Auk 
144 CHADBOURNE, Spring Plumage of the Bobolink. Avpel 
and there old-growth feathers, which are black, like the breeding- 
dress (cf. fig. 1); 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 
(of. fig. 4), and apparently change to the color of the autumn 
plumage later (ff 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 w/z¢e! light, 
show that the seemingly deep black color is really due to a drown- 
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 froma mirror covered with a white, 
highly glazed paper, and hung at an angle outside of a north window. 
2 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. 
