212 NATURAL HISTORY 
son approaches their nests. They seem not to be 
of a sociable turn, never with us congregating with 
their congeners in the autumn. Undoubtedly they 
havé a second brood, like the house-martin and 
swallow, and withdraw about Michaelmas. 
Though in some particular districts they may 
happen to abound, yet on the whole, in the south 
of England at least, is this much the rarest spe- 
cies ; 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 sandhills 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 adapt- 
ed to, the peculiar sort of insects which furnish 
their food. Hence it would 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 St. 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 de- 
serted building. They dip and wash as they fly 
sometimes, like the house-martin and swallow. 
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