Brewster on a CoUectio?! oj' Arizona Birds. 1 35 



The brilliant colors of these feathers have often been ascribed 

 to irregularities of surface, the traces of the cell cavities beino- 

 mistaken for pits on the surface That this is an error is at once 

 shown by examining a section. 



Before leaving the subject I cannot refrain from calling atten- 

 tion to the wonderful diversity of means einployed, as well as 

 their complexity in the production of feather colors. Amono- 

 the Parrots we have the most skilful painting combined with ac- 

 cidental colors. Yet all ornithologists base specific differences 

 on slight variations of color, and this in spite of the fact that 

 birds may change their color according as they are wet or drv, 

 owing to the nature of their food, or to slight diflerences in the 

 quantity of pigment. 



In this they are no doubt often right, but when we come to 

 varieties based on the very fiiintest distinctions of color and form, 

 we may well pause till more is known of avian physiologv. 



EXPLANATION OF PLATE I. 



I^/£: I. Diagramatic representation of the effect of a fihn on light. 

 Fig. 2. Transverse section of a barb of CJilorophanus atrocrhtatiis; 

 Hartnack 3-9 im. the light part j-ellow, the dark part dark brown. 



Fig. ?. Transverse section of a barb of Cyanociifa crisfafu. Mart. 



3-9 ''"• 



Fig. 4. Same of Cyauospiza cyanca $ . 



Fig. J. Two sections of a barbule of a Peacock. 



Fig. 6. Section of barb of Sialic/ sialis much magnified. 



ON A COLLECTION OF BIRDS LATELY MADE 

 BY MR. F. STEPHENS IN ARIZONA. 



BY WILLIAM BREWSTER. 



( Conthiued from p. 9./.) 



33. Peucedramus olivaceus ( Giraud) Cones. Olive- 

 headed Warbler. — The Olive-headed Warbler, one of 

 Giraud's famous '■'sixteen" Texas species, has found an unques- 

 tioned place in our fauna only on the strength of three Arizona 

 specimens, taken by Mr. Henshaw at Mount Graham, in Septem- 



