EVOLUTION OF THE COLORS OF BIRDS. 141 



bird is found in arid districts, this color has been 

 bleached out to a brownish or grayish. The more 

 special colors are black and yellow. The male of 

 Pyrocephalus rubineus mexicanus is scarlet and brownish 

 black. The female is colored a plain brown olive, 

 which is a mixture of red and black. The blue jays are 

 generally colored some shade of blue in the adult, 

 together with black and white, but a mixture of these 

 shades would produce the grays of the young and of the 

 less specialized forms as Perisoreus and Picicorvus. The 

 adult male red-winged blackbirds are black and scarlet, 

 the female brown. The meadow lark is brownish or 

 grayish in its generalized color, and black, white and 

 yellow in the specialized shades. I am not certain that 

 the combination of black and yellow (olive-greenish) 

 together with white would produce the grayish-brown of 

 the back, but if this instance be an exception, it is not 

 a very glaring one. The term brown is a very loose one 

 and may cover a great variety of color effects. It may 

 be produced either by a combination of black and red, 

 or of black and green; or it may be due to the structure 

 of the feather. If a certain amount of gas bubbles are 

 contained in a feather where the pigment is dark, it 

 will produce a brown effect, or a black feather with a 

 frayed edge may appear brown. There is probably no 

 white pigment in birds' feathers, this effect being 

 structural or due to the absence of pigment. 



Among the orioles, the colors of the specialized males- 

 are black and yellow (the orange being merely an inten- 

 sification of this) while the primitive color as exhibited by 

 the females and young is olive green. Plates XVI and 

 XVII showing the heads of a number of representative 

 species in the generalized and specialized stage illustrates 

 this instance. It might appear that Icturus spurius with 

 its reddish brown color was an exception to this law, but 



