808 



It is evident, consequently, that the real dynamic significance 

 of the birds of this district at this time was to be found wholly in the 

 fifteen most abundant species, the remainder being virtually negligible 

 as a general ecological factor.* These fifteen species are arranged 

 in the order of their frequency in the following table, which shows 

 for each the number of individuals seen, the ratio of its numbers to 

 the number of all the birds observed, and the average number of the 

 species per square mile of the area under observation. 



Tabi<e I. The Fifteen Most Important Birds, 

 Indiana Line to Quincy, August 28 to October 17, 1906 



Species 





English sparrow 



Crow-blackbird 



Meadow-lark 



Crow 



Cowbird 



Horned lark 



Mourning-dove 



Swamp-sparrow.: 



Goldfinch 



Myrtle warbler 



White-throated sparrow 



Field-sparrow 



Vesper-sparrow 



Quail 



Flicker 



Totals 



If we exclude the English sparrow from consideration, as an 

 obnoxious alien whose habits should not be permitted to influence 

 opinion concerning the ninety-two species of our native birds, we 

 must compute the ratios of abundance for the native species with 

 reference to the 3184 such birds identified on this trip. This is an 

 average of 579 per square mile, instead of 874, the former number. 

 To obtain 85 per cent, of all the native birds seen we must add to the 

 above list the next most abundant species, which are the robin, the 

 bluebird, the killdeer, and the blue jay. The following table shows 



*A species represented by a relatively small number of birds may 

 have a special ecological significance if it is concentrated in a special class 

 of situations; and may, indeed, be especially important ecologically if the 

 class of situations in which it is concentrated is especially important. This 

 aspect of the general problem must be reserved for discussion when a larger 

 mass and a more comprehensive variety of data are available. 



