its appearing before the last week in April; and in some
of our late frosty, harsh springs, it has not been seen till the
beginning of May. This species usually arrives in pairs.

The swift, like the sand-martin, is very defective in architecture,
making no crust, or shell, for its nest; but forming it of dry grasses
and feathers, very rudely and inartificially put together. With all my
attention to these birds, I have never been able once to discover one in
the act of collecting or carrying in materials; so that I have suspected
(since their nests are exactly the same) that they sometimes usurp upon
the house-sparrows, and expel them, as sparrows do the house and sand-
martin; well remembering that I have seen them squabbling together at the
entrance of their holes; and the sparrows up in arms, and much
disconcerted at these intruders. And yet I am assured, by a nice
observer in such matters, that they do collect feathers for their nests
in Andalusia, and that he has shot them with such materials in their
mouths.

Swifts, like sand-martins, carry on the business of nidification quite in
the dark, in crannies of castles and towers, and steeples, and upon the
tops of the walls of churches under the roof; and therefore cannot be so
narrowly watched as those species that build more openly; but, from what
I could ever observe, they begin nesting about the middle of May; and I
have remarked, from eggs taken, that they have sat hard by the 9th June.
In general they haunt tall buildings, churches, and steeples, and breed
only in such; yet in this village some pairs frequent the lowest and
meanest cottages, and educate their young under those thatched roofs. We
remember but one instance where they breed out of buildings, and that is
in the sides of a deep chalk-pit near the town of Odiham, in this county,
where we have seen many pairs entering the crevices, and skimming and
squeaking round the precipices.

As I have regarded these amusive birds with no small attention, if I
should advance something new and peculiar with respect to them, and
different from all other birds, I might perhaps be credited; especially
as my assertion is the result of many years' exact observation. The fact
that I would advance is, that swifts tread, or propagate, on the wing;
and I would wish any nice observer, that is startled at this supposition,
to use his own eyes, and I think he will soon be convinced. In another
class of animals, viz. th