WATER BIRDS 



multitudes in the fall— all in somber plumage 

 —are made up of young of both sexes and of 

 adult females; but it is not so clear, although 

 it is a fact that the flocks also contain adult 

 males which are in the so-called eclipse plu- 

 mage. The males of nearly all species of 

 ducks, soon after the period of courtship is 

 over, change, by moulting, from their conspic- 

 uous nuptial dress to the quiet and dull-col- 

 ored dress of the female. This is what is 

 meant by going into the eclipse plumage, and 

 the fact is in itself a strong argument in favor 

 of the theory of sexual selection. 



In the case of the eider, the drakes in nup- 

 tial plumage are wonderfully brilliant in their 

 dress of creamy white, jet black, deep blue and 

 pale green. It is evident that they appreciate 

 their own beauty, for during courtship they 

 display their charms by various antics, inclu- 

 ding the rising up from the water so as to show 

 the splendid black belly shield otherwise hid- 

 den. In all situations, whether on the open 

 sea or on land, among ice, rocks, spruces or 

 mosses, they are extremely conspicuous, while 

 the duck, in the modest but tasteful dress of 

 brown, is always difficult to distinguish. Im- 

 mediately after the courtship period the drake 



143 



