BIRDS-YOUNG LIKE BOTH ADULTS. 479 



diately replaced by colored ones.'" Tlie actual duration of life 

 is known in but few birds, so that we can hardly judge by this 

 standard. And, with reference to the period at which the po'wer 

 of reproduction is gained, it is a remarkable fact that various 

 birds occasionally breed whilst retaining their immature plum- 

 age.'" 



The fact of birds breeding in their immature plumage seems op- 

 posed to the belief that sexual selection has played as important 

 a part, as I believe it has, in giving ornamental colors, plumes, 

 &c., to the males, and, by means of equal transmission, to the 

 females of many species. The objection would be a valid one, 

 if the younger and less ornamented 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 Ibis tantalus as a rare event, as does Mr. Swinhoe, in 

 regard to the immature males of Oriolus."" If the young of any 

 species in their immature plumage were more successful in win- 

 ning 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 ultimately be modified.™ If, on the other hand, 



™ Mr. Blyth, in Charles worth's 'Mag. of Nat. Hist.' vol. i. 1837, p. 

 300. Mr. Bartlett has informed me hi regard to gold-pheasants. 



3' I have noticed the following eases in Audubon's 'Ornith. Bio- 

 graphy.' The redstart of America (Muscapica ruticilla, vol. i. p. 203). 

 The Ibis tantalus takes four years to come to full maturity, but some- 

 times breeds in the second year (vol. iii. p. 133). The Grus amerl- 

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

 plumage (vol. iii. p. 211). The adults of Ardea caerulea 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 plum- 

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

 ■White-headed eagle (Falco leucocephalus, 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) Uke- 

 wise breed before they attain their full plumage. 



"s See the last foot-note. 



3° 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 

 whilst retaining their larval structure. Fritz MuUer has shown 

 ('Facts and Arguments for Darwin,' Eng. trans. 1860, p. 79) that the 

 rrales of several amphipod crustaceans become sexually mature whilst 

 joung; and I infer that this is a. case of premature breeding, because 



