SELBORNE, _Feb._ 26_th_, 1774.
Dear Sir,--The sand-martin, or bank-martin, is by much the least of any
of the British hirundines, and as far as we have ever seen, the smallest
known hirundo; though Brisson asserts that there is one much smaller, and
that is the _hirundo esculenta_.
But it is much to be regretted that it is scarce possible for any
observer to be so full and exact as he could wish in reciting the
circumstances attending the life and conversation of this little bird,
since it is _fera natura_, at least in this part of the kingdom,
disclaiming all domestic attachments, and haunting wild heaths and
commons where there are large lakes; while the other species, especially
the swallow and house-martin, are remarkably gentle and domesticated, and
never seem to think themselves safe but under the protection of man.
Here are in this parish, in the sand-pits and banks of the lakes of
Wolmer forest, several colonies of these birds, and yet they are never
seen in the village, nor do they at all frequent the cottages that are
scattered about in that wild district. The only instance I ever remember
where this species haunts any building, is at the town of Bishop's
Waltham, in this county, where many sand-martins nestle and breed in the
scaffold-holes of the back wall of William of Wykeham's stables; but then
this wall stands in a very sequestered and retired enclosure, and faces
upon a large and beautiful lake. And indeed this species seems so to
delight in large waters, that no instance occurs of their abounding, but
near vast pools or rivers; and in particular it has been remarked that
they swarm in the banks of the Thames in some places below London-bridge.
It is curious to observe with what different degrees of architectonic
skill Providence has endowed birds of the same genus, and so nearly
correspondent in their general mode of life; for while the swallow and
the house-martin discover the greatest address in raising and securely
fixing crusts or shells of loam as cunabula for their young, the bank-
martin terebrates a round and regular hole in the sand or earth, which is
serpentine, horizontal, and about two feet deep. At the inner end of
this burrow does this bird deposit, in a good degree of safety, her rude
nest, consisting of fine grasses and feathers, usually goose-feathers,
very inartificially laid together.
Perseverance will accomplish anything, though at first one would be
disinclined to believe that this weak bird, with her soft and tender bill
and claws, should ever be able to bore the stubborn sand-bank without
entirely disabling herself; yet with these feeble instruments have I seen
a pair of them make great despatch, and could remark how much they had
scooped that day, by the fresh sand which ran down the bank, and was of a
different colour from that which lay loose and bleached in the sun.
In what space of time these little artists are able to mine and finish
these cavities I have not been able to discover, for reasons given above;
but it would be a matter worthy of observation, where it falls in the way
of any naturalist to make his remarks. This I have often taken notice
of, that several holes of different depths are left unfinished at the end
of summer. To imagine that these beginnings were intentionally made in
order to be in the greater forwardness for next spring, is allowing
perhaps too much foresight and _rerum prudentia_ to a simple bird. May
not the cause of these _latebroe_ being left unfinished arise from their
meeting in those places with strata too harsh, hard, and solid, for their
purpose, which they relinquish, and go to a fresh spot that works more
freely? Or may they not in other places fall in with a soil as much too
loose and mouldering, liable to flounder, and threatening to overwhelm
them and their labours?
One thing is remarkable--that, after some years, the old holes are
forsaken and new ones bored; perhaps because the old habitations grow
foul and fetid from long use, or because they may so abound with fleas as
to become untenantable. This species of swallow, moreover, is strangely
annoyed with fleas; and we have seen fleas, bed-fleas (_pulex irritans_),
swarming at the mouths of these holes, like bees on the stools of their
hives.
The following circumstance should by no means be omitted--that these
birds do not make use of their caverns by way of hybernacula, as might be
expected; since banks so perforated have been dug out with care in the
winter, when nothing was found but empty nests.
The sand-martin arrives much about the same time with the swallow, and
lays, as she does, from four to six white eggs. But as this species is
cryptogame, carrying on the business of nidification, incubation, and the
support of its young in the dark, it would not be so easy to ascertain
the time of breeding, were it not for the coming forth of the broods,
which appear much about the time, or rather somewhat earlier than those
of the swallow. The nestlings are supported in common like those of
their congeners, with gnats and other small insects, and sometimes they
are fed with _libelluloe_ (dragon-flies) almost as long as themselves. In
the last week in June we have seen a row of these sitting on a rail near
a great pool as perchers, and so young and helpless, as easily to be
taken by hand; but whether the dams ever feed them on the wing, as
swallows and house-martins do, we have never yet been able to determine,
nor do we know whether they pursue and attack birds of prey.
When they happen to breed near hedges and enclosures, they are
dispossessed of their breeding holes by the house-sparrow, which is on
the same account a fell adversary to house-martins.
These hirundines are no songsters, but rather mute, making only a little
harsh noise when a person approaches their nest. They seem not to be of
a sociable turn, never with us congregating with their congeners in the
autumn. Undoubtedly they breed a second time, like the house-martin and
swallow; and withdraw about Michaelmas.
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 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 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, _Papilion
de Montagna_.