“I do not recollect,” said my uncle; “but if I am right in my ideas of their swiftness, the widest part of that sea would be the affair of a few hours. It has been estimated that a swallow usually flies a mile in a minute; and sixteen or seventeen hours daylight will give about a thousand miles for a single day’s journey at that velocity. Now when you recollect that here we see those birds continue on the wing the whole day without the least appearance of being tired, we can only account for the extraordinary fatigue of those which perched on the Colonel’s ship, by supposing their flight to have continued for several days; and thus three or four days’ exertion might have brought them from a country bordering on the southern tropic.”
I reminded my uncle of the account we had lately read in Dr. Brewster’s Journal of Science, about the rapid flight of the wild pigeons that cross America in search of food.
“Yes,” said he, “and there is a curious fact recorded in that paper, which satisfactorily demonstrates, that the sustained velocity with which some birds remove from one district to another, in search of food, is not confined to the instinctive energy which belongs to the time of annual migration, but that it is their habitual and daily practice. The circumstance to which I allude is this: pigeons have been killed in New York, whose craws were still filled with fresh rice, which must have been collected in Carolina; and, therefore, as the pigeon digests its food very quickly, they could have been but a few hours performing a journey of three hundred miles. But we need not go so far off for examples of the ease and rapidity with which pigeons go to great distances in quest of some favourite food; for it is well known that in the vetch season in Norfolk, the Dutch pigeons come over in the morning, and return to Holland in the evening.”
Mary shewed us a passage in the voyage of La Pérouse, which proves that swallows do go a long way to the southward. “A swallow of the common species, undoubtedly lately come from Europe, followed us for some time without alighting on the vessel, but soon directed its flight towards the African coast, where it was sure of finding the insects on which it feeds. We were in 28° N. lat., and 22° W. long.” Adanson also asserts that he witnessed the arrival on the coast of Senegal, on the 6th of October, in the evening, of real European swallows; and he ascertained that they are never seen there but in autumn and winter.
My aunt has often observed them collected in large companies on trees, and on the roofs of houses, previous to their flight in September; and the direction they take at that season is to the southward.
My uncle then told us, that his old and highly respected friend Dr. Jenner, who, you know, lived just on the other side of the Severn, used to remark, that if swallows really did creep into holes and crevices to hibernate, they would surely appear in a languid state when they came out again—in the same way that all those quadrupeds who pass the winter in a state of torpor, are very much emaciated when they revive. The hedgehog, for instance, at the approach of winter, retires to its nest covered with fat, which is entirely absorbed when it awakens on the return of spring; whereas when the swallows appear in April, they are plump and strong upon the wing.
Mary added, that swallows have two broods during the summer, and that she had somewhere read, that it was only the strong early brood that took flight to warmer regions; but that the young birds hatched late in the year, being incapable of distant migration, seek shelter in holes and hollow trees, and wherever they can lurk in safety in the winter.
Mary afterwards shewed me a passage about swallows in Latrobe’s Journal, a book which I have more than once mentioned to you. He writes from the settlement of Groenkloof, to the north of Cape Town.
“Every morning I am greeted by the pleasant chirping of two swallows which have a nest in the corner of my room, under the ceiling. There is hardly a room, kitchen, or outhouse, in the country, without these inmates, and it would be thought next to murder to kill them. They build their nests of clay in the shape of a bottle; they line them with the softest down, and, though they leave the country during the winter, the same birds always return to the same nests after their emigration. As the room doors usually stand open in the day, they go in and out whenever they please; but if the door is shut, they give notice of their wish to go abroad, by a gentle piping and flying about the room; and no one thinks it troublesome to let them out: indeed, I have often left my bed to open the door for them.”
I forgot to mention that my uncle told us there was no country in the world which was not visited by these little swift-winged creatures. They were seen, for a short time, even in the frozen regions of Baffin’s Bay and Melville Island; and Captain Franklin says, they made their first appearance at Great Bear Lake the middle of May, to feast on the mosquitoes and other insects that abound on the northern shores of America. Wentworth says, they may be literally called cosmopolites.