BANK SWALLOW. 



19 



operations, it never makes use of its claws for digging ; indeed it is im- 

 possible it could, for they are indispensable in maintaining its position, 

 at least when it is beginning its hole. 



I have further remarked, that some of this swallow's holes are as 

 nearly circular as if they had been planned out with a pair of compasses, 

 while others are more irregular in form ; but this seems to depend 

 more on the sand crumbling away than upon any deficiency in the 

 original workmanship. The bird, in fact, always uses its own body to 

 determine the proportions of the gallery, the part from the thigh to the 

 head forming the radius of the circle, though it does not trace this 

 out as we would do, by fixing a point for the centre, around which to 

 draw the circumference. On the contrary, it perches on the circum- 

 ference with its claws, and works with its bill from the centre outwards, 

 and hence it is that in the numerous excavations recently commenced, 

 which I have examined, I have uniformly found the termination funnel- 

 shaped ; the centre being always much more scooped out than the cir- 

 cumference. The bird consequently assumes all positions while at 

 work in the interior, hanging from the roof of the gallery with its back 

 downwards, as often as standing on the floor. I have more than once, 

 indeed, seen a Bank Swallow wheeling slowly round in this manner on 

 the face of a sand bank, when it was just breaking ground to begin its 

 gallery. 



This manner of working, however, from the circumference to the 

 centre, unavoidably leads to irregularities in the direction, which would 

 not so readily occur by reversing the procedure ; for though the radius 

 formed by a part of the bird's body is subject to little variation, yet the 

 little that does occur, from the extension or contraction of the neck, 

 must tend to throw it out of the right line. Accordingly, all the 

 galleries are found to be more or less winding on to their termination, 

 which is at the depth of from two or three feet, where a bed of loose 

 hay and a few of the smaller breast feathers of geese, ducks, or fowl, 

 is spread with little art for the reception of the eggs. 1 



It may not be unimportant to remark 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 unmixed sand or disturbs the 

 horizontality of the floor, which rather slopes a trifle upwards, and of 

 course the lodgment of rain is thereby prevented. White says he has 

 frequently observed holes of different depths left unfinished at the end 

 of summer ; and rejecting the first notion which occurred to him, that 

 these beginnings were intentionally made in order to be in the greater 



1 Sepp, Nederlandsche Yogelen, i. Deel. 

 c 2 



