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[23] <div class="figcenter illowp100" id="ich4" style="max-width: 46.875em;"> <ANTIMG class="w100" src="images/i_ch4.jpg" alt="Flying Birds" /> <div class="caption">Fast Enough for Me! </div> </div> <h2 class="nobreak" id="IV">IV THE BIRDS OF FASTEST FLIGHT IN THE BRITISH ISLES</h2> Some little time ago, a correspondence appeared in the <cite>Observer</cite>[4] and the <cite>Field</cite>[5] as to which is the quickest bird in flight. Various correspondents, some of them well-known naturalists, writers of repute, and sportsmen of experience, expressed their views, by no means unanimous, on the question. I have always been greatly interested in the subject, and for many years past in the North of Scotland have been in the habit of watching bird life in some of the wildest and most inaccessible parts of the country. [24] I have examined the evidence contained in the valuable and interesting correspondence mentioned above, and have also obtained all the information I could get elsewhere from books of authority and persons who have had special opportunities of observation. At the present day a valuable and novel class of evidence is available—that of observers in aeroplanes. Upon all the material thus obtained I have tried to form an impartial opinion. There appear to me to be four points to be borne in mind before arriving at any conclusion as to which bird is the quickest in flight, and the maximum speed of which each bird is capable. Emphasis is laid on the first three of the following points in some of the letters in the correspondence above referred to, but I think that the fourth point is of at least equal importance. 1. Ground speed must be distinguished from air speed. 2.The path of flight must be horizontal. 3.There must be something to show that the bird is flying at its maximum speed. 4.There must be a standard length of flight to which the test is to be applied. [25] 1. Ground speed must be distinguished from air speed. It is not generally realised that a bird has two speeds: its speed relative to the ground and its speed relative to the air. “Ground speed” is “air speed” as influenced by the wind. In a perfectly still atmosphere “ground speed” and “air speed” are the same. To quote one of the writers in the <cite>Field</cite> of February 11, 1922: “The wind has no effect on the speed at which a bird is capable of driving itself through the air. Take a parallel case, substitute for the bird a caterpillar, and for the atmosphere in which the bird is flying a sheet of paper. The caterpillar can always crawl at a constant speed across the paper, although it is possible to increase the relative speed of a caterpillar to the ground by moving the sheet of paper.” Or to put the same distinction in the words of another writer in the same number of the <cite>Field</cite>: “It is the speed of the object over the ground or still water that matters; and if the medium (i.e. air or water) in which the object under discussion is either flying or floating is also in movement, then the pace over the ground will naturally be correspondingly increased or decreased.” [26] Wind, of course, varies in two ways (1) direction and (2) velocity, and is uniform only at a given height. The direction of the wind must necessarily be either along the line of flight of the bird, against it, or at an angle with it. In the first of these instances the speed of the bird over the ground is determined merely by adding the velocity of the wind to, and in the second by subtracting it from the air speed of the bird, in the same way as a swimmer’s speed is increased or reduced by the speed of the current. The third case is more complicated, as in this calculation allowance must be made for “drift,” i.e. the tendency of a bird under such circumstances to deviate from its desired course. It is, however, unnecessary to say anything further as to this third case, as the comparison of speeds of various birds can only be made satisfactorily by ascertaining their speeds under identical conditions in horizontal flight. 2. The path of flight must be horizontal. In the words[6] of Captain C. F. A. Portal, D.S.O.: “If any one has seen a peregrine stooping [27]from 1000 feet at between 150 and 200 miles per hour at a partridge, and has later seen the same peregrine chase the same partridge from a standing start, he will appreciate the importance of considering only level flight. In the first instance, the hawk is nearly 100 miles per hour faster than the quarry, in the second, he can only just overtake it at all. There is no conceivable way of measuring the speed of these downward flights accurately, but no one who has done any hawking will deny that 120 miles per hour is within the power of a great many species. When we come to consider level flight, there is a very different story.” <div class="figcenter illowp50" id="i026fp" style="max-width: 41.9375em;"> <ANTIMG class="w100" src="images/i_026_fp.jpg" alt="" /> <div class="caption">THE PEREGRINE FALCON. By V. R. Balfour-Browne. </div> </div> 3. There must be some evidence to show whether the bird is flying at its maximum speed or not. As was recently pointed out in an interesting article[7] by Colonel R. Meinertzhagen, D.S.O.: “Birds have two speeds: a normal rate, which is used for everyday purposes and also for migration, and an accelerated speed, which is used for protection, or pursuit, and which in some cases nearly doubles the rate of their normal speed; some of the heavier birds can probably only accelerate to a slight extent. In this conclusion I am naturally[28] excepting courtship flight, which is usually of an accelerated nature.” To quote the words of Major C. R. E. Radclyffe:[8] “The only possible test we can accept is where two birds are matched one against the other, and we are certain they are both trying their hardest. No better test than this is the case of a hawk pursuing its quarry, when it means to one of them its food and to the other its life.” The same writer draws attention to a common fallacy: “It is,” he says,[8] “purely a matter of optical illusion to imagine that a smaller-sized bird is flying faster than a larger bird of similar shape and make; for example, a snipe on rising ground seems to go much faster than a woodcock, similarly a teal than a duck, and possibly this may be so for a short distance, but put up the first two together, and also the last two, and let there be a peregrine after them—as I have seen many times—and the scene is amazing to a man who is not a falconer, as the smaller bird is overhauled first every time by the falcon, and presumably they are all trying their hardest.... I have dozens of times put up a peregrine over ponds and marshes where teal and ducks were sitting together, and[29] then flushed the wild fowl all simultaneously. In every case without any exception the first bird overhauled and brought to the ground has been a teal and in the case of a long flight, when every bird has been flying for its life, the further they go the further the teal lag behind the wild ducks. The same remarks apply to woodcock and snipe, to black game and grouse, to pheasants and partridges—all of which I have flushed simultaneously in front of hawks.” In dealing with the same point in a letter written to me, Major Radclyffe makes the following interesting observations: “... Few people realize that a pheasant flies much faster than a partridge when they have both been going a short distance. If you flush an old cock pheasant and a covey of partridges together in a big field of turnips, you will see the partridges are quickest ‘off the mark’ and away with a bit of a lead, but the pheasant will catch them, and be first over the fence if they have 200 or 300 yards to go. “Again take as an example a woodcock and a snipe. I have several times flushed these two birds together, and in no time the woodcock has left the snipe far behind him, and yet I believe[30] that ninety-nine sportsmen out of a hundred would say the snipe flies faster than the woodcock. “I have seen woodcocks give my hawks some great long-distance flights before they are overtaken and turned; but a snipe has no show at all when trying to keep ahead of a peregrine or merlin in straight flight.” In his letter to the <cite>Field</cite> already referred to, Major Radclyffe further says: “There is no doubt whatever that the heavier bird of similar type is far the faster on the wing when once it gets going.” It was suggested in one of the letters to the <cite>Field</cite> that whilst this is no doubt the general rule there is at least one exception to it. “If asked,” said the writer, “to quote any instance when the smaller bird is faster than a larger one of similar type, I should say that the pochard (Fuligula ferina) is faster on the wing than the common mallard, as I have seen the former pass mallards on the wing when both have been flying before a falcon. But from my experience of over thirty years as a falconer, a naturalist, and a shooter, I should say that the above case is one of the rare exceptions where the heaviest bird is not the fastest on the wing if each bird is trying its hardest and best.” [31] Colonel Meinertzhagen, whilst agreeing that the heavier bird of similar type is the faster flier once it gets going, has kindly sent me the following observations on the foregoing statements as to the pochard and mallard. “The common pochard is not a bird of ‘similar type’ to a mallard, the one being a diving duck and the other surface-feeding. They differ in the proportion of wing area to body weight, also in bone structure. The pochard and all diving duck, probably fly faster than surface-feeding duck under similar conditions, having heavier bodies in proportion to the wing area than is ever found among surface-feeding duck. The eider duck, which is even heavier than the ordinary diving duck (Nyroca), probably flies faster than them all when once started.” 4. There must be a standard length of flight to which the test is to be applied. If the question were asked, “Who is the faster runner, A or B?” the reply would surely be “To what distance are you referring?” A short or a long distance? Applying the analogy, it is obvious that a bird might be much faster than another for a short distance, but if the[32] flight has to be prolonged, may not have the lasting powers of another bird, and therefore would be beaten on the longer course. It seems likely that the fact of not considering one or other of these points may account for the difference in regard to some of the views held by observers of experience. For instance, may it not account for the fact that there is such a marked difference of opinion as to whether the peregrine is faster than the golden plover? May it not be true that for a short distance the latter bird may be the faster flier, but that in consequence of its lack of staying power it is overtaken before it goes half a mile unless it can elude its pursuer by twists and turns. In this connection it is worth recalling the experiences of that acute and accurate observer Charles St. John[9]: “The golden plover,” he writes, “is a favourite prey, and affords the hawk a severe chace before he is caught. I have seen a pursuit of this kind last for nearly ten minutes—the plover turning and doubling like a hare before greyhounds, at one moment darting like an arrow into the air, high above the falcon’s head; at the next sweeping round some bush or headland—but in vain. The[33] hawk with steady relentless flight, without seeming to hurry himself, never gives up the chace till the poor plover, seemingly quite exhausted, slackens her pace, and is caught by the hawk’s talons in mid-air and carried off to a convenient hillock or stone to be quietly devoured.” Colonel Meinertzhagen has been so kind as to consider the observations I have made above, and writes: “I should doubt whether the golden plover has less staying power than the peregrine. The former migrates long distances (thousands of miles, in the case of the American golden plover, a bird almost identical with ours, which goes from Labrador to Brazil by sea), whereas the peregrine is nowhere believed to be a regular or persistent migrant over long distances. It is more probable that the peregrine is a faster bird than the golden plover and that the latter becomes exhausted by continued acceleration and fear, whereas the peregrine is accustomed to long periods of accelerated flight and is stimulated by hunger.” Again in reference to the difference of opinion as to whether the teal is faster than the mallard, may it not be possible that both views may be correct? in other words, that it depends upon the[34] length of flight which the writer is considering. It may be noticed that Major Radclyffe in the passage which I have quoted above (p. 28) seems to consider it may be possible that for a short distance the teal may be faster than the mallard, though he has no doubt that the latter bird will very soon overtake the former. The falconer has certainly more and better opportunities of seeing birds flying at their maximum rate of speed than any one else. “He also has,” to use Captain Portal’s words, “the advantage of possessing in his trained hawk a known quantity with which to compare the performances of other birds.” Captain Portal has flown hawks at many different kinds of birds during the last fifteen years, and has made certain estimates which have been arrived at after a great deal of comparison and analysis of data obtained while hawking, shooting, flying in aeroplanes, travelling in cars and trains, and walking in the country. He says:[10] “My figures cannot be correct for every member of each species, as I have seen one partridge in an October covey fly quite 15 per cent faster than any of its companions when all were at full speed. All[35] I have tried to do is to strike an average for the species, the speed given being the maximum pace at which the bird can cover the ground in level flight through still air.” The speeds given for the peregrine and merlin are those of good trained birds; the wild ones are faster. Here are the figures: <table class="autotable fs80" summary=""> <tr> <td class="tdl">Golden Plover</td> <td class="tdc">70</td> <td class="tdc">miles</td> <td class="tdc">per hour.</td> </tr> <tr> <td class="tdl">Teal and Blackcock</td> <td class="tdc">68</td> <td class="tdc">”</td> <td class="tdc">”</td> </tr> <tr> <td class="tdl">Peregrine</td> <td class="tdc">62</td> <td class="tdc">”</td> <td class="tdc">”</td> </tr> <tr> <td class="tdl">Pheasant and Grouse</td> <td class="tdc">60</td> <td class="tdc">”</td> <td class="tdc">”</td> </tr> <tr> <td class="tdl">Mallard</td> <td class="tdc">58</td> <td class="tdc">”</td> <td class="tdc">”</td> </tr> <tr> <td class="tdl">Merlin and Blue Rock  </td> <td class="tdc">55</td> <td class="tdc">”</td> <td class="tdc">”</td> </tr> <tr> <td class="tdl">Partridge</td> <td class="tdc">53</td> <td class="tdc">”</td> <td class="tdc">”</td> </tr> <tr> <td class="tdl">Green Plover }</td> </tr> <tr> <td class="tdl">Jackdaw}</td> <td class="tdc">48</td> <td class="tdc">”</td> <td class="tdc">”</td> </tr> <tr> <td class="tdl">Wood Pigeon</td> <td class="tdc">45</td> <td class="tdc">”</td> <td class="tdc">”</td> </tr> <tr> <td class="tdl">Starling</td> <td class="tdc">44</td> <td class="tdc">”</td> <td class="tdc">”</td> </tr> <tr> <td class="tdl">Kestrel</td> <td class="tdc">43</td> <td class="tdc">”</td> <td class="tdc">”</td> </tr> <tr> <td class="tdl">Rook</td> <td class="tdc">40</td> <td class="tdc">”</td> <td class="tdc">”</td> </tr> <tr> <td class="tdl">Landrail</td> <td class="tdc">35</td> <td class="tdc">”</td> <td class="tdc">”</td> </tr> </table> The speed attained by golden plover when pressed has been estimated by airmen at over 60 miles per hour.[11] Colonel R. Meinertzhagen, from whom I have also quoted above, states that he finds, “after eliminating abnormal conditions and observations based on meagre evidence, that the normal and[36] migratory flight in miles per hour (ground speed) is as follows: <table class="autotable fs80" summary=""> <tr> <td class="tdl">Ducks</td> <td class="tdc">44-59</td> </tr> <tr> <td class="tdl">Geese</td> <td class="tdc">42-55</td> </tr> <tr> <td class="tdl">Waders</td> <td class="tdc">34-51</td> </tr> <tr> <td class="tdl"></td> <td class="tdl">(but mostly from 40 to 51)</td> </tr> <tr> <td class="tdl">Starlings</td> <td class="tdc">38-49</td> </tr> <tr> <td class="tdl">Falcons</td> <td class="tdc">40-48</td> </tr> <tr> <td class="tdl">Corvidae</td> <td class="tdc">31-45</td> </tr> <tr> <td class="tdl">Tame Pigeons</td> <td class="tdc">30-36</td> </tr> <tr> <td class="tdl">The smaller Passeres</td> <td class="tdc"> 20-37”</td> </tr> </table> Amongst the birds which are claimed by different high authorities to be the fastest British birds are the swift, the peregrine, the golden plover, the teal, the wild duck, and the curlew. It is curious that in the various controversies on the subject no one appears to have contended that the golden eagle may possibly be the fastest flier amongst British birds. This may be because, except in certain parts of the country, the eagle is never seen, and there is necessarily very little opportunity of comparing his speed with that of other birds. In particular the falconer, whose opportunities of comparing the speed of birds are, as I have already stated, greater than those of any other class of men, has no opportunities in the case of the eagle. Moreover, the flight of the eagle, like that of some of the fastest flying birds,[37] for instance, the blackcock, is very deceptive. He is in fact flying much faster than he appears to be—“The eagle’s flight, when passing from one point to another, is peculiarly expressive of strength and vigour. He wends his way with deliberate strong strokes of his powerful wing, every stroke apparently drawing him on a considerable distance, and in this manner advancing through the air as rapidly as the pigeon or any other bird which may appear to fly much more quickly.”[12] <div class="figcenter illowp100" id="i036fp" style="max-width: 62.5em;"> <ANTIMG class="w100 p2" src="images/i_036_fp.jpg" alt="" /> <div class="caption">WINTER SUNSHINE—WILD GEESE AT THE FOOT OF THE APPLECROSS HILLS. From a Photograph by The Lady Anne Murray of Loch Carron. </div> </div> The answer to the question, Which of the two birds, the eagle or the peregrine, is the faster flier, must even on a horizontal flight be a matter of pure conjecture. On the one hand, the peregrine has the advantage of pointed wings which make for increased wing power and speed, whilst the eagle’s wings are rounded. On the other hand, there is a great similarity between the general build and structure of the two birds, and there is the fact emphasised by Major Radclyffe in the letters from which I have quoted above, that, as between two birds of different size but of similar shape and make, the larger and heavier bird will almost invariably fly faster than the smaller and[38] lighter one once the former really gets going. It is, of course, true that the peregrine is much quicker in its movements and more agile than the eagle. It is constantly under the necessity of flying at its fastest (which the eagle is not) in order to secure its food; in other words, to use the language of a stalker in discussing this question with me: “The peregrine requires a warm diet, and lives on its prey. The eagle, on the other hand, will eat carrion.” The peregrine is probably quicker off the mark than the eagle, but this does not necessarily mean that he flies more quickly than the eagle once the latter gets going. Stalkers have unusual opportunities of seeing these two birds in flight, and almost all those with whom I have discussed this question believe that on a horizontal flight the peregrine is faster than the eagle. This in my opinion is probably the correct view. It must not be forgotten that the Northern falcons, or, as they are generally called, the gyrfalcons, are entitled to rank as British birds, although they are rare visitors to these Isles. They are (1) the gyrfalcon or Norwegian variety (Falco gyrfalco), (2) the Iceland falcon (Falco islandus), (3) the Greenland falcon (Falco candicans).[39] The gyrfalcon is a very rare visitor here, two recorded specimens only having been obtained here and one of these is doubtful. The Iceland falcon is a rare visitor also, although identified examples have been obtained here from time to time. The Greenland falcon is an irregular winter and spring visitor, but there are more recorded instances of this species than in the case of the Iceland falcon. The former bird, the prevailing ground colour of which is white, is the most beautiful of all birds of prey. By some authorities it is considered merely a race of the Iceland falcon, which it resembles in size and habits. The eggs of the two birds resemble one another. All these Northern falcons are about the same size and larger than, though very similar in structure to, the peregrine falcon. Speaking generally, the difference in length is about 5 inches, in wing 2 inches. They have been very highly valued in Europe for hawking, and, as would be expected from their superior size and similar structure, are undoubtedly faster than peregrines. Writing in the <cite>Field</cite> for March 15, 1923, Major Radclyffe says:[13] [40] “All the gyrfalcons are much faster on the wing than peregrines, 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. <div class="figcenter illowp100" id="i040fp" style="max-width: 62.5em;"> <ANTIMG class="w100 p2" src="images/i_040_fp.jpg" alt="" /> <div class="caption">THE SPINE-TAILED SWIFT. By V. R. Balfour-Browne. </div> </div> 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[41] 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: <table class="autotable fs80" summary=""> <tr> <td class="tdl"></td> <td class="tdl" colspan="2"> Length.</td> <td class="tdl" colspan="2"> Wing.</td> </tr> <tr> <td class="tdl">Common Swift</td> <td class="tdl">6·75</td> <td class="tdc">inches</td> <td class="tdl">6·8</td> <td class="tdc">inches</td> </tr> <tr> <td class="tdl">Alpine Swift</td> <td class="tdl">8</td> <td class="tdc">”</td> <td class="tdl">8·45</td> <td class="tdc">”</td> </tr> <tr> <td class="tdl">Needle-tailed Swift </td> <td class="tdl">8</td> <td class="tdc">”</td> <td class="tdl">8·1</td> <td class="tdc">”</td> </tr> </table> 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[42] 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[43] 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.” [44] 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[45] 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: <table class="autotable fs80" summary=""> <tr> <td class="tdl">1. The Peregrine,</td> </tr> <tr> <td class="tdl">2. The Hobby,</td> </tr> <tr> <td class="tdl">3. The Merlin,</td> </tr> <tr> <td class="tdl">4. The Golden Plover,</td> </tr> <tr> <td class="tdl">5. The Pochard,</td> </tr> <tr> <td class="tdl">6. The Blue Rock Pigeon,</td> </tr> </table> 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: [46] “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[47] 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, <cite>Field Studies of some Rarer British Birds</cite>,[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;[48] 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[49] 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[50] 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,[51] 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[52] 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[53] 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] [54] 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 [55]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 <cite>A History of the Birds of Europe</cite>,[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 [56]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[57] 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[58] 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 <cite>Field</cite>[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[59] 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,[60] 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. We all know by experience the great force exerted by a wind of a velocity even as low as thirty miles an hour, which most people would call a hurricane. But it is not perhaps so generally[61] known that in proportion to its weight, other things such as shape and specific gravity being similar, a small body experiences much greater resistance than a large body. The resistance of the air to the fine particles of vapour which constitute a cloud is such that they only fall at the same rate of a few feet per hour. And in the case of two birds of similar shape and specific gravity, but one eight times the weight of the other, the larger bird would ultimately attain a velocity roughly twice as great as the other, if both fell for a sufficient distance to attain their limiting velocities, i.e. the velocity at which the resistance offered by the air is equal to the attraction of gravity. Similarly if the one bird were four times the weight of the other, the velocity ultimately attained under the conditions mentioned would be roughly one and a half times as great as the other. In “Notes by an Old Stalker” in the <cite>Field</cite> for September 9, 1922 (p. 370) there appears the following interesting account of a duel between a golden eagle and a peregrine which the writer himself witnessed: “Although by a long way our most powerful bird, the eagle is by no means a match for some[62] much smaller combatants. Once I saw an eagle soaring placidly along when from a range of precipices immediately below him a falcon shot up into the air. Without a moment’s hesitation he attacked the giant bird. The eagle at once joined combat, and through the telescope I could see his efforts to hit his adversary with beak and wing. One blow from either and it would be all over with the falcon; but the latter evidently realised this and regulated his tactics accordingly. The movements of the eagle were slow and cumbrous compared to the rapid action and lithe activity of his adversary. Every time he dodged the eagle’s stroke and, wheeling rapidly, got in his blow before the huge bird could recover himself. That the eagle was in a great rage was evident, for I could hear him emitting sounds that resembled nothing so much as the bark of a terrier. Finally, realising the hopelessness of the contest, he took to flight. I previously knew that the eagle was fast on wing, but the speed he now exhibited was a revelation to me. With half-extended, half-curved wings, showing never a tremor, he cleft the air straight as a bullet. The falcon pursued, but, being left hopelessly behind, soon gave up the chase.” [63] The flight of the eagle here described was obviously a glide or downward flight, when, as I have pointed out, gravity would assist his speed to a greater extent than it would in a bird of less weight—the peregrine. In the case of a bird of prey descending from a height on its quarry, the nearer its downward flight is to the vertical the faster will it descend. In coming down on its prey, neither the eagle nor the falcon completely closes its wings, probably because if it did so, it would lose control. This is also true of the gannet or solan goose, which has been described as the largest and noblest-looking of our sea fowl. The great speed which a bird of large size can attain in downward flight can to some extent be realised by watching the gannet when he drops head first as he descends perpendicularly on to the fish in the water. I have carefully examined and compared the skeletons of the eagle and peregrine and have tried to form some idea as to the relative muscular power and driving force of the two birds, and bearing in mind the facts stated above, and the greatly superior size and weight of the eagle, it seems reasonable to conclude on principle that the eagle is probably faster than the gyr-falcon or peregrine[64] in a downward flight, assuming that both birds are putting forth all their powers. As regards the evidence of eye-witnesses, I have discussed this question with many stalkers. The majority of them have never seen the eagle stoop at its quarry and strike it a blow which sends it to the ground as the peregrine so often does—though they have seen the eagle seize its quarry in the air or pounce on it on the ground and carry it off. Only a few of these, however, have any doubt as a result of what they have heard from other stalkers and keepers that the eagle on occasion does adopt the former method. It is, however, an undoubted fact that although the eagle generally captures birds which he is pursuing by seizing them in his talons or, to use the falconer’s term, binding on them, he occasionally stoops on and strikes them in the air, sending them hurtling to the ground in the same way as the peregrine does. The reason why the eagle so rarely adopts this method is probably because it can secure its prey without doing so, and further if it were to exert all its powers when descending from a considerable height at an angle near the vertical on a grouse,[65] blackcock, or ptarmigan (which do not usually fly very high above the ground), it would incur a serious risk of injury in consequence of being carried on by its impetus and dashing against the rocks or ground after striking down its prey. <div class="figcenter illowp60" id="i064fp" style="max-width: 50.75em;"> <ANTIMG class="w100 p2" src="images/i_064_fp.jpg" alt="" /> <div class="caption">THE GOLDEN EAGLE. By V. R. Balfour-Browne. </div> </div> The interesting, and I think significant, fact is that although some of these stalkers with whom I have discussed the question think that the peregrine probably flies faster than the eagle, every one of them who has seen the eagle kill its quarry in this way (and I know several) has told me that in his opinion the eagle in its final rush is faster than the peregrine. It is also important in this connection to bear in mind the fact on which Major Radclyffe lays such stress—that it is an optical illusion to imagine that a smaller-sized bird is flying faster than a larger bird of similar shape and make, and that, as he says, ninety-nine sportsmen out of a hundred would probably tell you that a snipe flies faster than a woodcock—whereas the converse is true. An old keeper in the North, whom I have known for many years, told me that he had seen the eagle stoop at and strike his quarry in this way on two occasions, and that it moved in its final downward flight[66] with the same lightning-like rapidity as the peregrine. John Finlayson, the head stalker at Killilan, wrote to me last February as follows: “I have once plainly seen the eagle driving after grouse and striking it down very similar like what the peregrine falcon does. It happened at the north end of Corrie-ach. I was going up to Patt from Mulbuie way. A covey of grouse came tearing down from the low end of Aonachbuie in front of me, about 300 yards away, and an eagle in hot pursuit, wings gathered up, and making a swishing noise; going through the air it struck one down, with a cloud of feathers knocked out when it did so. The eagle glided up a little, then balanced and dropped down where the bird fell; it was a little over a ridge out of my view; when I got up to the place I saw the eagle well up the glen going fast with the bird in its talons.” My gamekeeper, Donald McIver, who has lived all his life in Ross-shire, on one occasion saw an eagle strike and kill a blackcock. This is his account of it. “In the forest of Strathconan, where I was for a number of years, I once saw a very fine sight of an eagle pursuing a blackcock. The blackcock got up at the head of a very deep[67] corrie and came over at a very great height. The eagle was about and soon after it. I could see him overtake the bird, and I would say that he struck him the same way as the peregrine does with his claw. I saw something drop, but could not make out what it was at the time; then the eagle doubled in the air and caught the bird before it reached the ground. None of the other eagles I have seen after their prey have struck it like this in the air. They have always clutched at their prey, but this time the eagle struck the bird and went right past him. I was not far off, and could hear a tremendous noise of the wings. When the eagle doubled back and caught the bird in the air I would judge that the bird would be as high up as three hundred feet, and when he doubled back I should think he was not fifty. “Perhaps the narrowness of the corrie might be the reason for him taking the bird in the way he did—I went to the place and found the head of the blackcock; there was about three inches of skin hanging to the head, a tear like what would be done with the claw. This is the only time I ever saw an eagle kill a bird in the air, but it was a grand sight. This happened in January 1895, in Corrie Vullin, Strathconan.” [68] This amazing feat in aerial gymnastics is no doubt also performed on rare occasions by the peregrine. One of the most experienced of living falconers wrote to me as follows: “I have seen a very celebrated falcon which I owned for years bring off a remarkable trick several times. She used to strike at the back of the grouse’s head, and I have seen her just scalp the grouse, taking a piece out of its skull not as large as a pea, and thus killing the bird in mid-air just as if it was shot; often, when the grouse was high above the ground, I have seen the falcon then take a sharp turn in the air as the grouse was falling, like a spinning leaf, and pick it up in her feet before it could touch the ground—a very wonderful sight.” An old friend of mine, who is head stalker in one of our best-known deer forests and whose veracity I have every reason to accept, told me an interesting story which further illustrates what fine feats in the air the peregrine falcon can perform. He said that on one occasion he saw a falcon strike and carry off a crow. As the falcon was circling higher and higher up, carrying off this crow, it was mobbed by a considerable number of other crows. For some time it ignored them, continuing its steady upward circling flight until[69] one crow, becoming rather bolder than the rest, provoked the falcon into retaliation. Dropping the crow it was carrying, the falcon stooped on the troublesome crow, struck and killed it and, turning with extraordinary rapidity, caught in the air the dead crow which it had been carrying, and then recommenced its upward flight without further trouble from the crows. <div class="figcenter illowp100" id="i068fp" style="max-width: 62.5em;"> <ANTIMG class="w100 p2" src="images/i_068_fp.jpg" alt="" /> <div class="caption">WHERE THE GOLDEN EAGLE REIGNS. From a Photograph by Frank Wallace. </div> </div> The marvellous speed of the golden eagle and peregrine in their final rush, when stooping from a height at their quarry, must be seen to be believed. Few persons have been so fortunate as to have this opportunity in the case of the golden eagle, although this grand bird is often to be seen in some forests and has no doubt increased in numbers in recent years. On the other hand, there are of course many persons who have seen both the wild peregrine and the trained gyrfalcon and peregrine strike down their quarry. The well-known ornithologist and wild-fowler, Mr. W. H. Robinson of Lancaster, in a letter in the <cite>Field</cite> of January 28, 1922, after stating from his own experience that the peregrine can overtake the golden plover and the curlew with the greatest ease, says: “To my mind one of the fastest things I have[70] ever witnessed is the last effort of a peregrine in chase of a wild duck when, fast as is the accelerated speed of a mallard, it seems almost to be standing still in the air when the peregrine stoops over it.” Any one who has seen this, as I am glad to say I have, will assuredly echo these words. It is of course pure speculation whether, in the comparatively short flight of an eagle or falcon stooping in its final downward rush at its prey, its speed exceeds the maximum speed of the spine-tailed swift. Those, however, who have seen the last effort of the eagle or falcon in a flight of that unique kind will never believe, without scientific demonstration to the contrary, that any other bird in the British Isles can fly faster. <div class="figcenter illowp69" id="idonald" style="max-width: 28.875em;"> <ANTIMG class="w100" src="images/i_donald.jpg" alt="" /> <div class="caption">Donald </div> </div> <hr class="chap" /> <div style="break-after:column;"></div>

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