COLOR AND CONCEALMENT 93 



by the character of its haunts, its colors, unchecked by any need for 

 concealment, may make it conspicuous.* 



Inconspicuousness is achieved primarily, not alone in birds but 

 also in most other animals, by that disposition of color which makes 

 them darkest where they receive the most light, and palest where they 

 are most in shadow. This is the far-reaching principle of counter- 

 shading discovered by Abbott H. Thayer and announced by him in 

 1896 (The Auk, 1896, pp. 124, 318). Of it Poulton remarks: "For ages the 

 artist has known how to produce the appearance of solid objects stand- 

 ing out on his canvas, by painting in the likeness of the shadows. It 

 has remained for this great artist-naturalist to realize the logical anti- 

 thesis, and show how solid objects may be made to fade away and 

 become ghost-like, or even invisible, by painting out the shadows." 



Thayer's experiments in conclusive demonstration of this law may 

 be repeated, even if crudely, by taking, say, four bits of wood shaped 

 to resemble a bird's body, or, failing these, several symmetrical pota- 

 toes of about the same size. Run a stout wire rod through these objects, 

 leaving intervals of about eight or ten inches and, selecting a spot not 

 in direct sunlight, support the rod at both ends, on uprights which will 

 raise it six or eight inches from the ground. The models should be uni- 

 formly colored to resemble the earth against which they are seen, and 

 the resemblance may be heightened by sprinkling some of the earth 

 upon them. 



If the secret of protective coloration is an exact likeness in color 

 between an animal and its background, these models should be essen- 

 tially invisible, whereas they are exceedingly conspicuous. Now, in 

 imitation of nature, paint out the shadow on the lower half of two of the 

 models by grading through earth color laterally, to pure white on the 

 lower median line, when it will be seen that at a distance of thirty 

 feet or more these white-bottomed models have, in a magical manner, 

 become nearly if not quite invisible, although they are still the same 

 color on the upper half as the untoucheH models, which are plainly 

 visible at a distance of at least forty or fifty yards. 



To prove that this result is due to the disposition of color, as 

 regards light and shade, rather than tb~ color alone, turn the models so 

 that the white is uppermost, thus reversing nature's law, and thereby 

 rendering the two models which before were indistinguishable even 

 more prominent than those which are uniformly colored. 



Such, in briefest outline, is an explanation of Thayer's law of coun- 

 ter-shading, for a fuller description of which, as well as of its various 

 modifications, the student is referred to Thayer's work on "Concealing 

 Coloration." Thayer's law of obliterative markings is also presented 

 in this book. This explains the pattern of coloration or markings of 

 counter-shaded birds which bear on their plumage a picture of the 

 background against which they are most commonly seen by their 



*In this connection see Reighard on the colors of coral-reef fishes. Papers from 

 Tortugas Lab. of Cam. Inst. Wash., 1908, pp. 261-325. 



