AVES FALCONID/E. 657 



Back : Interscapular region barred with black on a dull bluish lead- 

 colored ground, the lighter shade prevailing over the dark because of the 

 broad bluish lead-colored tips of each feather; there are three to four 

 strong dark bars on each of the feathers of this region ; on the middle and 

 lower back the black bars are much narrower and farther apart and become 

 sagittate in shape as the rump is reached ; the rump and upper tail- 

 coverts are light slate-color, with sagittate markings and bars, chiefly con- 

 cealed, on each feather ; the effect on the back is that of dark brownish 

 black, shaded with bluish lead-color ; that of the middle and lower back, as 

 well as the rump and upper tail-coverts, light slate-blue with dark mark- 

 ings so narrow as not to affect the tone. 



Fig. 335. 



Falco cassini. Adult male, P. U. O. C. 7903. Natural size. 



Tail : Bluish slate at base, shaded somewhat with ash toward the tip ; 

 the slate-blue of the wide interspaces at the base becomes less defined 

 toward the end of the tail and shaded more or less with ashy, while the 

 narrow black bars of the basal portion gradually widen till they are as 

 wide as the interspaces toward the tip ; each rectrix broadly tipped with 

 fulvous. This tip is usually very much worn even in birds in otherwise 

 perfect plumage, and this is due to the feeding habits of this hawk, the 

 tail being pressed down on the dead duck or other prey, held in the strong 

 talons. 



Wings : Upper wing-coverts like the interscapular region in color and 

 marking; from above, the quills are dull brownish black, with almost 

 obsolete bars or spots of dull slate on most of these feathers ; the inner 



