18 bulletin: museum of compakative zoology. 



In all my examples of hypoleucus the entire surface of the plumage which 

 covers the under side of the wing is clear, immaculate white. Two birds have 

 some concealed slaty or brownish on a very few of the longer coverts lying near 

 the edge of the wing, but this is so restricted in extent and situated so near 

 the bases of the feathers as to be scarcely noticeable, even when the plumage 

 is violently ruffled ; nor can it, I think, be fairly regarded as representing 

 any real approach to the conspicuous and practically universal dark mottling 

 found on the under wing coverts of B. craveri. 



B. hypoleucus, as represented in my collection, invariably has the whole 

 inner web of the first primary pure white to within about an inch and one 

 half of the extremity of the feather. Beyond this point the white gradually 

 recedes from the shaft, terminating on the inner edge of the feather about three 

 quarters of an inch from its tip. The shaft itself, with an exceedingly narrow 

 space (a mere hair line) bordering it inwardly, is brownish white. With each 

 succeeding quill the white retreats farther and further from the tip of the 

 feather, at the same time losing something of its purity. Beyond the sixth or at 

 most the seventh primary it is rarely appreciable excepting at the extreme bases 

 of the feathers. None of my examples of craveri show well defined white areas 

 on any of the quills, although the brown of their primaries is often a shade or 

 two lighter on the inner than on the outer web and sometimes changes insen- 

 sibly into l)ro\vnish white near the bases of the feathers. 



Two of Mr. Frazar's specimens ((^ No. 18,288 and 9 No. 18,294), both taken on 

 the same date (March 1), are young, about one-half grown and stiU clothed, for 

 the most part, in down. This, over the up])er parts, is seal brown, slightly 

 redder as well as paler than in adult birds and with fine transverse markings 

 of whitish besprinkling the back and rump — but not the crown nor the wings. 

 The throat is grayish, the abdomen white. On the jugulum and breast the 

 down has been replaced by true feathers — those of the second stage of plu- 

 mage and everywhere silky white save on the sides of the breast, where they are. 

 flecked with minute spots of blackish. The sides of the body with the under 

 as well as the upper surfaces of the wings are covered with down of nearly the 

 same shade of brown as that of the crown and back, but there are also a few 

 budding wing coverts, as well as quills, the expanding tips of which are de- 

 cidedly darker in color. 



Other specimens in my series illustrate practically every stage through which 

 the young pass in arriving at maturity. They show that the natal down is 

 shed first on the breast, next on the throat and abdomen, next on the wings, 

 next on the back, next on the chin, next on the center of the crown, next on 

 the forehead, last of all on the occiput and sides of the crown. "With the dis- 

 appearance of the last shreds of down the bird completes what I suppose must 

 he called its first winter plumage, although this in specimens which, like mine. 

 were hatched and reared in January and February is really assumed in early 

 spring. After perfecting this plumage the young can be distinguished from 

 their parents only by their shorter and weaker bills, by the darker (nearly dead 

 black) coloring of their upper parts and by the presence of numerous fine but 



