36 



NORTH AMERICAN FAUNA 69 



Ga., (fig. 15) in the spring of 1964. The physical features of these 

 two areas were quite similar. Red ash, American elm, water oak, 

 sweetgum, and hackberry formed an important part of the forest 

 in both areas. 



In Monkey John Swamp the density of the combined layers of 

 the upper canopy and lower trees was about 90 percent. The 

 undergrowth, almost entirely scrub palmetto, averaged about 3 

 feet in height, with about 800 plants per acre. Most of the ground 

 area beneath the palmettos was dry. Wet spots under the palmettos 

 in the territory of a Swainson's Warbler were generally avoided. 



In the scrub palmetto habitat of Bayou Boeuf Swamp, I found 

 a population density of 10 territorial males per 100 acres in April 

 1957. 



Western Kentucky 

 R. M. Mengel (1965, p. 69) states that the ridge bottoms — 



the driest habitat of the alluvial forests, contain the finest broadleaf forest 

 and the richest small bird populations of the region. It is in such areas that 

 Swainson's Warbler is most numerous. 



These are the cane ridges so favored by the Swainson's V/arbler 

 in the lower Mississippi Valley. 



SOUTHERN APPALACHIANS 



In the Southern Appalachians the Swainson's Warbler is pri- 

 marily associated with the moist lower slopes of mountain ravines 

 and various drainage systems of the Mixed Mesophytic Forest 

 Region. On these lower slopes, where the proportion of hemlock 

 in the mesic forest increases, rhododendron is often the main 

 understory species ; and it is within this association (figs. 16-17) 

 that the warbler is most often found. It also occurs in some cove 

 hardwood forests (fig. 18), where the understory may be com- 

 posed of a heterogeneous growth of deciduous shrubs, and in other 

 habitats. 



In areas where the Swainson's Warbler is locally common, indi- 

 viduals of a population may "spill over" from optimum to marginal 

 habitats, as cited by Brooks and Legg (1942, p. 70-80), who in 

 West Virginia found a singing bird near the top of a ridge in a 

 thicket beneath dead chestnut (Castanea dentata) trees. Parnell 

 and Quay (1964, p. 139) reported a few Swainson's Warblers in 

 dry sites, such as an oak-hickory forest in Toxaway Gorge in 

 western North Carolina. 



