The Audubon Societies 51 



different. Similarly but not in exactly the same way the color-effects on the 

 surfaces of smooth or peculiarly grooved feathers will be different. Rainbow 

 colors, or iridescence, are produced by light on some feathers of the latter 

 description. We are all familiar with the gleaming, scintillating plumage of the 

 Hummingbird, or the iridescent colors of the common Crackle. Only the tips 

 of metallic feathers show color, and these show it only on the upper side. The 

 laws explaining this strange action of Hght on feathers are found in the study 

 of physics. They do not belong to elementary bird-study, but for all who go 

 out in the field to observe birds it is not unimportant to have an inkling of 

 these few facts about the coloring of feathers. 



A great variety of patterns as well as of colors is characteristic of feathers. 

 Comparatively few birds or species of birds have plain feathers. Markings 

 may be regular, forming a sort of pattern, as on the head of the Woodcock or 

 the breast of the Flicker, or they may be confined to a few feathers, forming 

 wing-bars, tail-spots, patches or bands on the breast or elsewhere. How they 

 are changed by wear will be referred to in the next exercise. Much study has 

 been devoted to the colors and patterns of feathers. It is known that some birds 

 are protected by their plumage, inasmuch as the color and pattern of their 

 feathers blend so perfectly with the immediate vicinity of their feeding- and 

 nesting-areas that they are practically invisible when quiet. If an enemy 

 appears, their surest means of defence is to keep still until actually flushed. 



Just how important protective coloration is to birds in general is not known, 

 but it seems to be true that species like the Ruffed Crouse or Whip-poor-will, 

 for example, are far more invisible to the ordinary observer than highly colored 

 species like the Scarlet Tanager. 



There is still another fact of much interest about the color of feathers, that 

 is, unnatural, or what is better known as abnormal color. Normal color, as we 

 know, is what is regularly found in healthy birds that feed on a regular diet. 

 Abnormal color is found oftentimes in unhealthy birds or in those that are fed 

 on a pecuhar diet. It is not uncommon to find caged birds showing unnatural 

 or abnormal colors. Red canaries may be reared on a certain diet. Sometimes 

 birds that ordinarily are green or orange or quite red look almost wholly 

 yellow; but this is an abnormal condition. Occasionally, one hears of a white 

 Crow, or a white Robin. Such birds, for other reasons, have no coloring-matter 

 in their feathers. More rarely one hears of a black Sparrow or an almost black 

 Blue Jay, and this is the result of too much coloring-matter in the feathers. 

 Changes in climate also affect the plumage of certain species. 



Feathers, we learn, therefore, are not only comphcated in structure, but their 

 colors and markings are very diverse. Natural or normal coloration is due to 

 three causes: first, coloring-matter; second, coloring-matter and structure with 

 reference to light; and, third, structure alone with reference to Ught. The 

 colors and patterns of feathers may sometimes serve to protect a bird when it 

 is still, but not all birds are protectively colored and marked. 



