Jhap. XLV. Birds — Gradation of Characters. 443 



recently given of the humming-birds near Bogota, in which 

 certain individuals alone have the " central tail-feathers tipped 

 " with beautiful green." In the female of the Urosticte I 

 noticed extremely minute or rudimental white tips to the two 

 outer of the four central black tail-feathers ; so that here we 

 have an indication of change of some kind in the plumage oi 

 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 B. 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 Urosticte should have been specially 

 selected for the sake of ornament, for the next succeeding genus 

 in the family takes its name of Metallura from the splendour of 

 these feathers. We have, moreover, good evidence that humming- 

 birds take especial pains in displaying their tail-feathers ; Mr. 

 Belt, 54 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 shew off back and front The 



" expanded white tail covered more space than all the rest of the 

 " bird, and was evidently the grand feature in the performance. 

 " Whilst one male was descending, the other would shoot up 

 " and come slowly down expanded. The entertainment would 

 " end in a fight between the two performers ; but whether the 

 " most beautiful or the most pugnacious was the accepted 

 " suitor, I know not." Mr. Gould, after describing the peculiar 

 plumage of the Urosticte, adds, " that ornament and variety is 

 " the sole object, I have myself but little doubt." 55 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 ordinary struggle for life, 

 but in rivalry with other males, and would have left a larger 

 number of offspring to inherit their newly-acquired beauty. 



44 'The Naturalist in Nicaragua,' 55 'Introduction to the Irocbi- 



.874, p. 112 li.u<e,' 1861, p. 110. 



