It has often excited in the minds of some, how migrating birds could support themselves so long on wing, so as to accomplish their journies, and at the same time live without food during their voyage. These circum stances have induced many to deny the existence of mi gration, and has excited others to form the most extrava gant theories on the subject, to account for the preserva tion of these birds during the winter months. But the dif ficulties which have been stated, are only in appearance, and vanish altogether if we attend to the rapidity of the flight of birds.
The rapidity with which a hawk and many other birds occasionally fly, is probably not less than at the rate of one hundred and fifty miles in an hour. Major Cartwright, on the coast of Lab•adore, found, by repeated observations, that the flight of an eider duck (4nas mollissima) was at the rate of ninety miles an hour. Besides, it is generally known, that a falcon which belonged to Henry the Fourth of France, escaped from Fontainbleau, and in twenty-four hours afterwards was found at Alalta, a distance computed to be no less than thirteen hundred and fifty miles ; a ve locity to fifty-seven miles an hour, supposing the falcon to have been on wing the whole time. But as such birds never fly by night, and allowing the day to be at the longest, his flight was perhaps equal to seventy-five miles an hour. It is probable, however, says Montagu, that he neither had so many hours of light in the twenty four to perform his journey, nor that he was retaken the moment of his arrit al. But if we es en restrict the migra tory flight of birds to the rate of fifty miles an hour, how easily can they perform their most extensive migrations And we know, in the case of woodcocks, and perhaps all other migrating birds, that they r.II general take advantar. of a fair wind with which to perform their flights. This breeze perhaps aids them at the rate of thirty or forty miles an hour ; nay, with three times greater rapidity. even in a moderate breeze, if we are to give credit to the statement of cErial navigators, who seem to consider the rate of the motion of winds as in general stated too low.
It has been already observed, that many species do net perform their migrations at once, but reach the end of their journey by short and easy stages. There is little exertion required from such ; while those who execute their move ments at one flight, (if there be any that do so,) may in a very short time, perhaps a day, by the help of a favourable breeze, reach the utmost limits of their journey. Many
birds, we know, can subsist a long time without food ; but there appears to he no necessity for supposing any such abstinence, since, as Catesby remarked, every day affords an increase of warmth and a supply of food. Hence we need not perplex ourselves in accounting for the continu ance of their flight, or their sustenance in the course of it. Such journies would be long indeed for any quadruped, while they are soon pet formed by the feathered tribes.
It is often stated as a matter of surprise, how these birds know the precise time of the year at which to execute their movements, or the direction in which to migrate :— Who calls the council, states the certain (lay, Who forms the phalanx, and who points the way But this is merely expressing a surprise, that a kind and watchful Providence should bestow on the feathered crea tion, powers and instincts suited to their wants, and calcu lated to supply them. How, we ask, does the curlew, when perched upon a neighbouring muir during the flow ing of the tide, know to return at the first of the ebb, to pick up the accidental bounty of the waves ? How are the sea fowl, in hazy weather, guided to the sea-girt isles they inhabit, with food to their young, which they have pro cured at the distance of many miles ? 46 The inhabitants of St Kilda," says Martin, a take their measures from the flight of these fowls, when the heavens are not clear, as from a sure compass ; experience sheaving, that every tribe of fowls bend their course to their respective quarters, though out of sight of the isle. This appeared clearly in our gra dual advances ; and their motion being compared, did ex actly quadrate with our compass." In the course of these annual migrations, birds are some times overtaken by storms of contrary wind, and carried far from their usual course. In such cases, they stray to un known countries, or sometimes are found at sea in a very exhausted state, clinging to the rigging of ships. Such accidents, however, seldom happen, as these birds, year after year, arrive in the same country, and even return to the same spot. The summer birds of passage return not, it is true, in such numbers as when they left us ; but, amidst all the dangers of their voyage, the race is pre served.