ADAPTATION FOR THE INDIVIDUAL 1 15 



pictures. They are so conspicuous that we recognize 

 them at once. More common in my region than the 

 jay or the cardinal is the red-eyed vireo. This crea- 

 ture moves industriously in and out among the leaves 

 of our trees. It is persistently in motion, is nearly 

 constant in song 1 , and is a bird of fair size, being 

 larger than our English sparrow, though smaller than 

 a robin. Many a nature lover will recognize twenty- 

 five or thirty birds at sight without any difficulty, and 

 not know the vireo. Yet the vireo is more common 

 than two-thirds of the birds he knows. There can be 

 but one reason for this; the bird is inconspicuous. 

 The olive-green of its back, with its light under parts, 

 serves to hide it completely amid the foliage. Even 

 the bird-lover learns to find it first by its jerky song, 

 and then by watching for its movements among the 

 leaves. 



One aspect of protective coloration has been 

 brought to our attention by the artist, Mr. Abbott N. 

 Thayer. He first clearly explained why it is that ani- 

 mals are usually so much lighter on the under side than 

 they are upon the upper. Mr. Thayer proves his posi- 

 tion by taking some ordinary cobblestones and paint- 

 ing one of them a uniform color and placing it upon 

 a board painted the same color. One would think the 

 stone would be inconspicuous; as a matter of fact, is 

 quite easily seen. The underside of the stone, turned 



