BREWSTER'S WARBLER. 313 



est the growth of the young of tliis pair in their shiw [irogi-ess from the nestling 

 plumage to the first winter plumage. When first seen, on the 15th of June, 

 these young Ijirds were probably not more than two clays out of the nest, and 

 both Dr. Tyler and myself saw, or thouglit we saw, a deeper yellow tint on 

 their breasts and liellies than we had hitherto seen on young chrysopierae and 

 leucobronchiales of the same age; by the 20th of June, however, this yellow 

 tinge was much less pronounced, and by the 25th of the month, when the tails 

 of the little birds were about three quarters of their full length, the yellow was 

 scarcely apparent, the young still wearing the ju\enile dress. Dr. Tyler had 

 fastened a platinum band on the leg of one of the little birds of this family on 

 the 15th of June; we were thus enabled to note the change of color in the same 

 individual as the days wore on, — a change tloubtless due to the loss of tlie 

 fugacious, veiling, yellow tips of the juvenile feathers. 



On the 27th of June we saw the first signs of the post-juvenile moult in 

 the loss of one set of wing-coverts with its yellowish bar. By the first of July 

 the contour feathers of the juvenile plumage were being extensively replaced 

 by those of the first winter plumage. As in former seasons (1910, 1911) a marked 

 difference was apparent in the amount of yellow on the under jjarts of the dif- 

 ferent indi\'iduals of the same brood. In at least one of tlie brood now under 

 consideration tlie yellow tint was very faint and it was clear e\'en at this early 

 date that this young one was a leucobroncliidli.^; in other meml^ers of this same 

 brood the secontl winter jilumage displayed a strong yellow tint on the throat 

 and along each side of the breast and belly, following the area of the picryla 

 veniralis and leaving an ash-colored longitudinal liand along the median line 

 of the abdomen, caused by the retention of some of the juvenile set of feathers. 

 As time went on, the yellow color gradually became fainter and restricted for 

 the most part to the I)i'east, leaving the throat and abdomen ashy white; the 

 growth of a l)lack trans-ocular stri])e and yellow wing-coverts now perfected 

 the garb of Helminthophila Iciieobroncln'aUs. On the 12th of .luly at least two of 

 this brood of young birds were as slightly tinged with yellow as the young 

 leucohronchialis figuretl on the plate of my memoir of 1911 (fig. 1). Not one 

 of this brood developed the least trace of the black throat and broad cheek- 

 patch of H. chnjsopkra. 



As I have previously saiil, the varying amount of yellow, at tlie same date, 

 in different young Brewster's Warblers of the same brood was noticeable in 

 all of the years in which we observed the growth of the winter plumage in these 

 birds. This may be the result of different degrees of precocity in the individ- 



