307 



or even inconvenienced, and that nothing can escape the meshes of 

 their well-trained observation. 



One of these observers, Mr. H. A. Ray, also a University stu- 

 dent, is primarily responsible for the record of distances and kinds 

 of surface over which they travel, carrying for this purpose a 

 pedometer whose action has been carefully tested and repeatedly 

 checked, and a mechanical tally or "lumber-counter" — both used to 

 make a record of the number of paces traveled over each crop or other 

 kind of surface vegetation. 



The reports of their travel made to me by Mr. Gross contain 

 every needful detail as to date and time of dav; to precise location 

 of their line of march ; to temperature, wind, and other features of the 

 weather ; to distances traveled in succession over each field or other 

 distinguishable area; to vegetation, wild or cultivated, on each tract; 

 and to the species and numbers of birds identified on each area and 

 in each kind of crop. 



General Results of Observations. 



The present paper is a discussion of the product of one of their 

 earlier trips, made from August 28 to October 17, 1906, across the 

 state from east to west, from the Indiana line beyond Danville, 111., 

 to Quincy, on the Mississippi River. It has to do with autumnal 

 conditions in the central part of the state, and is merely preliminary to 

 a comprehensive report on the whole investigation. 



The entire distance covered by these observations is 191.86 miles, 

 and the strip from which all birds were accurately determined and 

 numbered was 150 feet in width for this whole distance. The area 

 thus covered was 3519 acres, or 5^ square miles. It included every 

 kind of surface, soil, and vegetation traversed by the observers, with 

 the exception of forests of too lofty or too dense a growth for a 

 complete and certain recognition of their bird population. 



The whole number of birds identified was 4804, of which 1620 

 were English sparrows and 3184 were of native species. The aver- 

 age number of birds seen was 25 for each mile of the trip, which is 

 1.36 for each acre covered, or 874 for each square mile. The English 

 sparrows averaged .46, and the native species .9, per acre, or 295 

 per square mile for the sparrows and 579 per square mile for the 

 native birds. The total number of species recognized was 93 ; but 

 90 per cent, of the individual birds seen, belonged to 20 of these 

 species, leaving but 10 per cent, for the other 73 species. Indeed, 15 

 species included 85 per cent, of the individual birds observed, leav- 

 ing for the other 81 species but 728 birds — an average of 130 birds 

 per square mile, or one bird to each five acres. 



