334 CALIFORNIA ACADEMY OF SCIENCES. 



being much duller in the female and wanting in the 

 young. How this color can be accounted for in accord- 

 ance with the law of the assortment of pigments I do 

 not see at present, for it would seem that some species in 

 the family should be colored olive green. The different 

 species of the genus Sitta are very distinctively marked. 

 As the sexes are alike it is difficult to decide how im- 

 portant sexual selection may have been in originating 

 these markings and the same is true of Parus. The 

 latter genus has been especially susceptible to the influ- 

 ences of climate, a large number of the species breaking 

 up into geographical races. Psaltriparus is equally in- 

 fluenced by climate. Little inconspicuous marks are 

 generally the most difficult to explain, and this is no- 

 tably the case with Psaltriparus. Of what possible 

 utility can be the brown head as contrasted with the 

 gray back? It is present in both sexes so could hardly be 

 looked upon as the result of sexual selection, nor is it 

 conspicuous enough to be of use as a recognition mark. 

 If, however, some other bird inhabiting the same ter- 

 ritory looked very much like Psaltriparus but without 

 the brown cap, it might serve at close range as a dis- 

 criminative mark. 



FAMILY SYLVIIDAE. THE WARBLERS, KINGLETS, 

 AND GNATCATCHERS. 



(7) Adult male generally more conspicuously colored 

 than female; young like adult female, or (8) with a 

 peculiar first plumage. 



Prevailing colors, black, white, olive green, yellow, 

 orange, red, bluish gray. 



The colors of this specialized family may be explained 

 by sexual selection and the assortment of pigments. 

 The similarity to the Mniotiltidse and Motacillidse in 

 point of coloration is quite striking, the olive green, 



