184 SAND-MAETIFS. 



one would be disinclined to believe that this weak bird, with 

 her soft and tender bill and claws, should ever be able to 

 bore the stubborn sand-bank, without entirely disabling her- 

 self ; yet with these feeble instruments have I seen a pair of 

 them make great dispatch, and could remark how much they 

 had scooped that day, by the fresh sand which ran down the 

 bank, and was of a different colour from that which lay loose 

 and bleached in the sun. 



In what space of time these little artists are able to mine 

 and finish these cavities I have never been able to discover, 

 for reasons given above ; but it would be a matter worthy of 

 observation, where it falls in the way of any naturalist, to 

 make his remarks. This I have often taken notice of, that 

 several holes of different depths are left unfinished at the 

 end of summer. To imagine that these beginnings w r ere 

 intentionally made, in order to be in the greater forwardness 

 for next spring, is allowing, perhaps, too much foresight and 

 skill to a simple bird. May not the cause of these latebrce 

 being left unfinished arise from their meeting in those places 

 with strata too harsh, hard, and solid for their purpose, which 

 they relinquish, and go to a fresh spot that works more freely? 

 or may they not in other places fall in with a soil as much 

 too loose and mouldering, liable to founder, and threatening 

 to overwhelm them and their labours ? 



One thing is remarkable, that, after some years, the old 

 holes are forsaken, and new ones bored ; perhaps because the 

 old habitations grow foul and fetid from long use, or because 

 they may so abound with fleas as to become untenantable. 

 This species of swallow, moreover, is strangely annoyed with 

 fleas; and we have seen fleas, bed-fleas, (jpulex irritans,) 

 swarming at the mouths of these holes, like bees on the 

 stools of their hives. 



The following circumstance should by no means be 

 omitted, that these birds do not make use of their caverns 

 by way of hybernacula, as might be expected ; since banks 

 so perforated have been dug out with care in the winter, 

 when nothing was found but empty nests. 



The sand-martin arrives much about the same time with 

 the swallow, and lays, as she does, from four to six white 

 eggs. But, o.s this species is cryptogams, carrying on the 

 business of nidification, incubation, and the support of its 



