2O2 



ANIMAL BIOLOGY 



things. Nature allows few opportunities for making a 

 living to go to waste. 



With relatively few exceptions most birds, in one way or 

 another, are of value to man. There are the game birds 

 such as ducks, geese, plovers, snipe, quail and many others 

 whose value is obvious. There are scavengers, such as 

 the sea gulls which devour all sorts of refuse that floats on 

 the water, and the vultures and buzzards which eat de- 



FIG. 156. Yellow-bellied sapsucker. 



caying flesh. The accumulated excreta of birds, which is 

 called guano and which occurs in great quantities on cer- 

 tain islands on which the birds congregate, is much em- 

 ployed as a fertilizer of the soil. The plumage of birds is 

 greatly in vogue for purposes of decoration, as well as 

 for various other purposes of a more practical nature. 

 But by far the greatest value of birds lies in their whole- 

 sale destruction of insects and other injurious forms of 

 animal life. Much study has been devoted to the food 



