ever, the extreme southern tip receives less than 50 

 per cent during the growing season. The average annual 

 snowfall ranges from 9-9 inches in the south to 18.6 

 inches in the north, but snow normally remains on the 



Fig. 1. — Counties in southern Illinois (indicated by 

 dotted pattern) in which bobwhite crops were collected 

 from hunters for the investigation reported in this publication. 



ground for only a short time. The above data, compiled 

 from long-record weather stations in Illinois, were taken 

 from Page (1949). 



The study area embraces a zone of transition for 

 floral, faunal, physiographic, and edaphic provinces. 

 In biotic communities, farming practices, and cultural 

 mores, a fusion of the North and the South is evident. 



The Western Mesophytic Forest and the Oak-Hickory 

 Forest tegions are found here (Braun 1950). The Oak- 



Hickory Forest is extensively interspersed with prairie, 

 whereas the Western Mesophytic Forest is marked by 

 hilly terrain with mixed mesophytic communities. King & 

 Winters (1952:3, 22) estimated that 39 per cent of Illi- 

 nois had originally been forested, whereas 11 per cent 

 was forested in 1948. The greater part of the present] 

 forested area of the state is in the study area, particu- 

 larly in the 11 southernmost counties where, in 1948, 

 18 per cent of the total land in some counties to over 

 40 per cent in others was timbered (King & Winters 

 1952:21). 



Four major soil associations occur in southern Illi- 

 nois (U.S. Department of Agriculture 1938:1056-7, 1067, 

 1104, 1134; and map accompanying). These range from 

 extensive alluvial deposits along the Ohio and Missis- 

 sippi rivers to mature upland soils. Soil fertility is gen- 

 erally low, but the land responds well to careful culti- 

 vation and sound conservation practices. Four major 

 physiographic provinces are represented (Leighton, Ek- 

 blaw, & Horberg 1948), ranging from rugged hills in the 

 south to gentle plains in the north. Approximately four- 

 fifths of the area was glaciated. 



Four farming-type areas occur in southern Illinois 

 (Ross & Case 1956:32): general farming and dairy, gen- 

 eral farming, grain and livestock, and general farming 

 and fruit. There is no sharp distinction between the 

 farming-type areas; land use varies considerably even 

 within each of these areas (Ross & Case 1956:51-62). 



The acreage in corn ranges from 20 per cent of the 

 land in some counties to 31 per cent in others, soybeans 

 from 9 to l6 per cent, wheat from 4 to 20 per cent, pas- 

 ture from 23 to 43 per cent, hay from 5 to 9 per cent, 

 and idle land from 6 to 11 per cent. The largest com 

 acreages are in regions influenced by extensive river 

 bottoms. The acreage planted to soybeans has increased 

 in recent years. Most of the wheat is in the central part 

 of the area. 



METHODS OF ANALYSIS 



The average volume per unit — such as a seed or an 

 insect — was found for each kind of food by determining 

 the volume of a large number of units of that food and 

 dividing this total volume by the number of units. 



In all but a few cases, volume was determined by 

 the displacement method. The volume of ver\' small 

 seeds could not be determined without a displacement 

 medium. Lead shot and sand as displacement media 

 proved unsatisfactory. Water was a suitable displace- 

 ment medium for the determination of the average unit 

 volume of most seeds and insects. Objects that floated 

 were forced below the surface with a small screen of 

 known volume. Certain seeds and all soft-bodied animals 

 such as slugs and larvae were measured in their natural 



