WHITE-RUMPED SANDPIPER 185 



A young white rump about two-thirds grown and almost on the point of flight 

 was captured on August 1. Others seen a few days later <>n the shore of 

 Knksunittuk Bay were capable of short flights. As an experiment, I tried 

 several times to keep individual young alive at my base tent on the Takuirbiug 

 River, but they invariably died within about 24 hours regardless of the best 

 care. 



Plumages. — The down}* young white rumped is much like the 

 downy young of other tundra nesting species of sandpipers. From 

 the stilt sandpiper it can be distinguished by its much shorter legs 

 and shorter and slenderer bill, from the Baird by its more buffy 

 face and breast, these parts being pure white in bairdi, and from the 

 least by paler and duller browns in the upper parts and by white, 

 instead of buffy terminal tuft spots. The crown, back, rump, wings, 

 and thighs are variegated or marbled with " Sanford's brown," or 

 " tawny,'" and black, dotted, except on the front half of the crown, 

 which is mainly bright brown, with whitish terminal tufts. The fore- 

 head, a broad superciliary stripe, the sides of the head, throat, and 

 breast are pale buff or buffy white; the remaining under parts are 

 grayish white. A median frontal stripe of black terminates in 

 " tawny " toward the bill ; there are extensive black areas on either 

 side of the crown and on the occiput. The nape is grizzly, buff, gray 

 and dusky. 



In juvenal plumage the crown is sepia with **taw*ny" edgings; the 

 back, rump, tertials, and scapulars are sepia, with " tawny " edges, 

 and some of the feathers of the mantle and scapulars are also white 

 tipped ; the under parts are white, but the breast is suffused with light 

 buff and narrowly streaked with dusky; the median and lesser wing 

 coverts are broadly edged with light buff or whitish. 



The postj u venal molt of the body plumage usually occurs in Sep- 

 tember and October, mainly in the latter month, but sometimes not 

 until November. The upper body plumage is not all molted, so that 

 first winter birds can be distinguished by tawny or buffy edged 

 feathers in the mantle and by the juvenal wing coverts. The next 

 partial prenuptial molt apparently removes all traces of immaturity. 



Adults have a prenuptial molt, beginning in March, of the under- 

 body plumage, most of the upper-body plumage, sometimes the tail, 

 and some of the wing coverts. But this is almost immediately pre- 

 ceded by the delayed molt of the remiges in January and February, 

 so that it seems to be a nearly complete prenuptial molt, which is 

 barely finished before the birds start on their long northward migra- 

 tion. The postnuptial molt of adults, beginning in August and 

 often lasting into October, involves only the body plumage, the tail, 

 and some scapulars, tertials, and wing coverts. The gray winter 

 plumage, so different from the brightly colored spring plumage, is 

 seldom seen in its completeness before the birds go south. 



