WILD LIFE OF ORCHARD AND FIELD 



verify by observing their operations early in the 

 morning through an opera-glass, when they begin 

 in the spring to form their excavations. In this 

 way we have seen one of these birds cling with its 

 sharp claws to the face of a sand-bank, and peg in 

 its bill as a miner would his pickaxe, till it had 

 loosened a considerable portion of the hard sand, 

 and tumbled it down among the rubbish below. 

 In these preliminary operations it never makes use 

 of its claws for digging; indeed, it is impossible 

 that it could, for they are indispensable in main- 

 taining its position, at least when it is beginning 

 its hole. We have further remarked that some of 

 these martins' holes are nearly as circular as if 

 they had been planned out with a pair of compass- 

 es, while others are more irregular in form; but 

 this seems to depend more on the sand crumbling 

 away than upon any deficiency in its original 

 workmanship. The bird, in fact, always uses its 

 own body to determine the proportions of the gal- 

 lery, the part from the thigh to the head forming 

 the radius of the circle. It does not trace this out 

 as we should do, by fixing a point for the centre 

 around which to draw the circumference; on the 

 contrary, it perches on the circumference with its 

 claws, and works with its bill from the centre out- 



