her body round and round within it ; gkied into parchment with her saliva ; 

 and there it hung, a tiny cup that might be mistaken for the nest of a hornet. 



But that was not quite the end ; this particular Vireo wrought a row of 

 embroidery around the middle of every cup she made. The embroidery was 

 always the same. As she wrought once she wrought again. 



The Utility of Birds in Nature 



By Edward Howe Forbush 



There is no subject in the field of natural science that is of greater interest 

 than the important position that the living bird occupies in the great plan of 

 organic nature. 



The food relations of birds are so complicated and have such a far-reaching, 

 effect upon other forms of life that the mind of man may never be able to fully 

 trace and grasp them. The migrations of birds are so vast and widespread that 

 the movements of many species are still more or less shrouded in mystery. We 

 do not yet know, for instance, just where certain common birds pass some of 

 the winter months. Some species sweep in their annual flights from Arctic 

 America to the plains of Patagonia, coursing the entire length of the habitable 

 portion of a hemisphere. Many of the birds that summer in northern or tem- 

 perate America winter in or near the tropics. Some species remain in the colder 

 or temperate regions only long enough to mate, nest and rear their young, and 

 then start on their long journey toward the equator. 



The annual earth-wide sweep of the tide of bird life from zone to zone 

 renders the study of the relations of birds to other living forms throughout their 

 range a task of the utmost magnitude. This vast migration at once suggests the 

 question, Of what use in nature is this host of winged creatures that with the 

 changing seasons sweep over land and sea? 



Our first concern in answering this question is to determine what particular 

 office or function in the economy of nature birds alone are fitted to perform. The 

 relations they may bear to the unnatural and semi-artificial conditions produced 

 by the agriculturist may then be better understood. The position occupied by 

 birds among forces of nature is unique in one respect at least ; their structure 

 fits them to perform the office of a swiftly moving force of police, large bodies 

 of which can be assembled at once to correct disturbances caused by abnormal 

 outbreaks of plant or animal life. This function is well performed. A swarm 

 of locusts appears, and birds of many species congregate to feed upon locusts. 

 An eruption of field mice, lemmings or gophers occurs, and birds of prey gather 

 to feast from far and near. 



This habit of birds is also serviceable in clearing the earth of decaying 

 materials, which otherwise niiglu pollute both air and water. A great slaughter 



89 



