42 PROTECTIVE COLORATION. are generally dull brown or gray, like the ground, leaves, or grasses about tliem, while tree-liaunting Ijirds, espe- cially those that live in the foliage or feed from blossoms, are, as a rule, brightly colored. In this class belong Hummingl)irds, Orioles, the gayer - plumaged Finches, Taiiagers, 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 wearer's 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 parts are
- See his papers -on The Law which Underlies Protective Colora-
tion, in The Auk (New York city), vol. siii, pp. 124-129, 318-320, eleven figures.
