1664 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 3 



humeral, spinal, ulnar, femoral, and crural. Mouth, externally gape 

 yellow; beak (pale) yellow. ,, Van Tyne and Drury (1959) describe 

 an 8-day-old nestling as "bill, Cadmium Yellow to Cartridge Buff 

 (at rictus); mouth lining, near Deep Corinthian Red; legs and feet, 

 near Ecru Drab. The head, back, and lesser wing coverts of this 

 bird were covered (along the usual tracts) with long natal down, Hair 

 Brown in color. Not the slightest trace of down remained on an 

 eleven-day female in the same nest (nor on an older fledgling collected 

 nearby two days later). The eleven-day nestling weighed 32.3 grams 

 and was extremely fat (2.3 grams of free fat were removed from the 

 underparts). The fledgling was also very fat." 



Juveniles differ from first-year birds chiefly in body plumage. 

 Their upper parts, according to Witherby et al., are dusky or buffish- 

 gray streaked with black, the mantle being most buffy and heavily 

 streaked; the underparts are buffy with dusky markings on upper 

 breast and flanks, whitish-buff in the center of breast and belly, dusky 

 gray on chin and center of throat. The median wing coverts are 

 grayish-black tipped with white, not white as in first winter birds; 

 the lesser coverts differ in being grayish-black fringed with grayish- 

 white, rather than black with buffish-white tips or white flecks. 

 The sexes are similar, but the females have more black on the second- 

 aries and outer rectrices. In comparing five juveniles from Frobisher 

 Bay, Baffin Island, with three from Wainwright, Alaska, Richard 

 Graber (MS. 55) found the Alaskan specimens tended to be "buffier" 

 throughout, the buffiness being especially noticeable on the auriculars. 



The first winter plumage is acquired by an incomplete postju venal 

 molt in which the juvenal wings (except the median and lesser 

 coverts) and tail are retained. The resulting plumage strongly re- 

 sembles that of adults, but in young males the flight feathers are 

 darker than those of adults, and the brown of the upper parts may be 

 darker. First-year females have darker secondaries than older 

 females. 



The juveniles molt while flocking, often near the coast, though some 

 may complete it inland. At high latitudes in Canada and Greenland 

 the juveniles molt very rapidly, and acquire their new plumage by 

 late August or early September. One young bird we collected at 80° 

 N. in Ellesmere Island had nearly completed its postjuvenal molt by 

 August 17. 



The adults acquire their fall plumage by a postnuptial molt that is 

 complete or nearly so. The males start molting about fledging time, 

 as early as mid- July in parts of the Canadian Arctic Archipelago and 

 Greenland, the females slightly later. By late July and early August 

 both sexes are molting heavily, and they seek secluded places where 

 they are met singly or in small groups that may include both sexes 



