BIRDS— GRADATION OF CHARACTERS. 437 



"tiful green." In the female of the Urosticte I noticed extremely- 

 minute or rudimental white tips to the two outer of the four cen- 

 tral black tail-feathers, so that here we have an indication of 

 change of some kind in the plumage of this species. If we grant the 

 possibility of the central tail-feathers of the male varying in 

 whiteness, there is nothing strange in such variations having 

 been sexually selected. The white tips, together with the small 

 white ear-tufts, certainly add, as the Duke of Argyll admits, to 

 the beauty of the male; and whiteness Is apparently appreciated 

 by other birds, as may be inferred from such cases as the snow- 

 white male of the Bell-bird. The statement made by Sir R. 

 Heron should not be forgotten, namely, that his peahens, when 

 debarred from access to the pied peacock, would not unite with 

 any other male, and during that season produced no offspring. 

 Nor is it strange that variations in the tail-feathers of the Uros- 

 ticte should have been specially selected for the sake of ornament, 

 for the ndxt succeeding genus in the family takes its name of 

 Metallura from the splendor of these feathers. We have, more- 

 over, good evidence that humming-birds take especial pains in 

 displaying their tail-feathers; Mr. Belt," after describing the 

 beauty of the Florisuga mellivora, says, "I have seen the female 

 "sitting on a branch, and two males displaying their charms in 

 "front of her. One would shoot up like a rocket, then suddenly 

 "expanding the snow-white tail, like an inverted parachute, 

 "slowly descend in front of her, turning round gradually to show 



"off back and front The expanded white tall covered 



"more space than all the rest of the bird, and was evidently the 

 "grand feature in the performance. Whilst one male was de- 

 "seending, the other would shoot up and come slowly down ex- 

 "panded. The entertainment would end in a fight between the 

 "two performers; but whether the most beautiful or the most pug- 

 "nacious was the accepted suitor, I know not." Mr. Gould, after 

 describing the peculiar plumage of the Urosticte, adds, "that orna- 

 "ment and variety is the sole object, I have myself but little 

 "doubt. '"^ If this be admitted, we can perceive that the males 

 which during former times were decked in the most elegant and 

 novel manner would have gained an advantage, not in the or- 

 dinary struggle for life, but in rivalry with other males, and 

 would have left a larger number of offspring to inherit their new- 

 ly-acquired beauty. 



" 'Tlie Naturalist in Nicaragua," 1874, p. 112. 

 ^ 'Introduction to the Trochilidae,' 1861, p. 110. 



29 



