BAJVK-SWALLOWS. 253 



or fowls is spread with little art for the reception of the 

 four to six white eggs. It may not be unimportant to re- 

 mark, also, that it always scrapes out with its feet the sand 

 detached by the bill ; but so carefully is this performed 

 that it never scratches up the unmined sand, or disturbs 

 the plane of the floor, which rather slopes upw^ard, and of 

 course the lodgment of rain is thereby prevented." 



Sometimes the nest is carried to a far greater depth than 

 two or three feet, as in a case observed by Mr. Fowler, in 

 Beverly, Massachusetts, where, in order to get free of a 

 stony soil, where pebbles might be dislodged and crush the 

 eggs, the tunnel was carried in nine feet, while neighboring 

 birds in better soil only went a third as far. In one place 

 the burrows will be close to the top of the bluff; in another 

 near the bottom, according as fancy dictates, or the birds 

 have reason to fear this or that enemy. English writers 

 agree that occasionally their bank - swallows do not dig 

 holes, but lay in the crannies of old walls, and in hollows 

 of trees. This is never done, that I am aware of, in the 

 United States ; but in California a closely allied species, the 

 rough-winged swallow, " sometimes resorts to natural clefts 

 in the banks or adobe buildings, and occasionally to knot- 

 holes." On the great plains, however, our Cotyle burrows 

 in the slight embankments thrown up for a railway-bed, in 



