The Theory of Sexual Selection. 381 



may find lying about the woods and fields. In many 

 cases a marked preference is shown for particular 

 objects as, for instance, in the case of the Syrian 

 nut-hatch, which chooses the iridescent wings of 

 insects, or that of the great crested fly- catcher, which 

 similarly chooses the cast-off skins of snakes. But 

 no doubt the most remarkable of these cases is that 

 of the baya-bird of Asia, which after having com- 

 pleted its bottle- shaped and chambered nest 1 , studs it 

 over with small lumps of clay, both inside and out, 

 upon which the cock-bird sticks fire-flies, apparently 

 for the sole purpose of securing a brilliantly decorative 

 effect. Other birds, such as the hammer-head of 

 Africa, adorn the surroundings of their nests (which 

 are built upon the ground) with shells, bones, pieces 

 of broken glass and earthenware, or any objects of a 

 bright and conspicuous character which they may 

 happen to find. The most consummate artists in this 

 respect are, however, the bower-birds ; for the species 

 of this family construct elaborate play-houses in the 

 form of arched tunnels, built of twigs upon the ground. 

 Through and around such a tunnel they chase one 

 another ; and it is always observable that not only is 

 the floor paved with a great collection of shells, bones, 

 coloured stones, and any other brilliant objects which 

 they are able to carry in their beaks, but also that the 

 walls are decorated with the most gaudy articles 

 which the birds can find. There is one genus, in 

 Papua, which even goes so far as to provide the 

 theatre with a surrounding garden. A level piece of 



1 The chambers are three in number. The two upper ones are 

 occupied respectively by the male and the sitting female. The lower 

 one serves as a general living room when the young are hatched. 



