Chap. XVI.] THE YOUNG LIKE ADULTS OF SAME SEX. 211 



In Aithuriis polytmus (one of the humming-birds) the 

 male is splendidly colored black and green, and two of 

 the tail-feathers are immensely lengthened; the female 

 has an ordinary tail and inconspicuous colors ; now the 

 young males, instead of resembling the adult female, in 

 accordance with the common rule, begin from the first to 

 assume the colors proper to their sex, and their tail-feath- 

 ers soon become elongated. I owe this information to 

 Mr. Gould, who has given me the following more striking 

 and as yet unpublished case : Two humming-birds be- 

 longing to the genus Eustephanus, both beautifully col- 

 ored, inhabit the small island of Juan Fernandez, and 

 have always been i-anked as specifically distinct. But it 

 has lately been ascertained that the one, which is of a rich 

 chesnut-brown color with a golden-red head, is the male, 

 while the other, which is elegantly variegated with green 

 and white, with a metallic-green head, is the female. Now 

 the young from the first resemble to a certain extent the 

 adults of the corresponding sex, the resemblance gradu- 

 ally becoming more and more complete. 



In considering this last case, if as before we take the 

 plumage of the young as our guide, it would appear that 

 both sexes have been independently rendered beautiful ; 

 and not that the one sex has partially transferred its 

 beauty to the other. The male apparently has acquired 

 his bright colors through sexual selection in the same man- 

 ner as, for instance, the peacock or pheasant in our first 

 class of cases ; and the female in the same manner as the 

 female Rhynchsea or Turnix in our second class of cases. 

 But there is much difficulty in understanding how this 



of Tanagra rubra can be distinguished from the young females (Audu- 

 bon, ' Ornith. Biography,' vol. iv. p. 392), and so it is with the nestlings 

 of a blue nuthatch, Dendrophila frontalis of India ( Jerdon, ' Birds of India,' 

 vol. i. p. 389). Mr. Blyth also informs me that the sexes of the stone- 

 chat, Saxicola rubicola, are distinguishable at a very early age. 



