THEIR RELATION TO ANIMALS 133 



We have here two questions of very great interest and 

 importance and the answer to the one does not by any 

 means determine the answer to the other. That all 

 these birds and other animals eat untold thousands 

 of insects each year is undoubtedly true, and that this 

 is an important factor in limiting the number of speci- 

 mens, is unquestionable; but compared with the num- 

 bers destroyed by disease, by climatic conditions and 

 by other insects, the figures are really insignificant. 

 It goes without saying that these remarks are based 

 on normal, natural conditions, for it is quite possible 

 to change the conclusion under control. For instance, 

 if I turn a flock of guinea-hens into a field infested 

 with grasshoppers, the fate of those hoppers is sealed, 

 provided there are guineas enough to eat them. I 

 have seen some fields of alfalfa, however, in the foot- 

 hills of the Rocky Mountains, where the grasshoppers 

 were so numerous that all the guineas within the county 

 would make no serious impression on them. 



As to the food of birds we are left in little doubt. 

 Many species have been shot in large numbers at all 

 seasons and have had the stomach contents carefully 

 determined and classified. One striking fact that 

 appears from all the lists that have been published, is 

 that the large majority of insect feeders among the 

 birds pick up anything they can get hold of most easily, 

 and that the commonest reasonably palatable forms 

 are those most frequently taken. Naturally, though, 

 this does not apply to birds fitted for a special diet like 

 the woodpeckers. Among the other animals almost 

 the same conclusion applies, again making exceptions 

 of such creatures as moles and others which are natur- 

 ally limited to underground forms or to species occur- 

 ring in limited or specialized areas. 



One consequence of this is that a great many eco- 



