100 CENTRAL ILLINOIS 
FREQUENCY (PER GENT OF COUNTS) 
a 
(oe) 
40 
30 
20 
10 
/9 05 nn Mg 92, "90. /9 39 9 Ey /9 ee 996 /9 So 
Fig. 13.—Frequency of occurrence of the red-tailed hawk in central [Illinois calculated for 5-year periods beginning in 
1905 and ending in 1954. The year indicates the beginning of the 5-year period. 
1.10 
1.00 h 
c CENTRAL ILLINOIS 
40 
30 
.20 fe) 
NUMBER OF BIRDS 
‘So. Si Sy. ‘925 ‘S25 ‘930 935 ‘9g, 94. 195, 955 
Fig. 14, — Average numbers of red-tailed hawks reported per observer-hour in central [llinois, 1905-1955. 
