Railway Birds and Flowers 123 



of surface, and afford little of the sheltering cover 

 which most of the smaller birds love. But even the 

 naked and perpendicular side of a cutting is often 

 seized upon as a nesting-site by a colony of sand- 

 martins, if a layer of soft and workable sand 

 chances to be exposed. The difficulty of finding 

 suitable nesting- quarters is the greatest problem 

 of the sand-martins' summer life ; they are often 

 prevented from settling in neighbourhoods which 

 fully satisfy their other chief need of an abundant 

 supply of winged insect food, because of the absence 

 of any suitable sandy face in which they can drive 

 their narrow nesting- tunnels. In places where there 

 are neither sandpits, dry, natural scarps, nor steep 

 and sandy river banks, the railway often comes 

 to the sand-martins' rescue by laying bare some 

 suitable stratum in the soil. There is something 

 almost touching in the eagerness with which the 

 little, mouse-grey swallows will seize upon some 

 narrow layer of sand which may chance to be exposed 

 at the summit of a cutting in solid rock, and fill 

 this scanty habitable fringe with their crowded 

 orifices and all the play and flicker of their active 

 life. Yet there is no other bird which habitually 

 haunts the deeper and steeper cuttings, except a 

 few pied wagtails ; and even the broader and 

 gentler grass-clothed slopes which slant upward 

 from the metals in soft soils are still too much 

 subject to damp and cold to be regularly frequented 

 by the birds which haunt the line. 



Stretches of embankment, on the other hand, are 

 often as perfectly adapted to the needs of the smaller 



