THE SECOND PROBLEM OF BIRD LIFE. 145 



becomes national, as the olive skin and dark hair of the 

 Italian, and the fair hair and white skin of the Scandinavian. 



If climate can alter a man's color, why should it not affect 

 the birds' ? It does. The suns of the desert bleach them ; 

 the humidity of wet and dripping forests removes the brighter 

 hues and leaves dull blues and grays and browns predominant ; 

 and tropical warmth and brightness seem to tone up the colors 

 by some secret chemistry of the sun. It is not so much that 

 birds choose regions that correspond to them in tone, as that 

 they are changed to harmonize with the surroundings they 

 prefer to live in. The object of safety is not so vividly before 

 the bird that he would leave his favorite food because his coat 

 did not match the scenery ; but natural causes work upon him 

 against his will to secure for him what he would not seek for 

 himself. 



The result here is safety. The principle is, — Animals 

 involuntarily tend to acquire a color that accords ivitJi their usual 

 habitat ; or, in simpler words, they become like the color of 

 the places they live in. 



We have touched the secret spring of a great truth in this 

 principle, and now that the door is open before us we have no 

 time to go farther. We cannot fully appreciate how well this 

 principle explains many difficulties until we know more; 

 until we have seen how the gayest bird even may be pro- 

 tected by his brilliancy and the plainest favored by his shad- 

 ings ; how certain patterns of coloration resemble inanimate 

 things, and how, unless a bird is favored by its color or by its 

 sense, it is likely to have a short life. But we have learned 

 that even if in the beginning all birds had been of one color, 

 they could not always have remained alike, and that there is 

 safety in a color that blends with the surroundings. 



