68 Wonders of the Bird World 



(Fig. 4) of West Africa, the males of which are olive in 

 colour like the females of the majority of Sun-birds. 

 Both sexes are alike plain- 

 plumaged, and the only orna- 

 ment of the male is the yellow 

 pectoral tuft which would appear 

 to be the first approach to a 

 4 . Head of a, ohcura, decorative plumage. 



A further evidence of the 



mode in which the brighter colours may first have been 

 donned is shown in the young birds, the males of certain 

 species at first resembling the females, but differing from 

 them by dusky shading in the places where the metallic 

 colours are prevalent in the adult males, pointing out 

 in this survival the primitive indication of progress in the 

 male plumage from the sober colour which anciently 

 both sexes shared. One further case occurs to my mind, 

 that of our common Kestrel Hawk (Cerchneis tinnunculus}. 

 In the Birds of prey the sexes are generally alike in 

 plumage, but the female is the larger and more powerful 

 bird of the two. In the European Kestrel, however, 

 the male is distinctly superior in colour to the female, 

 the latter bird being rufous, barred with black, the tail 

 being similarly patterned. In the male, however, the head 

 is blue-grey, and so are the rump, upper tail-coverts 

 and tail-feathers, the latter having a black band near the 

 end. One sign of a very old female is the appearance of 

 a shade of grey over the tail, as if there were a certain 

 inherent tendency in the species towards the acquisition of 

 a blue tail. The young male at first resembles the female 

 and has a rufous tail, but the first indication of blue-grey 

 colour appears on the rump and upper tail-coverts, as if 

 the original inclination of the male to become grey had 

 commenced in this portion of the bird's body, and had 

 since become hereditary. The grey on the head appears 



