126 SEXUAL SELECTION : EIEDS. Part IL 



" having the whole of the feathers bhie, while others 

 " have the eight central ones tipped A\ith beautiful 

 " green." It does not appear that intermediate gra- 

 dations have been observed in this or the following 

 cases. In the males alone of one of tlie Australian 

 parrakeets "the thighs in some are scarlet, in others 

 " grass-green," In another parrakeet of the same 

 country "some individuals have the band across the 

 •' wing-coverts bright-yellow, while in others the same 

 "' jDart is tinged with red." ^^ In the United States 

 some few of the males of the Scarlet Tanager {Tanagra 

 rubra) have '''a beautiful transverse band of glowing 

 " red on the smaller wing-coverts ; " ^^ but this variation 

 seems to be somewhat rare, so that its j^i'^servation 

 through sexual selection would follow only under 

 unusually favourable circumstances. In Bengal the 

 Honey buzzard (Pernis cristata) has either a small 

 rudimental crest on its head, or none at all ; so slight a 

 difference however would not have been worth notice, 

 had not this same species possessed in Southern India 

 "a well-marked occipital crest formed of several gra- 

 '' duated feathers." ^^ 



The following case is in some resj^ects more interest- 

 ing. A pied variety of the raven, with the head, breast, 

 abdomen, and parts of the wings and tail-feathers white, 

 is confined to the Feroe Islands. It is not very rare 

 there, for Graba saw during his visit from eight to 

 ten living specimens. Although the characters of this 

 variety are not quite constant, yet it has been named 

 by several distinguished ornithologists as a distinct 

 species. The fact of the pied birds being pursued and 



34 Gould, ' Handbook of Birds of Australia,' vol. ii. p. 82 and (jS. 



35 Audubon, ' Ornitholog. Biography," 1838, vol. iv. p. 389. 



s*"' Jerdon, ' Birds of India,' vol. i. p. 108 : and Mr. Blyth, in ' Land 

 and Water,' 1868, p. 381. 



