Habitat

Breeding Range

Nests on barrier, marsh, and spoil islands on the coast, and on islands in lakes inland. Also in gallery forest and in stands of trees within marshes and mangrove swamps. Nest sites are in interior and coastal wetlands, including those within the southeastern mixed forest, outer coastal plain forest, savanna, prairie parkland, and prairie bushland ecoregions of the United States (Bailey 1978). Historically, the largest populations foraged in interior freshwater marshes and swamps of the Everglades (Bancroft 1989, Ogden 1994).

Most nesting birds forage in freshwater wetlands, even when breeding on coastal islands, owing to nestlings’ need to maintain salt balance (Bildstein et al. 1990, Johnston and Bildstein 1990). Inland feeding habitat mainly shallow seasonal sedge marshes and shallow cypress swamps, as well as lawns, pastures, and shallow ponds. Coastal feeding habitat salt marsh in the north and lagoonal salines and mangrove swamp in the south (Custer and Osborn 1978, Kushlan 1979a, Henderson 1981, Bildstein 1983).

In s. Florida Everglades (Kushlan 1979a), most ibises use shallow marshes (47% of observations), sawgrass-lined shallow ponds (29%), and shallow ponds surrounded by willow trees (15%). In coastal areas, ibises use mangrove-lined streams and ponds (61%), sparsely vegetated marshes called marl prairies (19%), and tidal mangrove swamp (14%); density of foraging birds positively correlated with % open prairies (Surdick 1998). Ciconiiform birds in general prefer open, sparse emergent vegetation (Lantz 2008). In central Florida, they use flooded pastures (56%), isolated marshes (22%), and marshes at the edges of lakes (19%). In N. Carolina, ibises use coastal habitats, 85% in Spartina marsh, 11% in tidal creeks (Custer and Osborn 1978). In the Okefenokee Swamp, GA, wet prairies, blackgum forest, and clear-cuts (Stinner 1983); in Louisiana, commercial crayfish ponds, especially those being drained (Martin and Hamilton 1985).

Generalized microhabitat requirements are broad, as the birds feed in nearly any shallow water or on land in soft substrate or ground vegetation such as lawns and exposed salt marsh. Take prey from the surface of the ground, buried in soil, or within rooted and floating aquatic plants. Also probe in damp mud, especially for crayfish or crab burrows, from which they extract prey. Typically feed in water less than 20 cm deep, generally in 5–10 cm. Use wide range of feeding opportunities, provided prey are available, water levels sufficiently shallow, and substrate soft enough for probing. Although their sample size was low, Gawlik and Crozier (2007) showed that water depth was a more important ibis foraging habitat cue than change in water depth (drying rate).

In coastal S. Carolina, feeding ibises shift from bottomland cypress swamp and old ricefields managed for waterfowl to salt marshes as their nestlings begin to fledge in early summer (Wayne 1910, Bildstein et al. 1990, DeSanto et al. 1997). In salt marshes, they use high marsh areas dominated by the short form of salt-marsh cord grass; less so areas along creekbanks dominated by the tall form of cord grass (Henderson 1981).

Spring And Fall Migration

Shift toward coastal areas outside of the breeding season, depending primarily on local water conditions and hence prey availability inland.

Winter Range

Few data. Predominantly coastal, especially in and near mangrove swamps, Spartina marshes, and coastal lagoons, where they often specialize on fiddler crabs (Uca). In Florida Bay, forage on mud-flats and swallow tidal wetlands (JH). In S. Florida, wintering birds regularly found in freshwater marshes in large numbers, moving across the landscape following drying pools of water.