Part 4

In the back-bone, or vertebral column, we find three principal regions, each of which will merit distinct notice.

The _cervical region_, or that portion belonging to the neck (Fig. 12, _b_), is exceedingly variable in its proportionate length, and forms the only flexible portion of the spine; it performs, indeed, the functions of an arm, at the end of which the beak, the chief instrument of prehension, is situated. The number of vertebræ entering into the composition of this part of the skeleton is very variable; in the Swan there are as many as twenty-three, in the Crane nineteen, while in the Sparrow there are only nine. As a general rule, it may be observed that the neck of a bird is never so short as not to be able to reach to every part of the body; in many aquatic species it is remarkably elongated, whether they swim upon the surface by means of webbed or natatory feet, like the Swan, or wade into rivers and marshes, like the Crane or the Heron. Throughout the entire class a very beautiful contrivance is observable in the S-shaped curvature of this region, the joints of the upper vertebræ being so disposed that they will bend forwards, while in the lower part they can only be bent backwards, thus enabling the bird to lengthen or shorten its neck with the utmost facility and gracefulness.

But if flexibility is thus admirably provided for in the cervical region, in the thoracic portion of the skeleton which has to support the framework of the wings, and sustain the efforts of the powerful muscles connected with flight, firmness and rigidity become essential requisites, and, accordingly, in the dorsal region, every means has been employed to prevent those movements which in the neck are so advantageously permitted. The vertebræ of this region (Fig. 12, _c_) are therefore so consolidated as to be almost immovable; and, moreover, splints of bone laid along the back materially add to its stability and strength. There are likewise two sets of ribs, one firmly lashed to the back-bone, the other strongly attached to the sides of the sternum; these dorsal and sternal ribs are moreover united to each other by firm connections, and a thorax is thus formed, possessing sufficient mobility to perform the movements connected with respiration, but still affording a strong basis for muscular action; nay, still further to strengthen this part of the skeleton, from the hinder margin of each dorsal rib a broad flat plate of bone (Fig. 12, _f_) is prolonged backwards, so as to overlap the rib next behind, and thus bind the whole together as firmly as possible.

The sternum or breast-bone (Fig. 12, _e_) is developed in proportion to the size of the three pectoral muscles subservient to flight, and is prolonged beneath into a deep keel-like projection. In the cursorial races, such as the Ostriches and the Apteryx, whose wings are not available for flying, the keel is entirely wanting.

Whoever considers the position of the hip-joint in the skeleton of a bird, and reflects how far it is necessarily removed behind the centre of gravity when the bird walks with its body in a horizontal position, will at once perceive that the hinder portion of the spinal column, having to support the whole weight of the body under the most disadvantageous circumstances, and at the same time to give attachment to the strong and massive muscles that wield the thigh, must be consolidated and strengthened in every possible manner, and that even the slight degree of movement permitted in the region of the back would here be inadmissible. Most of the hinder vertebræ are, therefore, solidly conjoined into a single piece (Fig. 12, _r_, _s_), sufficiently strong and massive to bear the great strain to which it is continually subjected, leaving only a few of the hindmost pieces (Fig. 12, _d_) free, upon which the feathers of the tail are supported.

The fore limb of a bird, although used for the purpose of flight, when stripped of the feathers and quills that, as we have already seen, form the extensive surface of the wing, will be found very much to resemble the human arm in its general arrangement, presenting only such modifications as are required for the performance of its peculiar function.

The framework of the shoulder consists of three bones (Fig. 12, _h_, _i_, _k_), named respectively the _scapula_ or _shoulder-blade_, the _clavicle_ or _collar-bone_, and the _coracoid bone_. The scapula (_h_) is a long and comparatively slender piece placed upon the ribs, and embedded in the muscles, to which it gives attachment. The coracoid bone (_k_) is the strongest piece of the shoulder; it supports the wing at one extremity, while at the opposite it is firmly united to the sternum by a broad and massive joint. But the most peculiarly formed part of the shoulder is the _furculum_, or "merry-thought," as it is usually called (_i i_), consisting of the two collar-bones united, so as to form but a single fork-shaped apparatus, the presence of which materially enlarges and strengthens the shoulder, without unnecessarily adding to the weight. It is by the union of the three last-mentioned bones that a place is made for the socket of the shoulder, with which the wing is more immediately connected.

The skeleton of the wing presents the bone of the arm, called the _humerus_ (Fig. 12, _l_), and the two bones of the fore-arm, named respectively the _radius_ (_m_) and the _ulna_, or _cubit_ (_n_). The _wrist_, or _carpus_, consists of two bones (_b' o_), and the metacarpus (_p_) is likewise made up of two pieces; these, with two, or sometimes three, rudimental fingers (_p' q q_), complete the framework of the wing. The largest finger consists of two, or sometimes of three joints; a second offers but a single joint; and the third, when present, is a mere appendage to the carpus, representing a sort of apology for a thumb.

The bones of the leg likewise exhibit the same parts as exist in the human skeleton, but modified. The _thigh_, or _femur_ (Fig. 12, _t_), is a short and strong bone, to which succeeds the leg, consisting of two bones (_u_), named the _tibia_ and the _fibula_, but the latter is generally very imperfectly developed. That part which is commonly considered to be the leg consists of the bones of the ankle and a part of the foot (the tarsal and metatarsal bones) consolidated into a single piece, called by anatomists the _tarso-metatarsal_ bone, but known to ornithologists as the _tarsus_ (_x_). At the lower extremity of the tarsus are three joints that support the three front toes (_z, z_), while a fourth toe (technically called the _hallux_) (_y_), which is directed backwards, is attached to it by the intervention of a small accessory piece. In the gallinaceous order there exists a bony spur, considered by some as representing a fifth toe.

In order to facilitate the description of a bird, it is usual for the ornithologist to consider its exterior as being mapped out into sundry _regions_ (see Fig. 13), to each of which has been assigned a definite and appropriate name; with the names of these regions, and their precise application, it is requisite that the reader should be intimately acquainted.

A bird, like any other vertebrate animal, is divisible into the head, the body, and the limbs; under one or other of which divisions all subordinate parts may be classed.

The head consists of the _skull_ and the _bill_, and is joined to the body by the _neck_. Commencing with the bill, we see that it is composed of two pieces, corresponding to the jaws of quadrupeds; that which is above is called the _upper mandible_ (Fig. 13, 1), that which represents the under jaw is called the _lower mandible_ (2). The upper mandible contains the _nostrils_ (3); its highest part is called the _culmen_ or _ridge_ (4), while the corresponding ridge of the lower mandible is called the _gonys_ or _keel_ (9).

The lateral edges of the mandibles which meet when the bill is closed are called the _margins_. In some birds the margins of the upper mandible fold over those of the lower, while in others the edges meet; when this is the case, the line of junction between the two is called the _commissure_ (5).

In many birds the upper mandible is continued far back over the forehead, and there dilated, so as to form a _casque_ or _helmet_. In rapacious birds and parrots there is a belt of soft naked skin at the base of the upper mandible, named the _cere_, in which the nostrils are placed, while around the eye is a space, often denuded of feathers, called the _ophthalmic_ region (11).

The HEAD is that part which lies immediately over the skull, extending from the base of the beak to the commencement of the neck. The _front_ or _forehead_ (12) is that part of the head which lies close above the nostrils; then follows the _crown_ or _summit_ (17), which occupies the middle or centre of the head, forming that part which is usually occupied by the crest in birds so ornamented. The _hind head_(18) commences at the declivity of the skull; its lower portion is called the _nape_ (19).

On the sides of the head the following parts have received distinct names:--The feathers that cover the ears, to save repetition, are usually called the _ears_ (20): they are generally rather more rigid and their webs more disconnected than the surrounding feathers. The space between these and the corner of the mouth (usually called the _gape_)(13), is termed the _cheek_.

The parts of the NECK are thus designated:--The back of the neck is called the _upper neck_, or _nucha_ (23), beneath which is the _lower neck_ or _auchenium_. The under-side of the neck is divided into three regions; first, there is the _chin_ (7), or that small space just beneath the lower mandible; to the chin succeeds the _upper throat_ (8), between which and the broad part of the body is the _lower throat_ (15).

The BODY presents the following regions: first there is the _breast_ (22), which extends over the space which covers the breast-bone. To this succeeds the _belly_ (29), which is terminated by the _vent_ or _crissum_ (30). Immediately behind the vent are the _under-tail covers_ (32), which are frequently of a different colour from the surrounding feathers.

On the upper aspect of the body we have the _interscapular region_, sometimes called the _back_ (24), to which succeeds the _lower back_ (26), which terminates at the _rump_, or that part where the _upper-tail covers_ (42) are inserted.

Last of all comes the TAIL, composed of long stiff feathers, called the _tail-feathers_ (31), concerning which it is only necessary to observe that the two middle tail-feathers are the _intermedial_, while those on the sides are the _lateral_ tail-feathers.

The WING of a bird will be found to present a structure worthy of our highest admiration. The object aimed at in the arrangement of its different parts is evidently to obtain a very large and firm expanse of surface, by employing the smallest possible quantity of material. For the purposes of flight it is obviously necessary that the superficial extent of the wings shall be sufficiently ample, not only to sustain the weight of their possessor in the thin and yielding element in which it flies, but, by the vigour of their stroke and the violence of their impulse, to propel the bird with a rapidity proportioned to the occasion, and, moreover, by the lightness of their touch and the accuracy of their movements, to steer and steady its course through all the varied evolutions whereby it is enabled to capture prey, or sportively display the wonderful activity conferred upon the feathered tribes.

We have already seen, while examining the construction of the skeleton, that the bony framework of the wing essentially resembles that of the human arm, and that the limb when stripped of its feathers is no more adapted for flying than our own. The needful expansion is obtained altogether by the addition of the quill feathers, which, as explained in a preceding page, combine in their structure all the qualities requisite for the intended purpose, lightness, firmness, strength, elasticity, and extent of surface: the central part of the arm or wing forms merely a basis of support, into which the quills and other appendages to the wing are securely implanted. It will therefore be easily understood that the importance of the individual quills as instruments of flight will depend very much upon the position they hold in the wing, of which they form so considerable a portion, and, consequently, that they have received names expressive of their relative efficiency. Those that are affixed to the bones representing the hand (Fig. 12, _p_, _q q_), by the length of their stroke, and the peculiarity of their arrangement, are obviously of primary importance, both from their size and the situation they occupy, and have consequently been named the "_primaries_," or the "_primary quills_," (Figs. 2, _f_; 13, 35); they might be called with equal propriety the "_hand-quills_," a term more particularly expressive of the parts to which they are attached. Upon the relative length and other proportions of the primary quills the shape and mechanical power of the instrument principally depend; if the first primary be the longest, the termination of the wing is sharp and pointed (_acuminate_), as in most birds that are remarkable for the swiftness of their flight; whereas if the second, third, or fourth of these quills should exceed the others in this respect, the wing becomes more and more rounded (_obtuse_), and the perfection of its action visibly deteriorated.

The "_Secondary Quills_," or "_Secondaries_" (Figs. 2, _c_; 13, 34), are exclusively sustained by the bones of the fore-arm (Fig. 12, _m_, _n_); from their situation being much nearer to the shoulder-joint than the preceding, the extent of their sweep is more limited, and their stroke much feebler; they are, consequently, as their name indicates, of secondary importance in locomotion.

The _Spurious_, or _Bastard Quills_ (Figs. 2, _e_; 13, 33), are attached to the rudimental bone that represents the thumb (Figs. 2, _g_; 12, _p_); their size is diminutive, and their use in flight comparatively unimportant.

The _Wing Covers_ or _Coverts_ (Fig. 13, 37) are small feathers arranged in several rows, which overlap and strengthen the bases of the quills; they are often variously coloured, and thus afford important features whereby different species may be distinguished. Besides the above, there are certain conventional terms employed by the ornithologist that will require enumeration. The arm-part of the wing in the living bird is generally known as the _shoulder_ (27); the elbow-joint is the _flexum_; while that part of the fore-arm which corresponds to the edge of the wing is denominated the _shoulder-margin_ (6).

The names appropriated to the different parts of the hinder-limb have been already sufficiently indicated when describing the composition of the skeleton.

There are many birds which have stripes of variously coloured feathers situated above, before, and behind the eye; while others sometimes occur at the base of the lower mandible. To all these distinct names have been appropriated. A _superciliary_ stripe is situated _above_ the eye, occupying a position analogous to that of the human eyebrow. An ordinary eye-stripe is either _anterior_, _posterior_, or _entire_. It is called _anterior_ when it only occupies the space between the eye and the bill; _posterior_ when it commences behind the eye, and advances towards or unites with the ear-feathers; and _entire_ when it is both posterior and anterior. A _maxillary_ stripe commences at the base of the under mandible, and descends on the sides of the neck.

Such is the by no means very long list of names of parts used by the ornithologist in his description, and which in the course of the present volume will necessarily be of very frequent occurrence.

The oil with which birds preen their feathers, and the glands that supply it, constitute a remarkable provision peculiar to the feathered creation. Embedded among the feathers at the root of the tail, there is on each side a small nipple, yielding upon pressure a butter-like substance, which the bird extracts by squeezing the orifice with its bill. By means of the oil, or rather ointment, thus procured, it dresses its feathers, either for the purpose of increasing their brilliancy, or, as in the case of the swimming birds, to make them impenetrable to wet.

The pairing of birds is a feature in their history which draws a broad line of distinction between the feathered tribes and the generality of quadrupeds. Among mammiferous quadrupeds the young derive their nutriment during the earlier period of their existence entirely from the maternal breast, the male parent contributing nothing towards its support; but in the winged races the callow brood derive their supply of food from the industry of both parents, whose united exertions are not more than is requisite to procure the needful supply. In this circumstance we may see a reason for the faithful love of the feathered mate as contrasted with the vagrant disposition of the quadruped. The parental fondness of birds towards their young has escaped no observer; no historian of nature is silent upon this subject. "How well they caress them," says Derham, "with their affectionate notes, lull and quiet them with their voice, put food into their mouths, cherish and keep them warm, teach them to peck and eat, and gather food for themselves, and, in a word, perform the part of so many nurses deputed by the Sovereign Lord and preserver of the world to help such young and shiftless creatures."

It would lead us far beyond the limits of our space were we to do more than indicate the close relationship that exists between the exalted temperature and warm clothing of the feathered creation and the wonderful instinct which urges them to build nests for the reception of their eggs, or the still more remarkable blind perseverance with which they devote themselves to the task of incubation. "There is nothing," says Paley, "either in the aspect or in the internal composition of an egg which could lead even the most daring imagination to conjecture that it was hereafter to turn out from its shell a perfect living bird. From the contents of an egg would any one expect the production of a feathered goldfinch? To suppose the female bird to act in this process from a sagacity and reason of her own is to suppose her to arrive at conclusions there are no premises to justify." And yet HE who made the egg not only ordained that such should be the result of the simple process of incubation; but, as though to confound scepticism, by giving, as it were, the last touch to HIS inscrutable work, provided the young bird with the means of escaping from incarceration, by attaching to the end of its beak a little hammer, called the "bill-scale," the only use of which is to crack the egg-shell, and allow the little prisoner to come forth. (See Fig. 14.)

With these few prefatory remarks, we leave our author in the reader's hands, at the same time promising that he will find in the succeeding pages a rich store of valuable information.

CLASSIFICATION OF BIRDS.

Those who are familiar with modern works on ornithology will have observed that it is usual to commence the history of the feathered tribes by a description of the vultures--the most disagreeable and least intelligent of the race. Some writers, however, consider the singing birds as entitled to the first place, the remaining members of the heterogeneous multitude being arranged according to the pleasure of individual naturalists more or less acquainted with their subject. For our own part, we recognise in the parrots the qualifications most fitted to entitle them to take the precedence, and it is, consequently, with these that we shall commence our history. Ornithologists, moreover, differ widely among themselves as regards the relation that exists between the parrots and other members of the class to which they belong, either placing them in a group by themselves, in a manner never intended by Nature, or associating them with toucans, woodpeckers, and cuckoos, with which they possess but few characteristics in common. Under these circumstances, we have considered ourselves at liberty to adopt our own views upon the subject, and have, accordingly, constituted for the parrots a distinct order, under the quaint but expressive name of

CRACKERS (_Enucleatores_),

in allusion to the facility with which, owing to the construction of their beaks, they are enabled to crack nuts, and other hard seeds, that form the usual staple of their food.