Notes on the Plumage of North American Birds 203 



range of the Plumbeous Gnatcatcher, and here it is so nearly non-migratory 

 that its slight movements, if there are any, cannot be traced. 



BLACK-TAILED GNATCATCHER 



The Black-tailed Gnatcatcher is a non-migratory species in southern 

 California and to the central part of Lower California. 



Notes on the Plumage of North American Birds 



THIRTY-THIRD PAPER 

 By FRANK M. CHAPMAN 



(See Frontispiece) 



Blue-gray Gnatcatcher {Polioptila ccerulea. Figs, i, 2). — In nestling 

 plumage both sexes of this species are alike. They closely resemble the adult 

 female, but have a brownish tint on the upper parts. At the first fall (post- 

 juvenal) molt, as Dwight has shown, the body plumage and wing-coverts are 

 shed, but the wing-quills and tail-feathers are retained. Both male and female 

 now resemble the adult female (Fig. 2). 



There is a partial spring (prenuptial) molt when the young male acquires 

 the black frontal band of the adult male, from which it cannot thereafter be 

 distinguished. 



The Western Gnatcatcher {Polioptila ccerulea obscura) is somewhat duller 

 above than the eastern race, and has the white tip of next to the outer 

 tail-feather less than one inch in length. It is found west of the Rocky Moun- 

 tains and north to northern California. 



Plumbeous Gnatcatcher {Polioptila plumhea. Figs. 3, 4). — The adult 

 male of the Plumbeous Gnatcatcher differs conspicuously from the Blue- 

 gray Gnatcatcher in having a black cap. The females and males in nestling 

 plumage, in which the cap is wanting, may be known by the smaller amount of 

 white in the tail, the inner webs of the outer feathers having only a narrow white 

 tip. Young males in first winter plumage have more or less black in the crown, 

 usually over and behind the eye, and not on the forehead, as in the adult Blue- 

 gray Gnatcatcher. The full black cap appears to be acquired before the first 

 nesting season. 



Black-tail Gnatcatcher {Polioptila calif ornica, Figs. 5, 6). — The name 

 'plumbeous' might better be applied to this species than to the preceding one, 

 since, as the plate shows, it is more plumbeous both above and below than 

 either of our other Gnatcatchers. The brownish wash of the flanks, and, in 

 winter specimens, on the back, also distinguishes it, while it has even less 

 white on the tail than the preceding species. 



