Kitabı oku: «Science in Arcady», sayfa 5

PRETTY POLL

It is an error of youth to despise parrots for their much talking. Loquacity isn't always a sign of empty-headedness, nor is silence a sure proof of weight and wisdom. Biologists, for their part, know better than that. By common consent, they rank the parrot group as the very head and crown of bird creation. Not, of course, because pretty Poll can talk (in a state of nature, parrots only chatter somewhat meaninglessly to one another), but because the group display on the whole, all round, a greater amount of intelligence, of cleverness, and of adaptability to circumstances than any other birds, including even their cunning and secretive rivals, the ravens, the jackdaws, the crows, and the magpies.

What are the efficient causes of this exceptionally high intelligence in parrots? Well, Mr. Herbert Spencer, I believe, was the first to point out the intimate connection that exists throughout the animal world between mental development and the power of grasping an object all round so as to know exactly its shape and its tactile properties. The possession of an effective prehensile organ—a hand or its equivalent—seems to be the first great requisite for the evolution of a high order of intellect. Man and the monkeys, for example, have a pair of hands; and in their case one can see at a glance how dependent is their intelligence upon these grasping organs. All human arts base themselves ultimately upon the human hand; and even the apes approach nearest to humanity in virtue of their ever-active and busy little fingers. The elephant, again, has his flexible trunk, which, as we have all heard over and over again, usque ad nauseam, is equally well adapted to pick up a pin or to break the great boughs of tropical forest trees. (That pin, in particular, is now a well-worn classic.) The squirrel, once more, celebrated for his unusual intelligence when judged by a rodent standard, uses his pretty little paws as veritable hands, by which he can grasp a nut or fruit all round, and so gain in his small mind a clear conception of its true shape and properties. Throughout the animal kingdom generally, indeed, this correspondence, or rather this chain of causation, makes itself everywhere felt; no high intelligence without a highly developed prehensile and grasping organ.

Perhaps the opossum is the very best and most crucial instance that could possibly be adduced of the intimate connection which exists between touch and intellect. For the opossum is a marsupial; it belongs to the same group of lowly-organized, antiquated, and pouch-bearing animals as the kangaroo, the wombat, and the other belated Australian mammals. Now everybody knows the marsupials as a class are nothing short of preternaturally stupid. They are just about the very dullest and silliest of all existing quadrupeds. And this is reasonable enough, when one comes to think of it, for they represent a very antique and early type, the first rough sketch of the mammalian idea, if I may so describe them, with wits unsharpened as yet by contact with the world in the fierce competition of the struggle for life as it displays itself on the crowded stage of the great continents. They stand, in short, to the lions and tigers, the elephants and horses, the monkeys and squirrels, of Europe and America, as the Australian blackfellow stands to the Englishman or the Yankee. They are the last relic of the original secondary quadrupeds, stranded for ages in a remote southern island, and still keeping up among Australian forests the antique type of life that went out of fashion in Europe, Asia, and America before the chalk was laid down or the London Clay deposited on the bed of our northern oceans. Hence they have still very narrow brains, and are so extremely stupid that a kangaroo, it is said—though I don't vouch for it myself—when struck a smart blow, will turn and bite the stick that hurts him instead of expending his anger on the hand that holds it.

Now, every Girton girl is well aware that the opossum, though it is a marsupial too, differs inexpressibly in psychological development from the kangaroo and the wombat. Your opossum, in short, is active, sly, and extremely intelligent. He knows his way about the world he lives in. 'A 'possum up a gum-tree' is accepted by the observant American mind as the very incarnation of animal cleverness, cunning, and duplicity. In negro folk-lore the resourceful 'possum takes the place of Reynard the Fox in European stories: he is the Macchiavelli of wild beasts: there is no ruse on earth of which he isn't amply capable, no artful trick which he can't design and execute, no wily manoeuvre which he can't contrive and carry to an end successfully. All guile and intrigue, the 'possum can circumvent even Uncle Remus himself by his crafty diplomacy. And what is it that makes all the difference between this 'cute Yankee marsupial and his backward and belated Australian cousins? Why, nothing but the possession of a prehensile hand and tail. Therein lies the whole secret. The opossum's hind foot has a genuine opposable thumb; and he also uses his tail in climbing as a supernumerary hand, almost as much as do any of the monkeys. He often suspends himself by it, like an acrobat, swings his body to and fro to get up steam, then lets go suddenly, and flies away to a distant branch, which he clutches by means of his hand-like hind feet. If the toes play him false, he can 'recover his tip,' as circus-folk put it, with his prehensile tail. The consequence is that the opossum, being able to form for himself clear and accurate conceptions of the real shapes and relations of things by these two distinct grasping organs, has acquired an unusual amount of general intelligence. And further, in the keen competition of the American continent, he has been forced to develop an amount of cleverness and low cunning which leaves his Australian poor relations far behind in the Middle Ages of evolution.

At the risk of seeming to run off at a tangent and forsake our ostensible subject, pretty Poll, altogether, I must just pause for one moment more to answer an objection which I know has been trembling on the tip of your tongue any time the last five minutes. You've been waiting till you could get a word in edgeways to give me a friendly nudge and remark very wisely, 'But look here, I say; how about the dog and the horse in your argument? They've got no prehensile organ that ever I heard of, and yet they're universally allowed to be the cleverest and most intelligent of all earthly quadrupeds.' True, O most sapient and courteous objector. I grant it you at once. But observe the difference. The cleverness of the horse and the dog is acquired, not original. It has probably arisen in the course of their long hereditary intercourse and companionship with man, the cleverest and most serviceable individuals being deliberately selected from generation to generation, as dams and sires to breed from. We can't fairly compare these artificial human products, therefore, with wild races whose intelligence is all native and self-evolved. Moreover, the horse at least has to some slight extent a prehensile organ in his very mobile and sensitive lip, which he uses like an undeveloped or rudimentary proboscis to feel things all over with. So that the dog alone remains as a contradictory instance; and even the dog derives his cleverness indirectly from man, whose hand and thumb in the last resort are really at the bottom of his vicarious wisdom.

We may conclude, then, I believe, that touch, as Mr. Herbert Spencer admirably words it, is 'the mother-tongue of the senses;' and that in proportion as animals have or have not highly developed and serviceable tactile organs will they rank high or low in the intellectual hierarchy of nature. Now, how does this bear upon the family of parrots? Well, in the first place, everybody who has ever kept a cockatoo or a macaw in domestic slavery is well aware that in no other birds do the claws so closely resemble a human or simian hand, not indeed in outer form or appearance, but in opposability of the thumbs and in perfection of grasping power. The toes on each foot are arranged in opposite pairs—two turning in front and two backward, which gives all parrots their peculiar firmness in clinging on a perch or on the branch of a tree with one foot only, while they extend the other to grasp a fruit or to clutch at any object they desire to take possession of. True, this peculiarity isn't entirely confined to the parrots alone, as such. They share the division of the foot into two thumbs and two fingers with a whole large group of allied birds, called, in the charmingly concise and poetical language of technical ornithology, the Scansorial Picarians, and more generally, known to the unlearned herd (meaning you and me) by their several names of woodpeckers, cuckoos, toucans, and plantain-eaters. All the members of this great group, of which the parrots proper are only the most advanced and developed family, possess the same arrangement of the digits into front-toes and back-toes. But in none is the arrangement so perfect as in the parrots, and in none is the power of grasping an object all round so completely developed and so pregnant in moral and intellectual consequences.

All the Scansorial Picarians, however (if the reader with his proverbial courtesy will kindly pardon me the inevitable use of such very bad words), are essentially tree-haunters; and the tree-haunting and climbing habit, as is well beknown, seems particularly favourable to the growth of intelligence. Thus schoolboys climb trees—but I forgot: this is a scientific article, and such levity is inconsistent with the dignity of science. Let us be serious! Well, at any rate, monkeys, squirrels, opossums, wild cats, are all of them climbers, and all of them, in the act of clinging, jumping, and balancing themselves on boughs, gain such an accurate idea of geometrical figure, perspective, distance, and the true nature of space-relations, as could hardly be acquired in any other manner. In one word, they thoroughly understand space of three dimensions, and the tactual realities that answer to and underlie each visible appearance. This is the very substratum of all intelligence; and the monkeys, possessing it more profoundly than any other animals, have accordingly taken the top of the form in the competitive examination perpetually conducted by survival of the fittest.

So, too, among birds, the parrots and their allies climb trees and rocks with exceptional ease and agility. Even in their own department they are the great feathered acrobats. Anybody who watches a woodpecker, for example, grasping the bark of a tree with its crooked and powerful toes, while it steadies itself behind by digging its stiff tail-feathers into the crannies of the outer rind, will readily understand how clear a notion the bird must gain into the practical action of the laws of gravity. But the true parrots go a step further in the same direction than the woodpeckers or the toucans; for, in addition to prehensile feet, they have also a highly-developed prehensile bill, and within it a tongue which acts in reality as an organ of touch. They use their crooked beaks to help them in climbing from branch to branch; and being thus provided alike with wings, legs, hands, fingers, bill and tongue, they are in fact the most truly arboreal of all known animals, and present in the fullest and highest degree all the peculiar features of the tree-haunting existence.

Nor is that all. Alone among birds or mammals, the parrots have the curious peculiarity of being able to move the upper as well as the lower jaw. It is this strange mobility of both the mandibles together, combined with the crafty effect of the sideways glance from those artful eyes, that gives the characteristic air of intelligence and wisdom to the parrot's face. We naturally expect so clever a bird to speak. And when it turns upon us suddenly with a copy-book maxim, we are in no way astonished at its surpassing smartness.

Parrots are vegetarians; with a single degraded exception to whom I shall recur hereafter, Sir Henry Thompson himself couldn't find fault with their regimen. They live chiefly upon a light but nutritious diet of fruit and seeds, or upon the abundant nectar of rich tropical flowers. And it is mainly for the sake of getting at their chosen food that they have developed the large and powerful bills which characterise the family. You may have perhaps noted that most tropical fruit-eaters, like the hornbills and the toucans, are remarkable for the size and strength of their beaks: if you haven't, I dare say you will generously take my word for it. And, per contra, it may also have struck you that most tropical fruits have thick or hard or nauseous rinds, which need to be torn off before the monkeys or birds for whose use they are intended, can get at them and eat them. Our little northern strawberries, and raspberries, and currants, and whortleberries, developed with a single eye to the petty robins and finches of temperate climates, can be popped into, the mouth whole and eaten as they stand: they are meant for small birds to devour, and to disperse the tiny undigested nut-like seeds in return for the bribe of the soft pulp that surrounds them. But it is quite otherwise with oranges, shaddocks, bananas, plantains, mangoes, and pine-apples: those great tropical fruits can only be eaten properly with a knife and fork, after stripping off the hard and often acrid rind that guards and preserves them. They lay themselves out for dispersion by monkeys, toucans, and other relatively large and powerful fruit-eaters; and the rind is put there as a barrier against small thieves who would rob the sweet pulp, but be absolutely incapable of carrying away and dispersing the large and richly-stored seeds it covers.

Parrots and toucans, however, have no knives and forks to cut off the rind with; but as monkeys use their fingers, so the birds use for the same purpose their sharp and powerful bills. No better nut-crackers and fruit-parers could possibly be found. The parrot, in particular, has developed for the purpose his curved and inflated beak—a wonderful weapon, keen as a tailor's scissors, and moved by powerful muscles on either side of the face which bring together the cutting edges with extraordinary energy. The way the bird holds the fruit gingerly in one claw, while he strips off the rind dexterously with his under-hung lower mandible, and keeps a sharp look-out meanwhile on either side with those sly and stealthy eyes of his for a possible intruder, suggests to the observing mind the whole living drama of his native forest. One sees in that vivid world the watchful monkey ever ready to swoop down upon the tempting tail-feathers of his hereditary foe: one sees the canny parrot ever prepared for his rapid attack, and ever eager to make him pay with five joints of his tail for his impertinent interference with an unoffending fellow-citizen of the arboreal community.

Still, there are parrots and parrots, of course. Not all this vast family are in all things of like passions one with another. The great black cockatoo, for example, the largest of the tribe, lives almost entirely off the central shoot or 'cabbage' of palm-trees: an expensive kind of food, for when once the 'cabbage' is eaten the tree dies forthwith, so that each black cockatoo must have killed in his time whole groves of cabbage-palms. Others, again, feed off fruits and seeds; and not a few are entirely adapted for flower-haunting and honey-sucking.

As a group, the parrots are comparatively modern birds. Indeed, they could have no place in the world till the big tropical fruits and nuts were beginning to be developed. And it is now pretty certain that fruits and nuts are for the most part of very recent and special evolution. To put it briefly, the monkeys and parrots developed the fruits and nuts, while the fruits and nuts returned the compliment by developing conversely the monkeys and parrots. In other words, both types grew up side by side in mutual dependence, and evolved themselves pari passu for one another's benefit. Without the fruits there could be no fruit-eaters; and without the fruit-eaters to disperse their seeds, there could just to the same extent be no fruits to speak of.

Most of the parrots very much resemble the monkeys and other tropical fruit-feeders in their habits and manners. They are gregarious, mischievous, noisy, and irresponsible. They have no moral sense, and are fond of practical jokes and other schoolboy horseplay. They move about in flocks, screeching aloud as they go, and alight together on some tree well covered with berries. No doubt, they herd together for the sake of protection and screech both to keep the flock in a body and to strike alarm and consternation into the breasts of their enemies. When danger threatens, the first bird that perceives it sounds a note of warning; and in a moment the whole troop is on the wing at once, vociferous and eager, roaring forth a song in their own tongue which may be roughly interpreted as stating in English that they don't want to fight, but by Jingo, if they do, they'll tear their enemy to shreds and drink his blood up too.

The common grey parrot, the best known in confinement of all his kind, and unrivalled as an orator for his graces of speech, is a native of West Africa; so that he shares with other West Africans that perfect command of language which has always been a marked characteristic of the negro race. He feeds in a general way upon palm-nuts, bananas, mangoes, and guavas, but he is by no means averse, if opportunity offers, to the Indian corn of the industrious native. His wife accompanies him in his solitary rambles, for they are not gregarious. In her native haunts, indeed, Polly is an unsociable bird. It is only in confinement that her finer qualities come out, and that she develops into a speech-maker of distinguished attainments.

A very peculiar and exceptional offshoot of the parrot group is the brush-tongued lory, several species of which are common in Australia, India, and the Molucca Islands. These pretty and interesting creatures are in point of fact parrots which have practically made themselves into humming-birds by long continuance in the poetical habit of visiting flowers for food. Like Mr. Oscar Wilde in his æsthetic days, they breakfast off a lily. Flitting about from tree to tree with great rapidity, they thrust their long extensible tongues, pencilled with honey-gathering hairs, into the tubes of many big tropical blossoms. The lories, indeed, live entirely on nectar, and they are so common in the region they have made their own that all the larger flowers there have been developed with a special view to their tastes and habits, as well as to the structure of their peculiar brush-like honey-collector. In most parrots the mouth is dry and the tongue horny; but in the lories it is moist and much more like the same organ in the humming-birds and sun-birds. The prevalence of very large and brilliantly coloured flowers in the Malayan region must be set down for the most part to the selective action of these æsthetic and colour-loving little brush-tongued parrots.

Australia and New Zealand, as everybody knows, are the countries where everything goes by contraries. And it is here that the parrot group has developed some of its strangest and most abnormal offshoots. One would imagine beforehand that no two birds could be more unlike in every respect than the gaudy, noisy, gregarious cockatoos and the sombre, nocturnal, solitary owls. Yet the New Zealand owl-parrot is, to put it plainly, a lory which has assumed all the outer appearance and habits of an owl. A lurker in the twilight or under the shades of night, burrowing for its nest in holes in the ground, it has dingy brown plumage like the owls, with an undertone of green to bespeak its parrot origin: while its face is entirely made up of two great disks, surrounding the eyes, which succeed in giving it a most marked and unmistakable owl-like appearance.

Now, why should a parrot so strangely disguise itself and belie its ancestry? The reason is plain. It found a place for it ready made in nature. New Zealand is a remote and sparsely-stocked island, peopled by mere casual waifs and strays of life from adjacent but still very distant continents. There are no dangerous enemies there. Here, then, was a clear chance for a nightly prowler. The owl-parrot with true business instinct saw the opening thus clearly laid before it, and took to a nocturnal and burrowing life, with the natural consequence that it acquired in time the dingy plumage, crepuscular eyes, and broad disk-like reflectors of other prowling night-fliers. Unlike the owls, however, the owl-parrot, true to the vegetarian instincts of the whole lory race, lives almost entirely upon sprigs of mosses and other creeping plants. It is thus essentially a ground bird; and as it feeds at night in a country possessing no native beasts of prey, it has almost lost the power of flight, and uses its wings only as a sort of parachute to break its fall in descending from a rock or tree to its accustomed feeding-ground. To get up again, it climbs, parrot-like, with its hooked claws, up the surface of the trunk or the face of a precipice.

Even more aberrant in its ways, however, than the burrowing owl-parrot, is that other strange and hated New Zealand lory, the kea, which, alone among its kind, has abjured the gentle ancestral vegetarianism of the cockatoos and macaws, in favour of a carnivorous diet of singular ferocity. And what is odder still, this evil habit has been developed in the kea since the colonization of New Zealand by the English, those most demoralizing of new-comers. The settlers have taught the Maori to wear tall hats and to drink strong liquors: and they have thrown temptation in the way of even the once innocent native parrot. Before the white man came, in fact, the kea was a mild-mannered fruit-eating or honey-sucking bird. But as soon as sheep-stations were established in the island these degenerate parrots began to acquire a distinct taste for raw mutton. At first, to be sure, they ate only the sheep's heads and offal that were thrown out from the slaughter-houses picking the bones as clean of meat as a dog or a jackal. But in process of time, as the taste for blood grew upon them, a still viler idea entered into their wicked heads. The first step on the downward path suggested the second. If dead sheep are good to eat, why not also living ones? The kea, pondering deeply on this abstruse problem, solved it at once with an emphatic affirmative. And he straightway proceeded to act upon his convictions, and invent a really hideous mode of procedure. Perching on the backs of the living sheep he has now learnt the exact spot where the kidneys are to be found; and he tears open the flesh to get at these dainty morsels, which he pulls out and devours, leaving the unhappy animal to die in miserable agony. As many as two hundred ewes have thus been killed in a night at a single station. I need hardly add that the sheep-farmer naturally resents this irregular proceeding, so opposed to all ideals of good grazing, and that the days of the kea are now numbered in New Zealand. But from the purely psychological point of view the case is an interesting one, as being the best recorded instance of the growth of a new and complex instinct actually under the eyes of human observers.

One word as to the general colouring of the parrot group as a whole. Tropical forestine birds have usually a ground tone of green because that colour enables them best to escape notice among the monotonous verdure of equatorial woodland scenery. In the north, to be sure, green is a very conspicuous colour; but that is only because for half the year our trees are bare, and even during the other half they lack that 'breadth of tropic shade' which characterises the forests of all hot countries. Therefore, in temperate climates, the common ground-tone of birds is brown, to harmonise with the bare boughs and leafless twigs, the clods of earth and dead turf or stubble. But in the evergreen tropics green is the right hue for concealment or defence. Therefore the parrots, the most purely tropical family of birds on earth, are mostly greenish; and among the smaller and more defenceless sorts, like the familiar little love-birds, where the need for protection is greatest, the green of the plumage is almost unbroken. Of the tiny Pigmy Parrots of New Guinea, for instance, Mr. Bowdler Sharpe says: 'Owing to their small size and the resemblance of their green colouring to the forests they inhabit, they are not easily seen, and until recent years were very hard to procure.' And of the green parrot of Jamaica, Mr. Gosse remarks: 'Often we hear their voices proceeding from a certain tree, or else have marked the descent of a flock on it; but on proceeding to the spot, though the eye has not wandered from it, we cannot discover an individual. We go close to the tree, but all is silent and still as death. We institute a careful survey of every part with the eye, to detect the slightest motion, or the form of a bird among the leaves, but all in vain. We begin to think they have stolen off unperceived; but on throwing a stone into the tree, a dozen throats burst forth into a cry, and as many green birds rush forth upon the wing. Green may thus be regarded as the normal or basal parrot tint, from which all other colours are special decorative variations.

But fruit-eating and flower-feeding creatures, like butterflies and humming-birds—seeking their food ever among the bright berries and brilliant flowers, almost invariably acquire in the long run an æsthetic taste for pure and varied colouring, and by the aid of sexual selection this taste stereotypes itself at last in their own wings and plumage. They choose their mates for colour as they choose their foodstuffs. Hence all the larger and more gregarious parrots, in which the need for concealment is less, tend to diversify the fundamental green of their coats with crimson, yellow, or blue, which in some cases take possession of the entire body. The largest kinds of all, like the great blue and yellow or crimson macaws, are as gorgeous as Solomon in all his glory: and they are also the species least afraid of enemies; for in Brazil you may often see them wending their way homeward openly in pairs every evening, with as little attempt at concealment as rooks in England. In the Moluccas and New Guinea, says Mr. Wallace, white cockatoos and gorgeous lories in crimson and blue are the very commonest objects in the local fauna. Even the New Zealand owl-parrot, however, still retains many traces of his original greenness, mixed with the dirty brown and dingy yellow of his acquired nocturnal and burrowing nature.

If fruit-eaters are fine, flower-haunters are magnificent. And the brush-tongued lories, that search for nectar among the bells of Malayan blossoms, are the brightest-coloured of all the parrot tribes. Indeed, no group of birds, according to Mr. Alfred Russel Wallace (who ought to know, if anybody does), exhibits within the same limited number of types so extraordinary a diversity and richness of colouring as the parrots. 'As a rule,' he says, 'parrots may be termed green birds, the majority of the species having this colour as the basis of their plumage, relieved by caps, gorgets, bands and wing-spots of other and brighter hues. Yet this general green tint sometimes changes into light or deep blue, as in some macaws; into pure yellow or rich orange, as in some of the American macaw-parrots; into purple, grey or dove-colour, as in some American, African, and Indian species; into the purest crimson, as in some of the lories; into rosy-white and pure white, as in the cockatoos; and into a deep purple, ashy or black, as in several Papuan, Australian, and Mascarene species. There is in fact hardly a single distinct and definable colour that cannot be fairly matched among the 390 species of known parrots. Their habits, too, are such as to bring them prominently before the eye. They usually feed in flocks; they are noisy, and so attract attention; they love gardens, orchards, and open sunny places; they wander about far in search of food, and towards sunset return homeward in noisy flocks, or in constant pairs. Their forms and motions are often beautiful and attractive. The immensely long tails of the macaws and the more slender tails of the Indian parroquets, the fine crest of the cockatoos, the swift flight of many of the smaller species, and the graceful motions of the little love-birds and allied forms, together with their affectionate natures, aptitude for domestication, and power of mimicry, combine to render them at once the most conspicuous and the most attractive of all the specially tropical forms of bird life.'

I have purposely left to the last the one point about parrots which most often attracts the attention of the young, the gay, the giddy, and the thoughtless: I mean their power of mimicry in human language. And I believe I am justified in passing it over lightly. For in fact this power is but a very incidental result of the general intelligence of parrots, combined with the other peculiarities of their social life and forestine character. Dominant woodland animals, indeed, like monkeys, parrots, toucans, and hornbills, at least if vegetarian in their habits, are almost always gregarious, noisy, mischievous, and imitative. And the imitation results directly from the unusual intelligence; for, after all, what is the power of learning itself—at least, in all save its very highest phases—but the faculty of accurately imitating another? Monkeys for the most part imitate action only, because they haven't very varied or flexible voices. Parrots and many other birds, on the contrary—like the starling and still more markedly the American mocking-bird—being endowed with considerable flexibility of voice, imitate either songs or spoken words with great distinctness. In the parrot the power of attention is also very considerable, for the bird will often try over with itself repeatedly the lesson it has set itself to learn. But people too generally forget that at best the parrot knows only the general application of a sentence, not the separate meanings of its component words. It knows, for example, that 'Polly wants a lump of sugar' is a phrase often followed by a present of food. But to believe it can understand an abstract expression, like the famous 'By Jove! what a beastly lot of parrots!' is to confound learning by rote with genuine comprehension. A careful review of all the evidence makes almost every scientific observer conclude that at most a parrot knows a word of command as a horse knows 'Whoa!' or a dog knows the order to hunt for rats in the wainscot.