Their bodies being flat they can enter a very narrow crevice;
and where they cannot pass on their bellies they will turn up
edgewise.
The particular formation of the foot discriminates the swift from
all British hirundines; and indeed from all other known birds, the
hirundo melba, great white-bellied swift of Gibraltar, excepted; for
it is so disposed as to carry 'omnes quatuor digitos anticos' all its
four toes forward; besides, the least toe, which should be the back-
toe, consists of one bone alone, and the other three only of two
apiece. A construction most rare and peculiar, but nicely adapted to
the purposes in which their feet are employed. This, and some
peculiarities attending the nostrils and under mandible, have
induced a discerning naturalist* to suppose that this species might
constitute a genus per se.
(* John Antony Scopoli, of Carniola, M.D.)
In London a party of swifts frequents the Tower, playing and
feeding over the river just below the bridge; others haunt some of
the churches of the Borough next the fields; but do not venture,
like the house-martin, into the close crowded part of the town.
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