2 14 SEXUAL SELECTION : BIRDS. Part 1L 



cause. Some birds moult so early, that nearly all 

 the body-feathers are cast off before the first wing- 

 feathers are fully grown ; and we cannot believe that 

 this was the primordial state of things. When the period 

 of moulting has been accelerated, the age at which 

 the colours of the adult plumage were fi^rst developed 

 would falsely appear to us to have been earlier than 

 it really was. Tliis may be ilkistrated by the practice 

 followed by some bird-fanciers, who pull out a few 

 feathers from the breast of nestling bullfinches, and 

 from the head or neck of young gold-pheasants, in 

 order to ascertain their sex ; for in the males these 

 feathers are immediately replaced by coloured ones.^^ 

 The actual duration of life is known in but few birds, so 

 that we can hardlv iudf^e bv this standard. And with 

 reference to the period at which the po\\ers of repro- 

 duction are gained, it is a remarkable fact that various 

 birds occasionally breed whilst retaining their immature 

 plumage.^^ 



The fact of birds breeding in their immature plumage 

 seems opposed to the belief that sexual selection has 



3c Mr. Blyth, in Cliarlesworth's ' Mag. of Nat. Hist.' voL i. 1837, p. 

 300. Mr. Bartlett lias informed me in regard to guld-pheasants. 



3' I have noticed tlie following cases in Audubon's 'Ornith. Bio- 

 graphy. The Eeilstart of America' (Muscicapa ruticilla, vol. i. p. 

 203). The Ibis tantalus takes four years to come to full maturity, but 

 sometimes breeds in the second year (vol. iii. p. 133;. The Grus Ameri- 

 canus takes the same time, but breeds before acquiring its full plumage 

 (vol. iii. p. 211). The adults of Ardea ccerulea arc blue and the young 

 white; and white, mottled, and nuiture blue birds may all be seen 

 breeding together (vol. iv. p. 58 j : but Mr. Blyth informs me that cer- 

 tain lierons apparently are dimorphic, for white and coloured individuals 

 of the same age may be observed. The Harlequin duck {Anas his- 

 trionica, Linn.) takes three years to acquire its full plumage, though 

 many birds breed in the second year (vol. iii. p. 614), The White- 

 headed Eagle (Faleo leucocephalm, vol. iii. p. 210) is likewise 

 known to breed in its immature state. Some species of Oriolus (ac- 

 cording to Mr. Blyth and Mr. Swinhoe, in ' Ibis' July, 1863, p. 68) 

 likewise breed before they attain their full plumage. 



