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.