152 PROBLEMS OF BIRD LIFE. 



that it belongs to a bird, therefore many of the bird's orna- 

 ments are a protection against discovery. "This makes, for 

 instance, the mallard's dark green head tend to detach itself 

 from his body and to join the dark green of the shady ledge, 

 or the ruby of the humming-bird to desert him and to appear 

 to belong to the glistening flower he is searching." In this 

 way, bright or strongly contrasting crown patches, throat 

 patches, necklaces, and collars may be seen to have a use other 

 than mere ornament, and crests often help to conceal birds by 

 disguising familiar outlines. The cedar bird and the ruffed 

 grouse are experts in evading notice by throwing themselves 

 into strange attitudes and erecting their crests. Curves are 

 what betray the bird; broken outlines or stiff lines conceal 

 him. Therefore the ruffed grouse, when in a tree, lays all his 

 feathers flat, stands stiffly at his greatest height, with his neck 

 stretched as far as he can reach or crooked sharply at an angle. 

 I have stood within two rods of a ruffed grouse, in fair sight, 

 and that not many years since, and have decided that he was 

 a very strange branch on a willow bush, before it flashed 

 upon me what I was looking at. 



The most beautiful arrangement for protective color is also 

 the commonest, and though nearly every bird and animal prof- 

 its by it, no man ever discovered it until a few years ago. It is 

 called the " law of gradation." Nearly every bird, you know, 

 is lighter on the breast than on the back, and it is almost a rule 

 that birds not uniformly colored, like the crow and the black- 

 birds, shall be white or gray or buffy along the belly and beneath 

 the tail, even if they have dark breasts and throats. Why this 

 is so, is as simple as it is interesting. 



Every bird, standing in his usual positions, cuts off a portion 

 of the light that falls from above and so casts a shadow on 

 his own breast and under surface. We do not see the shadow, 



