THE NATURALIST

Otago Witness, Issue 3775, 20 July 1926, Page 78

THE NATURALIST

THE FLIGHT OF BIRDS.

By Cbyptos.

(Fob tub Witnem.) I. Is there anyone with sight who has not seen birds fly? So commonplace is this phenomena that the many and varied forms of wings, and the peculiarities of flight which are associated with them, are not often distinguished. We accept the fact, but even the most scrupulous artists and sculptors rarely show a good understanding of the shape of various wings oz a their position in the flight of different birds. Also it must be confessed that any attempt to explain exactly how birds fly, just as with the explanations of the phenomena of soaring, fail. We can state the more obvious factors which are indispensable to flight and the nature of its mechanism, but the subtleties and delicate adjustments of actual flight evade us. Y 7. P. Pycraft, in his iK'ok “Birds m l light,” says concerning lue relation of the size and the shape of wings to the type of flight: “Our appreciation, however, of this supreme mode of locomotion will be materially quickened if we make a point of studying the varied forms of flight as opportunities present themselves. “To begin with, it is woyth noting that the size of the wing decreases with the sise of the body to be lifted—up to a certain point, of course. This, perhaps, may seem a strange statement to make. But it can be readily verified. Compare, for example, the size of the body in Telation to the wings in the case of the butterfly and the dragon-fly on the one hand, and the partridge and the crow on the other. The two first-named, by comparison, have enormous wings. “Birds, it will be noticed, which haunt woods or thickets have short, rounded wings, like the wren, the pheasant, or the tawny owl. Such, on the other hand, as live in the open, like the gull and the swallow, have long, pointed wings. The reason for this is fairly plain. Birds which must steer their course through the intricate mazes of a wood or a thicket would find their flight seriously hampered by long wings. . . . . . Most of us, probably, at one time or another” (he is describing mainly birds of England) “in taking a walk through the woods, have been startled almost out of our wits by a sudden ‘whirr’ of wings at our very feet; made by some crouching pheasant waiting till the very last minute before revealing himself by taking flight. This alarming noise is due to the shortness and stiffness of the quill, or flight, feathers. With pinions moving with incredible speed, the bird is off like a rocket. Not seldom, probably, it owes its life to this ability to disconcert its enemies till it has put a safe distance between itself and danger. “By way of contrast, let us take the absolutely silent, easy movements of the owl, stealing. forth in the twilight of a summer’s evening, seeking whom he may devour. Here, again, we have a meaning in the mode of flight. Here silence is more than golden; it means life itself. Nimble-footed, sharp-eared mice and rats must be snatched up before even the breath of suspicion can reach them. The uncanny silence of this approach is rendered possible only I>y what may be called a ‘muffling’ of the wings. If or the flight feathers are not ©ply of great breadth, but they are covered, as it were, with velvet pile, the *barbules’ of the wingquills which form \.the agents by which the ‘web’ of the quill is held together, having their upper spurs produced into long thread-like processes, which extinguishes any possibility of a warning ‘swish.’ “John Bright, in one of his magnificent perorations, caused his spell-bound listeners to catch their breath, when, conjuring up a vision of the Angel of Death, he remarked, ‘We can almost hear the rustle of his wings.’ One realises the vividness of that imagery when one hears, as on rare occasions one may, the awe-inspiring rustle of the death-dealing swoop of the falcon or the sparrow-hawk, as he strikes down liis victim. “But the swish •* and whistle of wings often stirs the blood with delicious excitement, as when one is out on some cold dork night ‘flighting,’ which is to say, awaiting mallard passing overhead on the ■way to their feeding ground, or in watching the hordes of starlings or swallows settling down to roost in a reed-bed. No words can describe these sounds, but those to whom they are familiar know well the thrill of enjoyment they beget. There is no need here to muffle the sound of the wing-beat. The falcon vies with the lightning in his speed ; escape is wellnigh hopeless. Neither have the swallows need for silence; indeed, on these occasions they add to the music of their wings the enchantment of their twittering.* , The writer, too, has vivid memory of the sound of the wings of innumerable starlines flying in vast concourse round and about their roosting place. Some eighteen years ago, at Waianawa, about twelve miles to the east of Invercargill, ft was no uncommon sight to see probably many hundreds of thousands of starlings father together and roost in the branch**

of a small patch of manuka, some acre or two in extent. Each evening, for miles around, flocks of birds could be seen wending their way toward this place. Here fifty, here seventy, and there a larger lot of a few hundred, flying high and in an oval flock, would pass from their feeding grounds to join the evergrowing mass liovering over or flying round their roosting spot. The first arrivals would fly round and round above the manuka, low down. In a short time the air would become thick with the dark shapes flying and wheeling in ever-grow-* mg circles, first round the scrub, but later extending far over the adjoining bush. From our place of observation, a barn directly under their line of flight, it was a great and wonderful sight to see and hear them as they passed in a neverending stream only a few feet above our heads and darkening the early twilight by their numbers. After circling thus, sometimes for more than half an hour, sometimes silently, sometimes uttering harsh cries, they would condense into a great cloud over their immediate perching places, and suddenly sink from sight. Usually, however, they would rise again with a harsh cry several times befpre settling finally about dusk.

About that time the sight was so strange that it was no uncommon thing for people to come long distances just to watch the performance. I do not know whether it still occurs in this place, but I do not think that such numbers of birds gathered into that flock either before or after the few seasons about 1908. Such are some of the general aspects of varieties of flight. "Next week will be mentioned what we know of the mode of flight.