THE BIRDS 275 



erect a huge, umbrella-shaped mass of straw and sticks in the 

 branches of trees, which often contain as many as three hundred 

 nesting holes, forming a regular " bird-warren." 



Instances of birds occupying the same nest are rare, but the 

 emus, cassowaries, and ostriches are known to follow this practice, 

 several females depositing their eggs in the same depression in the 

 ground. More than thirty eggs are sometimes deposited in a 

 single ostrich's nest, and their incubation is undertaken by one 

 cock bird, the hens only occasionally sharing in the duty. 



In most cases the necessary warmth for the incubation of the 

 eggs is supplied by the brooding of the parent bird, but in tropical 

 regions certain birds brood their eggs only at night, leaving them 

 by day buried in the ground under the hot rays of the sun ; this 

 course is pursued by the small Egyptian plover (Aegyptius pluvialis), 

 and the ostriches inhabiting the hottest parts of their breeding 

 range. 



The Megapods, or "mound builders," a family of shy terrestrial 

 birds, chiefly confined to the Australian regions, have relinquished 

 brooding altogether, and leave the hatching of their eggs to the 

 natural agencies of the sun and the warm earth. Those of one 

 species (Megacephalum maleo), inhabiting the hilly districts of North 

 Celebes and the Sanghir Islands, come down to the beaches in 

 the breeding season and scrape holes in the volcanic sand just 

 above high-water mark for the reception of their eggs. The holes 

 are three or four feet deep, and from four to five feet in diameter, 

 one hole being the joint property of several birds, who deposit 

 their eggs therein, numbering from two to eight, at intervals, it is 

 stated, of from ten days to a fortnight. The eggs as they are 

 laid are covered with the sand and left to hatch of themselves, 

 and the young birds, which emerge from the shell fully feathered, 

 soon push their way up through the loose soil and run away inland. 

 The brush turkey of Eastern Australia has similar habits, but 

 here a regular mound of earth and decayed leaves is formed by 

 several females, sometimes reaching six feet in height, and measuring 

 from twelve to fourteen feet in diameter at the base. This mound 

 is hollowed out like a cup, and the eggs, which usually number 

 from twenty to thirty, are placed in it in successive circular 

 layers, the small ends pointing downwards, each layer being 

 covered in with earth. These mounds are usually found in 



