THE SAND MARTIN. 



75 



successive spots with its beak, until it discovers a suitable local- 

 ity. It then works in a circular direction, using its legs as a 

 pivot, and by dint of turning round and round, and pecking 

 away as it proceeds, soon chips out a tolerably circular hole. 

 After the bird has lived for some time in the tunnel, the shape 

 of the entrance is much damaged by incessant passing to and fro 



of the inmates, but while the burrow is still new and untenant- 

 ed, its form is almost cylindrical. In all cases the tunnel slopes 

 gently upward, so as to prevent the lodgment of rain, and its 

 depth is exceedingly variable. About two feet and a half is a 

 fair average length. Generally, the direction of the burrow is 

 quite straight, but sometipies it takes a curve, where an obstacle, 

 such as a stone or a root, has interrupted the progress of the bird. 

 Should the stone be a large one, the Sand Martin usually aban- 



