502 SwARTH, California Forms of Psaltriiparus. [oct. 



geles County Museum of History, Science and Art, where are 

 housed the Daggett, Lamb, Law, Richardson, and Willett collec- 

 tions. x\ltogether, four hundred and thirty-three specimens were 

 examined in the present connection. 



Variation : There is probably hardly another species of bird, as 

 plainly colored as the California Bush-tit and with as few distinctive 

 markings, which shows such a wide range of variation in appearance 

 in individuals taken under different circumstances. This variation 

 has proved a constant obstacle toward an understanding of the 

 several California species and subspecies of Psaltriparus, for it is 

 only in large series taken at many different points that there appears 

 to be any sign of law and order controlling the observed differences. 

 Even the large number of specimens available in the present study 

 is not sufficient to illustrate all of the phases of the situation, though 

 it does appear to be ample for the deduction of the conclusions at 

 which I have arrived. 



Birds of this genus are subject to at least four kinds of variation. 

 They diflfer: (1) seasonally, through fading and abrasion; (2) at 

 diflferent ages, adult and juvenal plumages being readily distin- 

 guishable; (3) geographically (the various species and subspecies, 

 or geographical races) ; and (4) in one species, melanotis (not occur- 

 ring in California), there is sexual difference, the male and female 

 being strikingly different. But this last is a phase of the subject 

 that need not be considered here. 



Seasonal Variation: The changes in appearance undergone 

 during the year by the California Bush-tit {P. minimus minimus 

 and P. minimus calif ornicus) , aside from the alteration brought 

 about by the molt, are unusually striking for so plain colored a bird. 

 In the Horned Lark {Otocoris alpestris), the Snow Bunting {Plectro- 

 phenax nivalis) and others, conspicuous patterns are revealed by the 

 continued abrasion of the feathers ; while in birds such as the Blue 

 Grosbeak {Guiraca coerulea) the brilliant color of the whole body is 

 disclosed through the same agency, but in the bush-tits there are 

 no such underlying markings. The altered appearance is in this 

 case largely due to change of color, — fading of the feathers, and 

 not to the removal of feather tips differently colored from the rest 

 of the plumage. The pileum and the remainder of the upper parts 

 are differently colored in P. minimus, and are differently affected by 



