Chap. XV I. Birds — Young like both Adults. 



487 



Class VI. The young in their first plumage differ from each other 

 according to sex ; the young males resembling more or less closely the adult 

 males, and the young females more or less closely the adult females. — 

 The cases in the present class, though occurring in various groups, aro 

 not numerous ; yet it seems the most natural thing that the young 

 should at hrst somewhat resemble the adults of the same sex, and 

 gradually become more and more like them. The adult male blackcap 

 {Sylvia atricapilla) has a black head, that of the female being reddish- 

 brown ; and I am informed by Mr. Blyth, that the young of both sexes 

 can be distinguished by this character even as nestlings. In the family 

 of thrushes an unusual number of similar cases have been noticed ; thus, 

 the male blackbird (Turdus merula) can be distinguished in the nest 

 from the female. The two sexes of the mocking bird (Turdus polygluttus, 

 Linn.) differ very little from each other, yet the males can easily be 

 distinguished at a very eaily age from the females by shewing mure 

 pure white. 46 The maies or a forest-thrush and of a rock-thrush 

 (Orocctes erythrogastra and Petrocincla cyanea) have much of their 

 plumage of a fine blue, whilst the females are brown ; and the nestling 

 males of both species have their main wing and tail-feathers edged with 

 blue, whilst those of the female are edged with brown. 47 In the young 

 blackbird the wing feathers assume their mature character and become 

 black after the others ; on the other hand, in the two species just named 

 the wing- feathers become blue before the others. The most probable 

 view with reference to the cases in the present class is that the males, 

 differently from what occurs in Class f., have transmitted their colours 

 to their male offspring at an earlier age than that ;tt which they were 

 fhvt acquired; for, if the males had varied whist quite young, their 

 characters would probably have been transmitted to both sexes. 48 



In Aithurus polytmus, a humming-bird, the male is splendidly coloured 

 black and green, and two of the tail-feathers are immensely lengthened ; 

 the female has an ordinary tail and inconspicuous colours; now the 

 young males, instead of resembling the adult female, in accordance 

 with the common rule, begin from the first to assume the c< lours proper 

 to their sex, and their tail-feathers 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 belonging to the 

 genus Eustephanus, both beautifully coloured, inhabit the small island 

 of Juan Fernandez, and have always been ranked as specifically dis- 

 tinct. But it has lately been ascertained that tlie one, which is of a 

 rich chesnut brown colour with a golden-red head, is t e mule, whilst 

 the other, which is elegantly variegated with green and white with a 

 metallic-green head is the female. Now the young from the first 



46 Audubon, ' Ornith. Biography,' 

 vol. i. p. 113. 



47 Mr. C. A. Wright, in 'Ibis,' 

 vol. vi. 1864-, p. 65. Jerdon, ' Birds 

 of India,' vol. i. p. 515. See also on 

 the blackbird, Blyth in Charles- 

 worth's ' Mag. of Nat. History,' vol. 

 i. 1837, p. 113. 



48 The following additional cases 

 may be mentioned ; the young males 

 of Tanagra rubra can be distinguished 

 fiom the young females (Audubon, 



' 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 

 stonechat, Saxicola rubicola, are 

 distinguishable at a very early age. 

 Mr. Saivin gives ('Proc. Zoolog. Soc' 

 1870, p. 206), the case of a hum- 

 ming-bird, like the following one ii 

 Eustephanus. 



