths (Land 1970, Wetmore 1965, Ridgely and Gwynne 1989, Stiles and Skutch 1989, Howell and Webb 1995).

In Trinidad and Tobago, nests in mangrove swamps and feeds in salt-water swamps, exposed mudflats, and along the coastal shoreline (ffrench et al. 1980). Prefers bays, lagoons, mangroves, clear reef shallows, and even sewage ponds in the Netherlands Antilles (Voous 1983).

In continental South America, species again absent in highlands; found predominantly in coastal mangroves, mudflats, and swamps and less commonly inland in freshwater swamps, marshes, ponds, and along large rivers (Meyer de Schauensee and Phelps 1978, Hilty and Brown 1986, Tostain et al. 1992, Araya and Chester 1993, Haverschmidt and Mees 1994).