A

DISCOURSE

ON THE

EMIGRATION OF BRITISH BIRDS;

OR,

THIS QUESTION AT LAST SOLVED,

Whence come the Stork, and the Turtle, the Crane, and the Swallow; when they know, and observe, the appointed Time of their Coming?

OF SUMMER BIRDS OF PASSAGE.

As our little migratory summer visitants are most numerous, and the most remarkable for their regular annual appearance; as they have in every clime, and every country, more attracted the notice of mankind, we think proper to begin with them; and first of the Swallow tribes.

Before we offer to the reader's consideration our own opinion, concerning the manner these, and other summer birds of passage, dispose of themselves in the bleak and gloomy season, we shall, pursuant to our proposal, lay before him the many chimerical notions, the many groundless conjectures, the many foolish, unreasonable, impertinent, and incongruous hypotheses, which have, from time to time, been advanced * on this topic. We shall not only mention the tales which superstition has raised, or credulity received, but also the sentiments and observations of substantial creditable authors; particularly of those learned naturalists, whose works are an honour to themselves, and a treasure to the British nation.

*We beg to be excused for introducing a legion of inconsistent fables, which, in merit, are hardly worth perusal. Our intention here is not to convince, by argumentative proofs, but only to amuse and entertain the reader, by reciting, and exploding the variety of laughable suppositions and glaring errors, which have from time to time appeared. Indeed, I am no advocate for burlesque, but I cannot repress the humoursome passion on such a ludicrous occasion.

1

Among naturalists, there are four opinions how these birds encounter the winter. The first is supported by great antiquity, which is, that they hide themselves in hollow trees, in caverns of rocks, in sand-pits, in old buildings, under the earth, &c. Here they are supposed to continue in a torpid state; have no sensible evacuations; breathe little, or not at all; and most of the viscera cease from their functions. In this condition they are said to remain, till, by length of time maturating the process, or by new heats, the fluids are attenuated, the solids are stimulated, and the functions begin where they left off.

Aristotle and Pliny are strenuous advocates for this conjec ture; their accounts, though not invariably the same, almost entirely coincide. They assert, that swallows do not remove to warmer climes, but either retreat into sand-banks, or winter in the hollows of rocks, and lose their plumage during that period. Many reputable naturalists have adopted the former part of their opinion, and pretend to affirm that some species have been discovered in a torpid state. Thus one in particular delivers it as a fact, that heaps of swallows have been found lying in the cliffs of the rocks that impend over the sea: it is also said, these birds have been discovered in the chalky cliffs of Suffolk, at the fall of a great fragment some time since. In many other places, (Mr. Pennant saithy they have been found, but I will not vouch for the truth of it; as first, in a decayed hollow tree, that was cut down near Dolgelie, in Merionethshire; secondly, in a cliff near Whitby in Yorkshire, where, in digging out a fox, whole bushels of swallows were found in a torpid condition; thirdly, in an old lead mine, in Flintshire, vast numbers of swallows, it is said, were seen clinging to the timber of the shafts, seemingly asleep; on flinging some gravel on them, they just moved,

*Mr. Pennant, to whom this account was transmitted, thinks: there is a partial migration of these birds; he is of opinion, that the majority of them remove to distant countries, and that the feeble, late hatches conceal themselves in this island all the winter.

He endeavours to strengthen this supposition by arguments very unphilosophical, and not at all satisfactory.If it should (saith this. writer) be demanded, why swallows alone are found in a torpid state, and not the other many species of soft billed birds, which disappear about the same time, the following reasons may be as-. signed: no birds are so much on wing as swallows; none fly with such swiftness and rapidity; none are obliged to such sudden and various evolutions, in their flight, none are at such pains to take their prey; none exert their voices more incessantly;, all these occasion a vast expense of strength and spirits, and may give such a texture to the blood, as other animals cannot experience; and so

but never attempted to fly, or change their situation. Klein also gives an instance of swifts being found in a torpid state. *· The following account of some swallows on the Rhine, was communicated to Mr. Peter Collinson, by Mr. Achard, and was read before the Royal Society the twenty-first of April, 1763.

"In the latter end of March," says he "I took my passage down the Rhine, to Rotterdam. A little below Basil, the south bank of the river was very high and steep, of a sandy soil, sixty or eighty feet above the water."

"I was surprised at seeing, near the top of the cliff, some boys tied to ropes, hanging down, doing something. The singularity of these adventurous boys, and the business they so daringly attempted, made us stop our navigation, to inquire into the meaning of it. The watermen told us, they were searching the holes in the cliffs for swallows, or martins, which took refuge in them, and remained there all the winter, until warm weather, and then they came abroad."

"The boys being let down by their comrades to the holes, put in a long rammer, with a screw at the end, such as is used. to unload guns, and, twisting it about, drew out the birds. For a trifle I procured some of them. When I first had them, they seemed stiff and lifeless; I put one of them in my bosom between my skin and shirt, and laid another on a board, the sun shining full and warm upon it; and one or two of my companions did the like.

"That in my bosom revived in about a quarter of an hour; feeling it move, I took it out to look at it, and saw it stretch itself upon iny hand; but perceiving it not sufficiently come to itself, I put it in again; in about another quarter, feeling it flutter pretty briskly, I took it out, and admired it. Being now perfectly recovered, before I was aware, it took flight; the covering of the boat prevented my seeing where it went.. The bird on the board, though exposed to a full sun, yet I' presume, from a chillness of the air, did not revive so as to be able to fly."

Such is this gentleman's account, on which the following observations were made by Mr. Collinson:

"What I collect from Mr. Achard's relation is, that it was the practice of the boys annually to take these birds, by their apparatus, and ready method of doing it; and, the frequency

dispose, or we may say, necessitate this tribe of birds, or part of them at least, to a repose more lasting than that of any other. British Zoology.

*Hist. Av. 204..

of it was no remarkable thing to the watermen; next, it confirmed my former sentiments, that some of the swallow tribe go away, and some stay behind, in these dormitories, all the winter. If my friend had been particular as to the species, it would have settled that point."

Notwithstanding the authority of Aristotle, Pliny, Klein, Penuant, Achard, and others, we cannot assent to the above cirsumstances, viz. that swallows lie torpid in caverns of rocks, hollow trees, &c. The innumerable testimonies of an opposite nature, which continually croud in upon us, sufficiently convince us that this conjecture, which so many have adhered to, and which has so long been maintained, is in reality only a superstitious error. The internal conformation of swallows, is a proof that they cannot remain dormant during the winter. Anatomists inform us, that all those animals which are designed by nature for a temporary torpidity, have something in their make different from others, to fit them for that condition, and enable them to remain so long a timewithout sustenance. This is not the case with any of our summer emigrants, as has been proved by experiment. *

The birds seen by Mr. Achard, at the latter end of March, we presume, were only sand-martins, which are a species that arrive very early in this country, and at their first coming, always repair to the sand-banks, &c. where they continue the whole summer. Possibly they were scooping out their respective apartments to breed, and nestle in, when they were taken by the boys, and instead of being benumbed by the cold, as was imagined, might only be hurt by the cruel method of drawing them out of the holes. +

* See page 183.

+ As this occurrence, which Mr. Achard relates, happened at the latter end of March, it is pretty obvious the species seen at that time were sand-martins. For at this period (unles the spring proves remarkably backward) the greater part of this tribe have reached our island. Swallows, house-martins, and sometimes swifts, are seen in our country flying about the air in great numbers at the latter end of March; and frequently the majority of these birds, as well as the rest of our summer guests, are arrived at that time. Undoubtedly, therefore, the species observed by this gentleman was the same as we have conjectured above. But we will suppose, did swallows actually lie torpid during the winter, the genial season. would certainly have called them abroad before the latter end of March, and it would be very extraordinary to find a single one wrapt. up, sleeping in its winter dormitory, so late in the season. What then can be more plain, than that our assertion, in contradistinction to that of Mr. Achard's, right, is just? Beside, as a farther demonstration of the truth of what, we have advanced, I have fre

We do not deny but that there are undeniable instances of a few being found in a dormant state, at the beginning of winter; but in all probability they were only stragglers, which were hatched too late to join in the general emigration. Incapable of assembling with the great rendezvous, like bats at the commencement of the frigid season, these young birds flit, and wander about, till pinched by the cold inclement air, for a transient shelter, they retreat into antique buildings, hollow trees, under the eaves of houses, &c. or find their way into some obscure recess, where they continue motionless, insensible, and rigid for several days, or perhaps weeks, before they expire. Often these unfortunate stragglers are reanimated by an unseasonable hot day, leave their hidingplaces, and are seen skimming the air in pursuit of flies. So late as the middle of November, which is full a month after the departure of the majority of the tribe, I have frequently observed a straggler or two, either perched in the sun, fluttering about wildly from place to place, or feebly sweeping the atmosphere for food. Extraordinary as it may appear, on the 3d of December, 1771, I saw a martin fiying about as vigorously as though it had been in the midst of summer. My curiosity was greatly excited at this remarkable phenomenon.* For a considerable while I was unable to account for it, and could not imagine from whence it came, or how it could preserve itself so long. To say it remained torpid for upwards of two months, would be talking extravagantly and inadvertently; or to assert, that it had taken it's long excursion over the ocean from a remote clime, would be equally as unreasonable and unphilosophical. Having since maturely and deeply considered this occurrence, I believe I have at last attained the general solution, which is, that it was a bird bred here, and being left behind at the migration of the rest, made a shift to support itself in our country for a considerable time. This is still the more probable, as the two months

quently seen near my residence, (a) sand-martins drawn out of lofty sand-banks by boys, as early in the season, and with the same apparatus, as that described by Mr. Achard. The birds taken in this manner were undoubtedly retired to those recesses for the purposes of building; and I cannot entertain that wild, that ridiculous notion, that they had lain there all the winter.

Having then made no researches in natural history, and being quite a novice in ornithology, I must confess I was inclined to believe that martins, swallows, &c. laid motionless all the winter; but now innumerable evidences of an opposite nature convince me of the contrary.

(4) i. e. At Market-Lavington, in Wiltshire.