Chapter 16

Uncle Thomas tells about the Migrating Instinct of Animals.--Of the House Swallow of England; and the Esculent Swallow, whose Nest is eaten by the Chinese.--He tells also about the Passenger Pigeon of America; of the Myriads which are found in various parts of the United States; of the Land-Crab and its Migrations, and of those of the Salmon and the Common Herring.

"Uncle Thomas, I heard to-day of a swallow which for many years returned to the same window, and built its nest in the same corner. Now as I believe swallows are birds of passage, and leave this country to spend the winter in warmer climates, I wish you to explain to me how it is that they can return from such distances to the same spot."

"That is a question, Frank, which I cannot very well answer, but so many instances of the kind have been observed as to leave no doubt as to the fact. It has sometimes been known even to penetrate into the house, and attach its nest to articles of furniture.

"At Camerton Hall, near Bath, a pair of swallows built their nest on the upper part of the frame of an old picture over the chimney; and, coming into the room through a broken pane in one of the windows, they continued to use the same place for their nest for three successive years, and would probably have continued to do so, but the room having been put into repair, they could no longer obtain access to it."

"Is it want of food which makes birds migrate, Uncle Thomas?"

"Principally, I should say that it is so, Frank, but in shifting from one place to another they only fulfil an instinct impressed on them by their Creator for the preservation of their species. Thus, for instance, an old swallow might know by experience, that when its food fails here, it begins to become plentiful elsewhere, but the young bird which had never been more than a few miles from the place where it was hatched, can have no such experimental knowledge; yet, when the season arrives, we find the whole flock ready to set out. I dare say you have all seen them, Boys, gathering in flocks and resting on the house tops, as if taking breath before setting out on their long journey."

"Oh, yes, Uncle Thomas, I have often seen them doing so, but I have heard that they dive to the bottom of lakes and ponds, and remain there till winter is over."

"Many foolish stories are told of swallows being found in such situations, Harry, but they are now well known to be fables. There is no doubt that they migrate in the same way as many other birds. Last autumn I watched with great pleasure the movements of a flock, which was evidently preparing for their arduous flight.

"For several evenings they assembled in large numbers on a tree at a short distance from my house, and, after remaining seated for some time, one of them, who appeared to be commander-in-chief, kept flying about in all directions, and at length, with a sharp and loudly repeated call, he darted up into the air. In an instant the whole congregation were on the wing, following their leader in a sort of spiral track. In a little time they had risen so high that I lost sight of them, but after a short absence they again returned and took up their position on the tree which they had just left.

"This manoeuvre they continued for some time, till one day they set off in reality, and I saw no more of them for the winter."

"I read, somewhere, Uncle Thomas, that the Chinese eat swallows' nests. I cannot understand this, Sir; surely the mud and clay, of which swallows' nests are composed, would make but an indifferent repast."

"I dare say they would, Frank, if they were made of clay and mud, as the nests of our swallows are; but such is not the case. Various opinions are entertained as to the substance of which the nest of the esculent swallow is made. Sir George Staunton, who accompanied Lord Macartney in his embassy to China, gives a very interesting account both of the swallow and of its nest.

"In the Cass," says Sir George, "a small island near Sumatra, we found two caverns running horizontally into the side of the rock, and in these were a number of those birds' nests so much prized by the Chinese epicures. They seemed to be composed of fine filaments, cemented together by a transparent viscous matter, not unlike what is left by the foam of the sea upon stones alternately covered by the tide, or those gelatinous animal substances found floating on every coast. The nests adhere to each other and to the sides of the cavern, mostly in horizontal rows, without any break or interruption, and at different depths from fifty to five hundred feet. The birds that build these nests are small grey swallows, with bellies of a dirty white. They were flying about in considerable numbers, but were so small, and their flight was so quick, that they escaped the shot fired at them. The same sort of nests are said to be also found in deep caverns at the foot of the highest mountains in the middle of Java, at a distance from the sea; from which source it is thought that the birds derive no materials, either for their food, or the construction of their nests, as it does not appear probable they should fly in search of either over the intermediate mountains, which are very high, or against the boisterous winds prevailing thereabouts. They feed on insects, which they find hovering over stagnated pools between the mountains, and for the catching of which their wide opening beaks are particularly adapted. They prepare their nests from the best remnants of their food. Their greatest enemy is the kite, who often intercepts them in their passage to and from the caverns, which are generally surrounded with rocks of grey limestone or white marble. The colour and value of the nests depend on the quantity and quality of the insects caught, and perhaps also on the situation where they are built. Their value is chiefly ascertained by the uniform fineness and delicacy of their texture; those that are white and transparent being most esteemed, and fetching often in China their weight in silver.

"These nests are a considerable object of traffic among the Javanese, many of whom are employed in it from their infancy. The birds, after having spent nearly two months in preparing their nests, lay each two eggs, which are hatched in about fifteen days. When the young birds become fledged, it is thought the proper time to seize upon their nests, which is done regularly three times a year, and is effected by means of ladders of bamboo and reeds, by which the people descend into the caverns; but when these are very deep, rope-ladders are preferred. This operation is attended with much danger, and several perish in the attempt. The inhabitants of the mountains generally employed in this business begin always by sacrificing a buffalo, which custom is observed by the Javanese on the eve of every extraordinary enterprise. They also pronounce some prayers, anoint themselves with sweet-scented oil, and smoke the entrance of the cavern with gumbenjamin. Near some of the caverns a tutelar goddess is worshipped, whose priest burns incense, and lays his projecting hands on every person preparing to descend. A flambeau is carefully prepared at the same time, with a gum which exudes from a tree growing in the vicinity, and which is not easily extinguished by fixed air or subterraneous vapours."

"But how are the nests eaten, Uncle Thomas? Are they prepared in any way, or are they fit for use as they are taken down?"

"They are always prepared before they are eaten. The finest sort, which are of a clear colour, and not unlike isinglass, are dissolved in broth, to which they are said to give an exquisite flavour. After being soaked, they are sometimes introduced into the body of a fowl and stewed; but I am not quite versed in all the mysteries of a Chinese kitchen, so you must be satisfied with these two modes of preparation."

"Thank you, Uncle Thomas."

"I have only one more story to tell you about the swallow, Boys, and then I must turn to two or three other animals, whose peregrinations exhibit as strong instances of instinct as it does."

"A swallow's nest, built in the west corner of a window facing the north, was so much softened by the rain beating against it, that it was rendered unfit to support the superincumbent load of five pretty full grown swallows. During a storm the nest fell into the tower corner of the window, leaving the young brood exposed to all the fury of the blast. To save the little creatures from an untimely death, the owner of the house benevolently caused a covering to be thrown over them, till the severity of the storm was past. No sooner had it subsided, than the sages of the colony assembled, fluttering round the window, and hovering over the temporary covering of the fallen nest. As soon as this careful anxiety was observed, the covering was removed, and the utmost joy evinced by the group, on finding the young ones alive and unhurt. After feeding them, the members of this assembled community arranged themselves into working order. Each division taking its appropriate station, commenced instantly to work, and before night-fall they had jointly completed an arched canopy over the young brood in the corner where they lay, and securely covered them against a succeeding blast. Calculating the time occupied by them in performing this piece of architecture, it appeared evident that the young must have perished from cold and hunger, before any single pair could have executed half the job."

"How very kind, Uncle Thomas! Had they been reasoning creatures, they could not have behaved more properly."

"I dare say not, Frank. Such traits overstep the limits of _instinct_, and almost trespass on that of reason."

"You asked, Frank, if it was want of food which prompted the flight of migratory animals from one place to another. In some cases it is so, undoubtedly; as for instance, in that which I am now going to tell you about, the American passenger pigeon; it is from the work of the great naturalist, Wilson.

"The migrations of these pigeons appear to be undertaken rather in quest of food than merely to avoid the cold of the climate; since we find them lingering in the northern regions around Hudson's Bay so late as December, and since their appearance is so casual and irregular, sometimes not visiting certain districts for several years in any considerable numbers, while at other times they are innumerable. I have often witnessed these migrations in the Genesee country, often in Pennsylvania, and also in various parts of Virginia, with amazement; but all that I have seen of them are mere straggling parties, when compared with the congregated millions which I have since beheld in the western forests in the states of Ohio, Kentucky, and the Indiana territory. These fertile and extensive regions abound with the nutritious beech nut, which constitutes the chief food of the wild pigeon. In seasons when these nuts are abundant, corresponding multitudes of pigeons may be confidently expected. It sometimes happens, that having consumed the whole produce of the beech trees in an extensive district, they discover another at the distance of perhaps sixty or eighty miles, to which they regularly repair every morning, and return as regularly in the course of the day, or in the evening, to their place of general rendezvous, or, as it is generally called, the roosting place. These roosting places are always in the wood, and sometimes occupy a large extent of forest. When they have frequented one of these places for some time, the appearance it exhibits is surprising. The ground is covered to the depth of several inches with their droppings; all the tender grass and underwood destroyed; the surface strewed with large limbs of trees, broken down by the weight of the birds clustering one above another, and the trees themselves, for thousand of acres, killed as completely as if girdled with an axe. The marks of this desolation remain for many years on the spot, and numerous places could be pointed out, where for several years after scarcely a single vegetable made its appearance.

"When these roosts are first discovered, the inhabitants from considerable distances visit them in the night with guns, clubs, long poles, pots of sulphur, and various other engines of destruction. In a few hours they fill many sacks, and load their horses with them. By the Indians, a pigeon roost or breeding place is considered an important source of national profit and dependence for the season, and all their active ingenuity is exercised on the occasion. The breeding place differs from the former in its greater extent. In the western countries before mentioned, these are generally in beech woods, and often extend in nearly a straight line across the country for a great way. Not far from Shelbyville, in the state of Kentucky, about five years ago, there was one of these breeding places, which stretched through the woods in nearly a north and south direction, which was several miles in breadth, and was said to be upwards of forty miles in extent. In this tract almost every tree was furnished with nests wherever the branches could accommodate them. The pigeons made their first appearance there about the 10th of April, and left it altogether with their young before the 25th of May.

"As soon as the young were fully grown, and before they left the nests, numerous parties of the inhabitants, from all parts of the adjacent country, came with waggons, axes, beds, cooking utensils, many of them accompanied by the greater part of their families, and encamped for several days in this immense nursery. Several of them informed me that the noise in the woods was so great as to terrify their horses, and that it was difficult for one person to hear another speak without bawling in his ear. The ground was strewed with broken limbs of trees, eggs, and young squab pigeons which had been precipitated from above, and on which herds of hogs were fattening; hawks, buzzards, and eagles were sailing about in great numbers, and seizing the squabs from their nests at pleasure; while from twenty feet upwards to the tops of the trees, the view through the woods presented a perpetual tumult of crowding and fluttering multitudes of pigeons, their wings roaring like thunder, mingled with the frequent crash of falling timber; for now the axemen were at work, cutting down those trees which seemed to be most crowded with nests, and contrived to fell them in such a manner, that in their descent they might bring down several others, by which means the falling of one large tree sometimes produced two hundred squabs, little inferior in size to the old pigeons, and almost one mass of fat. On some single trees, upwards of one hundred nests were found, each containing one young only, a circumstance in the history of this bird not generally known to naturalists. It was dangerous to walk under these fluttering and flying millions, from the frequent fall of large branches, broken down by the weight of the multitudes above, and which in their descent often destroyed numbers of the birds themselves.

"I had left the public road to visit the remains of the breeding place near Shelbyville, and was traversing the woods with my gun on my way to Frankfort, when about one o'clock, the pigeons which I had observed flying the greater part of the morning northerly, began to return in such immense numbers as I never before had witnessed; coming to an opening by the side of a creek called the Benson, where I had a more uninterrupted view, I was astonished at their appearance. They were flying with great steadiness and rapidity, at a height beyond gun-shot, and several strata deep, and so close together, that could shot have reached them, one discharge could not have failed in bringing down several individuals. From right to left as far as the eye could reach, the breadth of this vast procession extended, seeming every where equally crowded. Curious to determine how long this appearance would continue, I took out my watch to note time, and sat down to observe them. It was then half-past one; I sat for more than an hour, but instead of a diminution of this prodigious procession, it seemed rather to increase both in numbers and rapidity, and anxious to reach Frankfort before night, I arose and went on. About four o'clock in the afternoon, I crossed the Kentucky river at the town of Frankfort, at which time the living torrent above my head seemed as numerous and as extensive as ever; and long after this, I observed them in large bodies that continued to pass for six or eight minutes, and these again were followed by other detached bodies, all moving in the same south-east direction, till after six in the evening. The great breadth of front which this mighty multitude preserved would seem to intimate a corresponding breadth of their breeding place, which, by several gentlemen who had lately passed through part of it, was stated to me at several miles. It was said to be in Green County, and that the young began to fly about the middle of March. On the 17th of April, forty-nine miles beyond Danville, and not far from Green River, I crossed this same breeding place, where the nests for more than three miles spotted every tree; the leaves not being yet out, I had a fair prospect of them, and was really astonished at their numbers. A few bodies of pigeons lingered yet in different parts of the woods, the roaring of whose wings was heard in various quarters around me.

"The vast quantity of food which these multitudes consume is a serious loss to the other animals, such as bears, pigs, squirrels, which are dependent on the fruits of the forest. I have taken from the crop of a single wild pigeon a good handful of the kernels of beech nuts intermixed with acorns and chesnuts. To form a rough estimate of the daily consumption of one of these immense flocks, let us first attempt to calculate the numbers above mentioned, as seen in passing between Frankfort and the Indian Territory. If we suppose this column to have been one mile in breadth (and I believe it to have been much more), and that it moved at the rate of one mile in a minute, four hours, the time it continued passing, would make its whole length two hundred and forty miles. Again, supposing that each square yard of this moving body comprehended three pigeons, the square yards in the whole space, multiplied by three, would give two thousand two hundred and thirty millions two hundred and seventy-two thousand pigeons!--an almost incredible multitude, and yet far below the actual amount. Computing each of these to consume half a pint of mast (nuts, and other seeds of trees) daily, the whole quantity, at this rate, would equal seventeen millions four hundred and twenty-four thousand bushels per day! Heaven has wisely and graciously given to these birds rapidity of flight, and a disposition to range over vast uncultivated tracts of the earth; otherwise they must have perished in the districts where they resided, or devoured the whole productions of agriculture, as well as those of the forests.

"The appearance of large detached flocks of these birds in the air, and the various evolutions they display, are strikingly picturesque and interesting. In descending the Ohio by myself, I often rested on my oars to contemplate their aerial manoeuvres. A column of eight or ten miles in length would appear from Kentucky high in air, steering across to Indiana. The leaders of this great body would sometimes gradually vary their course, till it formed a large bend of more than a mile in diameter, those behind tracing the exact route of their predecessors. This would continue sometimes long after both extremities were beyond the reach of sight; so that the whole with its glittering undulations marked a space on the face of the heavens resembling the windings of a vast majestic river. When this bend became very great, the birds, as if sensible of the unnecessarily circuitous route they were taking, suddenly changed their direction, so that what was in column before became an immense front, straightening all its indentures until it swept the heavens in one vast and infinitely extended line. Other lesser bodies also united with each other as they happened to approach, and with such ease and elegance of evolution, forming new figures and varying these as they united or separated, that I was never tired of contemplating them. Sometimes a hawk would sweep on a particular part of the column from a great height, when almost as quick as lightning that part shot downwards out of the common track, but soon rising again, continued advancing at the same height as before. This inflection was continued by those behind, who, on arriving at this point, dived down almost perpendicularly to a great depth, and, rising, followed the exact path of those that went before.

"Happening to go ashore one charming afternoon to purchase some milk at a house that stood near the river, and while talking with the people within doors, I was suddenly struck with astonishment at a loud rushing roar, succeeded by instant darkness, which for the first moment I took for a tornado about to overwhelm the house, and every thing around, in destruction. The people observing my surprise, coolly said, 'It is only the pigeons,' and on running out, I beheld a flock thirty or forty yards in width, sweeping along very low between the house and the mountain or height that formed the second bank of the river. These continued crossing for more than a quarter of an hour, and at length varied their bearing, so as to pass over the mountain, behind which they disappeared before the rear came up."

"That is amazing, Uncle Thomas; two thousand millions of live birds! I can scarcely form an adequate idea of such a mass of living creatures."

"There is something almost overwhelming in the idea, Frank; and yet in some parts of the world are to be found flocks of animals hardly less surprisingly numerous, when we consider how much less they are fitted for moving about, travelling at stated intervals from the mountains to the sea coast, and returning again to their old habitations, after having fulfilled the purposes for which this instinctive feeling was implanted in them."

"Which animals do you mean, Uncle Thomas?"

"I allude to the land-crab, which is a native of the Bahamas, and also of most of the other islands between the tropics. They live in clefts of the rocks, or holes which they dig for themselves among the mountains, and subsist on vegetables. About the months of April and May, they descend to the sea coast in a body of millions at a time, for the purpose of depositing their spawn. They march in a direct line towards their destination, and seldom turn out of their way, even should they encounter a wall or a house, but boldly attempt to scale it. If, however, they arrive at a river, they wind along the course of the stream, and thus reach the sea.

"In their procession they are as regular as an army under the command of an experienced general, and are usually divided into three battalions. The first body consists of the strongest males, which march forward to clear the route and face the greatest dangers. The main body is composed of females, which are formed into columns, sometimes extending fifty or sixty yards in breadth and three miles in depth. Three or four days after these follows the third division or rear guard, a straggling undisciplined tribe, consisting both of males and females, but neither so robust nor so vigorous as the former.

"Though easily drowned, a certain proportion of moisture seems necessary to the existence of these animals, and the advanced guard is often obliged to halt from the want of rain. The females, indeed, never leave the mountains till the rainy season has fairly set in. They march chiefly during the night, but if it happens to rain during the day, they always profit by it. When the sun is hot they halt till evening. They march very slowly, and are sometimes three months in gaining the shore. When alarmed they run in a confused and disorderly manner, holding up and clattering their nippers with a threatening attitude, and if suffered to take hold of the hand they bite severely. If in their journey any of them should be so maimed as to be unable to proceed, the others fall upon it and devour it.

"Arrived at the coast, they prepare to cast their spawn. They go to the edge of the water, and suffer the waves to wash twice or thrice over their bodies, and then withdraw to seek a lodging upon the land. After a short time the spawn becomes ready for being deposited, when they again seek the sea-side, and leave the spawn to be brought to maturity by the heat of the sun. Much of the spawn, which exactly resembles the roe of a herring, is devoured by the fishes; that which escapes soon arrives at maturity, and millions of little crabs are then to be seen slowly travelling towards the mountains.

"The old ones in the mean time seek to return to their old haunts, but so feeble are they that they seem scarcely able to crawl along. Some of them, indeed, are obliged to remain in the level parts of the country till they recover, making holes in the earth, which they block up with leaves and dirt. In these they cast their old shells, after which they soon recover, and become so fat as to be delicious food.

"At the season of their descent from the mountains, the natives of the islands which they inhabit, eagerly wait for them and destroy them in thousands. On their descent they are only taken for the roe or spawn, the flesh being then poor and lean: on their return from the sea-side they are in greatest repute, being then fat and high flavoured.

"The crab-catchers adopt various modes of securing them, but they are obliged to be very cautious, for when the animals perceive themselves attacked, they throw themselves on their back, and snap their claws about, pinching whatever they lay hold of very severely. The crab-catchers, however, soon learn to seize them by the hind legs, in such a manner as that the nippers cannot reach them."

"You said, Uncle Thomas, that the fishes watched the descent of the crabs, that they might feed on the spawn. Do you think that they are endowed with reasoning powers, as well as the higher classes of animals, Uncle Thomas?"

"No doubt of it, Frank. Old Isaac Walton, the most amusing author on angling who ever wrote, tells many curious stories about fishes, of their coming to be fed at the sound of a bell, and so forth.

"Many fishes exhibit the migratory instinct quite as distinctly as those animals which I have just told you about. The salmon leaves the sea, and seeks its way up the rivers, stemming their most rapid currents, and scaling highest waterfalls with a pertinacity which can only be the result of an instinct implanted in them by their Creator."

"And the herring, Uncle Thomas; does not it come every year from the Polar seas to spawn on our shores? I read a very interesting account of their progress southwards somewhere lately."

"I can tell you where, Frank; I will show it you, and when you have read it aloud, I will point out one or two mistakes, which it is as well to clear your mind of. It is in old Pennant's work; here it is; will you read it to us, John?"

"With pleasure, Uncle Thomas.

"This mighty army begins to put itself in motion in the spring. They begin to appear off the Shetland Islands in April and May. This is the first check this army meets in its march southward. There it is divided into two parts; one wing of those destined to visit the Scottish coast takes to the east, the other to the western shores of Great Britain, and fill every bay and creek with their numbers; others proceed towards Yarmouth, the great and ancient mart of herrings; they then pass through the British channel, and after that in a manner disappear. Those which take to the west, after offering themselves to the Hebrides, where the great stationary fishery is, proceed towards the north of Ireland, where they meet with a second interruption and are obliged to make a second division; the one takes to the western side and is scarcely perceived, being soon lost in the immensity of the Atlantic, but the other, which passes into the Irish sea, rejoins, and feeds the inhabitants of most of the coasts that border on it. The brigades, as we call them, which are separated from the greater columns, are often capricious in their motions, and do not show an invariable attachment to their haunts."

"Thank you, John. Now all this sounds very fine, and seems very systematic. It has but one objection--it is quite untrue. It is in the first place more than doubtful if the herring frequents the Polar seas at all; and in the second place, the most distinguished naturalists are of opinion that it never leaves the neighbourhood of our own shores, but merely retires to the deep water after it has spawned, and there remains till the return of another season calls it again to the shores to undergo a similar operation. So you see, Frank, it does not follow that an interesting account of an animal's habits is necessarily a true one."