Colors of Feathers 



those found in black feathers, but with the addition of from 5 to 8 per cent of 

 copper, and these birds lose their red color when washed by the rain-, but regain 

 it again when dry. The water in which they bathe is said to become reddish. 



The second kind of coloring results from the combination of a pigment with 

 certain structural peculiarities, such as ridges and furrows, in the surface of the 

 feather itself. Such colors as violet and blue, usually green and sometimes 

 yellow, belong under this heading. In transmitted light feathers with these 

 colors show only the color of the pigment. "For instance, the deep green or 

 blue feathers of a Parrot will thus appear only gray or yellowish. The same 

 happens when their polished surface is scratched or crushed ; the blue color 

 instantly disappears, showing only the 

 blackish underlying pigment, or yellow 

 pigment in green feathers. When thor- 

 oughly wetted in a bath the feathers of 

 the back of an Amazon Parrot appear 

 brown without a trace of green." 

 NEWTON. 



The third form of coloring, or apparent 

 coloring, includes the exquisitely beautiful 

 prismatic or metallic colors, such as those 

 found in Hummingbirds, the Birds of 

 Paradise, Peacocks, Doves or Pigeons, 

 Starlings, Grackles, and very many other 

 birds. The manner in which these effects 

 are produced has given rise to much spec- 

 ulation, and an extensive literature exists 

 upon the subject, but even now the ques- 

 tion can hardly be considered as definitely settled. The commonly accepted 

 hypothesis is that . metallic colors are due entirely to the structure of the 

 surface of certain parts of the feathers, such as striae, ridges, knobs, or 

 pits, in combination often with extremely thin, transparent, colorless layers, 

 these elements, it is asserted, acting as prisms and changing the color as the 

 direction of the light and the position of the eye change. Recently Dr. R. M. 

 Strong appears to have demonstrated that the above explanation fails to meet 

 certain of the physical requirements of the case. In investigating the metallic 

 colors of feathers from the sides of the neck of the domestic Pigeon, he failed to 

 find striae or other inequalities on the outer surface of the barbules that were 

 sufficiently numerous or uniform enough to produce the observed colors by 

 diffraction, but he did find that the barbules within the metallic area were strik- 

 ingly different from those outside it. Instead of lying vertically, as in the non- 

 metallic areas, they are turned so that one side faces upward, thus giving a 

 much greater reflecting surface. The dorsal face of these barbules is provided 

 with an outer transparent wall which encloses cell-cavities filled with pigment, 

 this coloring-matter being in the form of spherical granules in the metallic-colored 

 barbules, whereas in the non-metallic-colored areas the granules are of the 



FIG. 2. Two enlarged barbs of a feather, 

 showing interlocking barbules and barbicels. 



