BIRDS AS CONSERVATORS OF THE FOREST. 237 



girds ff)af Destroy Insects. 



One very important means which Nature has provided for the restriction of 

 these pests within reasonable bounds is found in the insect-eating birds, many 

 species of which spend the most of their lives upon trees, and subsist upon the 

 insects found thereon. The insectivorous habits of birds have been matters of 

 common observation for centuries, but their scientific demonstration has been 

 reserved for more modern times. The examination of birds' stomachs has shown 

 that nearly all of the smaller species, and .many of the larger ones, such as the 

 crow, subsist largely upon insects in the summer time, while rearing their young, 

 and, as a general rule, all the small birds feed their nestlings on this food no 

 matter what the adults may eat. It is perhaps unnecessary to say that birds do 

 not select their food with any special reference to the good or harm they may 

 be doing to man, and those persons who expect to find in them a series of 

 beneficent organisms wisely designed to do a certain amount of good and no 

 harm are doomed to disappointment. 



In the selection of their food, birds are either guided by their natural tastes 

 or driven by a blind necessity, and it may be stated as a general rule that each 

 species eats that kind of food which it finds by its own special method of 

 foraging — that is, a flycatcher eats such insects as it catches in midair, and 

 blackbirds and other terrestrial species such as they find upon the ground, while 

 cuckoos, woodpeckers, and titmice gather their food mostly from trees. It does 

 not follow, however, that birds eat all the insects which are found in their own 

 peculiar haunts, but when they have a special method of their own they rarely 

 abandon it for any other. 



To what extent birds are guided by a natural taste in their selection of food 

 is a point which is far from being settled. Whether a bird will pass by an 

 abundant supply of insects in order to secure others that are more to its taste is 

 a question which, aside from its biological interest, has an important bearing 

 upon the economic side of ornithology. This problem can not be solved by 

 stomach examination alone, but requires also patient and delicate field observation, 

 combined with a thorough knowledge of the available food supply of the locality 

 under consideration. 



Some insects are supposed to be especially protected from birds by color, smell 

 or taste, but stomach examinations have seemed to demonstrate that such devices 

 are of but little use when brought in opposition to the keen senses and sharp 

 appetites of their feathered enemies. The same method of investigation has 

 shown that protective coloration is not so potent a factor in saving insects from 



