CHAPTER XIII 
ANIMAL COMMUNITIES OF THICKETS AND FOREST MARGINS 
I. INTRODUCTION 
The forest margin or forest edge is a familiar natural situation. 
About Chicago there are groves of trees which are probably exactly as 
they were before settlement. The forest ends; the prairie begins. The 
line between the two is markedly a narrow border of shrubs and rank 
weeds, usually only a few feet wide. In other places the forest ends at 
a marsh side, lake side, or stream side, but almost always with the 
thicket of shrubs and rank weeds. A remarkably large number of 
animals belong to this forest margin. Some of these have been discussed 
in connection with the margins of bodies of water (chap. x), and the 
marsh forest (chap. x). The borders between forest and _ prairie 
remain to be discussed. These will be roughly separated into high and 
low forest margin, depending upon height above ground-water level. 
The relations of these formations to the other forest margins will be 
indicated in the tables. 
II. Low Forest MARGIN SuUB-FORMATIONS 
(Stations 45, 49; Table LXIII) (Fig. 254) 
Low forest margin is usually the border between swamp forest and 
low prairie. There was originally much of this in the Lake Chicago 
plain. One point of special study is the border of the Wolf Lake marsh 
forest (see p. 189). 
I. SUBTERRANEAN-GROUND STRATUM 
The ground is inhabited by earthworms and cicada nymphs, etc. 
No burrowing mammals have been recorded, but it is probable that 
the skunk sometimes breeds in this stratum. 
The cricket (Nemobius maculatus) occurs under fallen leaves, sticks, 
etc., with an occasional snail (Polygyra monodon). The lubberly locust 
often deposits its eggs in the ground (40). Sowbugs and forest-floor 
forms make up most of the remaining species. 
The northern yellowthroat, the song sparrow, and the common 
shrew sometimes nest on the ground. The skunk is sometimes a feeding 
resident. 
