are. | CHADBOURNE, Spring Plumage of the Bobolink. 145 
pigmented matter is more uniformly scattered throughout. (Com- 
pare figs. 6 and 7.) 
No difference between the pigmented matter of the spring and 
fall feathers was detected by the usual chemical and microchemi- 
cal tests, which will be described more fully in another connection.! 
RESULTS : — Summing up the more important points brought 
out by our study of the spring plumage of the Bobolink, we have 
seen that : — 
1. Color-change in the individual feather is fact, not theory. 
2. ‘Color-change of the plumage without moulting’ is also 
Jact, not theory ; and the change to breeding dress in the male 
Bobolink sometimes takes place without a so-called ‘ moult.’ 
3- Different individuals of the same species vary as to 
‘moulting’’ when assuming the spring plumage; and the 
fact that one Bobolink ‘moulted’ is no proof that all 
Bobolinks do the same. 
4. The contradictory statements of writers are accounted 
for by this individual variation; and such statements are 
not to be passed over as so-called ‘ errors of observation.’ 
gy Color-change and feather-change are two distinct pro- 
cesses, neither being the direct cause of the other; and 
each occurs separately, as well as both together. 
6. So-called ‘moulting’ (whether based on pin-feathers or 
on feather-loss), does not prove the absence of color- 
change ; but to be valid, the proof must be based on the 
loss of all the old feathers from the tracts concerned. No 
such evidence has as yet been recorded. 
7. Microscopically, the black and the buff feathers of the 
Bobolink differ only in the massing of the brown pigmented 
matter nearer the surface of the former ; while it is more 
uniformly distributed in the latter. The usual tests fail to 
distinguish the pigmented material of the breeding from 
that of the fall plumage. 
1 Since the above was written, I have obtained similar proof that the Indigo 
Bunting (Passerina cyanea) also shows a like “ individual variation ” in regard 
to its spring change of plumage, — a male having developed the full breeding 
dress without appreciable feather-loss ; while another male, which I saw sev- 
eral times, had a considerable number of pin-feathers, and also many cast-off 
feathers in the cage. 
xo 
