142 Chadbourne, spying Plumage of the. Bobolink. I April 



same species must ' moult ' also ; but have we any proof that this 

 is the case ? None whatever ! The physical condition must vary 

 in different individuals, be they men or birds ; and hence the 

 need of new feathers and the power of producing them, must vary 

 also; and it is certainly more probable that Nature would be 

 guided by the condition of the individual bird, than that the 

 rulings of modern systematists would be followed. In short some 

 Bobolinks '■tiimilt ' in springs others do not. 



To return to my Bobolink : — The first black spot appeared on 

 March 28 and consisted of a single feather, which macroscopic- 

 ally and microscopically, was evidently not of recent growth, the 

 edge being quite uneven and no remains of the enveloping sheath 

 being present. (Plate Ljr, fig. 3.) Subsequent specimens were 

 similar to it in all essential details. In some of the changing 

 feathers the black first developed around several foci, scattered 

 about the surface of the vane, from which the dark effect spread, 

 until the isolated spots became confluent and the whole was the 

 uniform black shade of the spring dress. In other examples the 

 dark color gradually extended towards the periphery, starting from 

 the proximal portion of true vane and medially from along the 

 rhachis.i 



In about three weeks from the time the first black feather was 

 noticed the full black and white breeding dress of our familiar 

 songster was complete. No chestnut was at any time seen on the 

 breast or under parts, nor was there the white on the centre of the 

 breast and abdomen, which is so prominent in the CorumbA bird.'"* 



' As there was no feather-loss it seemed unnecessary to mark and follow up 

 the intermediate steps through which any one feather passed ; moreover, it is 

 impossible to mark a feather without injuring it, and my previous attempts had 

 not been encouraging. (C/". Auk, XIII, Oct. 1894, p. 323.) 



* The majority of the white feathers on the breast of the Corumba bird 

 showed no color except white in the vane proper — i.e., exclusive of the downy 

 parts of the feather, which were a pale slate color. Some of these white 

 feathers were not fully maticre, while others are more or less worn and of old 

 growth. Even supposing that all the worn white feathers would have been 

 ' moulted ', those which were still immature would hardly be cast off before the 

 time the Bobolink appears in the South when no such completely white feathers 

 are normally found. My Bobolink showed none of this white marking on the 

 breast or abdomen, nor did it have the chestnut shading, which is so prominent in 



