Imagens das páginas
PDF
ePub

fall previous to alighting (fig. 107, below). Birds which fish on the wing, as the osprey and gannet, precipitate themselves from incredible heights, and drop into the water with the velocity of a meteorite—the momentum which they acquire during their descent materially aiding them in their subaqueous flight. They emerge from the water and are again upon the wing before the eddies occasioned by their precipitous descent have well subsided, in some cases rising apparently without effort, and in others running along and beating the surface of the water for a brief period with their pinions and feet.

The Flight of Birds referable to Muscular Exertion and Weight. -The various movements involved in ascending, descending,

[graphic]

FIG. 107.-The Red-headed Pochard (Fuligula ferina, Linn.) in the act of drop

ping upon the water; the head and body being inclined upwards and forwards, the feet expanded, and the wings delivering vigorous short strokes in a downward and forward direction.-Original.

wheeling, gliding, and progressing horizontally, are all the result of muscular power and weight, properly directed and acting upon appropriate surfaces—that apparent buoyancy in birds which we so highly esteem, arising not from superior lightness, but from their possessing that degree of solidity which enables them to subjugate the air, —weight and independent motion, i.e. motion associated with animal life, or what is equivalent thereto, being the two things indispensable in successful aërial progression. The weight in insects and birds is in great measure owing to their greatly developed muscular system, this being in that delicate state of tonicity

which enables them to act through its instrumentality with marvellous dexterity and power, and to expend or reserve their energies, which they can do with the utmost exactitude, in their apparently interminable flights.

Lifting-capacity of Birds.—The muscular power in birds is usually greatly in excess, particularly in birds of prey, as, e.g. the condors, eagles, hawks, and owls. The eagles are remarkable in this respect—these having been known to carry off young deer, lambs, rabbits, hares, and, it is averred, even young children. Many of the fishing birds, as the pelicans and herons, can likewise carry considerable loads of fish ;? and even the smaller birds, as the records of spring show, are capable of transporting comparatively large twigs for building purposes. I myself have seen an owl, which weighed a little over 10 ounces, lift 21 ounces, or a quarter of its own weight, without effort, after having fasted twenty-four hours ; and a friend informs me that a short time ago a splendid osprey was shot at Littlehampton, on the coast of Sussex, with a fish 5 lbs. weight in its mouth.

There are many points in the history and economy of birds which crave our sympathy while they elicit our admiration. Their indubitable courage and miraculous powers of flight invest them with a superior dignity, and secure for their order almost a duality of existence. The swallow, tiny and inconsiderable as it may appear, can traverse 1000 miles at a single journey; and the albatross, despising compass and landmark, trusts himself boldly for weeks together to the mercy or fury of the mighty ocean. The huge condor of the Andes lifts himself by his sovereign will to a height where no sound is heard, save the airy tread of his vast pinions, and, from an unseen point, surveys in solitary grandeur the wide range of plain and pasture-land ;2 while the bald eagle, nothing daunted by the din and indescribable confusion of the queen of waterfalls, the stupendous Niagara, sits composedly on his

the mouth

1 The heron is in the habit, when pursued by the falcon, of disgorging the contents of his crop in order to reduce his weight.

? The condor, on some occasions, attains an altitude of six miles.

giddy perch, until inclination or desire prompts him to plunge into or soar above the drenching mists which, shapeless and ubiquitous, perpetually rise from the hissing waters of the nether caldron.

[graphic][merged small]

AERONAUTICS.

« AnteriorContinuar »