Notes on the Plumage of North American Birds 



THIRTY-EIGHTH PAPER 

 By FRANK M. CHAPMAN 



(See frontispiece) 



Sage Thrasher {Oroscoples monlanus, Fig. i). — In nestling or juvenal plum- 

 age the Sage Thrasher is streaked above as well as below, and the ground-color 

 of the upperparts is browner, but after the postjuvenal molt young and old 

 birds are indistinguishable. 



There is no sexual difference in the plumages of this species, and summer 

 specimens differ from winter ones only in being somewhat more sharply streaked 

 and less buffy below, and in lacking the whitish margins to the inner wing- 

 feathers. There are no geographical races of the Sage Thrasher. 



Mockingbird {Mimus polyglottos, Fig. 2). — When it leaves the nest the 

 Mockingbird bears a general resemblance to its parents, but the breast and 

 sides are thickly spotted with dusky and the upperparts are browner. At the 

 postjuvenal molt these differences disappear and in its first winter plumage 

 the young of the preceding summer cannot be distinguished from older birds. 

 There is no spring molt, and summer plumage differs from winter plumage 

 only in being grayer and more worn. 



The male Mockingbird usually has slightly more white in the wings and 

 tail than the female, but the difference is not sufficient to permit of the identi- 

 fication of the sexes in life. 



Two forms of the Mockingbird are found in the United States. The Eastern 

 Mockingbird (M. p. polyglottos) ranges west to eastern Nebraska and eastern 

 Texas; the Western Mockingbird (M. p. leucoplerus) is found from the western 

 limit of the range of the eastern race westward to the Pacific. These two forms 

 very closely resemble one another, but the western bird is slightly paler above 

 and more buffy below. 



Catbird (Dumatella caroUnensis, Fig. 3). — The plumage of the Catbird is 

 essentially alike in both sexes and at all seasons. The nestling is duller through- 

 out and the lower tail-coverts are paler, but these slight differences disappear 

 with the postjuvenal molt. Some females have the crown and upperparts 

 slightly browner than in the male but they vary too little to make the sexes 

 certainly distinguishable. The Catbird shows no geographic variation through- 

 out its wide range. 



Brown Thrasher {Toxostoma nifum, Fig. 4). — The plumage of the Brown 

 Thrasher is alike in both sexes; the young birds closely resemble their parents, 

 and there are practically no seasonal variations in color. The nestling has more 

 or less dusky in the upperparts and, as usual with young birds, the streaks 

 below are less distinct than on the adult, but with the postjuvenal molt these 

 differences are lost, and for the remainder of its life a Brown Thrasher does not 

 differ materially from our figure. 



(172) 



