the airy tree-tops. The frequent black in their costumes, though it often 

 fits in very well with their tree-top background-picturing and 'ruptive' pat- 

 terns, seems on the whole to be a concession to the time they spend among 

 dark trunks and branches fairly within the forest. Practically all these party- 

 colored tropical birds have counter shading, in the main relations of their 

 colors, however much its smooth gradation is broken and interrupted by the 

 bold patterns, and however irregular and acrobatic may be their feeding- 

 postures. The multiplicity and variety of bright-colored vegetable forms in 

 the sunlit crown of a tropical forest make a great variety of 'ruptive' pat- 

 terns and colors effective for the disguisement of its birds. As has been told 

 in an earlier chapter, ruptive patterns are often intricately commingled both 

 with iridescence and with appendages, all three factors working toward the 

 one end, ' obliteration. ,' It is in the tropics, — in the tree-tops and in the forest- 

 borders — that we find the highest development of all three principles, both 

 separate and combined. Iridescence is not second in importance to ruptive 

 pattern, nor is it less widely and variously used. Appendages also play a 

 very important part, as we have shown. 



One more component principle of 1 ruptive' coloration, prominent in the 

 costumes of tropical wood-birds, must be here explained. This is the fre- 

 quent juxtaposition of complementary colors. Just as brilliant iridescence 

 tends to range from one color to its full opposite, or " complementary " — as 

 from red to green — so, when two bright colors occur side by side in a ruptive 

 pattern, they are usually not kindred, but complementary. Thus we find 

 green-breasted trogons with red bellies, purplish-blue-breasted trogons with 

 orange bellies, orange-yellow tanagers with steel-purple backs, and so on. 

 Not only are the colors thus placed intensified by mutual contrast, but, by the 

 very added sharpness of their difference, the ' disruptive' effect is heightened. 

 The opposed patches seem less than ever to belong to one and the same ob- 

 ject. A bright color tends even to create its complementary* Look at a 

 rich yellow flower, or some other small yellow object, against white paper. 



* See the footnote on p. 19, Chapter I. 



