COLORS AND PLUMAGE OF BIRDS 47 



tection from their enemies; hence the term, "pro- 

 tective coloration." Many birds that live on the 

 ground, such as the ruffed grouse and woodcock, are 

 so similar in appearance to their surroundings that 

 the birds are rendered almost invisible. 



Many birds are protected by the law of coun- 

 ter-shading. The back which is exposed to the light, 

 is darker than the breast, which is in the shadow, and 

 the sides gradually shade from dark above to light 

 below. The effect of this gradation in coloring is to 

 make the bird so harmonize with its surroundings 

 that it is rendered much less conspicuous than it 

 would otherwise be. It is very common to find birds 

 with the under parts lighter colored than the upper 

 parts; such as the house wren, phoebe, red-eyed 

 vireo, cuckoo, and many others. This law has been 

 worked out and proved by means of interesting ex- 

 periments by Abbott H. Thayer. 



