BANK SWALLOW 



55 



elliptical holes in the cliffs. If you go up to them 

 and rap on the walls the startled cliff-dwellers re- 

 sponsible for these mural 

 decorations will often fly 

 out in a whirl about your 

 head. The excavations vary 

 in depth from twelve inches 

 to four feet, and are made 

 with a careful avoidance of 

 stones that might fall from 

 the roof upon the helpless 

 heads of the babes in the 

 bank. The eggs, being concealed, are white. 



The Swallow's habit of nesting in colonies is an 

 interesting example of the ' sociability of birds,' 

 which Mr. Widmann says can best be indulged 

 by long-winged birds like Swallows, as they can 

 more easily spread over the extent of territory 

 necessary for commissary reasons. 



FIG. 24. 

 Bank Swallow. 



