1620 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 3 



The adult winter plumage is acquired by a complete post nuptial 

 molt in July and August. D wight notes it as "practically indis- 

 tinguishable in many cases from the first winter plumage, but the 

 black on the chin and throat is more extensive, and the colors richer 

 and deeper, especially the whig edgings." At Cape Thompson the 

 complete molt begins during the last part of June and is essentially 

 complete in all members of the population by the end of August. 

 Timing of molt is similar for both sexes and takes about 50 days to 

 complete. The earliest dates for inception of the annual molt of 

 males and females were June 25 and July 2, respectively, while molt 

 started as late as July 5 in males and July 11 in females. Post- 

 juvenal molt was observed to begin as early as July 10. The striking 

 degree of synchrony manifest in the timing of molt accords with the 

 brevity of the arctic summer and the short time available for this 

 activity. 



The adult nuptial plumage of the male is acquired by a partial 

 prenuptial molt as in the young birds. Gabrielson and Lincoln (1959) 

 describe this plumage as follows: 



Head and chest deep black, relieved by a broad white or buffy stripe behind 

 eye, continued downward (vertically) behind ear coverts and then backward 

 along sides of chest; ground color of upperparts light grayish brown, with little 

 if any rusty tinge, even on wings ; sides narrowly streaked or striped with black ; 

 rest of underparts white; hindneck deep chestnut rufous; lesser wing coverts 

 grayish, feathers black in center. Outer tail feathers white, dusky along midrib 

 and on inner web toward base; the tail feathers narrowly edged with grayish white; 

 lining of wing and axillaries grayish white. Bill dark, lighter at base; legs and 

 feet black; iris brown. 



The plumages and molts of the female according to Dwight (1900) 



correspond to those of the male, but the black throat patch is never so extensive 

 and usually merely outlined with dull black streaks. The juvenal plumage is 

 indistinguishable from that of the male. The first winter plumage is much 

 veiled and streaked above with clove and cinnamon brown, the nape vinaceous; 

 below it is white obscurely black on the sides of the chin and with a small throat 

 patch, the sides and flanks black streaked. The first nuptial plumage is chiefly 

 the result of wear, a few white feathers being acquired by moult on the chin. 



Gabrielson and Lincoln (1959) describe the plumage of the adult 

 breeding female as follows: "A dull-colored bird, striped above with 

 dull black, rufous, and grayish white; an indistinct median light line 

 on crown; collar on hindneck pale rufous, finely streaked with dusky; 

 feathers of throat and breast black, concealed in part by grayish white 

 and pale buffy margins of feathers, producing a mottled or streaked 

 appearance; sides and flanks striped with dull black and pale rufous; 

 rest of underparts white; tail and wings as in male." The adult 

 winter plumage of the female is like that of the first winter with per- 

 haps more black on the throat. 



