' nests, and whether the heronry consists of a whole
grove of wood, or only of a few trees.

It gave me satisfaction to find we accorded so well about the
_caprimulgus_; all I contended for was to prove that it often chatters
sitting as well as flying; and therefore the noise was voluntary, and
from organic impulse, and not from the resistance of the air against the
hollow of its mouth and throat.

If ever I saw anything like actual migration, it was last Michaelmas Day.
I was travelling, and out early in the morning; at first there was a vast
fog, but, by the time that I was got seven or eight miles from home
towards the coast, the sun broke out into a delicate warm day. We were
then on a large heath or common, and I could discern, as the mist began
to break away, great numbers of swallows (_hirundines rusticae_)
clustering on the stunted shrubs and bushes, as if they had roosted there
all night. As soon as the air became clear and pleasant they were all on
the wing at once; and, by a placid and easy flight, proceeded on
southward towards the sea; after this I did not see any more flocks, only
now and then a straggler.

I cannot agree with those persons that assert that the swallow kind
disappear some and some gradually, as they come, for the bulk of them
seem to withdraw at once; only some stragglers stay behind a long while,
and do never, there is the greatest reason to believe, leave this island.
Swallows seem to lay themselves up, and to come forth in a warm day, as
bats do continually of a warm evening, after they have disappeared for
weeks. For a very respectable gentleman assured me that, as he was
walking with some friends under Merton Wall on a remarkably hot noon,
either in the last week in December or the first week in January, he
espied three or four swallows huddled together on the moulding of one of
the windows of that college. I have frequently remarked that swallows
are seen later at Oxford than elsewhere; is it owing to the vast massy
buildings of that place, to the many waters round it, or to what else?

When I used to rise in the morning last autumn, and see the swallows and
martins clustering on the chimneys and thatch of the neighbouring
cottages, I could not help being touched with a secret delight, mixed
with some degree of mortification; with delight, to observe with how much
ardour and punctuality those poor little birds obeyed the strong impulse
towards migration, or hiding, imprinted o