SELBORNE, _Sept._ 28_th_, 1774.
Dear Sir,--As the swift or black-martin is the largest of the British
_hirundines_, so it is undoubtedly the latest comer. For I remember but
one instance of 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. the insect, nothing is so common as to see the
different species of many genera in conjunction as they fly. The swift
is almost continually on the wing; and as it never settles on the ground,
on trees, or roofs, would seldom find opportunity for amorous rites, was
it not enabled to indulge them in the air. If any person would watch
these birds of a fine morning in May, as they are sailing round at a
great height from the ground, he would see every now and then, one drop
on the back of another, and both of them sink down together for many
fathoms with a loud piercing shriek. This I take to be the juncture when
the business of generation is carrying on.
As the swift eats, drinks, collects materials for its nest, and, as it
seems, propagates on the wing, it appears to live more in the air than
any other bird, and to perform all functions there save those of sleeping
and incubation.
This hirundo differs widely from its congeners in laying invariably but
two eggs at a time, which are milk-white, long, and peaked at the small
end; whereas the other species lay at each brood from four to six. It is
a most alert bird, rising very early, and retiring to roost very late;
and is on the wing in the height of summer at least sixteen hours. In
the longest days it does not withdraw to rest till a quarter before nine
in the evening, being the latest of all day-birds. Just before they
retire whole groups of them assemble high in the air, and squeak, and
shoot about with wonderful rapidity. But this bird is never so much
alive as in sultry thundery weather, when it expresses great alacrity,
and calls forth all its powers. In hot mornings several, getting
together in little parties, dash round the steeples and churches,
squeaking as they go in a very clamorous manner; these, by nice
observers, are supposed to be males serenading their sitting hens; and
not without reason, since they seldom squeak till they come close to the
walls or eaves, and since those within utter at the same time a little
inward note of complacency.
When the hen has sat hard all day, she rushes forth just as it is almost
dark, and stretches and relieves her weary limbs, and snatches a scanty
meal for a few minutes, and then returns to her duty of incubation.
Swifts, when wantonly and cruelly shot while they have young, discover a
little lump of insects in their mouths, which they pouch and hold under
their tongue. In general they feed in a much higher district than the
other species--a proof that gnats and other insects do also abound to a
considerable height in the air; they also range to vast distances, since
locomotion is no labour to them who are endowed with such wonderful
powers of wing. Their powers seem to be in proportion to their levers,
and their wings are longer in proportion than those of almost any other
bird. When they mute, or ease themselves in flight, they raise their
wings, and make them meet over their backs.
At some certain times in the summer I had remarked that swifts were
hawking very low for hours together over pools and streams, and could not
help inquiring into the object of their pursuit that induced them to
descend so much below their usual range. After some trouble, I found
that they were taking _phryganeae_, _ephemerae_, and _libellulae_ (cadew-
flies, may-flies, and dragon-flies), that were just emerged out of their
aurelia state. I then no longer wondered that they should be so willing
to stoop for a prey that afforded them such plentiful and succulent
nourishment.
They bring out their young about the middle or latter end of July: but as
these never become perchers, nor, that ever I could discern, are fed on
the wing by their dams, the coming forth of the young is not so notorious
as in the other species.
On the 30th of last June I untiled the eaves of a house where many pairs
build, and found in each nest only two squab, naked _pulli_; on the 8th
July I repeated the same inquiry, and found that they had made very
little progress towards a fledged state, but were still naked and
helpless. From whence we may conclude that birds whose way of life keeps
them perpetually on the wing would not be able to quit their nest till
the end of the month. Swallows and martins, that have numerous families,
are continually feeding them every two or three minutes, while swifts,
that have but two young to maintain, are much at their leisure, and do
not attend on their nest for hours together.
Sometimes they pursue and strike at hawks that come in their way, but not
with that vehemence and fury that swallows express on the same occasion.
They are out all day long in wet days, feeding about, and disregarding
still rain: from whence two things may be gathered; first, that many
insects abide high in the air, even in rain; and next, that the feathers
of these birds must be well preened to resist so much wet. Windy, and
particularly windy weather with heavy showers, they dislike, and on such
days withdraw, and are scarce ever seen.
There is a circumstance respecting the colour of swifts which seems not
to be unworthy of our attention. When they arrive in the spring, they
are all over of a glossy, dark soot-colour, except their chins, which are
white; but, by being all day long in the sun and air, they become quite
weather-beaten and bleached before they depart, and yet they return
glossy again in the spring. Now, if they pursue the sun into lower
latitudes, as some suppose, in order to enjoy a perpetual summer, why do
they not return bleached? Do they not rather perhaps retire to rest for
a season, and at that juncture moult and change their feathers, since all
other birds are known to moult soon after the season of breeding?
Swifts are very anomalous in many particulars, dissenting from all their
congeners not only in the number of their young, but in breeding but once
in a summer, whereas all the other British hirundines breed invariably
twice. It is past all doubt that swifts can breed but once, since they
withdraw in a short time after the flight of their young, and some time
before their congeners bring out their second broods. We may here remark
that, as swifts breed but once in a summer, and only two at a time, and
the other hirundines twice, the latter, who lay from four to six eggs,
increase at an average five times as fast as the former.
But in nothing are swifts more singular than in their early retreat. They
retire, as to the main body of them, by the 10th August, and sometimes a
few days sooner; and every straggler invariably withdraws by the 20th,
while their congeners, all of them, stay till the beginning of
October--many of them all through that month, and some occasionally to
the beginning of November. This early retreat is mysterious and
wonderful, since that time is often the sweetest season in the year. But
what is more extraordinary, they begin to retire still earlier in the
most southerly parts of Andalusia, where they can be in no ways
influenced by any defect of heat, or, as one might suppose, failure of
food. Are they regulated in their motions with us by a defect of food,
or by a propensity to moulting, or by a disposition to rest after so
rapid a life, or by what? This is one of those incidents in natural
history that not only baffles our searches, but almost eludes our
guesses!
These hirundines never perch on trees or roofs, and so never congregate
with their congeners. They are fearless while haunting their nesting-
places, and are not to be scared with a gun, and are often beaten down
with poles and cudgels as they stoop to go under the eaves. Swifts are
much infested with those pests to the genus called _hippoboscoe
hirundinis_; and often wriggle and scratch themselves in their flight to
get rid of that clinging annoyance.
Swifts are no songsters, and have only one harsh screaming note; yet
there are ears to which it is not displeasing, from an agreeable
association of ideas, since that note never occurs but in the most lovely
summer weather.
They never can settle on the ground but through accident, and, when down,
can hardly rise, on account of the shortness of their legs and the length
of their wings; neither can they walk, but only crawl; but they have a
strong grasp with their feet, by which they cling to walls. 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 the
British hirundines; and, indeed from all other known birds, the _hirundo
melba_, or 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_.
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.
The Swedes have bestowed a very pertinent name on this swallow, calling
it "ring swala," from the perpetual rings or circles that it takes round
the scene of its nidification.
Swifts feed on _coleoptera_, or small beetles with hard cases over their
wings, as well as on the softer insects, but it does not appear how they
can procure gravel to grind their food, as swallows do, since they never
settle on the ground. Young ones, over-run with _hippoboscoe_, are
sometimes found under their nests, fallen to the ground, the number of
vermin rendering their abode insupportable any longer. They frequent in
this village several abject cottages; yet a succession still haunts the
same unlikely roofs--a good proof this that the same birds return to the
same spots. As they must stoop very low to get up under these humble
eaves, cats lie in wait, and sometimes catch them on the wing.
On July 5th, 1775, I again untiled part of a roof over the nest of a
swift. The dam sat in the nest, but so strongly was she affected by
natural στοργὴ for her brood, which she supposed to be in danger,
that, regardless of her own safety, she would not stir, but lay sullenly
by them, permitting herself to be taken in hand. The squab young we
brought down and placed on the grass-plot, where they tumbled about, and
were as helpless as a new-born child. While we contemplated their naked
bodies, their unwieldy disproportioned abdomina, and their heads, too
heavy for their necks to support, we could not but wonder when we
reflected that these shiftless beings in a little more than a fortnight
would be able to dash through the air almost with the inconceivable
swiftness of a meteor, and perhaps in their emigration must traverse vast
continents and oceans as distant as the equator. So soon does Nature
advance small birds to their ἡλικία, or state of perfection, while
the progressive growth of men and large quadrupeds is slow and tedious!