Flanks or sides of body are the parts approximately covered by the closed wing.
Axillaries are the Lengthened feathers springing from the axilla or region beneath the base of the wing.
Supplementary bristles or hairs are those springing from the side of the forehead in front of the rictal bristles.
Naral bristles or hairs are those springing from the front of the forehead and covering the nostrils.
The measurements in this work are invariably in English inches and decimals, and are taken thus: - Length. - The distance from the tip of the bill to the tip of the longest tail-feather, unless otherwise stated. Tail. - The distance from the root of the tail, generally indicated both in the fresh and dried state by the presence of a piece of flesh on the underside, to the tip of the longest feather. Wing. - The greatest distance from the bend of the wing to the tip of the longest primary, measured straight.
When the wing is curved, it is flattened out for the purpose of measurement. Tarsus. - The distance from the centre of articulation of the tarsus with the tibia to the base of the middle toe. Bill. - The distance from the angle of the gape to the tip, measured straight.
BIRDS are warm-blooded vertebrate animals, oviparous, and covered with feathers. The anterior limbs are modified into wings. The skull articulates with the vertebral column by a single occipital condyle, and the jaw is connected with the skull by the intervention of a quadrate bone. The heart consists of four chambers, two auricles and two ventricles, and the right and left sides are completely separated from one another. There is only one aortic arch, the right.
It is usual to divide all living birds into two great subclasses, which are diagnosed from each other by the shape of the sternum. In one subclass, the Carinatae, the sternum is typically provided with a keel; in the. other, the Ratitae, the keel of the sternum is absent.
Although this primary division of birds is convenient in many ways, yet there are exceptions to its application which render a classification based on the shape of the sternum of doubtful utility. Some birds which from other points of view are undoubtedly Carinatae have the keel of the sternum little, if at all, developed.
I prefer therefore to divide birds at once into groups which I shall term Orders, and in doing so I shall avail myself of the recent studies of Mr. Seebohm. This gentleman, partly by independent osteological investigations of his own, and partly by utilizing the discoveries of other workers in the same or similar fields, has, without disturbing the usually accepted classification of birds to any great degree, arrived at an arrangement which possesses the merit of being precise and clear, so far as the materials at his disposal have enabled him to be so. He has, moreover, diagnosed the different Orders by characters which the least skilful can easily investigate and discover for themselves.
Mr. Seebohm divides birds into several large groups which he terms Orders, and these again into suborders which are equal to the groups which I, in accordance with the usual practice, prefer to call Orders. I do not propose to treat of the distinctions between the different Orders here, but to deal with them at the end of this work, as I gather from Mr. Seebohm that he contemplates a revision of them. The period of two years which, moreover, must elapse before the present work is completed cannot fail to be productive of much additional information and improvement with respect to the classification of birds.