266 THE STORY OF THE BIRDS 



We will conclude this necessarily brief sur- 

 vey of avine architecture by a detailed notice 

 of a few somewhat aberrant forms of nidifica- 

 tion. There is, for instance, the very curious 

 nest of the Hammer Head (Scopus umbretta). 

 This bird is about the size of a Raven, and yet 

 it builds a huge nest of sticks six feet in 

 diameter, which it either places in the fork of 

 a tree or on a ledge of rock. The external 

 model resembles that of the Wren, to select a 

 familiar example, but the internal arrangements 

 are very different. This globular stick-made 

 nest is said to contain three divisions, each 

 with so small an entrance that the bird gets 

 through it with apparent difficulty. Of these 

 chambers the top storey is the receptacle for 

 the eggs, the middle one is a kind of play-room 

 for the young birds when full grown, whilst 

 the basement is used for lookout purposes by 

 the old birds. Then we have the most extra- 

 ordinary methods of nidification prevailing 

 amongst the Mound Birds (Megapodiidae). 

 These birds, as we have already briefly stated, 

 bury their eggs in sand or amongst fermenting 

 vegetable matter, the heat from which eventu- 

 ally hatches them. Dr. Wallace, writing of this 

 peculiar habit, informs us in his delightful 



