and having trained and flown both species of these falcons for many
years I have been enabled to prove this beyond doubt.”
The swift has still to be considered. There are three species of
swifts which rank as British birds: the common swift (_Cypselus
apus_), the Alpine swift (_Cypselus melba_), and the spine-tailed
or needle-tailed swift (_Acanthyllis caudacuta_ or _Chaetura
caudacuta caudacuta_). The Alpine swift is a rare visitor here,
only about thirty having been satisfactorily identified at
different times from April to October in different parts of these
islands, but chiefly in the southern part of England. It breeds in
mountains throughout Central Europe, and eastwards to India. The
spine-tailed swift is even a rarer visitor here, only two recorded
instances of specimens having been obtained--one in Essex in 1846
and one (said to have been in company with another) in Hampshire
in 1879. It breeds in the mountains of North-eastern Asia, and in
winter goes as far south as Australia.
[Illustration: THE SPINE-TAILED SWIFT.
By V. R. BALFOUR-BROWNE.]
Swifts are perhaps the most powerfully winged, in proportion to
their weight, of all British birds. Their form is that which has
been found to make the fastest sailing vessel--full forwards and
lengthened, and tapering backwards. The difficulty in regard to
these birds, and particularly in regard to the Alpine swift and
the spine-tailed swift, is to obtain the necessary opportunities
and conditions for comparing their maximum speed with that of
other very fast birds. It is difficult to realise merely from a
consideration of the description and measurements of these three
swifts in the authoritative works of ornithologists how much larger
the Alpine swift and spine-tailed swift are than the common swift.
I have had opportunities of handling and examining the stuffed
specimens of these birds in the British Museum (Natural History) at
South Kensington, and should like to acknowledge here the courtesy
and assistance given to me at the Museum by Mr. W. P. Pycraft, Dr.
P. R. Lowe, and Mr. N. B. Kinnear.
The actual measurements of the three birds are as follows:
Length. Wing.
Common Swift 6·75 inches 6·8 inches
Alpine Swift 8 ” 8·45 ”
Needle-tailed Swift 8 ” 8·1 ”
It is not generally realised that the common swift, so well known
in this country, which looks so imposing in flight as it glides
overhead with wings extended, is hardly so large, when plucked, as
a man’s thumb-joint and weighs slightly over half an ounce.
Bearing in mind that as between two birds of the same build and
structure the larger will, when it gets going, fly faster than the
smaller one, it would naturally be expected, as is the undoubted
fact, that the Alpine swift and spine-tailed swift are faster
fliers than the common swift.
The falconer has in the case of the swift very little opportunity
of comparing its speed with that of the peregrine. This is partly
because the peregrine, whether it be the falcon (the female bird)
or the tiercel (the male bird), will probably not attempt to
kill the swift, it being too small a prey. There is the further
difficulty that the swift rarely continues on a level flight.
I have been so fortunate as to obtain the views of several
well-known authorities on this difficult question--the comparative
maximum speed of the swift and the peregrine.
Colonel Meinertzhagen says:
“I should certainly say that the swift is the fastest British bird,
both in its normal speed and accelerated. But any of the falcons
could catch it, if caught unawares, by stooping, or perhaps two
hunting together. If the swift had, say, ten seconds’ warning,[14]
I do not believe any falcon could touch it. As regards endurance,
those birds with the greatest endurance are the swifts, swallows,
petrels, and gulls. Swifts are probably endowed with the greatest
powers, being denied by nature the advantages of perching,
alighting on water, or resting on the ground. I have recently been
studying the power of flight of various groups of birds, and find
that the wings of the swift and petrel groups have wing outlines
best suited for both endurance and speed. The falcon has a wing
intended for short rapid flights and not for endurance.
“You have doubtless seen falcons hunting. When they set out on a
regular hunt they are not usually much faster than their quarry,
unless it is some unfortunate non-game bird, and they only
gradually overtake it. But I think a falcon usually makes full use
of surprise and force of gravity. If these fail, he often abandons
the chase, recognising that wearing a bird like a golden plover or
teal down by sheer endurance and honest straightforward flying is
a troublesome and not always successful task.”
Major C. R. E. Radclyffe writes:
“The point you raise _re_ the relative speed of swifts and other
birds is a difficult one to decide.
“I have, however, a strong recollection of a brother falconer (I
cannot remember who it was) telling me that his trained merlins
could easily overhaul a swift, and he told me that once or twice
they had killed them. But this was many years ago, and I am not
able to remember all the facts.
“I have often stood on the bridges here and watched swifts passing
in hundreds close past me. They appear to be moving very fast when
hawking after flies near the surface of a river.
“There is a long stretch of broad water in the river in front of my
house here, and often there are hundreds of swifts flying up and
down it. They go about half a mile dead straight and then turn back
over this stretch of the river.
“I have flown fast carrier pigeons along this same bit of water,
and they seem to do it in less time than the swifts. Only last
summer, at my place in Scotland, I was sitting on the banks of the
river watching some swifts, when a pair of blue rock pigeons came
from their nest in the cliff, going out to feed, and they went
clean past the swifts going in the same direction.
“Of course presumably the pigeons were in a hurry and the swifts
were not, and unless we are certain that both birds are trying
their hardest, you cannot accept these things as a test of speed.
“If I were asked to guess roughly at the six fastest flying birds
in the British Isles, I should place them as follows:
1. The Peregrine,
2. The Hobby,
3. The Merlin,
4. The Golden Plover,
5. The Pochard,
6. The Blue Rock Pigeon,
and the fastest game bird is undoubtedly the blackcock. I do not
know, however, if a capercailzie would not beat him if you could
get them both to take a long flight across the open, because,
generally speaking, in the case of birds of similar shape and
species, the heaviest bird is the fastest flying one.”
Captain G. S. Blaine, another falconer of long and varied
experience, has also been so kind as to give me his opinion on this
question. He writes:
“I cannot say whether a peregrine falcon could overtake and kill a
swift, but I do not think it would ever attempt the feat. Falcons
do not, as a rule, attack small birds. The male or tiercel will
sometimes stoop at them, but more in play than in earnest. The
female, I should think, would never attempt to catch anything
smaller than a thrush or starling.
“It is very difficult to estimate the relative speed of different
birds. To do so, one would have to judge correctly of the time
taken in passing a measured distance on a straight course. Very few
birds, especially swifts, fly absolutely straight ahead.
“A hobby has been known to catch swifts and swallows, and possibly
a merlin would do the same.
“A peregrine can fly faster than a merlin, but it would not be so
quick in turning and following a bird.
“I think a peregrine can fly faster than a teal or golden plover,
though, as you observe, the latter are quicker off the mark.”
There are very few recorded instances, as far as I have been able
to ascertain, in which a hawk has killed the common swift. In two
of these there was no evidence as to whether the hawk had not
taken the swift by surprise. But there is at least one recorded
instance in which a swift has been killed by a hobby in fair
flight. This is to be found in that delightful book, _Field Studies
of some Rarer British Birds_,[15] by Mr. William Walpole Bond. The
description of the race is so vivid that, with the author’s kind
permission, I reproduce it here.
“On June 14, 1907, as I lay in a spacious clearing of a big Sussex
woodland, a sudden swirl of wings gave me instant pause in my
meditations. Looking up, my eyes were held by a swift coasting
earthwards in frantic haste, hotly pursued by a hobby not many
yards in his wake. I literally held my breath with excitement, for
here was an occurrence of dreamland only. Speeding on about a level
with the tree-tops both birds measure the length of the long glade
in fractional time, and the hawk gains almost imperceptibly.
“Then the pursued makes a mighty effort; he rises gamely, even
slightly increasing his lead. Indeed it seemed he might shake off
his deadly courser. Alas, my friend, it is to no purpose; the
hobby has responded to your challenge, and now exhibits speed for
which--glorious flier though he be--I should never have given him
credit. Mounting with ease above his prospective prey, the lithe
hawk compels him to describe an arc and once again to start a
life--or death--struggle in a headlong slant across the clearing.
That flight is his last--the swift has shot his bolt. Now inches
only separate the birds, you could cover both with a very large
handkerchief. Next instant the hawk rises straight and stoops
strongly, pursuer and pursued become one. Binding to his quarry the
hawk is away over the trees at my back without so much as the most
momentary pause in the continuation of his eminently successful
‘shikar.’ Indeed, this continuity of action was possibly the most
pleasing part of a praiseworthy performance, since you might
reasonably have expected a break--however trivial--after what must
have been a long and arduous chase. As a fact, the death-stroke was
so featly and rapidly administered that, except that where a moment
before there had been two birds there was now only one, and that a
muffled clap and a few small dusky feathers twirling aimlessly in
the summer breeze suggested some sort of untoward happening, it
was difficult to realise that anything unusual had taken place.
“I have seen the irresistible death-stoop of the peregrine, the
lightning rush of the tiny merlin, I have watched the earthward
plunge after prey of buzzard, eagle, kite, and harrier; I have
revelled in the agile snatch of the sparrow-hawk, in the silent
hovering of the kestrel; and all have I enjoyed. Here was something
quite different and even far better. Never have I seen skill so
superb as was displayed by that hobby.”
It would therefore seem that the hobby, which is a peregrine in
miniature, flies faster than the common swift even on a horizontal
flight, but it is worthy of note that in both stoops referred to
in this delightful description, the hobby gained by reason of
gravity. True, he also gained altitude, but this may have been
better manœuvring for position and not necessarily a greater speed.
As the peregrine flies faster than the hobby, being a bird of the
same structure but larger, the peregrine could no doubt overtake
and kill the common swift if it would take the trouble to pursue so
small a bird.
Next, as to the Alpine swift. This bird is much larger than
the common swift--in length 8 inches as compared with 6·75
inches--whilst their wings are 8·45 inches and 6·8 inches
respectively, and as the two birds are of the same structure, one
would naturally expect that the Alpine swift would be much the
faster flier. The flight of the Alpine swift, like that of the
blackcock, which is probably the fastest flier amongst game birds
with the possible exception of the capercailzie, is very deceptive.
Colonel Meinertzhagen, in the article already mentioned, describes
some observations from an aeroplane in regard to the flight of a
large flock of common swifts feeding at an altitude of 6000 feet
over Mosul in Mesopotamia. He describes how they circled round
the aeroplane, which was flying at 68 miles an hour, and easily
overtook it. In commenting on this case he says: “The case of the
Mosul swifts is interesting. The birds were probably not on passage
but simply feeding. It is known that swifts travel great distances
in search of food and ascend great altitudes.
“In the Middle Atlas of Morocco, in the Himalayas, in Crete,
and Palestine, 4000 or 5000 feet and 50 miles or so in distance
seems nothing to these incomparable fliers. I have had splendid
opportunities of observing the Alpine, common, and spine-tailed
swifts (_Chaetura_), and it has been a great disappointment to
me that I have never been able to get a satisfactory estimate of
their rate of flight, as they never continue on a level course.
On a small island on the coast of Crete I was recently given a
good exhibition of what an Alpine swift can do. I was watching
some of these birds feeding round cliffs in which several pairs of
Eleonora’s falcons were about to breed. Now, this delightful falcon
is no mean flier, and as these swifts passed their cliff, the
falcons would come out against them like rockets. The swifts would
accelerate and would seem to be out of sight before the falcons
were well on their way. So confident were the swifts in their
superior speed, that every time they circled round the island they
never failed to ‘draw’ the falcons, and seemed to be playing with
them. I may add that these same falcons have little difficulty in
overhauling and striking a rock-pigeon--itself no mean performer. I
have also seen on record the case of falcons and swifts somewhere
in India, where the former failed time after time to come up with
his quarry. I, unfortunately, cannot trace the reference.
“I hesitate even to guess at the speed to which a swift can attain
when the necessity arises, but the main point is that this, the
fastest of birds, can increase his feeding speed of, say, 70 miles
per hour, to a velocity which must exceed 100 miles per hour.”
In the tables given above[16] Colonel Meinertzhagen estimates the
speed of the normal and migratory rate of flight of falcons at 40
to 48 miles an hour, whilst Captain Portal estimates the maximum
speed of the peregrine falcon in level flight through still air at
62 miles an hour. Captain Portal adds that the speed given is for
a good trained bird, and that a wild bird is faster.
In view of Colonel Meinertzhagen’s observations from his aeroplane
and the figures given above, it would appear to be certain that
the Alpine swift is faster than the peregrine falcon in horizontal
flight.
We have now to consider the speed of the spine-tailed or
needle-tailed swift. There seems to be no doubt that this bird is
a much faster flier than the Alpine swift, though at first sight
and without a careful examination of the skeletons, it is difficult
to state why this should be so. I have compared various specimens
of the two birds, and there appears to be little difference in
their size. Colonel Meinertzhagen, who has been so kind as to
discuss the subject with me, agrees that the spine-tailed swift is
the faster flier, and tells me that he thinks it is probably the
heavier bird of the two, and that this may account for its greater
rapidity of flight.
The wing of the Alpine swift is 8·45 inches, that of the
spine-tailed swift is 8·1 inches. The length of both birds is 8
inches,[17] although Dresser[18] gives the total length as 8·5 and
that of the spine-tailed swift as 8·1 inches.
The genus _Chaetura_, to which the needle-tailed swift belongs, is
easily distinguishable from the genus _Apus_ (to which the common
swift and Alpine swift belong) by the wedge-shaped tail in which
the shafts of the feathers are longer than the webs and protrude
like spines. The tail in the only species (_Chaetura caudacuta
caudacuta_) occurring in the British Isles, compared with that of
the Alpine swift, is very short. It is almost square, and has ten
feathers, which are very stiff and the shafts of which project 4-6
mm. (·156-·234 inch) beyond the web in a stiff point like that of
a needle or spine.[19]
The shafts of the primaries are very strong and the wings very
long. Gould[20] says, in reference to the spine-tailed swift, in a
passage which is quoted in Seebohm:[21] “The keel or breast bone
of this species is more than ordinarily deep and the pectoral
muscles more developed than in any of its weight with which I am
acquainted.” Probably the last-mentioned facts largely account for
its superiority in speed over the Alpine swift.
In an article entitled “The Twelve Swiftest Birds of
Australia,”[22] in which Mr. E. S. Sovenson gives the views of
himself and various friends of his as to the relative speed of
Australian birds, he says that after long observation he and they
have no hesitation in stating that the spine-tailed swift is the
swiftest Australian bird, and states that its speed has been
computed at 180 miles an hour.
“Besides its swiftness,” he writes, “it is almost tireless of wing,
being second only in that respect to the frigate bird, the bird
of eternal flight. Both have very long wings in relation to the
body--an indication of rapid flight. The swift, a bird of passage
which crossed the wide sea after breeding in Japan, is not known to
alight in Australia, where it spends a considerable time hunting
its insect prey in the upper air.”
In _A History of the Birds of Europe_,[23] Dresser writes: “The
present species (_Acanthyllis caudacuta_ or _Chaetura caudacuta
caudacuta_) and _Acanthyllis gigantea_ are said to be the swiftest
birds in existence. Tickell says that he never witnessed anything
equal to the prodigious swiftness of its movements.”
_Chaetura caudacuta cochinchinensis_ (which is to be found in
Malacca, Sumatra, and Cochin China) is a form of the spine-tailed
swift allied to that species (_Chaetura caudacuta caudacuta_) which
is so rare a visitor here. I have examined and compared numerous
specimens of these three species of spine-tailed swifts, and it
would seem practically certain, in view of their similarity in size
and structure, that their speed must be similar.
Mr. E. Stuart Baker, who has made experiments as to the speed
of the _Chaetura nudipes_ and the _Chaetura cochinchinensis_,
writes:[24] “Both these species have a normal flighting speed of
something very nearly approaching 200 miles an hour, enormously in
excess of the powers of any other bird with which I am acquainted.
In North Cachar, Assam, these birds used to fly directly over my
bungalow in Haflang, flying thence in a straight line to a ridge
of hills exactly two miles away, and when over the ridge at once
dipping out of sight. We constantly timed these swifts and found
that stop-watches made them cover this distance in from 36 seconds
to 42 seconds, _i.e._ at a rate of exactly 200 miles an hour to
171·4.”
Writing of the _Chaetura nudipes_ Mr. W. T. Blanford, F.R.S.,
says:[25] “This and the other large spine-tails are, I believe,
absolutely the swiftest of living birds. Their flight far exceeds
that of the Alpine swift, and I doubt if any falcon can approach
them in speed. They are generally seen in scattered flocks that
play about for a time and disappear at a pace that must be seen to
be appreciated.”
The same ornithologist refers[26] to the _Chaetura indica_ or
brown-necked spine-tailed swift, which is a larger species (length
about 9 inches, tail 2·6--wing 8--tarsus 6·8), as being “equal or
possibly even superior in speed to _Chaetura nudipes_--so wonderful
is their flight that Mr. H. R. P. Carter remarked that a flock of
Alpine swifts, passing over immediately after some of the present
species, ‘seemed to fly like owls after the arrow-like speed of the
spine-tails.’”
I think, therefore, that if the speed in horizontal flight is alone
to be considered, the spine-tailed swift is the fastest bird which
flies in the British Isles, that the Alpine swift comes next;
then come the northern falcons (or as they are usually called,
gyr-falcons) and the peregrine falcon, in the order named, except
in the case of a very short flight, in which case the Golden Plover
and teal, being faster off the mark and better sprinters, will fly
more quickly than the falcons, though they will, when the latter
really get going, be gradually overtaken.
There remains for consideration the speed of the golden eagle and
falcon in their downward flight, when stooping at their prey. There
is no certain method of comparing their respective speeds in this
unique kind of flight either with one another or with the speed
of other birds which never fly in this way. In considering the
question of the relative speed of the two birds in this particular
kind of flight, I will first deal with the matter on principle and
then consider such evidence of eye-witnesses as I have been able to
obtain. The falcon has of course one great advantage over the eagle
as regards equipment for swift flight. He has the long pointed
wings typical of the true falcon, whereas the eagle has rounded
wings. As between birds of similar size and spread of wings, the
bird with pointed wings is faster than the one with rounded wings.
Thus a blackcock is undoubtedly faster than a pheasant although
their bodies are about the same size, or to be more accurate the
blackcock is rather smaller than the pheasant. A striking instance
of this was recently given in the _Field_[27] by Mr. G. Denholm
Armour, who wrote: “Some years ago a friend asked me to come to
Argyllshire late in the autumn to shoot some black-game which lived
in the birch and fir woods hanging along the lower parts of the
hills.
“Our method was to place ourselves in a break in the line of woods
at the bottom of the hill, sending two or three men to drive the
wood towards us. The result was usually very high birds flying
downhill and very fast. On several occasions at the same time came
a blackcock and a cock pheasant, of which there were a few in
almost every drive. Incidentally, most of the pheasants we shot
were old birds with long spurs, so were very strong on the wing.
In each case--and I noticed several--the blackcock outflew the
pheasant by what seemed to be about 50 per cent in pace, leaving
him as a racing car would a ‘runabout.’
“The chance of comparison was very interesting, being between birds
of much the same weight and size, both started under the same
conditions, and I think ‘doing their best.’ Had the blackcock come
alone, I think his much slower wing beat would have made one think
him the slower flier of the two.”
The blackcock and grouse have wings exactly alike--but the
blackcock is heavier than the grouse and much faster.
With the exception of the difference in the wings mentioned above,
the structure of the eagle and falcon is very similar, and as has
been pointed out, the larger of two birds of similar structure once
it gets going is almost invariably faster, owing no doubt to its
superior muscular power and driving force.
In comparing the downward flight of the eagle and falcon it is also
necessary to recollect the advantage which the former has by reason
of its much greater weight.
It is difficult to obtain thoroughly reliable records of the
weights of the golden eagle and the different falcons; but so far
as I can ascertain, the weight of the eagle varies from 8½ to 12½
lb., that of the gyr-falcon from 3 to 3¾ lb., and that of the
peregrine from 2 to 3 ounces under 2 lb. to 2¾ lb., in each case of
course the female bird being heavier than the male.
But for the resistance of the air, all bodies, light or heavy,
small or large, would fall at the same rate. In fact, however,
as velocity increases a notable air resistance is set up which
increases rapidly. The velocity of a body falling freely _in vacuo_
is over forty miles per hour at the end of two seconds, over sixty
at the end of three seconds, and so on.