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prevails.t The observations of the summer of 1907 were made in the 
early part of the season (June 4 to July 1) for southern Illinois, at the 
middle of it (July 9 to 24) for central Illinois, and during the latter 
part of it (July 29 to August 3) for the northern part of the state. By 
this program observations of the early summer in southern Illinois were 
brought into comparison with those of late summer in the northern 
section, and it was hence not possible to distinguish clearly in all cases 
between regional and seasonal differences in the bird life of these sections. 
To minimize differences due to season merely, in order that those due 
to climate and other sectional factors might stand out more clearly, the 
field program of the second summer (that of 1909) was so arranged 
that observations were made in early, middle, and late summer in each 
section of the state, those for southern Illinois June 8 to 17, July 13 to 
21, and August 17 to 26; those for central Illinois June 22 to 29, July 
23 to 31, and August 28 to September 4; and those for northern Illinois 
June 30 to July 8, August 4 to 13, and September 6 to 15. Furthermore, 
in order to give greater variety and validity to the whole body of observa- 
tions of the two years taken together, those of the second year were 
given different location and range from those of the first. In 1907 
continuous trips had been made between widely separated points, but 
in 1909 certain places were chosen as centers of characteristic districts, 
and from these relatively short trips were made in various directions. 
In this second summer the total distance traveled by the observers 
was 654 miles, and the area covered by their observations was 11,624 
acres—an increase of 51 per cent. over that of the earlier year. Forty- 
one per cent. of the total area of 1909 was in northern, 33 per cent, in 
central, and 26 per cent. in southern Illinois. The area covered in the 
two summers was 19,317.6 acres. 
Notwithstanding the effort made to give a different range to the 
later observations, the general features of the country traversed in the 
two years were very similar, as is shown by the following table of the 
Crop AREAS, PER CENT., SUMMERS OF 1907 AND 1909 
Northern Tllinois Central Illinois Southern Illinois 
Crops 
1907 1909 1907 1909 1907 1909 
Corn 31 31 46 43 23 28 
Small grain* 27 24 26 28 21 35 
Forage crops 37 38 27 25 44 33 
Miscellaneous 5 7 1 4 12 14 
*Including stubble and plowed ground. 
{+ The significance of the north and south extension of the state is further illus- 
trated by the fact that three faunal zones are represented in its area, the lower 
austral in southern Illinois, the upper austral in central, and the transitional in the 
extreme northern part of the state. 
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