Wing (biology)

“ By these two contrivances,—the shape of the wing, and the shape and arrangement of the feathers,—the wing resists the air on its down-stroke and raises the bird a little at each flap, but at each up-stroke allows the air to slide off at the sides, and to pass through between the feathers, so that nothing is lost.
QUAIL (SCRATCHERS) .
So much for the way in which the bird is raised into the air. Rising in the air is not flying, for a balloon and a kite rise but do not fly. Now, how is a bird able to move forward? ”

“ In those wings which, during the period of repose, are folded up beneath the elytra, the mere extension of the wing in the dead insect, where no injection of fluid can occur, causes the nervures to fall into position, and the membranous portions of the wing to unfurl or roll out precisely as in the living insect, and as happens in the bat and bird. ”

“ The wings of the bird, if flying, are only visible as a thin grey film, bounded above and below by fine black threads, in form of a St Andrew’s cross,—the effect on the observer’s retina of the instantaneous reversal of the motion of the wing at each beat—the strokes being so rapid as to leave no more distinct image. ”

“ The flexion of the wing is most obvious when the bird is exerting itself, and may be detected in birds which skim or glide when they are rising, or when they are vigorously flapping their wings to secure the impetus necessary to the gliding movement. ”

“ But in humming-birds and swifts, the lower part of the wing is the longer.
In some birds, the wing, when spread out, is much longer than all the body. The wing folds up, something like a crab’s claw, or as you would shut a knife. In birds that are walkers, and not flyers, the first wing-bone is short. The penguin, which never flies, has a little short wing, which looks like a hand, without any arm. ”

“ The inner half of the wing is the passive part of the organ, while the external half, that which strikes the air, is the active part. A fly's wing makes 330 revolutions in a second, executing consequently 660 simple oscillations ”

“ Rising to a height of forty or fifty yards, he suddenly dashes in a zigzag, downward flight, with a violence and rapidity unsurpassed by even the most aërial species in their maddest moments, and, turning like lightning when almost touching the surface, he rises, to repeat the action again and again. The heavy appearance and slow, flopping movement, and the marvellous wing-feats, are in strange contrast. ”

“ They have fingers, and some birds' wings have claws; only you cannot see them, because they are all wrapped up in the skin and covered over with the feathers. Some day—not to-day, because you have had a long lesson already—I will show you a bird's wing with only its bones. ”

“ In its structure and in the muscular power that moves it, the wing of a bird is a wonderful piece of mechanism. A bird in flying strikes the air with its wings so rapidly that the movements cannot be accurately counted. The heron, which is a slow-flying bird, makes from one hundred [Pg 13] twenty to one hundred fifty downward strokes of its wings a minute. As each downward stroke must be preceded by an upward stroke, this means that the wings make from two hundred forty to three hundred separate movements a minute. ”

“ So infantile, so helpless and awkward upon the earth, so graceful and masterful on the wing, the child and darling of the summer air, reaping its invisible harvest in the fields of space as if it dined on the sunbeams, touching no earthly food, drinking and bathing and mating on the wing, swiftly, tirelessly coursing the long day through, a thought on wings, a lyric in the shape of a bird! ”

“ In Birds, wings are a typical feature, corresponding to the front limbs in all Vertebrates, which are constructed in the same way, whether they are arms as in Man, or forelegs as in Quadrupeds, or pectoral fins as in Fishes, or wings as in Birds. The wing in an Insect, on the contrary, is a flattened, dried-up gill, having no structural relation whatever to the wing of a Bird. ”

“ We read in every handbook of entomology that the wings only arise during the life of the caterpillar, and in a certain sense this is true, for the primary constituents or primordia of wings only develop into the fully formed wing during the larval period. ”

“ Finally, when the wing has reached the lowest point of its depression, it is not over the mass of air which it has just set in motion, because the motion of translation of the bird continually brings it into regions where the air is at rest. All of these conditions are evidently favorable to flight, since they increase the resistance of the air, which alone furnishes to the bird its support, and the reaction to its moving wing. ”

“ If you advance nearer, the whole flock suddenly taking to wing, fill the air with their harsh cries, and soon reaching a considerable height, range widely around, until, your patience being exhausted, you abandon the place. When thus taking to wing in countless multitudes, the snowy white of their under parts gladdens your eye, but anon, when they all veer through the air, the black of their long wings and upper parts produces a remarkable contrast to the blue sky above. ”

“ In birds which glide or skim, it has appeared to me that the wing is recovered much more quickly, and the down stroke delivered more slowly, than in ordinary flight—in fact, that the rapidity with which the wing acts in an upward and downward direction is, in some instances, reversed; and this is what we should naturally expect when we recollect that in gliding, the wings require to be, for the most part, in the expanded condition. ”

“ When, moreover, the wing ascends and descends to make the up and down strokes, it rotates within the facettes or depressions situated on the scapula and coracoid bones, precisely in the same way that the arm of a man rotates in the glenoid cavity, or the leg in the acetabular cavity in the act of walking. The ascent and descent of the wing in flying correspond to the steps made by the extremities in walking; the wing rotating upon the body of the bird during the down stroke, the body of the bird rotating on the wing during the up stroke. ”

“ The Wing ascends when the Body descends, and vice versâ.—As the body of the insect, bat, and bird falls forwards in a curve when the wing ascends, and is elevated in a curve when the wing descends, it follows that the trunk of the animal is urged along a waved line, as represented at 1, 2, 3, 4, 5 of fig. ”

“ If the supporting surface of the wing of a bird were made of skin, like the web of the foot of a swimming bird, it would be necessary to fold the wing for each upward stroke. It is here that the structure of feathers adapts itself to the rapid action required for movement in the air. ”

“ There are birds of many kinds, and therefore a great variety of wings and modes of flight. Birds with short, broad, rounded wings, with the under surface slightly concave and the upper surface correspondingly convex, usually have comparatively heavy bodies, and race through the air with rapid wing-beats and rather labored flight, and compass only short distances. ”

“ The Wing at all times thoroughly under control.—The wing is moveable in all parts, and can be wielded intelligently even to its extremity; a circumstance which enables the insect, bat, and bird to rise upon the air and tread it as a master—to subjugate it in fact. The wing, no doubt, abstracts an upward and onward recoil from the air, but in doing this it exercises a selective and controlling power; it seizes one current, evades another, and creates a third; it feels and paws the air as a quadruped would feel and paw a treacherous yielding surface. ”

“ The importance of the twisted configuration or screw-like form of the wing cannot be over-estimated. That this shape is intimately associated with flight is apparent from the fact that the rowing feathers of the wing of the bird are every one of them distinctly spiral in their nature; in fact, one entire rowing feather is equivalent—morphologically and physiologically—to one entire insect wing. ”

“ Wonderfully the two eagles circled round one another in mighty, still-winged glidings, effortless, majestic, masterly, sometimes together, sometimes apart, drawing ever away northward with scarcely a wing-flap, without, it seemed, any visible force to drive them, till they swam, like specks on the eye-ball, miles away and upwards round the white-mantled peaks. ”

“ The pectoral muscles of a bird are reproduced by two strong springs which are extended by the upward motion of the wings and store up energy for the down-stroke. Close attention is also being paid to the actual shape of a bird’s wing, which is not flat but hollow on its under side, and at the front has a slightly downward dip. “Aerocurves” are therefore likely to supersede the “aeroplane,” for Nature would not have built bird’s wings as they are without an object. ”

“ Of the last-named organs there are ordinarily three, forming a graceful tapering point to the wing, and giving to it the symmetry and proportion that are required for effective use. When the wing is folded, the hand extends obliquely downward and backward. ”

“ The wings are somewhat long, and in general rather narrow, commonly clear and transparent, with simple nervures disappearing before reaching the apex, and crossed by a few transverse ones, the neuration being greatly more simple than in the hymenoptera. At the base of the wing, we very frequently find two rounded membranous scales applied with their faces to each other, which are named wing-scales, alulets, or winglets. They are sometimes of considerable size, and doubtless aid the movements of the wings materially in the act of flying. ”

“ Even the outline of the wings is leaf-like, and leaf-veins are marked on the wing-covers with the most beautiful distinctness, and finally there is, especially in the light-green individuals, a spot at the wing tip which, by means of a mixture of brown, yellow, reddish, and violet colour-tones, mimics a decaying spot with astonishing fidelity. ”

“ The structure of the veins can be best observed on the under surface of the wing, where they are more prominent. The student should begin by completely denuding of scales a few wings of common species: the wing should be cut off and laid on a moistened piece of glass, to which it will adhere ”

“ Then you have a good opportunity of observing the peculiar motion of their wings, which seem to strike simply downwards and not also backwards, as with other birds; it is a quick jerking movement, the wing giving the impression of pausing the tenth of a second at the finish of the stroke before it is lifted again. ”

“ The bird that has been searched for and found puts itself into a very beautiful attitude, with wings half-spread and set at right angles to the body, ruff erected circularly, and head drawn back upon the shoulders, so that nothing is visible but the brilliant rosette of the spread ruff in the centre of the screen of wings, each wing showing a broad bar of brilliant white on its dusk-grey surface. ”

“ In old times they told fables of birds which had no feet, and lived always on the wing. There are no such birds. All birds have feet, all rest from flying. But the motion of flying is so beautiful and easy, that it is no wonder that birds of strong flight are much upon the wing. ”

“ Flexion of the Wing necessary to the Flight of Birds.—Considerable diversity of opinion exists as to whether birds do or do not flex their wings in flight. The discrepancy is owing to the great difficulty experienced in analysing animal movements, particularly when, as in the case of the wings, they are consecutive and rapid. My own opinion is, that the wings are flexed in flight, but that all wings are not flexed to the same extent, and that what holds true of one wing does not necessarily hold true of another. ”

“ Look near the ribs in the photograph, and there you will see those poor little wing-bones—wing-bones where there never was a wing. From our present point of view these wings are, however, more interesting and instructive than the most perfect wings of an eagle or a carrier-pigeon. Those wings in the apteryx may be incapable of flight, but they are full of instruction to the lover of Nature. As it is certain that they are absolutely of no use whatever to the bird, we may well ask, why are they there? They are not there to give assistance to the bird in his struggle for life ”

“ The wing of the bird, like that of the insect, is concavo-convex, and more or less twisted upon itself when extended, so that the anterior or thick margin of the pinion presents a different degree of curvature to that of the posterior or thin margin. ”

“ And it seems the more likely too, because the wing of a Bee is less in proportion to its body, then the other wing to the body of a Fly; so that for ought I know, it may be one of the quickest vibrating spontaneous motions of any in the world; and though perhaps there may be many Flies in other places that afford a yet more shrill note with their wings, yet ’tis most probable that the quickest vibrating spontaneous motion is to be found in the wing of some creature. ”

“ Thus, in flight, the air passes through the wing as it is raised, while in the downstroke the feathers are forced together to form a homogeneous surface.
Birds which fly much have the outer primaries of great length, giving the wing a pointed shape, as in swifts, while in species which fly but little, or frequent thickets, the outer primaries are very short, giving the wing a rounded appearance. ”