316 THE STRUCTURE AND LIFE OF BIRDS chap. 



she sits upon the nest. We might expect, then, that 

 she would be more soberly coloured than her partner. 

 And this is what we do find, with the remarkable 

 exception which so admirably supports Dr. Wallace's 

 theory, that among birds which nest in holes, so that 

 the hen as she sits is concealed, the bright colours 

 are very frequently common to both sexes. This is 

 the case e.g. with the Kingfisher. The hen Wood- 

 pecker is brilliantly coloured, though less so than the 

 cock. The conspicuously- coloured Pigeons sit exposed 

 upon the nest ; but Natural Selection only requires 

 that a species should have some means of maintaining 

 itself. The particular means which we find in opera- 

 tion is due to unknown causes. Thus the Pigeon's 

 great power of flight, and the ease with which he finds 

 food, may render protective coloration unnecessary 

 to him. 



There is good reason, then, why in most cases the 

 hen should be dull-coloured. But this affords no 

 explanation of the enormous plumes of the Peacock, 

 the Argus Pheasant, the Lyre Bird, and the Bird of 

 Paradise. 



Dr. Wallace's views on this subject I will give 

 in his own words : " The fact that they (long plumes) 

 have been developed to such an extent in a few 

 species is an indication of such perfect adaptation to 

 the conditions of existence, such complete success in 

 the battle for life, that there is in the adult male, at 

 all events, a surplus of strength, vitality, and growth 

 power which is able to expend itself in this way with- 

 out injury." x This is very strange as coming from the 



1 Darwinism, p. 293. 



