^'"Iso^^^l Chadbourne, Spring Plumage of flic Bobolink. \^Z^ 



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 x's fact^ not theory. 



2. ' Color-change of the plumage without moulting ' is also 

 fact, 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.' 



5. 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 bufi' 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. 



• Since the above was written, I have obtained similar proof that the Indigo 

 Bunting (^Passerina cyattea) 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. 

 '9 



