146 THE HUMAN SIDE OF BIRDS 



inclination, and thus preserves each httle habita- 

 tion. . . . Each nest is three or four inches in diam- 

 eter, which is sufficiently large for the bird; but as 

 they are in close contact around the roof, they ap- 

 pear to the eye to form a single edifice, and are only 

 separated by a small opening which serves as an 

 entry to the nest; and one entrance frequently is 

 common to three nests, one of which is placed at 

 the bottom, and the others on each side. It has 320 

 cells, and will hold 640 inhabitants, if each contains 

 a couple, which may be doubted. Every time, how- 

 ever, that I have aimed at a swarm, I have killed 

 the same number of males and females." 



Bird colonies are more or less common, since it 

 is often necessary to combine to build effective shel- 

 ters against the elements, or to unite their strength 

 in defence against their enemies. 



Perhaps no better example of law and order can 

 be found among birds than that observed by the 

 "Twelve Apostles bird." These interesting inliabi- 

 tants of Australia build their open circular nests 

 of mud and grass quite close together for mutual 

 protection. They work together like a group of 

 carpenters and when the nest is completed a num- 

 ber of the female birds lay one egg each in the com- 

 munity nest, and then one of the hen birds sets upon 

 the eggs. If, for any reason, she is killed, another 



