128 Thayer oh Protective Coloration. I April 



nature uses the complete gradation, like that of Grouse and 

 Sandpipers. Ground birds in general, such as Grouse, Sand- 

 pipers and Sparrows, are usually clothed throughout in colors 

 graded according to this principle. But the males of many 

 species of Pheasant are notable exceptions to this last state- 

 ment. 



Now there is still one more very beautiful phenomenon to 

 record. If the animal itself is obliterated by this mechanism of 

 nature, for what useful purpose beyond considerations of sexual 

 selections do his markings exist, since they are not obliterated ? 

 The answer is that the markings on the animal become a 

 picture of such background as one might see if the animal were 

 transparent. They help the animal to coalesce, in appearance, 

 with the background which is visible when the observer looks 

 past him. In many birds, for instance, those colors, which 

 would be seen by an enemy looking clown upon them, are laid 

 on by nature in coarser and more blotchy patterns than are the 

 colors on their sides, so that when you look down on them you see 

 that their backs match the mottled ground about them; whereas, 

 when you assume a lower point of view nearer their level, and 

 see more and more of their sides, you find them painted to match 

 the more intricate designs of the vegetation which is a little 

 farther off, and which, from this new stand point of the observer, 

 now forms the background. In this latter position, the head of 

 the animal, being the highest part of its body, is seen against 

 the most distant part of the background, whose details are still 

 more reduced by perspective. To correspond with this reduction 

 of strength in the more distant background, the details on the 

 sides of the animal's head are likewise reduced in their emphasis, 

 and like the more distant details are smaller in pattern. 



It is a most significant fact that throughout the animal king- 

 dom the highest development of the arrangement of color and 

 light described in this article, and the highest development of the 

 habit of standing or crouching motionless in full daylight to avoid 

 discovery, seem to coincide very closely. For instance, Gallina- 

 ceous birds, most Waders, and the Cat tribe have both the color 

 arrangement and the standing or the crouching habit highly 

 developed. Contrasted with these, for example, are the skunks 



