333 



that the effects of its transformations are noticeable even in the 

 picture itself; for it is evident, especially from the list of species 

 at the end of this paper, that there was some bird migration 

 southward during the Hfty days of this trip. Summer residents 

 of central Illinois diminish in numbers, or even wholly disap- 

 pear, during its course, winter residents come in, and migrants 

 to the south, not seen in the earlier days of the journey, be- 

 come abundant as they move across the line of march in the 

 western part of the state. 



Some of the effects of this migration were seen a fortnight 

 later in the very different picture of bird life presented on a 

 trip made l)y these same observers, October 31 and November 

 1, from Cairo, the southernmost point in Illinois, to Ullin,some 

 twelve and a half miles north. Here, instead of the scanty 

 average of 874 birds per square mile, as found in central Illinois, 

 there were over 9 to the acre, or 5882 to the square mile. 

 Two thirds of these were crow-l)lackbirds and robins — 45 per 

 cent, of the first and 23 per cent, of the second — and the next 

 most abundant species was the white-throated spaiTow (7 per 

 cent.), and next to that, the quail (4 percent.). The meadow- 

 lark was reduced to 2 per cent, of the birds observed; and, more 

 remarkable still, the English sparrow, to a little more than 1 

 per cent. Into the angle formed by the meeting of the Ohio 

 River with the Mississippi, birds from the north were dropping 

 down by thousands as into a huge pocket, to be held there, 

 no doubt, until cold weather or a diminution of their food 

 supply should drive them farther south. 



Definite conclusions of permanent value concerning the 

 numbers and significance of the bird life of the state evidently 

 can not be drawn until many such pictures as these have l)een 

 assembled, compared, and adjusted in their right relations; 

 and it has been the principal object of this paper to describe 

 and illustrate one process, at least, by which the materials 

 necessary to a correct general view of the ornithological 

 ecology of the state may be l)rought together and made 

 available. 



