CLASS AVES 423 



436. Economic Importance. — Birds are economically of great impor- 

 tance because of their use in various ways and also because of the service 

 they render as destroyers of injurious animals, particularly insects. 



Both the flesh of birds and their eggs are used as food. The feathers 

 of many species serve for adornment in a variety of ways and are also 

 used in the manufacture of down quilts and pillows. On islands off 

 the coast of Chile, where little rain falls and which are resorted to by sea 

 birds for breeding, the feces accumulate in enormous quantities. These 

 deposits, known as guano, are used as a source of fertiUzers. 



There are now large accumulations of data showing the great value 

 of birds as insect destroyers or as destroyers of other injurious animals. 

 Many hawks, owls, and other birds of prey, which are killed because 

 of their occasional depredations in the poultry yard and their attacks 

 upon game birds, should be considered beneficial because of the number 

 of field mice, ground squirrels, and other injurious mammals which they 

 destroy. It may be urged against birds that they destroy beneficial 

 insects as well as injurious ones, so in the case of every bird it becomes a 

 matter of striking a balance between the injuries done and the good 

 accomplished. However, when such balance sheets are made up for 

 birds, cases are very rare indeed in which a credit is not shown in favor 



of the bird. 



The problem of bird protection resolves itself into a matter of the 

 destruction of the very few relatively injurious types; the strict con- 

 servation of all w^hich are of value for their service in the destruction of 

 insect pests; and the restriction of the killing of game birds to such a 

 degree as to permit the greatest number of persons to profit by hunting 

 and at the same time prevent the destruction of the stock upon which 

 the existence of future generations depends. 



Several birds have been domesticated by man, some for many cen- 

 turies. Many of the numerous cultivated varieties of the common 

 domestic fowl were probably derived from a jungle fowl of India. The 

 domesticated pigeons are descended from a wild blue rock pigeon ranging 

 from Europe to Central Asia, and here again a great variety of cultivated 

 types have been developed. There are also to be included among 

 domesticated birds the geese; ducks, most of which have come from the 

 wild mallard; turkeys, which were natives of North America; and pea- 

 fowls, which originally were found in Oriental countries. Many birds 

 have been cultivated for their ability as singers, a conspicuous example 

 being the canary; and others, such as parrots, parrakeets, and love birds, 

 for their plumage. 



