SEXUAL SELECTION 625 



ers are immediately replaced by colored ones.** The actual 

 daration of life is known in but few birds, so that we caa 

 hardly judge by this standard. And, with reference to the 

 period at which the power of reproduction is gained, it is a 

 remarkable fact that various birds occasionally breed while 

 retaining their immature plumage." 



The fact of birds breeding in their immature plumage 

 seems opposed to the belief that sexual selection has played 

 as important a part, as I believe it has, in giving ornamental 

 colors, plumes, etc., to the males, and, by means of eq^ual 

 transmission, to the females of many species." The objec- 

 tion would be a valid one, if the younger and less orna- 

 mented males were as successful in winning females and 

 propagating their kind as the older and more beautiful 

 males. But we have no reason to suppose that this is the 

 case. Audubon speaks of the breeding of the immature 

 males of Ihis tantalus as a rare event, as does Mr. S win- 

 hoe, in regard to the immature males of Oriolus.'^ If the 

 young of any species in their immature plumage were more 

 successful in winning partners than the adults, the adult 

 plumage would probably soon be lost, as the males would 

 prevail which retained their immature dress for the longest 

 period, and thus the character of the species would ulti- 

 mately be modified. °' If, on the other hand, the young 



88 Mr. Blyth, in Charlesworth's "Mag. of Nat. Hist.," vol. i., 1837, p. 300. 

 Mr. Bartlett has infonued me in regard to gold pheasants. 



2' I have noticed the following cases in Audubon's "Ornith. Biography." 

 The redstart of America (Musca^pica ruticiUa, vol. i. p. 203). The Jbis Umtaliis 

 takes four years to come to full maturity, but sometimes breeds in the second 

 year (vol. iii. p. 133). The GVas a/merioanua takes the same time, but breeds 

 before acquiring its full plumage (vol. iii. p. 211). The adults of Ardea ccerulea 

 are blue, and the young white; and white, mottled, and mature blue birds may 

 all be seen breeding together (vol. iv. p. 58): but Mr. Blyth informs me that 

 certain herons apparently are 'dimorphic, for white and colored individuals of 

 the same age may be observed. The Harlequin duck (Anas histrionica, 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 (Fako Uncocephcdns, 

 vol. iii. p. 210) is likewise known to breed in Its immature state. Some species 

 of Oriolus (according to Mr. Blyth and Mr. Swinhoe, in "Ibis," July, 1863, 

 p. 68) likewise breed before they attain their full plumage. 



^ See the last footnote. 



" Other animals, belonging to quite distinct classes, are either habitually 

 or occasionally capable of breeding before they have fully acquired their adult 

 characters. This is the case with the young males of the salmon. Several 

 amphibians have been known to breed while retaining their larval structure. 

 Fritz Miiller has shown ("Facts and Arguments for Darwin," Eng. trans., 

 1869, p. 79) that the males of several amphipod crustaceans become sexually 

 mature while young; and I infer that this is a case of premature breeding, 



