TREE SPARROW 1151 



On August 21, my last day in the field, the tundras were dehiged 

 \^dth tree sparrows. Leaving the thickets where they had been 

 reared, tliey were feeding now on the grass seeds of the open flats. 

 The young were fully fledged, adults and immatures now indistin- 

 guishable, and the fall flocking had begun. 



Plumages. — The natal down has been described above. The 

 Juvenal plumage, worn by the fledgling until about 4 weeks of age, is 

 as follows (Baumgartner, 1938): Pileum dull cinnamon brown, 

 streaked by the black shafts of individual feathers, and more or less 

 edged with light buff; nape similar, the black shafts indistinct or 

 lacking, becoming grayer or buffer on sides of neck; feathers of back 

 and scapulars broadly centered ^vith black, edged vdth. light buff and 

 occasional touches of chestnut, especially the latter; rump and upper 

 tail-coverts light buff, indistinctly streaked or mottled with black; 

 sides of head and whole underparts light buff (shading to light smoke 

 gray on tlu-oat and becoming a rich buff on sides), heavily streaked 

 with soft black, especially on the breast, but not on lower abdomen and 

 under tail coverts. 



Except for the heavy streaking on the breast, the color pattern is 

 essentially like that of the adult plumage, \nth the distinct pileum 

 color terminated by a grayer nape, the broadly streaked back and 

 rich buff of the sides. The same facial expression is produced by a 

 light supercihary stripe, an irregular dark line under the eye, and a 

 definite postocular streak. The dark pectoral spot, contrary to 

 Beebe's (1907) assertion, can be identified among the heavy streakings 

 of the breast. A small patch of didl chestnut at the bend of the wing 

 is streaked ^vith black. The wings and tail are those of the first 

 winter. 



The first winter plumage is "acquired by a partial post-juvenal molt 

 in August which involves body plumage but apparently not the wings 

 or tail, young and old becoming indistinguishable" (Dwight, 1900). 

 This molt begins on the back and sides before the young are fully 

 grown, about the first of August, and does not reach its culmination 

 until after the middle of the month. The last juvenal feathers to 

 disappear are those of the nape, the dark postocular stripe, and scat- 

 tered streaky feathers of the throat and breast. None of the Churchill 

 birds collected up to August 19 were in complete winter dress, and feet 

 and bills were still pale. 



When the species arrived in Ithaca in October, traces of the molt 

 could still be discerned in 10 percent of those collected, of which 3 

 were young birds. 



The nuptial plumage, for old and first year birds alike, is "acquired 

 by wear, the huffy edging of the bade becoming grayish and the chest- 

 nut everywhere slightly paler" (D\nght, 1900). A certain amount 



646-737— R8—pt. 2 36 



