218 CALIFORNIA ACADEMY OF SCIENCES. 



especially constant^ In general, however, the brilliant 

 crimson, dark blue and white colors of the adult are re- 

 placed by mottled brownish and grayish hues in the 

 young. In all the above instances the adult colors were 

 probably first acquired by the male for recognition 

 (Dc adrolca nigre.scens), sexual he&Miy (Melaner pes erythro- 

 cephalus), or use in some other manner (Tyrannus). 

 The following are cases where the plumage of the young 

 is in general similar to the adult, but markedly paler or 

 duller. Swainson's warbler (Helminthophild swainsoni) — 

 young darker than adult, sooty-colored; shrikes (Lan- 

 ius) — young with colors duller on breast and smoky 

 brown on back, wavy markings on breast pronounced; 

 cliff swallow (Petrochclidon limifronf^), and barn swallow 

 (Chc.lidon erythrogaster) — young paler; white breasted 

 swallow (Tachycineta bicolor) and violet-green swallow 

 (T. fluddnsina) — bright colors o'f back of adult replaced in 

 the young by plain brown. 



Where there are seasonal differences in plumage it is 

 decidedly difficult to make sharp distinctions of classes. 

 Freciuently the sexes differ very decidedly in their breed- 

 ing dress, but only very slightly in winter, the naale 

 then assuming a plumage like that of the female. In 

 such istances the young generally resemble the winter 

 plumage of the adults, but may differ in being still more 

 plainly colored. The following list includes these forms: 

 Dr lulroica (luduhoni. Plcdvophc iui,x. 



Deiid riiicii, coroiiiifn. (Jidcuriu.-i. 



Deiidroicii inaculosa. Guiracn. airidea. 



Dcndroica puLiuirum. C<d(i mospiza melanocorys. 



Ciiiclus! mexicwnus. Dolichonyx nryzivorus. 



(ifothlyptK tricluts. Xaniliocephaliis. 



Imxiii,. Ageldius. 



Acd ntJuf^. Scolecophagus. 



Leucostictc. OtocuriR. 



Spinas. 



