330 • 



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

 ward during the fifty days of this trip. Summer residents of central 

 Illinois diminish in numbers, or even wholly disappear, during its 

 course, winter residents come in, and migrants to the south, not seen 

 in the earlier days of the journey, become 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 by 

 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-blackbirds 

 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 sparrow 

 (7 per cent.), and next to that, the quail (4 per cent.). 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 been assembled, com- 

 pared, and adjusted in their right relations; and it has been the prin- 

 cipal 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 brought together and 

 made available. 



