42 PROTECTIVE COLORATION. 



are generally dull l)rown or gray, like the ground, leaves, 

 or grasses about tlieui, while tree-haunting birds, espe- 

 cially those that live in the foliage or feed from blossoms, 

 are, as a rule, brightly colored. In this class belong 

 Hummingbirds, Orioles, the gayer - plumaged Finches, 

 Tanagers, Warblers, and many others. It is partly 

 owing to this fact that the erroneous idea concerning 

 the brilliant plumage of all tropical birds has become 

 established. The rich vegetation of the tropics furnishes 

 a home to a far greater number of brightly colored birds 

 than are found in temperate regions; still, they are not 

 more numerous than the dull-colored species that live on 

 the tree trunks, in the undergrowth, or on the ground, 

 where, owing to the nature of both their colors and 

 haunts, they are likely to be overlooked. 



Between these two extremes there are numerous in- 

 termediate groups, most of which conform to the general 

 law of protective coloration. There are, it is true, excep- 

 tions, but every close student of bird-life must be so im- 

 pressed with the dangers to which birds are exposed, that 

 he can not doubt that the chief object of color is usually 

 for its wearers concealment. 



The term " protective coloration " has lately received 

 fresh significance through the studies of Mr. Abbott H. 

 Thayer.* Mr. Thayer proves conclusively that protect- 

 ive coloration lies not so much in an animal's resem- 

 blance in color to its surroundings as in its gradation of 

 color. Thus he points to the fact that, as a rule, animals 

 are darker above than below — that is, those parts receiv- 

 ing the most light are darkest, while the parts receiving the 

 least light are palest. In effect it follows that the darker 

 upper parts are brightened, while the paler under j^arts are 



* See his papers -on The Law which Underlies Protective Colora- 

 tion, in The Auk (New York city), vol. xiii, pp. 124-129, 318-320, eleven 

 figures. 



