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[Annotation by Darwin:] P. Duncan "Literary Conglomerate" & Rate of flight of Birds

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with large tubs of water, containing reeds, on which they are said to cluster before submersion; but none attempted to enter it." Pennant gives credit to the idle tales respecting the torpidity of swallows, and attributes the peculiarity of their being found torpid, and no other soft-billed immigrant birds, to their continual flight, and consequent exhaustion. Aristotle, Pliny, Olaus Magnus, an archbishop, Etmuller, Collinson, and Achard, all assert that swallows are torpid in winter, and are found under water. The good archbishop was persuaded not only that swallows live under water, but that the clouds occasionally pour down mice. "It is enough," says Mr. Edwards, "to raise one's indignation, to see so many vouchers from so many assertors of this foolish and erroneous conjecture, which is not only repugnant to reason, but to all the known laws of nature."

In the year 1740 a pamphlet was published, asserting that swallows emigrate to the moon. The author gravely calculates that they are two months in going thither; and that, when they have passed our atmosphere into the thin æther, they have no occasion for food: he adds that, as these birds are very succulent and sanguine, their provisions are laid up in their bodies for

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their voyage; and, moreover, that they are in a kind of sleep or insensibility the greatest part of the journey. Reaumur says, many persons promised to send him swallows so benumbed, but no one kept his promise.

Animals retire to depths only which are within the variation of heat. The temperature of the earth, at eighty feet below the surface, is said to be the same all the year round; but at twenty feet, the temperature of the earth is not at its maximum till October, or at its minimum till March. Summer birds are never found slumbering with torpid animals. Swallows and small birds, hawks and owls, have been frequently known to alight on the masts, shrouds, and sails of ships, in their passage from one land to another. Adanson says that swallows arrive in Africa, on the coast of Senegal, in October, (the time when they quit Europe,) and leave it in April, never breeding there. Thus we can have no doubt of their destination in their autumn flights. The swallow is seen at Athens about the 18th of February; at Rome, (lat. 41,) on the 22nd of February; at Piacenza, (lat. 45,) March 20 ; at Tzaritza, (lat. 48,) April 4; at Catsfield, East Sussex, (lat. 51,) April 14; at Kendal, (lat.54,) April 17; and at Upsal, (lat.59,)

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May 9. This route of the swallow, toward the arctic circle, shows that the bird does not rely on its agility, and loiter in the torrid zone longer than is necessary. On the contrary, it travels slowly from climate to climate, until the sun is in seventeen or eighteen degrees of northern declination, and spring has made considerable advances in the ungenial climate of Sweden. The sand-martin, hirundo riparia, is commonly seen at the mouth of the river Kent, six or seven days before it arrives at Kendal, though the distance does not exceed six miles; but the town lies near the mountains, and the air is colder at that part of the valley than at the estuary.

Athenæus alludes to a custom of collecting alms on the arrival of the swallow in Athens, which practice was called chelidonizing, swallowizing. It was always accompanied (like our Christmas carols) with a hymn, of the beginning of which the following is a translation:

The swallow, the swallow is here,

With his wings all black, and his bosom all white,

He brings on the pride of the year,

With the gay months of love, and the days of delight.

Of the four species of swallows which are seen in England, the sand-martin arrives first,

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the chimney-swallow next, then the house-martin, and lastly the swift, which departs much sooner than the other three. On which Mr. White observes, "How strange it is, that the swift, which seems to live exactly the same life with the swallow and house-martin, should leave us before the middle of August invariably; while the latter stay often till the middle of October, and once I saw numbers of house-martins on the 7th of November. The martins, redwings, and fieldfares, were flying together;— an uncommon assemblage of summer and winter birds."

Thomson gives the following beautiful description of the departure of the swallow.

When Autumn scatters his departing gleams,

Warn'd of approaching winter, gather'd, play

The swallow people; and toss'd wide around,

O'er the calm sky, in convolution swift,

The feather'd eddy floats: rejoicing once,

Ere to their wintry slumbers they retire;

In clusters clung, beneath the mouldering bank,

And where, unpierc'd by frost, the cavern sweats.

Or rather, into warmer climes convey'd,

With other kindred birds of season, there

They twitter cheerful, till the vernal months

Invite them welcome back: for thronging, now

Innumerous wings are in commotion all.

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Swallows are said to forsake Rome during the malaria.

Different species of birds travel in distinct parties, according to their want of food, resembling in their flight the legions of a numerous army marching in different directions, the whole body being in motion together, south and north. They travel generally by night, and by moon-light, and not in misty dark nights, as Pennant affirms. When clouds have eclipsed the moon, they have been known to direct their course towards beacon lights, and many have been found dashed to pieces, by striking against them, at Cromer and other places. They generally fly high in the air, and, when the wind is not too strong, against the wind. They assume different figures in their flight; as the poet of nature observes, they

In figure wedge their way,

Intelligent of seasons, and set forth

Their airy caravan, high over seas

Flying, and over lands.

So steers the prudent crane

Her annual voyage, borne on winds; the air

Floats as they pass, fann'd, by unnumber'd plumes.

Another poet asks,

Who calls the council, states the certain day?

Who forms the phalanx, and who points the way?

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Starlings exhibit much variety and intricacy of evolutions, in their flight. They form themselves, perhaps, into a triangle, then shoot into a long pear-shaped figure, expand like a sheet, wheel into a ball, each individual striving to get into the centre, &c. with a promptitude more like parade movements than the action of birds. Wild-geese frequently fly in the figure of 7: some birds so much in a line, as to give rise to a ridiculous idea that they mutually rest their long necks on each other's backs. Larks, linnets, sparrows, and other small congregating birds, fly confusedly, without any form and order.

Birds are admirably constructed for flight, with strong pectoral muscles, hollow bones full of air cells, and feathers; and all of these most wonderfully contrived, when their wings are expanded, to support them in the air. The different species are, however, endowed with very different powers of flying; some, like the albatross, man-of-war bird, eagles, hawks, gulls, terns, and swallows, being able to keep long on the wing, and fly with great rapidity; others, like the ostrich, rails, and grebes, fly with difficulty, and short distances.

Observations of the rate of the flight of some

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birds have been made, but with what accuracy I know not. It has been said that a hawk can fly above 150 miles an hour. A falcon which escaped from Henry the Fourth's falconer at Milan, was caught, within twenty-four hours afterward, at Malta, 800 miles distant. As it is supposed not to have flown by night, it may have arrived some time before it was caught; and therefore probably travelled at the rate above mentioned. Colonel Thornton estimated the flight of a falcon in pursuit of a snipe, at nine miles in eleven minutes, not including the frequent turns. Mr. Cartwright took notice of the rate of an eider-duck, no very swift flyer, and found it to be at the rate of ninety miles an hour. Carrier-pigeons, which have been conveyed to a distance, and released for a wager, have returned at the rate of sixty miles an hour. The flight of the hirundo apus, or swift, must be much more rapid than that of the pigeon, and probably more than that of our swiftest hawk, for a short distance. The velocity of a bird's flight most probably depends on its specific levity, the extent of its wings in proportion to its body, and the surface which they present to the air; as may be noted in the

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swiftest birds, the albatross and frigate-bird: but this velocity depends, more particularly, on the strength and voluntary power inherent in the pectoral muscles. The most rapid and continuous animal motion, that I can conceive, is exhibited in very small animals, the sphynges and libellulæ. Too little has been hitherto observed on this subject, to know whether birds always rest in their flights from the interior of land to the sea-shore, before they take their course over the sea; or whether they proceed continuously on the wing, when they have once commenced their migration. Some observations have led to the conclusion, that some secret intelligence guides them to take the shortest route over seas, when not blown out of their course by high winds, through which it is probable that many perish in the ocean.

What is this secret instinct or intelligence, which guides birds in their destined course with such unerring certainty, so as not only to go or return to the same countries, but some of them even to the same spots which they have before visited,—is a subject which baffles the ingenuity of human inquiry.

A migratory bird, kept in a cage, will exhibit

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great efforts to escape, at the period of the migrations of his fellow birds; but at other times will remain quiet and contented in his prison.

The author of the Journal of a Naturalist observes, "Though we rarely see these birds in their transits, yet I have at times in a calm bright evening in November heard, high in the air, the redwing and the fieldfare on progress to a destined settlement, manifested by the signal notes of some leading birds to their scattered followers. These conductors of their flocks are certainly birds acquainted with the country over which they travel, their settlements here being no promiscuous dispersion; it being obvious that many pairs of birds return to their antient haunts, either old ones which had bred there, or their offspring. The butcher-bird successively returns to a hedge in one of my fields, influenced by some advantage it derives from that situation, or from a preference to the spot where hatched: but we have perhaps no bird more attached to particular situations than the gray fly-catcher; one pair, or their descendants, frequenting year after year the same hole in the wall.

"Enamour'd with their antient haunts,

"They hover round the well-known spot."

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Some have attributed their movements to the memory and experience of old birds, who act as guides; some, to acute observation and extensive powers of vision; others, to observation of the situation of the sun; but most, to an inexplicable instinct. The succession in which birds of passage arrive, has been a frequent object of investigation by naturalists.b

In this country, one of our earliest visitors is the wryneck; then the four species of swallows: of which the hirundo riparia, or sand-martin, arrives a week generally before the others; then hirundo urbica, the chimney-swallow; and with it, or shortly afterwards, the hirundo domestica; the last, hirundo apus, seldom appears till ten days after the others. The redstart, petty-chaps, black-cap, and other of the sylviadæ, arrive before the nightingale. The retreat of the cuckoo and wryneck is not known. Some fly-catching birds stay with us all the year, as the common wren, and the little golden-crested wren and wagtails. "The instinct of the swallow is indeed wonderful; it appears amongst us just at the time when insects become numerous and most troublesome, and continues with us

b For the autumnal migration of the sylviadæ, see London Magazine for January, 1830, No. xi.

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during the hot weather, in order to prevent them from multiplying too much. It disappears when these insects are no longer troublesome. It is never found in solitude: it is the friend of man, and always takes up its abode with us, that it may protect our houses and streets from being annoyed by swarms of flies." Their departure seems to be more irregular as to dates than their arrival, depending upon a climate more uncertain than that which they leave. Many birds congregate in vast flocks before departure, as swallows in this country. Migrating pigeons in America (a pleasing but melancholy sight) fly in such flocks, as not only to destroy all the crops where they alight, but to break down the boughs of trees on which they perch. Other birds, like the warblers, rails, quails, and cuckoos, seem to steal away imperceptibly.

Some birds make only short migrations, of which it is extremely difficult to assign the reason. Chaffinches, for example, which remain in France and Germany the greater part of the year, pass in great numbers into Holland in October and November; but they never breed there. The hen chaffinches only migrate from Sweden; whence the name of fringilla cælebs.

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Linnets change their residence in this country, from south to north alternately.

In the last edition of Bewick's Birds is a curious account of a swallow, communicated by the Rev. W. Trevylian, of Henbury. "It fell down a chimney, was caught and fed with flies, and became so tame as to perch on the head of the lady of the house for a long time. It was equally familiar with the other ladies of the family, and would take flies on the wing out of their hands when standing in a row or a circle. It would come from long distances when called, and remained with them during the autumn, a fortnight after other swallows had migrated; possibly too long, for, as it never was seen in the ensuing summer, it not improbably fell a victim to its gratitude and attachment." Nightingales, in their migrations to this island, are confined to the southern counties. Storks lay eggs twice a year, and being migrators, they lay one set of eggs in Africa, and another in Europe; acting like our tars, who are said not unfrequently to have families in different countries. "Storks in Smyrna are well aware of the predilection of the Turks for their preservation. They build their nests on the minarets, and on

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Turkish houses, and to them in their migratory existence they return year after year, but the dolce nido is never erected on a Christian roof." (Macfarlane's Travels in Turkey.) The Turks fancy they would migrate with them wherever they conquered. The inundation of rivers is said to influence the migration of ducks. Mr. Blackwall thinks that moulting has also a great influence on the movements of many birds.

Teminck has published the most accurate detail of the observations which have been made respecting their migration. Latham enumerates 4000 species of birds, but it is supposed that at least 5000 have been named. The northern zone does not contain more than 500. Wilson, in his American Ornithology, enumerates 400 in the United States, many of them like those of Europe. Most of the birds of Northern Africa are migratory, so the catalogue of that division is small. Southern Africa has about 500 species. The equatorial regions of Africa, not above 300. The equatorial regions of America, above 1000. India, 400. The Indian Isles, 1000. New Holland, 300. Many birds, as the egret, the stork, the ruffs, and others, have been scared from this island, by increased population of men, and increased cultivation of the soil. Bustards are

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nearly exterminated. The capercailly, or wood grouse, is now no longer found in Scotland. Snipes and woodcocks are not found in such abundance as formerly. The flamingo, which was formerly found in Italy, is now no more seen there, and, I believe, but little in the old world, though common in South America. The most migratory of all birds are the web-footed birds, the goose and duck tribe, as they can easily rest on the waves of the sea in their passage. Their visits to our coast depend on the severity of the winter.

Dr. Schinz, secretary to the provincial society of Zurich, has endeavoured to discover the laws according to which European birds are distributed. The country in which the bird produces its young is considered its proper one. The nigher the poles, the more do we find peculiar or stationary birds, and the fewer are the foreign species which appear. Greenland has not one bird of passage. Iceland has only one, which remains during the winter, and in spring takes its flight to still more southern regions. Sweden and Norway have more, and we find them still more numerous as we approach toward the centre of Europe. In the intertropical countries no bird emigrates. To the north of them they

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all do. Their propagation keeps pace with the supply of food. Spitzbergen has only one herbivorous species; for the sea affords more nutriment, and the rocks are populous with aquatic birds. In the frigid zone a much greater number of marsh birds is bred, than beyond the arctic circle, and in the warm countries of Europe. Snipes and woodcocks, which leave us in the spring, resort to northern regions, for a more abundant supply of food. In the East Indies, snipes are found in great abundance at all times of the year, in the marshy places.

Having given the foregoing account of the migrations of birds, I now proceed to that of fishes; which we must suppose to proceed from the same motives,—food, temperature, and breeding.

The migrations of fishes, which have attracted the most notice, are those from which we have derived the greatest benefit, such as those of the herrings, pilchards, salmons, and mackerel. Herrings are found in the highest northern latitudes, and as low as the northern coasts of France; but, except in one instance, brought by Dodd, of a few being caught in the bay of Tangier, none are ever found more southerly. They are met with in vast shoals on

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the coast of America, as low as Carolina. In Chesapeak bay, there is an annual inundation of these fish, which cover the shores in such quantities, as to become a nuisance. We find them again in the Chinese sea, and they probably reach Japan. The great winter residence of the herrings is within the arctic circle; there they continue for many months, in order to recruit themselves after the fatigue of spawning; the seas within that space swarming with their proper food, in far greater degree than those of our warmer latitudes. The mighty army puts itself in motion in the spring. They begin to appear off the Shetland Islands in April and May; but these are only the forerunners of the great shoal which arrives in June. Their approach is recognized by particular signs, such as the appearance of certain fishes, and of vast numbers of gannets and gulls, which follow the shoals, to prey on the herrings. But when the great body arrives, its breadth and depth is so great, as to change the appearance of the ocean itself. Sometimes they sink or disappear for ten or fifteen minutes, and then they rise again toward the surface. When the sun shines,

c The word heer, from whence our word herring, signifies an army in German and Anglo-Saxon.