144 CuADBOURNE, Spring Plumage of the Bobolink. I \pril 



and there old-growth feathers, which are black, like the breeding- 

 dress {cf. fig. i); and others of the new-growth, which are the 

 color of the Reed-bird plumage {cf. fig. 2). 



Male Bobolinks in autumn, after the cares of the breeding- 

 season are over, would probably require a complete renewal of the 

 plumage, and a color-change in the old-growth would hardly be 

 expected to occur. Pin-feathers typical of the black summer 

 dress can be occasionally found, however, if carefully looked for 

 {cf. fig. 4), and apparently change to the color of the autumn 

 plumage later {cf. fig. 5). 



We have now seen that feather-change and color-change in 

 some cases at least, do take place separately and entirely independ- 

 ent of each other, though the two are also often in progress at the 

 same time. Hence it necessarily follows that neither can be the direct 

 cause of the other ; but that color-change must be recognized as an 

 independent process., entirely distinct from so-called ' moulting.'' 



The color-changes in the feathers of the Bobolink, of which I 

 have now I think given sufficient proof, are the less surprising, in 

 view of the fact that the black feathers apparently contain very 

 little or no black coloring-matter. Thin transverse sections through 

 the exposed portion of the vane of black breast-feathers, when 

 examined with a high magnifying power and a strong white ^ light, 

 show that the seemingly deep black color is really due to a brozan- 

 ish pigmented material,-^ generally (always ?) grouped superficially 

 near the surface of the vane ; to some extent also to the thickness 

 of the part, and to the effect of the underlying structures. Thus 

 in the black spring specimen the granules are peripheral and 

 comparatively close together, though a smaller number are also 

 found in the deeper parts ; while in the autumn the granular 



' The most satisfactory light I have tried for color work with the micro- 

 scope is that from a clear sky, reflected from a mirror covered with a white, 

 highly glazed paper, and hung at an angle outside of a north window. 



- To show that there is a very large amount of brown coloring matter even 

 in breast feathers of the deepest black, it is only necessary to place such a 

 specimen between two pieces of clear glass, and hold it against a strong light. 

 The greater part, — sometimes the whole, — of the contour portion will appear 

 ochraceous, being brightest along the edges of the barbs and barbules, where 

 the parts are thin. This last, however, cannot be seen without a good magni- 

 fying glass. 



