312 SWALLOWS AND MARTINS 



are merely short tunnels abandoned on account of some obstacle a 

 stone or hard layer of grit which impeded further progress. Others 

 may be holes deserted, for one reason or another, after several years' 

 use. Others, again, may be in the possession of sparrows. The total 

 number of pairs in a colony may be a dozen or less, or a few hundreds. 



Sometimes sand-martins are content with ready-made holes in 

 walls or other places, but, as a rule, they prefer to excavate for them- 

 selves. The number of holes that are excavated in any given colony 

 in any given year depends partly on the number of pairs that are 

 nesting for the first time. The old birds return usually to their 

 former holes and refurnish them. It depends, partly again, upon the 

 nature of the earth in which the holes have been made, the softer and 

 looser kind, such as sand, being of course more liable to slip than the 

 harder and more compact. I have known the side of a sandpit give 

 way and come down when some of the young were still in the holes. 

 In the debris I found three nests and the bodies of five fledglings. 

 There were probably more buried out of sight. 



Before beginning definitely to excavate a hole, sand-martins 

 appear to spend some time making what one may call very literally 

 trial " scrapes " on the face of the cliff. They may be seen moving 

 along its surface, the tail and wings pressed against it, while the feet 

 all the while are scratching vigorously. "In this way a bird will 

 sometimes crawl, or rather wedge itself, about over the pit's face 

 (which, though it may be perpendicular or almost so, is yet full of 

 roughnesses and inequalities), appearing to seek either the most 

 yielding surface to scratch, or the best place to get fixed into whilst 

 scratching ; and in doing this it leaves a track on the sand or gravel 

 which is quite perceptible through the glasses, and which, I believe, 

 is made by the strongly bent-in tail as well as by the feet. It thus 

 clings with wings, tail, and body whilst scratching, far more than 

 clinging, with its claws." l 



There can be no doubt, however, that the bird makes use chiefly 



1 E. Selous, Bird- Watching, p. 327. 



