—- 
lad 
189 
_ percentage of the whole area of observation for each year which was 
in each of the principal farm crops. 
For the northern and central parts of the state the agreement 
between the two years is remarkably close, but there are noticeable 
differences between them in southern Illinois, due to the larger area in 
small grain in 1909, an increase evidently made at the expense of the 
forage crops. The comparison just made assures us, however, that any 
differences of importance noted in the bird life of the two years in the 
different sections were not attributable to differences in agricultural 
conditions. 
The most striking general difference was in the seeming greater 
abundance of birds in 1909, in all three sections of the state. It is best 
shown in the following table of the numbers of birds recognized and 
counted and the number per square mile in each section of the state 
and in the state as a whole. 
NUMBERS OF BIRDS SEEN AND NUMBERS PER SQUARE MILE, 
SUMMERS oF 1907 anp 1909 
Number of birds Numbers per square mile 
Section PLES ole. ari O 
1907 | 1909 | Both years 1907 | 1909 Both years 
Southern 2667 3973 6640 682 841 769 
Central 2047 6368 8415 650 1071 925 
Northern 3026 7647 10673 610 1021 857 
State 7740 17988 25728 644 990 852 
From this it appears that the number seen per square mile averaged 
54 per cent. larger for the whole state in 1909 than in 1907, and that the 
increase was especially striking in central Illinois, where it amounted 
to 65 per cent. That this was a general and not a local phenomenon 
in Illinois is shown by our tables of the number of birds per square mile 
of different crops in different sections of the state. From these it 
appears that the numbers per mile recorded in 1909 exceeded those of 
1907 in fields of corn, oats, stubble, plowed ground, pasture, orchards, 
woodlands, and yards and gardens and fell short of the 1907 numbers in 
wheat, meadow, shrubbery, and waste and fallow, and that the total 
of the areas of the first of these lists was 14,872 acres and that of the 
second list 4333 acres, the birds being more abundant in 1909 than in 
1907 on tracts aggregating nearly three and a half times as great an area 
as those in which the 1909 numbers were smaller than those of 1907. 
The possible causes of so sudden and so great an apparent increase 
in the bird population of the state are too numerous and too wide-spread 
to come within the range of our inquiries ; but the fact itself is important, 
especially as showing the need of prolonged investigation as a basis for 
