174 NATURAL HISTORY OF SELBORNE. 
Though in some particular districts they may happen to abound, 
yet in the whole, in the south of England at least, is this much the 
rarest species. For there are few towns or large villages but what 
abound with house-martins ; few churches, towers, or steeples, but 
what are haunted by some swifts; scarce a hamlet or single cottage- 
chimney that has not its swallow ; while the bank-martins, scattered 
here and there, live a sequestered life among some abrupt sand-hills, 
and in the banks of some few rivers. 
These birds have a peculiar manner of flying; flitting about with 
odd jerks, and vacillations, not unlike the motions of a butterfly. 
Doubtless the flight of all hirundines is influenced by, and adapted 
to, the peculiar sort of insects which furnish their food. Hence it 
wouid be worth inquiry to examine what particular genus of insects 
affords the principal food of each respective species of swallow. 
Notwithstanding what has been advanced above, some few sand- 
martins, I see, haunt the skirts of London, frequenting the dirty 
pools in Saint George’s Fields, and about Whitechapel. The 
question is where these build, since there are no banks or bold 
shores in that neighbourhood ; perhaps they nestle in the scaffold-: 
holes of some old or new deserted building. They dip and wash 
as they fly sometimes, like the house-martin and swallow. 
Sand-martins differ from their congeners in the diminutiveness of 
their size, and in their colour, which is what is usually called a 
mouse-colour. Near Valencia, in Spain, they are taken, says 
Willughby, and sold in the markets for the table; and are called by 
the country people, probably from their desultory jerking manner 
of flight, Papzlion de Montagna, 
