DIFFERENT MODES OF FLIGHT AND PROGRESSION IN BIRDS.
Mentioning the flight of the pigeon leads me to consider that of other
birds. All other animals have one determinate mode of progression, which
in every kind is always the same; birds alone have two modes of
moving--on the ground, and in the air. Some of them walk, such as the
crow, for instance; some hop, as the sparrow and the blackbird; some
run, as the partridge and the woodhen; while others throw one foot
before the other, like the stork and the crane. 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 had fallen
straight down from aloft; while others still 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
directly from the water. 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 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 others are always silent. Some fly with the breast
half upright, others with it held downwards, others fly obliquely, or
side-ways, and others follow the direction of the bill. The fact is,
that if we were to see several kinds at the same moment, we should not
suppose that they were adapted to the same element.
Those birds which are known as "apodes"[178] fly the most of all,
because they are deprived of the use of their feet. 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. 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 rest, but
these know no repose save in the nest; they are always either on the
wing or asleep.