206 SEXUAL SELECTION: BIRDS. Part H. 



those with duller plumage and grey legs were tlie males 

 or tlie young. In an Australian tree-creeper (Climac- 

 teris enjthrops) the female differs from the male in 

 " being adorned with beautiful, radiated, rufous mark- 

 " iiigs on the throat, the male having this part quite 

 " plain." Lastly in an Australian night-jar " the female 

 " always exceeds the male in size and in the brilliance 

 "other tints; the males, on the other hand, have two 

 " white spots on the primaries more conspicuous than 

 " in the female." ^^ 



We thus see that the cases in which female birds are 

 more conspicuously coloured than the males, with the 

 young in their immature plumage resembling the adult 

 males instead of the adult females, as in the previous 

 class, are not numerous, though they are distributed in 

 various Orders. The amount of difference, also, between 

 the sexes is incomparably less than that which frequently 

 occurs in the last class ; so that the cause of the differ- 

 ence, whatever it may have been, has acted on the fe- 

 males in the present class either less energetically or less 

 persistently than on the males in the last class. Mr. 

 Wallace believes that the males have had their colours 



-5 For tlie jMilvago, see ' Zoology of the Voyage of the " Beagle." ' 

 Birds, 1841, p. 16. For the Climacteris and night-jar (Eurostopodus), 

 see Gould's ' Han<lbook of the Birds of Australia,' vol. i. p. 602 and 97. 

 The New Zealand sliieldrake {Taclorna variecjata) offers a quite anoma- 

 l(yus case : the head of the female is piire ^\diitH, and her back is redder 

 than that of the male ; the head of the male is of a rich dark bronzed 

 colour, and his back is clothed with finely pencilled slate-coloured 

 feathers, so that he may altogether be considered as the more beautiful 

 of the two. He is Lirger and more pugnacious than the female, and 

 does not sit on the eggs. So that in all these respects this species 

 comes imder our first class of c ises ; but Mr. Sclater (' Froc. Zool. 

 Soc' 1866, p. 150) was much surprised to observe that the young of both 

 sexes, when about three months old, resembled in their dark heads and 

 necks the adult males, instead of the adult females; so that it would 

 appear in this case that the females have been modified, whil.-,-t the 

 males and the young have letained a former state of plumage. 



