great and vivid versatility of color and shade almost insures the ( matching ' 

 of some part of that surface with whatever forms its background. When part 

 of a bird's surface blends thus with his background, the remainder, in most 

 cases, looks un-bird-like. 



Iridescence should perhaps be considered second only to obliterative shad- 

 ing as a factor in the disguisement of birds; its universality attests its value. 



94 



