116 THE AMERICAN NATURALIST [Vol. XLV 



great protective value, as suggested by Davenport's fig- 

 ures. This, however, can hardly be the case in the pres- 

 ent statistics since if it be assumed that predaceous birds 

 killed relatively few barred chicks and relatively many 

 self-colored, then it must also be assumed that the other 

 unrecorded enemies showed a preference for barred 

 birds, since with all enemies taken together substantially 

 equal proportions of both kinds of birds were eliminated. 

 In other words, if we assume a selective elimination in the 

 case of predaceous birds, we are obliged to assume an 

 equal and opposite selective elimination on the part of 

 other unrecorded enemies. There is no evidence on which 

 such an assumption could be based. 



These figures, of course, cover only one year's expe- 

 rience, and are in no wise conclusive, but general obser- 

 vation indicates strongly that essentially the same re- 

 sult would be shown in other years if it were possible 

 to tabulate the figures. Unfortunately neither the 

 records of 1908 nor 1910 can be used for this purpose. 

 In 1908 there were almost no self-colored birds on the 

 range. In 1910, owing to the location of the houses 

 on the range and other circumstances which can not 

 be gone into in detail, thieves were active on the plant 

 and the birds taken were not a random sample of the 

 flock in respect to color. 1909 was a fortunate year 

 for such a study as the present one. The thieves con- 

 fined their attention to adult stock on a part of the plant 

 away from the chicks, and left the latter strictly alone. 



Definitely controlled observations regarding the elim- 

 ination of animals by natural enemies, covering a consid- 

 erable number of individuals and anything like a com- 

 plete range of enemies, are exceedingly scarce. The 

 whole question of the interplay of factors in the " strug- 

 gle for existence" constantly going on in the organic 

 world has been discussed very hugely from the a priori 

 standpoint, throughout the whole period since the ap- 

 pearance of the " Origin of Species." The " rabbit with 

 his legs a little longer," the "fox with the little keener 



