404 METAZOAN PHYLA 



and also in the case of a small sandpiper-like bird known as the phalarope. 

 The female of the African ostrich participates very little in incubation. 



Two types of young birds are recognized, depending upon the degree 

 of development at the time of hatching. Some are known as precocial 

 and form a group called nidifugae (nest-fleeing). They are covered 

 with down at the time of hatching, have their eyes open, and run or 

 swim as soon as their plumage is dried. Examples of this type of bird are 

 the fowls, ducks, geese, and water birds generally. An extreme case 

 is that of the brush turkeys of Australia and the East Indies. Neither 

 parent incubates; the eggs are hatched by the heat of the sun, and when 

 the young birds leave the eggs they are in full plumage and able to take 

 care of themselves. Others are known as altricial and form the group 

 nidicolae (nest-living). The young of these birds are naked and blind 

 at birth and gradually acquire the down plumage, which is later replaced 

 by a inormal plumage before they are able to leave the nest. Our ordinary 

 song birds all belong to this group. 



434. 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 fertilizers. 



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 which 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. 



