THE AUDUBON BULLETIN 



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IN THE SAG VALLEY 

 Photo by O. M. Schantz 



The wide valley 

 of the great river 

 that was once the 

 outlet of the ancient 

 lake, the predeces- 

 sor of Lake Michi- 

 gan, i s distinctly 

 traceable, and it 

 needs very little im- 

 agination when 

 looking south from 

 LaGrange to pic- 

 ture this mighty 

 stream filling the 

 present wide Des- 

 plaines valley from 

 brim to brim. When 

 the waters of the 

 lake gradually re- 

 ceded to lower levels, 

 the Desplaines and 

 Chicago rivers were 

 formed, and along 

 these streams beau- 

 tiful woodlands have 

 gradually grown up, containing a great variety of trees, shrubs, 

 and woody climbing plants, as well as a bewildering carpet of 

 annual and perennial herbaceous plant associations. The adjoin- 

 ing prairie lands have an equally interesting vegetation and on 

 the ridges wonderful oak forests grow, consisting largely of' 

 of the half dozen common varieties, with occasional specimens 

 of three oaks that have worked their way up from farther south. 

 The flood plains of the streams are timbered with a luxuriant 

 growth of trees that do not mind occasionally having their feet 

 in the water. In time the older ravines and certain favorable fer- 

 tile lands acquired a fine growth of hard maples and other trees, 

 that gradually come in as the forested areas progress in age and 

 suitable soil. Compared with the total area of the county, it is 

 not surprising that there are still more than 30,000 acres of 

 woodlands. Of these acres 20,000 have become the property of 

 the people for all time. 



As bird population is largery determined by the shelter af- 

 forded by the forests, and by the available food supply, the 

 wooded areas in Cook County indicate the possibility of an un- 

 usual resident and migrant bird life. While it is not probable 

 that the former great flocks of waterfowl will ever be duplicat- 

 ed in the shallow lakes in and bordering the county in the south- 

 east portion, the automatic creation into bird sanctuaries of all 

 the forest preserves, and the construction of artificial lakes, has 



