THE CLIMAX FOREST AND ITS PREDECESSOR 



229 



thistles and ground-cherry may be particularly abundant, or the 

 milkweed toss its balls of blossoms in profusion, while in the 

 autumn goldenrods, wild sunflower, and asters seem to run 

 riot here. 



The cottontail rabbit, 

 gray gopher (Fig. 319), 

 common shrew, jumping 

 mouse (Fig. 318), chip- 

 munk, and woodchuck 

 (Fig. 320) are the common- 

 est mammals of this forest 

 margin associatipn. Birds 

 are particularly abundant, 

 for the almost impenetrable growths of wild crab and hawthorn 

 make safe nesting sites, while the cover is good for ground birds. 

 Bobwhite, chewink, mourning dove, song sparrow, chipping 

 sparrow, goldfinch, indigo bunting, catbird, brown thrasher, 

 and shrike are all common in such haunts. Crabs and haws 



Fig. 318. — The jumping mouse, Zapus 

 hudsonius. 



Fig. 319. — Gray gopher, Citellus Jranklini 



are blossoming in the spring in mid-May, at which time 

 the warblers and vireos are passing over the Chicago region 

 in great waves of migration. They are then attracted to the 

 blossoming trees by the many insects that feed upon the 

 blossoms. 



Insect life is at all times abundant in this marginal association. 

 The herbaceous plants of spring and midsummer mentioned 

 above each attract a goodly number of characteristic guests, 



