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 Sub-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. 



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