The flight of the pigeon also leads me to consider that of other birds as well. All other animals have one determinate mode of progression, which in every kind is always the same; it is birds alone that have two modes of moving—the one on the ground, the other in the air. Some of them walk, such as the crow, for instance; some hop, as the sparrow and the blackbird; some, again, run, as the partridge and the woodhen; while others throw one foot before the other, the stork and the crane, for instance. Then again, in their flight, some birds expand their wings, and, poising themselves in the air, only move them from time to time; others move them more frequently, but then only at the extremities; while others expand them so as to expose the whole of the side. On the other hand, some fly with the greater part of the wings kept close to the side; and some, after striking the air once, others twice, make their way through it, as though pressing upon it enclosed beneath their wings; other birds dart aloft in a vertical direction, others horizontally, and others come falling straight downwards. You would almost think that some had been hurled upwards with a violent effort, and that others, again, had fallen straight down from aloft; while others are seen to spring forward in their flight. Ducks alone, and the other birds of that kind, in an instant raise themselves aloft, taking a spring from the spot where they stand straight upwards towards the heavens; and this they can do from out of the water even; hence it is that they are the only birds that can make their escape from the pitfalls which we employ for the capture of wild beasts.
The vulture and the heavier wild birds can only fly after taking a run, or else by commencing their flight from an elevated spot. They use the tail by way of rudder. There are some birds that are able to see all around them; others, again, have to turn the neck to do so. Some of them eat what they have seized, holding it in their feet. Many, as they fly, utter some cry; while on the other hand, many, in their flight, are silent. Some fly with the breast half upright, others with it held downwards, others fly obliquely, or else side-ways, and others following the direction of the bill. Some, again, are borne along with the head upwards; indeed the fact is, that if we were to see several kinds at the same moment, we should not suppose that they have to make their way in the same element.
CHAP. 55. (39.)—THE BIRDS CALLED APODES, OR CYPSELI.
Those birds which are known as “apodes”[3035] fly the most of all, because they are deprived of the use of their feet. By some persons they are called “cypseli.” They are a species of swallow which build their nests in the rocks, and are the same birds that are to be seen everywhere at sea; indeed, however far a ship may go, however long its voyage, and however great the distance from land, the apodes never cease to hover around it. Other birds settle and come to a stand, whereas these know no repose but in the nest; they are always either on the wing or else asleep.
CHAP. 56. (40.)—RESPECTING THE FOOD OF BIRDS—THE CAPRIMULGUS, THE PLATEA.
The instincts, also, of birds are no less varied, and more especially in relation to their food. “Caprimulgus”[3036] is the name of a bird, which is to all appearance a large blackbird; it thieves by night, as it cannot see during the day. It enters the folds of the shepherds, and makes straight for the udder of the she-goat, to suck the milk. Through the injury thus inflicted the udder shrivels away, and the goat that has been thus deprived of its milk, is afflicted with incipient blindness.