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THE AMEBIC AN NATURALIST [Vol. XLII 



Variation with Latitude 



The English sparrow decreases in abundance from 

 north to south, from 147 to the square mile in northern to 

 113 in central, and 82 in southern, Illinois. One hundred 

 sparrows in the northern part of the state are thus rep- 

 resented by 77 in the central and 56 in the southern part. 3 

 The native summer residents, on the other hand, increase 

 in numbers from north to south, the birds per square mile, 

 being 464, 537 and 600 for nothern, central and southern 

 Illinois, respectively. That is, 100 native birds in 

 northern Illinois were represented in mid-summer by 116 

 in central and 129 in southern Illinois. The decrease in 

 English sparrows from north to south is not sufficient to 

 offset the increase in the native species, the total numbers 

 per square mile for all summer birds in the three sections 

 of the state being 610, 650 and 682— or 100 birds in 

 northern for 107 in central and 112 in southern Illinois. 



This same gradation was much more pronounced in the 

 record of the winter residents. From the last of Novem- 



