CHAPTER XI 
ANIMAL COMMUNITIES OF SWAMP AND FLOOD-PLAIN FORESTS 
I. INTRODUCTION 
Swamp forests are those which arise in the areas formerly occupied 
by ponds and lakes and which grow in water or very wet soil. About 
Chicago the many coastal and morainic lakes of earlier periods have been 
filled by organic detritus and more or less completely occupied by trees. 
Often the trees have grown upon floating bogs such as sometimes occur 
about lakes, though sometimes they have sprung up on solid ground and 
compact organic detritus. 
II. Swamp Forest FORMATIONS AND ASSOCIATIONS 
We shall consider these forests genetically: the marsh which often 
appears first, the shrub stage which follows, and finally the forest. 
I.. THE ELM-ASH SWAMP FOREST COMMUNITIES 
a) The marsh association (Station 52; Table XLI).—One of the best 
examples of this community is at the north end of Wolf Lake, Ind. The 
youngest part is occupied by bulrushes and Hibiscus, and covered in the 
spring by about a foot of water which teems with small crustaceans, 
mosquito larvae, and red water-mites. Lymnaea reflex, usually about 
half the size of the specimens (100) of permanent ponds, and the small 
bivalve (Musculium) are present. As the season advances the water 
dries up and the eggs of the crustaceans and adult mollusks live through 
the dry season on the bottom of the pool. Above the water on the 
Hibiscus are the small Succinea retusa (91, 100), which belong to the 
forest edge and low prairie. 
b) Shrub association (forest edge sub-formation) (Station 52; Table 
LXIII).—Surrounding the central pool which we have described is 
usually a girdle of buttonbush. Here we recognize several strata. The 
subterranean stratum has few inhabitants. We have recorded none. 
The ground stratum is not inhabited by many animals. The wood- 
cock and the northern yellowthroat (108, 153) probably occasionally 
nest here on the ground, possibly also the common shrew (Sorex 
personatus St. Hil.) (142). There is no distinct field stratum, as the 
189 
