a, cranium; b, upper mandible; c, lower mandible; d, d, vertebræ; e, e, ribs; fgh, sternum; i, coracoid bone; jj, furcula; k, scapula; , humeral bone; mm, ulna; nn, radius; o, metacarpal bones; p, q, united sacrum and pelvis; r, ischium; s, ilium; tt, thigh-bone; uu, tibia; v, ankle-joint; ww, tarsus; 1, first or hind toe; 2, second or inner toe; 3, third or middle toe; 4, fourth or outer toe. powerful muscles which depress the wings, and receives great attention from naturalists, because its variations correspond with the differences in some of the most important characters and habits of birds. It generally exhibits a projecting ridge along the middle, which is proportionately largest in birds of Skeleton of Bird's Wing. fly. The clavicles or collar-bones, also, are generally united to form the fourchette (furcula) or merrythought bone, serving, along with two bones called the coracoid bones, to keep the shoulders separated, and to resist the compressing tendency of the action of the wings. The bones of the wing itself are regarded as corresponding to those of the anterior extremities in man and quadrupeds; the bones of the hand, however, being much disguised, and some of them wanting or rudimentary. In the accompanying cut of the bones of a bird's wing, a is regarded as the elbow-joint, b as the wrist-joint, c as the knucklejoint, d being the representative of a finger, e and f the rudimentary representatives of two others, whilst the winglet, g, formerly regarded as representing the thumb, is now rather supposed to be homologous to the forefinger. The wings, therefore, exhibit a structure entirely different from those of bats, in which the fingers are extremely elongated. The surface necessary for striking the air is provided by feathers larger and stronger than those of other parts of the body, called wing-feathers, quill-feathers, or quills. Of these, which exhibit an admirable combination of strength with lightness and elasticity, some spring from the part of the wing between 6 and d (in the figure of the bones of the wing); these are always the largest, and are called the primary wing-feathers, or simply primaries; those which spring from the part between a and b are called secondaries; and those which spring from the part between a and the shoulder-joint, are called tertiaries. At the base of the quills, on both sides of the wing, are feathers called wing-coverts, and these are likewise distinguished as primary, secondary, &c. The feathers which grow over the shoulder-blades are called scapulars. The feathers of the wings vary in length and strength, according to the mode of life d most powerful flight, and is wanting only in ostriches and a few other birds of allied genera which do not Bird's Wing, shewing Quills: a, primaries; b, secondaries; c, tertiaries; d, winglet. and power of flight in different B.; narrow, sharp, and stiff wings being indicative of swift and enduring flight. The tail-feathers serve the purpose of a rudder to guide the bird, and also that of balancing it in the air; they resemble in character the quills of the wings. They are also furnished with coverts above and below. Some B. have the tail rounded at the extremity; in some, it is square; in others, notched or forked. In many land B., the tail exhibits ornamental plumes, and remarkable developments of the plumage take place also in other parts of the body, in the form of crests, ruffs, shoulder-tufts, &c. The legs of B. consist of parts corresponding to those found in man and quadrupeds; but the thigh is short, and so concealed within the body, that it is not apparent as an external portion of the limb; the next division, often mistaken for the thigh, being the leg strictly so called, or tibia, which ends at what is really the heel-joint, although popularly regarded as the knee; and beneath this is the shank, or tarsus, which in some B. is very long, serving as a part not of the foot but of the leg, and formed by a single bone which represents both the tarsus and metatarsus. The feet are divided into toes, which are generally four in number, three before and one behind, differing from each other in length and in the number of joints or phalanges of which they are composed, the toe, which is directed backward, Few B. masticate their food in any degree, although being in general comparatively short, and consisting parrots do; upon being swallowed, it enters the only of two joints. A fifth toe or tarsal spur is crop or craw, sometimes called the first stomach, an found in some of the gallinaceous B.; and in some enlargement of the oesophagus or gullet, situated B., as Bustards, the hind-toe is wanting; the ostrich just before the breast-bone, and here it is moistened has only two toes, both directed forward, with the by a secretion, which is also by some B.-particuobscure rudiment of a third; and numerous B. larly by pigeons-employed as the first food for classed together in the order of Climbers (q. v.) or their young, the glands of the crop enlarging very Yoke-footed B., including Parrots, Cuckoos, Wood- much, so as to produce it in large quantity at the peckers, &c., have two toes before, opposed by two time when it is wanted for that purpose. The crop is toes behind, the foot being thus particularly adapted wanting in the ostrich, and also generally in B. that for grasping, so that parrots, as is well known, even feed on fish; and is of greatest size in those of which use it as a hand.-The feet of B. vary considerably the food consists of seeds or grain. It is generally according to their mode of life; and naturalists single, and on one side of the gullet; sometimes, as therefore depend very much upon them in classifi- in pigeons, it is double. A second stomach, or dilacation. In some the claws are strong and hooked; tation of the œsophagus, called the proventriculus or in others short, straight, and weak; in some the ventriculus succenturiatus, is generally largest in toes are all separate, in others more or less con- those B. in which the crop is wanting or small; and nected; in B. specially adapted for swimming, they in this the food is further softened and changed by are generally webbed or united by a membrane; in a secretion which is mixed with it. The third and other swimming-B., however, a membrane only principal stomach is the gizzard, which in B. of prey, extends along the sides of each toe. In most B. the fish-eating B., &c., is a mere membranous sac; but tarsus is feathered to the heel-joint; in some, how-in B. which feed on grain or seeds is very thick and ever, and particularly in waders, the lower part of it muscular, so that it acts as a sort of mill, and with is bare; the shank and toes are generally, although extraordinary power. In these B., also, a remarkable not always, destitute of feathers, and are covered provision is made for the perfect grinding down of with a scaly skin. Almost the only other parts the contents of the gizzard, by the instinct which of a bird often destitute of feathers, are the cere at leads them to swallow small rough pebbles or grains the base of the bill, and the combs and wattles of of sand, an instinct well exemplified in the common gallinaceous birds. domestic fowl.-The liver of B. is, in general, very large. The kidneys are large, but there is no urinary bladder, and the urine is at once poured into the cloaca, an enlargement of the intestine, at its termination, with which also the organs of generation communicate in both sexes. We are again indebted to M'Gillivray's excellent work for the following cut. In order to flight, it is indispensable that the centre of gravity of a bird should be under the shoulders; and when a bird stands, the feet are brought forward, and the head thrown back, so that the claws project beyond a vertical line passing through the centre of gravity of the whole body. This is generally accomplished so that the trunk is in an almost horizontal position, the fore-part only a little elevated; but in some B., which have a short neck and short legs, an erect attitude is necessarily assumed, so that the penguins of the southern seas present to navigators a somewhat ludicrous resemblance to regiments of soldiers on the beach. B., when they sleep, very generally place their head under their wing, and some of them also stand upon one foot, their equilibrium being thus more easily maintained. A remarkable contrivance, particularly to be observed in storks and other long-legged B., renders this posture unfatiguing; a locking of the bone of one part of the limb into a sort of socket in the bone of the part above it, so that it retains its place without muscular exertion; whilst a similar purpose is served by the tendons of the muscles which bend the claws passing over the joints of the leg in such a manner as to be stretched by the mere pressure there when the weight of the bird rests upon the legs, so that without any effort the claws retain a firm hold of the branch upon which it is perched.-Flying is accomplished by the action of the wings upon the elastic and resisting air; the muscles by which the stroke of the wing is given are powerful, those by which it is retracted are comparatively weak. Owing to the manner in which the first strokes of the wing must be given, few B. rise with facility from a level surface; and some of them, as swallows, and particularly swifts, rise from a perfectly level surface with great difficulty, and comparatively seldom alight where they cannot find an elevation from which, as it were, to throw themselves. The digestive apparatus of B. resembles that of mammalia; exhibiting, however, various modifica m b h ין Digestive Organs of Domestic Pigeon : a, bill; b, head; c, oesophagus; de, crop of extreme size; f, continuation of esophagus; g, proventriculus; hijkl, gizzard; h, upper muscle; i, j, lateral muscles; k, lower muscle;, tendon; mnopqr, intestine; s, trachea. The respiration of B. is very perfect, and their tions, according to the different kinds of food-some blood is from 12° to 16° warmer than that of mamB. feeding on flesh, others on fish, others exclusively malia; its circulation more rapid, and the energy on insects, others on seeds, others more indiscrimin- of all the vital processes proportionally great. B., ately on a variety of animal and vegetable substances. consequently, exhibit great liveliness; and upon the 109 admirable provision for the aëration of their blood they depend also for their powers of flight, which enable some of them to travel hundreds of miles with great rapidity and without exhaustion, whilst others soar to a prodigious height in the air. The heart resembles that of the mammalia in its form and structure; but the right ventricle, instead of a mere membranous valve, is furnished with a strong muscle, to impel the blood with greater force into the lungs. The lungs are small, and communicate with large air-cells (q. v.) in the cavities of the body, and even in the bones, so that the aëration of the blood takes place not only in the lungs but during its circulation through the body. An extraordinary proof of the use of these air-cells in respiration was afforded in a recorded instance of a large sea-fowl, which, when an attempt was made to strangle it, was kept alive by the air entering in a forcible current through a broken wing-bone. (Gosse, The Ocean, quoting Bennett's Whaling Voyage.) B. consume much more oxygen in proportion to their size than quadrupeds. The organs of the senses are similar to those of mammalia. In the senses of touch and taste, it is generally supposed that there is an inferior development, although parrots appear to possess the sense of taste in considerable perfection; and the bills of some B., which search among the mud for their food, are certainly very delicate organs of touch. But the sight is remarkably keen, and the eye possesses great powers of accommodation to different distances. B. perceive even small objects distinctly, at distances at which they would be quite indistinguishable to the human eye, and thus are enabled to seek their food. B. of prey also appear to possess in great perfection the sense of smell. The nostrils of all B. open on the upper surface of the bill. Hearing is acute in B., and particularly in nocturnal B., although the organs of this sense are less complicated than in mammalia, and there is seldom any vestige of an external ear. Singing-B. are extremely sensitive to differences of pitch. The voice and musical powers depend upon the conformation of the windpipe and larynx, which differs very much in different birds. Reproduction takes place by eggs (see REPRODUCTION and EGG), which are hatched after they have passed from the body of the mother. B. generally sit upon their eggs, their bodies supplying the warmth necessary to hatch them (see INCUBATION); and this office is usually undertaken by the female alone, but sometimes is shared by the male. In very warm climates, the ostrich leaves her eggs to be hatched by the heat of the sun, but in colder climates sits upon them. A very few B., as the cuckoo, deposit their eggs in the nests of other B., to be hatched by them. Some B. construct no nest, but lay their eggs on the bare rock, as many sea-fowl do, or in holes rudely scratched in the earth or sand; many, however, shew in the construction of their nests the most admirable instincts. See NESTS. The number of eggs varies, in a state of nature, from one to about twenty, being generally smallest in the larger B., and particularly in B. of prey. B. generally breed only once a year, but some B. twice. The care which B. take of their young is as admirable as the ingenuity which they display in nest-building, and more universal. Some B. are able to run about, and pick up food as soon as they leave the shell; others remain in the nest for days, or even weeks, and must be supplied with food by their parents. Many species are social, particularly at the breeding-season, and form large settlements, which they guard in common; and some even unite in the construction of large nests, which belong to a whole community. The rapacious B., and particularly the larger ones, are very solitary in their manner of life. B. change their feathers (moult), in general, once a year, and the colours of the plumage in many cases vary much in summer and winter. The change of colour, however, often takes place without change of feathers, and in B. which moult both in spring and autumn, the autumn moulting is much more complete than that of spring. The gayest plumage of many B. is assumed at the breeding-season, with which, also, the song of B. is connected. See SONG OF BIRDS. The plumage of the male is, in general, more gay than that of the female, all the young at first resembling the female in plumage. The plumage usually characteristic of the male is occasionally assumed by the female, and most frequently by females which have become unfit for the ordinary functions of their sex. The brain in B. differs in some important respects from that of mammalia (see BRAIN), presenting resemblances to the brain of reptiles and fishes; but it is of large size, often larger than even in quadrupeds. The manifestation of intelligence is not, however, usually so great in B. as in quadrupeds. Their nest-building, their migrations (see BIRDS OF PASSAGE), and many other things of greatest interest, must be ascribed to instinct. In the geographical distribution of B., the limits of species are not so exactly circumscribed by mountains, seas, and rivers, as in other classes of animals, their powers of flight enabling them to pass over these obstacles. Yet some species, and even groups, are found exclusively in certain regions: thus humming-birds are all American, penguins are found only in the southern seas, and B. of paradise are confined to New Guinea and the neighbouring islands. See SPECIES. The free movements of B. through seemingly boundless space, the joyous song of many, and the characteristic tones of all their brilliant colours, their lively manners, and their wonderful instincts— have from the earliest ages made a strong impres sion on men's minds, and in the infancy of intellect gave rise to many peculiar and mysterious associa tions with this class of creatures. Hence the flight of B. was made the foundation of a particular art of divination. See AUGURIES AND AUSPICES. Religion borrowed many of its symbols from them, and poetry many of its ornaments. In an economical point of view, B. are very important. The flesh and eggs of almost all B. may be eaten, although those of B. of prey and of fisheating B. are generally reckoned unpleasant. Their feathers are employed for various purposes of use and ornament; their dung is valuable for manure, and guano (q. v.) is nothing else than the accumulated dung of sea-fowls. Many B. are extremely useful in preventing the multiplication of insects and worms, and compensate in this way for the mischief which they occasionally do in fields and gardens. Domestic poultry are a source of considerable profit, upon account of their eggs, flesh, and feathers. POULTRY. Some kinds of B. of prey have been tamed, and trained to the use of the sportsman. See FALCONRY. See About 5000 existing species of B. are known. As to their systematic arrangement, see ORNITHOLOGY. The order of B. presents in the Dodo (q. v.) a remarkable and well-ascertained instance of the recent extinction of a species, and even of a genus. It is also a remarkable and interesting fact, that the greater part of the remains of extinct B. hitherto discovered are those of land-B. destitute of the power of flight, like the dodo, and the still existing ostrich, cassowary, emu, and apteryx. A particular interest BIRDS-BIRD'S FOOT. is attached to those of the gigantic Dinornis (q. v.) of New Zealand. See next article. BIRDS, FOSSIL While the animal and vegetable kingdoms of the paleontologist extend to as wide, or rather a wider, range than those of the historian of modern life, yet several divisions are scantily represented in the petrified remains preserved in the stony records of the earth's crust. This was to be expected from the conditions under which these fossiliferous strata were deposited. As these rocks are aqueous, chiefly marine, the relics of plants and animals whose natural habitats were in or near the water, must be common in a fossil state, whilst the remains of others with different habits will be comparatively rare, if present at all. Birds belong to this latter class. Their power of flight would save them from numerous casualties which would prove fatal to quadrupeds; and even if they did perish in water, the lightness of their bodies, produced by their internal cavities and the quantity of their feathers, would keep them floating until they decomposed, or became the food of predaceous animals. been, on the best evidence, referred by the brothers Rogers to the oolitic period. The beds had formed an ancient sea-beach, and over it, during the recession of the tide, had marched the animals, which have left on them their footsteps. Before the return of the tide, the inequalities had been filled up with dry air-drifted sand and mud, and on this was deposited a new layer of silt. The beds often exhibit ripple-marks, and occasionally small circular depressions, which have been formed by drops of rain. The traces of thirty-three species of B. have been distinguished; with them are associated the impressions of various lizards, chelonians, and batrachians. The size of the Ornithichnites (Gr. ornis, a bird, and ichnon, a trace or footprint), as the bird-tracks are called, so far exceed those that would be made by the largest living birds, that it was doubted whether their origin had been satisfactorily explained, until the discovery, in New Zealand, of the remains of the Dinornis. In one species, the imprint of the foot measures fifteen inches in length, and ten inches in breadth, excluding the hind claw, which is two inches long. The distance of the impressions from The earliest traces of birds consist of footprints each other varies from four to six feet. These meaon red argillaceous sandstones in the valley of Con-surements indicate a bird about four times the size necticut river, North America. These sandstones, of an ostrich, but probably not much larger than though long considered of a much older date, have some species of Dinornis. The footprints are for the ल Bird-tracks in New Red Sandstone. most part trifid, and shew the same number of joints as exist in the living tridactylous birds. No indications of the existence of birds have been discovered in the rocks of the cretaceous period. It does not follow, however, that the class Aves had no representatives during the ages when the chalk was being deposited. This is a deep-sea formation, and for the reasons already stated, it is not to be expected that the remains of this class should be found in these measures. And so also it would be rash to conclude, that the oolitic footprints give the date of the first appearance of B. on the globe. The bone of Cimiliornis Diomedeus, found in the chalk, which was described by Professor Owen as part of the humerus of a bird, is now believed to belong to a Pterodactyle. No true fossil remains of B. have been discovered in rocks older than the Eocene-gypseous deposits of Montmartre, where ten species have been found. Seven species have been described from strata of the Miocene period, the most important of which have been found in the Sewalik beds, associated with the remains of huge proboscidea. But the Pleistocene deposits have supplied more than half of the known fossil birds. The most remarkable of these are the bones of huge struthious B. of the genera Dinornis (q. v.), Palapteryx (q. v.), and Aptornis. Dr Mantell mentions the fossil eggs and bones of a bird still larger, called the Epyornis, from Madagascar. BIRD'S-EYE LIMESTONE is a division of the Trenton group of the Lower Silurians of North America, apparently equivalent to the Llandeilo flags, and containing, besides the remains of brachiopods, many enormous orthoceratites. BIRD'S-EYE VIEW is a term applied generally to modes of perspective in which the eye is supposed to look down upon the objects from a considerable height. If the eye is considered as looking perpendicularly down while it sweeps over each point of the scene in succession, we have an exact groundplan; no object covers another, horizontal angles and distances are exactly represented; while, on the other hand, no vertical angles or side-views appear. In sketching or drawing a locality for military or economical purposes, this kind of perspective is always used. The great difficulty is to represent at the same time the relative heights of mountains and steepness of acclivities. But the more usual kind of bird's-eye views differ from common perspective only in the horizontal line being placed considerably above the picture. In the 16th c., the only kind of views known were of the nature of ground-plans, and the artists of the 17th c. tried to combine this method with side views. BIRD'S FOOT (Ornithopus), a genus of plants of the natural order Leguminosa, sub-order Papilionaceae, deriving both its popular and its botanical name from the resemblance of the curved pods to BIRD'S FOOT TREFOIL-BIRDS OF PASSAGE. A species called the Winged Pea (L. tetragonolobus), remarkable for four membranous wings which run along its pods, a native of the south of Europe, is frequently cultivated in gardens in Britain amongst other annual flowers; but in some parts of Europe it is cultivated for its seeds, which are used as a substitute for coffee. birds' claws; the leaves are pinnate, with a terminal cultivation in every variety of soil and situation.leaflet. One species (0. perpusillus) is a native of Britain, growing on dry, sandy, or gravelly soils-a small plant of little importance, the flowers of which are white, striated with red. But O. sativus, an annual growing to the height of two or three feet, a native of Portugal, is cultivated in that country as green food for cattle, and is very succulent and nutritious. Like its British congener, it grows well on very poor soils. Its Portuguese name is Serradilla. BIRD'S FOOT TREFOIL (Lotus), a genus of plants of the natural order Leguminosa, sub-order Papilionacea. The pods are cylindrical, somewhat spongy within and imperfectly divided into many cells. The name B. F. T. is derived from the resemblance of the clusters of pods to a bird's foot. It has received the name Lotus from botanists, because a species of this genus is supposed to have been one of the plants so named by the Greeks. See LOTUS. The species, which are pretty numerous, are natives of the temperate and colder regions of the old world. The COMMON B. F. T. (L. corniculatus) is very abundant everywhere in Britain in pastures. It has a stem 6-12 inches in length, decumbent, and bearing umbellate heads of 8-10 yellow flowers, which have a rich honey-like smell. The leaves have three obovate leaflets, like those of the true Trefoils or Clovers, but at the base of each leaf-stalk there are also two large leaf-like ovate stipules. The plant is by some regarded as the shamrock (q. v.) of Ireland. It is eaten with great avidity by cattle, and its deeply penetrating roots adapt it well for very dry situations.-A larger species, otherwise very similar, by many regarded as merely a more luxuriant variety of this, with stem nearly erect, more compact heads of smaller flowers, and much smaller seeds, is the GREATER or NARROWLEAVED B. F. T. (L. major), which also is a common native of Britain, generally found in moist, bushy places. The characteristic differences remain under Some BIRDS OF PASSAGE are those birds which spend one part of the year in one country or climate and another part in another, migrating according to the season. No species of bird is known to hybernate (see HIBERNATION); and although many naturalists were at one time inclined to believe in the hybernation of swallows, this opinion has been entirely relinquished, and their annual migrations are fully ascertained. Birds avail themselves of their powers of wing to seek situations adapted for them in respect of temperature and supply of food, and even within the tropics there are birds which migrate as the seasons change from wet to dry, or from dry to wet. See BIRD OF PARADISE. The migration of birds, however, is more generally from north to south, or from south to north, in the temperate and colder regions of the globe, as winter passes into summer, or summer into winter; and B. of P. are commonly distinguished into Summer B. of P. and Winter B. of P., as they are summer or winter visitants; but, of course, those which are Summer B. of P. in one country are Winter B. of P. in another. They breed in the country in which they are Summer B. of P. The arrival of Summer B. of P. is always among the welcome signs of advancing spring, and is associated with all that is cheerful and delightful. In winter, flocks of swans, geese, and other waterfowl seek the British coasts and inland lakes and marshes from the frozen north; and at the same time, woodcocks, fieldfares, redwings, and many other birds which breed in more northern regions, regularly appear. birds come almost at the same date annually; others are more influenced by the character of the season, as mild or severe. Many sea-fowl are migratory, and the inhabitants of St Kilda and other isles, to whom they are of the greatest importance, depend with confidence upon their return almost at a particular day. The migrations of pigeons in North America are extraordinary, from the vast numbers of which the migrating flocks consist. See PIGEON. The whole subject of the migration of birds is one of great interest, particularly in reference to the instinct by which they appear to be guided. Birds of migratory species, which have been reared in confinement, become restless when the season for migration arrives, and in many species the migration seems to be little influenced by the state of the weather. It would seem that the youngest swallows are left behind, to follow the first migrating hosts of their species. The number of B. of P. is very considerable, nor are they all or mostly birds of long wing and powerful flight, but many short-winged birds are included among them. Some B. of P., as woodcocks, have, however, been found in a very exhausted state after their arrival; and it is to be considered that, both in the old and new world, distant migra tions are possible without long flights. Some birds possess such powers of wing, that they may easily pass over wide seas; and the rapidity of the flight of birds-from 50 to 150 miles an hour-partly explains the possibility of their migrations between distant parts of the world. It is believed that B. of P. habitually return to the same localities which they have inhabited in former years, and this seems to have been sufficiently established by proof, at least in regard to swallows. |