General Observations on Birds and on Poultry Breeding
Birds, the free tenants of land, air and ocean,
Their forms all symmetry, their motions grace;
In plumage, delicate and beautiful;
Thick without burthen, close as fishes' scales,
Or loose as full-blown poppies to the breeze.
—The Pelican Island.
Birds are classified primarily on their habits of life and, structurally, on the shape of the sternum or breastbone. The first sub-class of the class Aves or Birds is called Ratitæ, and includes all birds having a sternum without a keel; the birds belonging to this sub-class are all natives of warm climates, as the ostrich, emu, cassowary, and the remarkable apteryx of New Zealand with rudimentary wings, and a long slender bill. The other sub-class is that of the Carinatae, and includes all birds having a keel on the sternum, as the parrot, pigeon, swallow and duck.
Birds are grouped broadly in eight orders—Raptores, birds of prey, such as eagle, vulture and owl; Insessores, perching birds, such as the lark, swallow, sparrow, and all singing birds; Scansores, climbing birds, such as the parrot and cuckoo; Rasores, scratching birds, such as the common fowl, partridge and pheasant; Cursores, running birds, such as the ostrich and cassowary; Grallatores, wading birds, such as the crane, the snipe, the stork and the heron; Natatores, swimming birds, characterized by webbed feet, such as the duck, the pelican and the gull; and Saururæ, lizard-tailed birds, which include the fossil bird Archaeopteryx, remarkable for its tail, which is longer than its body. A more scientific classification, based partly on external, and partly on internal, characteristics, by Professor Huxley and other naturalists, subdivides birds into other orders. It will be seen that by a particular adaptation of function to environment in the case of the birds comprised in the eight orders enumerated above, the air, the forest, the marsh, the land and the water has each its appropriate kind of inhabitant.