142 CHADBOURNE, Sfring Plumage of the Bobolink. al 
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 ‘moult’ in spring, 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 Ia, 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.! 
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. (Cf 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 —7. ¢., exclusive of the downy 
parts of the feather, which were a pale slate color. Some of these white 
feathers were vot fully mature, 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 
