26 



NORTH AMERICAN FAUNA 69 



on the ground. In many habitats, the shrub stratum, or under- 

 growth, is composed mainly of a single species such as giant cane 

 in the floodplain forest, sweet pepperbush (Clethra alnifolia) in 

 the swamp forest, scrub palmetto in the bottomland forest, and 

 rhododendron (Rhododendron maximum) in the mixed mesophytic 

 forest. The structure of the undergrowth may be remarkably uni- 

 form, as in some canebrakes, palmetto thickets, and sweet pepper- 

 bush stands. 



GOASTAL PLAIN 



In the Coastal Plain Province, river floodplain forests and 

 swamps are the principal physiographic types in which the Swain- 

 son^s Warbler lives during the breeding season, or summer half 

 of the year. Since the terms swamp, riverbottom, hardwood 

 bottom, and floodplain forest are often used synonymously, an 

 explanation of these terms seems appropriate. The lowland forest 

 bordering a southern river is generally known to the forester or 

 plant geographer as a riverbottom or bottomland. It is usually a 

 complex of several forest communities, including swamps, flood- 

 plain forests (also known as hardwood bottoms), and riverfront 

 hardwoods. Most swamps are permanently flooded except during 

 droughts; they thus differ from floodplain forests which are 

 periodically flooded, usually in late winter or spring. There are 

 several types of swamps. Those in riverbottoms are known as 

 river or alluvial swamps; they are found in the lowest part of 

 the bottomland, either bordering the river or between the flood- 

 plain forest and adjacent uplands. Swamps found away from 

 riverbottoms are known as nonalluvial or inland swamps; good 

 examples are the Great Dismal and Okefenokee Swamps. 



Recognized as subdivisions within the floodplain or bottomland 

 forests of the lower Mississippi Valley are the first bottoms, and 

 the ridge bottoms (or cane ridges) . In low, poorly drained flats of 

 the first bottoms, the Overcup Oak-Bitter Pecan ( Quercus lyrator- 

 Carya aquatica) type is predominant. The Sweetgum- Water Oak 

 (Liquidambar styracifluor-Quercus nigra) type is found in the 

 better drained parts of the first bottoms. Sweet Pecan (Carya 

 illinoensis) , Sweetgum, and Southern Red Oak (Quercus falcata) 

 are prominent on the cane ridges. These subdivisions are not as 

 distinct or are non-existent in the South Atlantic coastal floodplain 

 forests. 



In floodplain and swamp forests, the main plant formations 

 selected by the warbler are usually canebrakes (figs. 9-12), scrub 

 palmetto, and sweet pepperbush. Greenbrier (Smilax spp.) is 



