GENERAL DISTRIBUTION OF BIRDS 19 



cause of the mower and the plow; the Kingfisher must still 

 have a bank for his burrow and the Cardinal a bush for his 

 lodge. 



There are always exceptions to rules, and the rules are 

 sometimes so greatly modified that by and by the modifica- 



Fig. 4 Music Pavilion 



tion becomes the rule and the old rule becomes the exception. 

 We find this quite true in bird life. We are all quite well 

 aware of the fact that birds have modified their nesting habits. 

 The Eave Swallow that once used the rocks and banks, now 

 uses human structures for the support of its clay-jug nests. 



