4 6 
Brown on Immaturity vs. Individual Variation. [January 
IMMATURITY VS. INDIVIDUAL VARIATION. 
BY NATHAN CLIFFORD BROWN. 
Many readers of the Bulletin are doubtless familiar with a 
phase of plumage of Zonotrichia albicollis , occurring in spring, 
which appears to be the normal dress of this species in imma- 
turity, indicating, therefore, that its representatives do not attain 
their finest livery until the second year of their existence. In this 
plumage the bird appears as follows : The back, wings, and tail 
are essentially as in most adult specimens. There are black 
maxillary stripes. The breast is dull gray, lacking the bluish 
cast seen in high plumage ; it is distinctly streaked. The throat 
is grayish-white or rather clear gray, either slightly or not at all 
contrasted with the breast. The yellow before the eye is very 
limited in extent and of a dull, greenish tint. The superciliary 
and median coronal stripes are gray mixed with brownish and 
dusky. Brown rather predominates in the other markings of the 
head. In the middle of the breast is a dusky spot, much as in 
Spizella munticolct. 
Feeling: that all the distinctive features of this attire indicated 
immaturity, I was surprised, in October of the present year 
(1882), to procure specimens of Z. albicollis unquestionably in 
their first year, as proved by careful dissection, clad in a dress 
practically identical with that of maturest spring birds. The cir- 
cumstance naturally suggests the existence of two geographical 
races of this species, but the true explanation appears to be offered 
by evidence which I have recently accumulated in two precisely 
analogous cases, — those of Loxia americana and L. leucoptera. 
The announcement that males of the two North American 
species of Loxia sometimes — nay often — assume their full red- 
dish dress in the autumn of their first year, will excite the surprise 
and perhaps the incredulity of ornithologists ; yet, unless osteo- 
logical data which I have always considered infallible are to go for 
nothing, they certainly do so, and the greenish and yellowish 
examples, commonly called immature, simply illustrate remark- 
able and extreme individual variation. 
