( Originally Published 1918 )
THE workman is known by his tools, and by the tools of the feathered creatures—that is to say, their beaks and claws—their way of life is not less easily recognized. If it were not already known to us, who could fail to infer the carnivorous disposition of the hawk from the shape of its beak—short, sharp, and hooked—and from the structure of its talons, armed as they are with pointed nails grooved underneath with a narrow channel after the manner of certain daggers, to facilitate the flow of blood from the wound?
Does it call for any extraordinary perspicacity to recognize, in the heron's long legs, veritable stilts which enable it to traverse, step by step, without getting wet, the inundated flats, as does the hunter in his long, waterproof marsh boots? And then, that long beak, pointed like a nail, does it tell us nothing? Does it not say that the bird bores deep in the tufts of rushes and in the soft mud to pull out reptiles and worms!"
It is the heron," put in Emile, "that the fable tells about when it says :
"The long-necked, long-beaked heron went walking; On its stilt-like legs one day it went stalking."
"Yes," said Uncle Paul, "that is the bird. Everything about the heron is long—legs, beak, neck. The length of its legs enables the bird to explore the swamp at its ease all day long with-out wetting a feather; its length of neck is needed that it may reach the ground with-out stooping; and the long beak is indispensable for burrowing in the tall tufts of grass where the reptile lurks, and for probing the mud where the worm buries itself."
"I begin to see now," said Jules, "how the character of a bird may be judged from its shape. The heron bears its trade stamped on its form."
"The duck, in its turn, makes an equally unmistakable announcement. Let us forget its habits, which are so familiar to us, and try to rediscover them in the shape of the legs and beak.
`The duck's beak is very wide and flat, and round at the end. Shall we compare it with the hen's beak, a slender pair of pincers that snaps up seeds and kernels one by one? Comparison is impossible. Do we see there a tool working in the manner of the heron's pointed probe? Still less. Shall we make it the equivalent of the bloody hooked beak of the bird of prey? No one would dream of such a thing, so great is the difference. But one sees at once in this wide, rounded beak a spoon shaped expressly for scooping up food from the water, just as our table-spoons enable us to take out pieces of bread or lumps of rice swimming in a thin soup. The duck dabbles, then : it dips up water in large spoonfuls—that is to say, in beakfuls—and seeks its food therein. It is a soup of the thinnest sort and, in itself, of no nutritive value. Consequently the liquid that fills the bird's mandible must be rejected, but at the same time it must be drained out in such a manner as to leave behind what little alimentary matter it may contain. For this purpose the edges of the beak are fringed with a row of thin, short blades which let the liquid run out when the bird has once filled its mouth."
"That 's an ingenious way to eat," remarked Jules. "In order to snap up what it takes a fancy to, perhaps a tadpole, or a little water shell, or a worm, the duck is obliged to fill its beak with water. To swallow the whole mouthful without sorting would simply stuff the crop with a useless liquid. What does the bird do? It closes the beak, and the water, driven back, runs out through the fringed edges as if through a grating. The tadpole alone remains behind the grating, and goes down into the stomach."
"You can see, any time," observed Louis, "the ducks on the pond dipping up water by the mouthful. It certainly isn't just for drinking that they work their beaks so."
"Certainly not," assented Uncle Paul; "they drain the water of the pond through the fringe of the beak to gather worms and other small aquatic prey.
"The spoon-shaped beak of the duck indicates the bird's dabbling habits; now let us see what the feet have to say. They are composed of three toes connected by an ample and supple membrane. Is that, I ask you, the footgear of a bird destined to long walks? With such a sole, so fine, so tender, and by its extent of surface exposing itself so much to the hardness of the stones, is the duck made for foot-racing? Note, on the contrary, the foot of the hen and the guinea-fowl, both untiring walkers. The toes are short, knotty, and sheathed with strong leather, without any connecting membrane. That is the true footgear of the pedestrian. But what will become of the duck on rough ground, with its wide sandals that a mere nothing can wound? You all know its pitiful walk. It waddles along, as ill at ease as a person afflicted with corns on the rough pavement of some of our streets. No, the duck is not made for walking.
"But in water those expanded feet will make vigorous swimming oars. If the bird throws them out behind, they spread wide open merely with the resistance. of the water; and their fan-shape gives them purchase enough to send the duck forward. When the duck draws them in again under its breast, they are closed automatically by the resistance of the liquid acting in a contrary direction; the membrane refolds in. the manner of a closed umbrella, thus doing away with all shock or recoil. The twofold essential of a perfect oar lies in its presenting to the water the greatest possible surface on the stroke, and the least possible surface on the recovery, so as to furnish adequate purchase against the water in the first movement and to offer only very feeble resistance in the second. If the oar moved alternately forward and backward while presenting the same extent of surface to the water and driven with the same vigor, the recoil would equal the advance and there would be no progress. Man, with all his skill, does not yet know how to ply his oar so that it shall offer this alternating maximum and minimum of surface. Therefore, in propelling a boat, he is obliged to bring the oars back to their first position through the air instead of through the water, which latter would be much more direct. The duck scorns this clumsy method: with its foot, which opens wide of itself in the backward thrust and closes again of its own accord in the return movement, it moves forward or puts about, without ever lifting the oars from the water.
"Thus the duck is an expert swimmer; the shape of its feet tells us as much, and a glance at any duck-pond demonstrates it. Who has not admired the aquatic evolutions of the bird, so awkward on land with its tender feet, so graceful when once on the water, its proper element? Sometimes they race with one another, whitening their breasts with a band of foam; sometimes, in order to explore the depths with their beaks, they plunge half-way in and point their tails heavenward; sometimes, also, yielding to the current, they let themselves drift idly downstream or hold their position by paddling a few strokes when necessary. Water is their chosen domain; there they take their recreation, seek their food, and enjoy their sleep.
"The membrane connecting the duck's toes is called a web, and the feet converted into oars by means of this membrane are spoken of as webbed. Similar feet are found in all good swimming birds such as the swan, teal, goose, and many others. Hence this group of birds, especially skilled in swimming, is designated by the term of palmipede, meaning web-footed."
"It is a palmipede, as also the goose, swan, and teal. All four are equally endowed with a large spoon-bill shaped for dabbling in the water; that is to say, a wide, round beak; but there are palmipedes, notably among sea-birds, that live on prey, on fish, and consequently are equipped with the crooked mandible appropriate for a predatory life. Such, to take but a single example, is the albatross, of which I here show you the picture. By its ferociously hooked beak it can easily be recognized as a sea pi, rate, an insatiable devourer of fish."
"I certainly don't like its looks," declared Emile. "But tell me now what name they give the heron on its tall stilts."
"The heron belongs to the group of stilt-birds or wading-birds. That is what they call all birds mounted on long legs for traversing the marshes."
"A bird on stilts is a stilt-bird; it would be hard to improve on that. It is just the kind of name I like."
`Instead of allowing ourselves to be turned from our theme by the heron and its stilts, let us come back, my little friend, to the palmipedes, the swimming birds. Clothing made expressly for the purpose is required by the bird that passes the greater part of its time on the water. It is indispensable that this clothing should keep out both cold and wet. Well, the plumage of an aquatic bird, especially in very cold countries, is a marvel of delicate precautions. The outside feathers are strong, placed very accurately one on the other and glossed with an oily varnish that water cannot wet. Have you ever noticed ducks as they come out of the water? They may have prolonged their bath for hours, swimming, diving, playing; but they leave the stream without getting the least bit wet. If a drop of water has got between their feathers, they have only to shake themselves a moment, and they are perfectly dry. That, you must agree, is a precious privilege, to be able to go into the water and not get wet."
"A privilege that, for my part," rejoined Emile,
I have often envied without being able to explain—the secret of a duck's keeping dry when right in the water."
"I will explain the secret to you. Watch the ducks as they come out of their bath. In the sun, some lying at ease on their stomachs, others standing up, they proceed to make their toilet with minute care. With their large beak they smooth their feathers, one by one, coat them over with an oily fluid, the reservoir of which is situated on the bird's rump. There, just at the base of the tail, is found, hidden under the down, a kind of wart of grease, from which oil oozes constantly. From time to time the beak presses the wart, draws from the oily reservoir, and then distributes here and there, methodically, all over the plumage, the oil thus obtained."
"That greasy wart might be called a sort of pomatum pot," suggested Emile.
"It is a pomatum pot, if that comparison pleases you. Thus greased, thus anointed with pomatum, feather by feather, the duck furnishes no foothold for moisture, because, as you all know, water and oil do not mix, and from an oiled surface drops of water run off without wetting it. Such is the secret of the duck's keeping itself dry when immersed in water."
"That is one of the most curious things I ever heard of," declared Jules, "and one that I should n't have known anything about for a long time if it hadn't been for Uncle Paul. Should I ever have guessed that the duck presses a certain wart on its rump to get the grease for oiling its feathers?"
"The duck's secret is known to all birds without exception; all have this oil-sac on the rump, and obtain from it the oil for giving luster to their plumage and making it impervious to wet; but aquatic birds are more abundantly provided in this respect. And it is only right that those most exposed to dampness should have the largest reservoir of this oily coating."
In all birds the fattest part is always the rump," said Louis. "Grease gathers there by preference, no doubt, to maintain the store of oil in the oil-sac?"
"Evidently. It is in this storehouse that the oil attains its perfect state and becomes the finished product that oozes from the sac. As to the making of it in the first place, nearly all parts of the body take part; and as the swimming bird uses a great deal of this pomatum, the result is that the palmipede tends to fatness and, as it were, sweats grease: witness the plump duck and goose, which carry under the breast a heavy, fat swelling. As a general rule, the web-footed fowl of our poultry-yards is analogous to the pig: it is a fat-factory. We divert to our own use the excess of fat accumulated primarily for the supply of the oil-sac on the rump and the maintenance of the luster that distinguishes the plumage.
"The palmipede, you see, is admirably protected against wet. Neither rain nor the finest drizzle can penetrate the first covering of feathers, always kept, as it is, well coated with the varnish laid on by the point of the beak. The bird can plunge into the deepest water, swim on its surface, or sleep there cradled by the waves, and the wet will not reach it. Neither will cold affect it, for under this outer covering is found a second, designed for resisting inclement weather and made of what is most efficacious for preserving the heat of the body. This under-clothing of aquatic birds is a down so delicate and soft that, unable to compare it with anything else, we have given it a special name, that of eider-down. In its proper place I will come back to this down. For the present let us confine ourselves to a general survey of the palmipedes, and of the duck in particular."