174 WILD LIFE IN A SOUTHERN COUNTY. 



The wall being old, some of the mortar had crumbled 

 it was not of the best quality and here and there 

 was a small cavity. These a portion of the birds tried 

 to enlarge, while others boldly laboured in places 

 where no such slight openings existed. It was interest- 

 ing to watch their patient efforts as they clung to the 

 perpendicular wall like bats. Now, two or three flew 

 off and described a few circles in the air, as if to rest 

 themselves, and then again returned to work. At 

 last, convinced of the impossibility of penetrating 

 the mortar, which was much harder beneath the 

 surface, they went away in a body with a general 

 twitter, leaving distinct marks of their shallow ex- 

 cavations. The circumstance was the more interest- 

 ing because the road was much frequented (for a rural 

 district), and many people stopped to look at them ; 

 but the birds did not seem in the least alarmed, 

 and evidently only left because they found the wall 

 impenetrable. Instinct, infallible instinct, certainly 

 would not direct these birds to such an unsuitable 

 spot. Neither was there any peculiar advantage to 

 attract them ; it was not quiet or retired, but the 

 reverse. The incident was clearly an experiment, 

 and when they found it unsuccessful they desisted. 



If we suppose this flight of martins to represent a 

 party emigrating from a sand quarry (there were 

 three such quarries within a mile radius), where the 

 population had overflowed, it seems possible to trace 

 the motive which animated them. I imagine that 

 the old birds drive the young ones away, when the 



