Habitat

Breeds mostly in coastal habitats, including estuaries, salt marshes, mangrove swamps, river deltas, lagoons, and salinas, but also frequently in freshwater areas (e.g., Florida Everglades and se. U.S. coastal plain; Belser and Post 1987). During 3 yr in Everglades (1987–1989), 75% of nests were in brackish or marine habitats, 25% in fresh water (Frederick et al. 1992). On Yucatán Peninsula, more likely to be found in saltwater habitats than fresh (Lopez-Ornat and Ramo 1992).

Generally breeds on islands or areas of higher ground that support small trees or shrubs, surrounded by open water or inundated wetland vegetation. Colonies usually surrounded by landscapes that include a variety of wetland habitats (see Bancroft et al. 1994; see also Breeding: nest site, and Food habits: feeding, below).

Little information. Migrants probably move among variety of wetland habitats during continental migration, especially along rivers and through coastal wetlands. Some migration over open water, with sightings 100+ km off Atlantic Coast of Florida (Stevenson and Anderson 1994); stopover habitats on intervening islands in Caribbean thus probably important but undocumented. Apparent trans-Gulf migration during spring suggests that coastal habitat in Louisiana and Mississippi may be important for incoming migrants (S. Cardiff unpubl. data).

In Florida, mangrove swamps (e.g., red mangrove [Rhizophora mangle], black mangrove [Avicennia germinans]), salt marshes, coastal mudflats, cypress (Taxodium distichum) swamps, canals, ditches, freshwater herbaceous marshes, and lake edges (Palmer 1962, Rodgers et al. 1996). In Louisiana, a variety of fresh- and saltwater wetland habitats; increasingly noted in aquaculture and rice culture impoundments (Fleury 1994). In Texas, CBC data suggest no use of habitat farther inland than Austin (Telfair 1979). In California, coastal lagoons and tidal flats in San Diego Co., usually along channels in glasswort (Salicornia) marshes (Garrett and Dunn 1981). In Central and South America, coastal mangrove swamps and mudflats; in Central America, to 1,500 m (freshwater; Costa Rica); northern birds thought to overlap extensively with southern races during winter.