230 Game Survey of the North Central States 



Abundance and Trend. There has been at least one attempt to actually 

 measure crow populations. Dr. A. O. Gross, from August to October, 1906, 

 counted all birds on a strip of land extending across the State of Illinois from 

 Danville to Quincy. On this transect he counted an average of forty-one crows 

 per square mile, or one crow per 16 acres. He found that crows constituted 7.1 

 per cent of all the birds observed. Quail constituted 1.4 per cent of all the birds 

 observed. In other words, he observed about six crows for every quail. He 

 worked without dogs, however, and thus may have missed a good many .quail, 

 whereas the extreme visibility of the crow made it impossible to miss any. This 

 difference in the ease of counting may have distorted the crow-quail ratio. 



The evidence on the general trend in abundance of crows is confusing. 

 There are clearly some localities where crows have decreased. In others they 

 are alleged to have increased. 



Jack O'Hara, of Janesville, Wisconsin, told me that crows are far more 

 abundant in Rock County now than they were when he began to hunt there in the 

 60s. 



Widmann believed that a decrease had occurred in Missouri at the time his 

 book was published in 1906. He says of the crow: "Constant warfare . . . 

 has greatly thinned its ranks during the last 20 years." 



Wheaton records a notable decrease in crows which took place near Colum- 

 bus, Ohio, in 1883, but Dawson in 1903 records them as abundant in the same 

 region. 



The most logical interpretation of such contradictory evidence is that the 

 crow, being a mobile migratory bird, free to follow fluctuations in the food supply, 

 is normally subject to heavy fluctuation in local abundance. It is more logical to 

 impute these fluctuations to movement than to any net change in the crow popula- 

 tion of the region as a whole. 



Arguing from general premises rather than detailed recorded facts, it is 

 logical to assume that the grain feed introduced by settlement produced an up- 

 ward trend in crows just as it did in most game birds, but that this increase has 

 since been offset to a greater or less extent by crow shooting. 



Crow Roosts as an Index to Abundance. An attempt was made dur- 

 ing the survey to map all crow roosts used by 1,000 or more birds. This mapping 

 was done only in Indiana, Wisconsin, and Missouri. Possibly half the actual 

 number of roosts were mapped. Map 18 shows these roosts as black squares. 

 Sometimes it was possible to ascertain for how many years a roost location had been 

 used. Where a date appears to the left of the roost symbol it indicates the 

 known age of that roost. 



I am convinced that the phenomenon of rdosts is closely associated with 

 abundance of crows. Thus during the Missouri survey, winter crows were ob- 

 served to be most abundant along the bottoms of the Missouri and Mississippi, 

 somewhat less so on the prairies, and not at all abundant in the Ozarks. A glance 



