Preface. 165 



The two opposite sections of the state also dilFer essentially in 

 the natural products of the soil, — the southern being clothed 

 with almost continuous forests, which in the bottom-lands are 

 remarkable for massiveness of growth and great variety of species, 

 while in the central and northern portions extensive prairies 

 largely prevail. Indeed, it is difficult to conceive of more com- 

 plete contrast than that afforded by the cypress swamps, cane- 

 brakes, and almost tropical luxuriance of vegetation of the 

 southern bottom forests, on the one hand, and the extensive, mon- 

 otonous northern prairies on the other. Intervening districts pre- 

 sent every conceivable combination of^:>rairie and woodland, while 

 particular sections possess special features, such as the line of high 

 precipitous bluffs along part of the western border, the romantic, 

 almost mountainous range of rugged hills traversing the 

 southern portion, from east to west, and tlie hilly region 

 northwestward. The prairies of central and northern Illinois 

 being a moditied continuation of the "Great Plains," a consid- 

 erable number of birds characteristic of, or peculiar to, the 

 "Campestrian District," together with others common to the 

 whole of the Western Region, are thus brought into contact with 

 eastern woodland forms; while the proximity of the Great 

 Lakes, on the northeast, secures the presence of many species 

 formerly considered of purely maritime or littoral habitat, 

 but which in reality occur, at one season or another, on 

 many of the larger streams of this inland state. Considering 

 also in this connection the very large preponderance of the 

 southern element in that portion of the state lying south of the 

 parallel of 39° (approximately), and also the influx of northern 

 forms during the winter season, it may be seen that no less than 

 five distinct faunae overlap on the area included within the 

 boundaries of the state of Illinois, — the eastern, which, in its 

 purity, of course largely predominates; the maritime and 

 littoral, by way of the Great Lakes and the St. Lawrence ; the 

 boreal, coming down from the high north in winter; the western, 

 extending eastward across the prairies to the border of the 

 wooded country; and, lastly, the southern, or "Austroriparian" 

 fauna, a very considerable element of which extends up the 

 Mississippi valley to at least the 38th parallel of north latitude. 



