206 CALIFORNIA ACADEMY OF SCIENCES. 



white-winged dove (Melopelia leucoptera) has the termi- 

 nal fourth of the tail white, the basal portion of the 

 feathers (except middle pair) being slaty. 



Among the hawks the tail is often the most character- 

 istic mark of recognition at a distance. The marsh 

 hawk (Circus hudsonicus) may always be distinguished 

 at a distance by his white rump patch, and the black 

 markings on the head of the sparrow-hawk (Falco spar- 

 verius) serve to distinguish it, and yet both these spe- 

 cies, and nearly all other hawks have some char- 

 acteristic marks upon the tail. Thus the tail of the 

 marsh hawk is tipped with white, with a broad blackish 

 subterminal band and several narrower bands anterior 

 to it. Accipiter has the tail crossed by several bands of 

 blackish and narrowly tipped with white. The tail of 

 Parabuteo is black, with the base and tip .white, while 

 in many species of Buteo it is crossed by a subterminal 

 band of blackish and with a white tip. There are very 

 many variations in the form of tail marking in the 

 genus Buteo, and these are doubtless discriminative 

 marks which were originated soon after the different 

 forms began to diverge. Among the red-tailed hawks 

 (Buteo borealis) the general color of the tail is a striking 

 example of a directive mark by which the species may 

 be known at a long distance. The different races vary 

 in the detailed characters of the tail, and these marks 

 are apparently discriminative in nature, all the mem- 

 bers of the genus having them in some form. In the 

 broad-winged hawk (Buteo latissimus) the ground color 

 is blackish, crossed by from two to four broad bands of 

 light brownish gray, while in Swainson's hawk (B. 

 swainsoni) there are nine or ten bands. In the white- 

 tailed hawk (B. albicaudatus) the ground color is white, 

 crossed by a broad subterminal band of black, and an- 

 terior to this by five bars or lines of slate or dusky. If 



