CHAPTER XXVII

BRANCH CHORDATA (_Continued_). CLASS AVES: THE BIRDS

THE ENGLISH SPARROW (_Passer domesticus_)

TECHNICAL NOTE.--The English sparrow may be found now in cities and villages all over the United States. It has become a veritable pest, and the killing of the few needed for the laboratory may be looked on as desirable rather than deplorable, as is the killing of birds in almost all other cases. The males have a black throat, with the other head-markings strong and contrasting (black, brown, and white), while the females have a uniform grayish and brownish coloration on the head.

Specimens are best taken alive, as shooting usually injures them for dissection. One can rely on the ingenuity of the boys of the class to procure a sufficient number of specimens. Observations on the habits of the birds should be made by the pupils as they go to and from school. For dissection use fresh specimens if possible. If desirable a pigeon or dove may be used in place of the sparrow.

=External structure.=--Note in the sparrow the same general arrangement of body parts as in the toad, the body being divided into _head_, _upper limbs_, _trunk_, and _lower limbs_. In the toad, however, all of the limbs are fitted for walking and jumping, whereas in the sparrow the anterior pair of appendages, the _wings_, are modified to be organs of flight, and the posterior limbs are specially adapted for perching. Note that the sparrow is covered with _feathers_, some long, some short, in some places thick and in others thin, but all fitting together to form a complete covering for the body. Note also that the anterior end of the head is prolonged into a hard bony structure, the _bill_, covered with horny substance. This horny substance together with the feathers and horny covering of the feet are modified portions of the skin. Note the long _quill-feathers_ attached to the posterior edge of the wing. By these the bird sustains its flight. Other long quill-feathers are attached to the posterior end of the body, forming the _tail_. By a system of muscles connected with these feathers they act together, serving as a rudder during flight and as a balancing contrivance when perching. Note just above the bill two openings protected by tufts of feathers. What are these openings? How are they connected with the _mouth_? Note the large _eyes_, and at the inner angle of each the delicate _nictitating membrane_ which can be drawn over the ball. Does the bird have external _ears_? Lift the feathers just above the tail (the upper tail-coverts) and note a small median gland, the _oil-gland_, from which the bird derives the oil with which it oils its feathers. Beneath the tail note the opening from the alimentary canal and from the kidneys and reproductive organs. This is called the _cloacal opening_.

Examine in detail some of the feathers. In one of the quill-feathers note the central _stem_ or _shaft_ composed of two parts, a basal hollow _quill_, which bears no web and by which the feather is inserted in the skin, and a longer, terminal, four-sided portion, the _rachis_, which bears on either side a _web_ or _vane_. Each vane is composed of many narrow linear plates, the _barbs_, from which rise (like miniature vanes) many _barbules_. Each barbule bears many fine _barbicels_ and _hamuli_ or _hooklets_. The barbs of the feather are interlocked. How is this effected? The feathers which overlie the whole body and bear the color pattern are called _contour-feathers_. How do they differ from or correspond with the quill-feathers in structure? Soft feathers called _down-feathers_ or _plumules_, cover the body more or less completely, being, however, mostly hidden by the contour-feathers; the barbs of these are sometimes not borne on a rachis, but arise as a tuft from the end of the quill. Certain other feathers which have an extremely slender stem and usually no vane, except a small terminal tuft of barbs, are called _thread-feathers_, or _filoplumules_. They are rather long, but are mostly hidden by the contour-feathers. In certain birds they stand out conspicuously, as the _vibrissæ_ about the nostrils.

In the determination of birds by the use of a classificatory "key" (see p. 359) it is necessary to be familiar with the names applied to the various external regions of the body and plumage, and with the terms used to denote the special varying conditions of these parts. By reference to figure 133 the names of the regions or parts most commonly referred to may be learned. A full account of all of the external characters with definitions of the various terms used in referring to them may be found in Coues's "Key to North American Birds."

TECHNICAL NOTE.--Pull the feathers from the body, being careful not to tear the skin.

In the fish and toad, already studied, the head is closely joined to the trunk. How is it with the bird? Observe that the _knee_ of the sparrow is covered by feathers and that it is the _ankle_ which extends down as the bare unfeathered part to the _digits_. How many digits have the feet of the bird? How are they arranged?

=Internal structure= (fig. 132).--TECHNICAL NOTE.--With a pair of scissors cut just beneath the skin anteriorly from the cloacal opening to the angle of the lower jaw. Pin the sparrow on its back by the wings, feet, and bill. Push back the skin from both sides and pin out.

Note the large powerful _pectoral muscles_. Note a hard median projection of bone, the _sternum_, which is a large keel-shaped bone with lateral expansions to which are attached the _ribs_. Where are the largest and most powerful muscles of the toad located? Where are they in the fish? In the bird the most powerful muscles are these pectoral muscles, which move the wings in flight.

TECHNICAL NOTE.--Cut the pectoral muscles from the left side of the sternum, push back and pin to one side. With a strong pair of scissors cut through the ribs on the left side of the sternum and through the overlying bones. Lift the whole sternum, with the right pectoral muscle attached, to the left side of the pan and pin it down. Cut through the membrane which covers the viscera and cover the dissection with water.

In this operation note the V-shaped _wishbone_ in front of the sternum. It is composed of the two _clavicles_ with their inner ends fused. Note the stout _coracoid_ bones extending from the anterior end of the sternum to the shoulder.

Note near the middle of the body the _heart_ with the large blood-vessels proceeding from it. Behind the heart lies the large reddish-brown _liver_, and on the left side below the liver is the large _gizzard_ or _muscular stomach_. Note the _viscera_ folded over themselves in the body-cavity. Push them temporarily aside and note in the dorsal region under the heart large pinkish spongy sacs, the _lungs_. These are attached by short tubes, the _bronchi_, to the long cartilaginous _trachea_. At the union of the bronchi with the trachea is a small expansion with cartilaginous walls, within which are stretched small bands of muscles. This organ is the _syrinx_, the song- or voice-apparatus of the bird. It should be cut open and carefully examined. Trace the trachea forward to its anterior end. It opens by a _glottis_ into the _larynx_, a slightly swollen chamber with cartilaginous walls. Note the U-shaped _hyoid bone_ surrounding the front of the glottis. Through a blowpipe or quill inserted into the glottis blow air into the trachea and observe the inflation of the lungs and of certain large _air-sacs_ in the abdomen, which communicate with them.

Beneath the trachea note the long _œsophagus_. Inflate the œsophagus with a blowpipe and note how distensible is its lower end near the breast. This distensible portion is called the _crop_. If the alimentary canal be drawn out straight the œsophagus will be found to run as an almost straight tube down the left side of the body to the gizzard. This latter organ has very thick muscular walls and in it the food is ground up among the small bits of gravel it contains. Extending from the gizzard near the entrance of the œsophagus note the long _pyloric loop_ of the intestine called _duodenum_. Within this loop is a long pinkish gland, the _pancreas_, which empties by a duct into the duodenum. Into the duodenum also the overlying liver empties its secretion of bile from the median-placed _gall-bladder_. From the duodenum the _small intestine_ or _ileum_ extends with many convolutions to its exit through the cloacal aperture. On the intestine near the cloacal opening note a pair of glandular structures, the _cæca_. The short part of intestine between the cæca and cloaca is called the _rectum_. On the left side of the body beneath the gizzard note a dark glandular structure, the _spleen_.

Make a drawing of the dissection as so far worked out.

TECHNICAL NOTE.--Remove the alimentary canal, cutting it free posteriorly at the cæca and anteriorly just above the muscular gizzard. Cut open the gizzard and note its structure. The contained sand and gravel grains are picked up by the bird as it eats.

On either side of the throat note the well-defined _thyroid gland_; in young sparrows will be noted on each side of the neck a mass of tissue, the remains of the _thymus gland_, which disappears in the adult.

Cut transversely through the lower end of the heart and note that the ventricles are wholly distinct, whereas in the toad and snake they are incompletely separated. In the bird there is a complete double circulation. Its blood is not mixed, the pure with the impure, as in the toad and snake. Blood passing through the _right auricle_ and _ventricle_ goes to the lungs; on its return to the heart purified, it enters the _left auricle_ and _left ventricle_ thence to pass out over the body through the arteries.

Note the large _aorta_ given off from the left ventricle. Note the two large branches, the _innominate arteries_, given off by it near its origin. Each innominate divides into three smaller arteries, a _carotid_, _branchial_, and _pectoral_. The aorta itself turns toward the back and continues posteriorly through the body as the _dorsal aorta_. To the right auricle come three large veins, the _right_ and _left præcavæ_ and the _postcava_. Each præcava is formed by three veins, the _jugular_ from the head, the _branchial_ from the wing, and the _pectoral_ from the pectoral muscles. The postcava comes from the liver. From the right ventricle go the short _right_ and _left pulmonary arteries_ to the lungs, and from the lungs the blood is brought to the left auricle through the _right_ and _left pulmonary veins_.

TECHNICAL NOTE.--For a detailed study of the circulation of the bird the teacher should inject the blood system of some larger bird, as a pigeon or fowl, for a class-demonstration. (For a guide, use Parker's "Zootomy," p. 209, or Martin and Moale's "How to Dissect a Bird," pp. 135-140 and pp. 148, 149.)

In the posterior dorsal region of the body-cavity will be found large three-lobed organs fitting into the spaces between the bones of the back on either side. These are the _kidneys_, and from their outer margins on each side a _ureter_ runs posteriorly into the cloaca. Overlying the anterior ends of the kidneys are the reproductive organs. In the male these glands consist of firm, whitish, glandular bodies. From each runs a long convoluted _vas deferens_, which enters the cloaca. This tube corresponds to the _egg-duct_ of the female. In the female the _right egg-gland_ and _egg-duct_ or _oviduct_ are wanting. The _left egg-gland_ appears as a glandular mass; during the breeding season yellow _ova_ or _eggs_ in various stages of development project from its surface. The oviduct opens by a funnel-shaped mouth near the _egg-gland_ and runs thence to the cloaca. The eggs pass from the egg-gland into the body-cavity, where they are caught in the upper end of the oviduct and carried down and out through the cloacal opening. It is in the oviduct that the egg derives its accessory covering, which consists of a white or albuminous portion, together with several enveloping membranes and the hard shell enclosing all.

Remove the top of the skull and note the large _brain_. What portions of the brain make up the greater part of it? Note the differences between this brain and that of the toad. Trace the principal _cranial nerves_. Work out the _spinal cord_ and principal _spinal nerves_. For an account of the nervous system of the sparrow see Martin and Moale's "How to Dissect a Bird," pp. 150-163.

TECHNICAL NOTE.--For a study of the skeleton of the sparrow a specimen should be cleaned by boiling in a soap-solution (see p. 452).

In the sparrow's _skeleton_ note the compactness of the _skull_ and the fusion of its bones. Observe the long _cervical vertebræ_ which support the skull, also the _thoracic vertebræ_ bearing the ribs and sternum. How many of each of these kinds of vertebræ are there? The vertebræ posterior to the thorax are more or less fused together to form the _sacrum_, which, with the _pelvic girdle_, supports the _leg-bones_. The bones of the tail consist of a number of very small vertebræ, some of which are fused together. Note the correspondence between the bones of the leg and those of the wing. What are the names of each of the bones of each limb, and what are the corresponding bones in the two limbs? The wings and legs being modified for different uses, their various bones have assumed different relations to each other and to the body, for they are bent at directly opposite angles and the attachment of muscles is different. Compare the skeleton of the bird with that of the toad. (For a detailed account of the skeleton of the bird see Parker's "Zootomy," pp. 182-209, or Martin and Moale's "How to Dissect a Bird," pp. 102-125.)

=Life-history and habits.=--The English sparrow was first introduced into the United States in 1850, and since that time has rapidly populated most of the cities and towns of the country. On account of its extreme adaptability to surroundings, its omnivorous food-habits and its fecundity it survives where other birds would die out. It also crowds out and has caused the disappearance or death of other birds more attractive and more useful. The sparrow annually rears five or six broods of young, laying from six to ten eggs at each sitting. Had it no enemies a single pair of sparrows would multiply to a most astonishing number. The sparrow has, however, a number of enemies, most common among them perhaps being the "small boy," but birds and mammals play the chief part in the destruction. The smaller hawks prey upon them, and rats and mice destroy great numbers of their young and of their eggs whenever the nests can be reached. The sparrow is omnivorous and when driven to it is a loathsome scavenger, though at other times its tastes are for dainty fruits. Its senses of perception are of the keenest; it can determine friend or foe at long range. The nesting habits are simple, the nests being roughly made of any sort of twigs and stems mixed with hair and feathers and placed in cornices or trees. A maple-tree in a small Missouri town contained at one time thirty-seven of these nests.

OTHER BIRDS.

Birds are readily and unmistakably distinguishable from all other kinds of animals by their feathers. They are further distinguished from the reptiles on one hand by their possession of a complete double circulation and by their warm blood (normally of a temperature of from 100-112° F.), and from the mammals on the other by the absence of milk-glands. There are about 10,000 known species of living birds; they occur in all countries, being most numerous and varied in the tropics. Birds are exceptionally available animals for the special attention of beginning students, because of their abundance and conspicuousness and the readiness with which their varied and interesting habits may be observed. The bright colors and characteristic manners which make the identification of the different kinds easy, the songs and flight, and the feeding, nesting and general domestic habits of birds are all excellent subjects for personal field-studies by the students. We shall therefore devote more attention to the birds than to the other classes of vertebrates, just as we selected the insects among the invertebrates for special consideration.

=Body form and structure.=--The general body form and external appearance of a bird are too familiar to need description. The covering of feathers, the modification of the fore limbs into wings, and the toothless, beaked mouth are characteristic and distinguishing external features. The feathers, although covering the whole of the surface of the body, are not uniformly distributed, but are grouped in tracts called _pterylæ_, separated by bare or downy spaces called _apteria_. They are of several kinds, the short soft plumules or down-feathers, the large stiffer contour-feathers, whose ends form the outermost covering of the body, the quill-feathers of the wings and tail, and the fine bristles or vibrissæ about the eyes and nostrils called thread-feathers. The fore limbs are modified to serve as wings, which are well developed in almost all birds. However, the strange Kiwi or Apteryx of New Zealand with hair-like feathers is almost wingless, and the penguins have the wings so reduced as to be incapable of flight, but serving as flippers to aid in swimming underneath the water. The ostriches and cassowaries also have only rudimentary wings and are not able to fly. Legs are present and functional in all birds, varying in relative length, shape of feet, etc., to suit the special perching, running, wading, or swimming habits of the various kinds. Living birds are toothless, although certain extinct forms, known through fossils, had large teeth set in sockets on both jaws. The place of teeth is taken, as far as may be, by the bill or beak formed of the two jaws, projecting forward and tapering more or less abruptly to a point. In most birds the jaws or mandibles are covered by a horny sheath. In some water and shore forms the mandibular covering is soft and leathery. The range in size of birds is indicated by comparing a humming-bird with an ostrich.

Many of the bones of birds are hollow and contain air. The air-spaces in them connect with air-sacs in the body, which connect in turn with the lungs. Thus a bird's body contains a large amount of air, a condition helpful of course in flight. The breast-bone is usually provided with a marked ridge or keel for the attachment of the large and powerful muscles that move the wings, but in those birds like the ostriches, which do not fly and have only rudimentary wings, this keel is greatly reduced or wholly wanting. The fore limbs or wings are terminated by three "fingers" only; the legs have usually four, although a few birds have only three toes and the ostriches but two.

As birds have no teeth with which to masticate their food, a special region of the alimentary canal, the gizzard, is provided with strong muscles and a hard and rough inner surface by means of which the food is crushed. Seed-eating birds have the gizzard especially well developed, and some birds take small stones into the gizzard to assist in the grinding. The lungs of birds are more complex than those of batrachians and reptiles, being divided into small spaces by numerous membranous partitions. They are not lobed as in mammals, and do not lie free in the body-cavity, but are fixed to the inner dorsal region of the body. Connected with the lungs are the air-sacs already referred to, which are in turn connected with the air-spaces in the hollow bones. By this arrangement the bird can fill with air not only its lungs but all the special air-sacs and spaces and thus greatly lower its specific gravity. The vocal utterances of birds are produced by the vocal cords of the syrinx or lower larynx, situated at the lower end of the trachea just where it divides into the two bronchial tubes, the tracheal rings being here modified so as to produce a voice-box containing two vocal cords controlled by five or six pairs of muscles. The air passing through the voice-box strikes against the vocal cords, the tension of which can be varied by the muscles. In mammals the voice-organ is at the upper or throat end of the trachea.

The heart of birds is composed of four distinct chambers, the septum between the two ventricles, incomplete in the Reptilia, being in this group complete. There is thus no mixing of arterial and venous blood in the heart. The systemic blood-circulation being completely separated from the pulmonic, the circulation is said to be double. The circulation of birds is active and intense; they have the hottest blood and the quickest pulse of all animals. In them the brain is compact and large, and more highly developed than in batrachians and reptiles, but the cerebrum has no convolutions as in the mammals. Of the special senses the organs of touch and taste are apparently not keen; those of smell, hearing, and sight are well developed. The optic lobes of the brain are of great size, relatively, compared with those of other vertebrate brains, and there is no doubt that the sight of birds is keen and effective. The power of accommodation or of quickly changing the focus of the eye is highly perfected. The structure of the ear is comparatively simple, there being ordinarily no external ear, other than a simple opening. The organs of the inner ear, however, are well developed, and birds undoubtedly have excellent hearing. The nostrils open upon the beak, and the nasal chambers are not at all complex, the smelling surface being not very extensive. It is probable that the sense of smell is not, as a rule, especially keen.

=Development and life-history.=--All birds are hatched from eggs, which undergo a longer or shorter period of incubation outside the body of the mother, and which are, in most cases, laid in a nest and incubated by the parents. The eggs are fertilized within the body of the female, the mating time of most birds being in the spring or early summer. Some kinds, the English sparrow, for example, rear numerous broods each year, but most species have only one or at most two. The eggs vary greatly in size and color-markings, and in number from one, as with many of the Arctic ocean birds, to six or ten, as with most of the familiar song-birds, or from ten to twenty, as with some of the pheasants and grouse. The duration of incubation (outside the body) varies from ten to thirty days among the more familiar birds, to nearly fifty among the ostriches. The temperature necessary for incubation is about 40° C. (100° F.). Among polygamous birds (species in which a male mates with several or many females) the males take no part in the incubation and little or none in the care of the hatched young; among most monogamous birds, however, the male helps to build the nest, takes his turn at sitting on the eggs, and is active in bringing food for the young, and in defending them from enemies. The young, when ready to hatch, break the egg-shell with the "egg-tooth," a horny pointed projection on the upper mandible, and emerge either blind and almost naked, dependent upon the parents for food until able to fly (altricial young), or with eyes open and with body covered with down, and able in a few hours to feed themselves (precocial young).

More details regarding the eggs, nest, and young of birds will be given later in this chapter.

=Classification.=--The class Aves is usually divided into numerous orders, the number and limits of these as published in zoological manuals varying according to the opinions of various zoologists. The rank of an order in this group is far lower than in most other classes. In other words, the orders are very much alike and are recognized mainly for the convenience in breaking up the vast assemblage of species. In North America practically all the ornithologists have agreed upon a scheme of classification, which will therefore be adopted in this book. According to this classification the eight hundred (approximately) known species of North American birds represent seventeen orders. Certain recognized orders, for example, the ostriches, are not represented naturally in North America at all. As birds can usually be readily identified, the species being easily distinguished by general external appearance, and as there are many excellent book-guides to their classification, the beginning student can specially well begin with them his study of systematic zoology, which concerns the identification and classification of species. In a later paragraph are given therefore some suggestions for field and laboratory work in the determination of local bird-faunæ. In the following paragraphs each of the American orders is briefly discussed, as is also the foreign order of ostriches.

=The ostriches, cassowaries, etc. (Ratitæ).=--The ostriches, familiar to all from pictures and to some from live individuals in zoological gardens and menageries, or stuffed specimens in museums, together with a few other similar large species, are distinguished from all other birds by having the breast-bone flat instead of keeled. There are about a score of species of ostriches and ostrich-like birds all confined to the southern hemisphere. In them the wings are so reduced that flight is impossible, but the legs are long and strong, and they can run as swiftly as a galloping horse. They are said to have a stride of over twenty feet. They use their legs also as weapons, kicking viciously when angered. The true ostriches (_Struthio camelus_) (fig. 135) live in Africa. They are the largest living birds, reaching a height of nearly seven feet and weighing as much as two hundred pounds. They are hunted for their feathers, and are now kept in captivity and bred in South Africa and California for the same purpose. About five million dollars' worth of ostrich-feathers are used each year. The eggs, which are from five to six inches long and nearly five inches thick, are laid in shallow hollows scooped out in the sand of the desert. The male undertakes most of the incubation, although when the sun is hot no brooding is necessary. The young (fig. 136) hatch in from seven to eight weeks, and can run about immediately.

The rheas, found in South America, and the cassowaries of Australia are the only other living ostrich-like birds. Their feathers are of much less value than those of the true ostrich.

=The loons, grebes, auks, etc. (Pygopodes).=--The loons, grebes, and auks are aquatic birds, living in both ocean and fresh waters. Their feet are webbed or lobed, and their legs set so far back that walking is very difficult and awkward. But all the birds of this order are excellent swimmers and divers. They are distinctively the diving birds. They have short wings and almost no tail. The dab-chick or pied-billed grebe (_Podilymbus podiceps_) is common in ponds over all the country. Its eggs are laid in a floating nest of pond vegetation and are often covered with decaying plants. The horned grebe (_Colymbus auritus_) is common west of the Mississippi in lakes and ponds. The loon or great northern diver (_Gavia imber_), found all over the United States in winter, is the largest of this group, reaching a length (from bill to tip of tail) of three feet. It is black above with many small white spots, and with a patch of white streaks on each side of the neck and on the throat; it is white on breast and belly. The female is duller, being brownish instead of black.

The auks, guillemots, puffins, and murres (fig. 137) are ocean birds which gather, in the breeding season, in countless numbers on the bleak rocks and inaccessible cliffs of the northern oceans. Each female lays a single egg (in some cases two or at most three) on the bare rock or in a crevice or sort of burrow. These birds mostly fly well, but are especially at home in the water, feeding exclusively on animal substances found there. A famous species is the great auk (_Alca impennis_), which has become extinct in historical times. The last living specimen was seen in 1844.

=The gulls, terns, petrels, and albatrosses (Longipennes).=--The Longipennes are water-birds, mostly maritime, with webbed feet and very long and pointed wings. They are all strong flyers, and most of them are beautiful birds. Their prevailing colors are white, slaty or lead-blue, black, and, in the young, mottled brownish. They subsist chiefly on fish, but any animal substance will be eagerly picked up from the water; some of the gulls forage inland. Occasionally great flocks may be seen following a plow near the shore and feeding on the grubs and worms exposed in the freshly-turned soil. Some of the gulls, like the great black-backed gull (_Larus marinus_), attain a length of two and one-half feet. The terns (_Sterna_) are mostly smaller than the gulls, have a bill not so heavy and not hooked, and have the tail forked.

The fulmars, shearwaters, petrels, and albatrosses are strictly maritime. The albatrosses are very large, the largest being three feet long with a spread of wing of seven feet. They are often found flying easily over the open ocean at great distances from land. Like the auks and puffins, the fulmars and shearwaters gather in extraordinary numbers on rocky ocean islets or cliffs of the coast to breed.

=The cormorants, pelicans, etc. (Steganopodes).=--The Steganopodes are water-birds with full-webbed feet, and prominent gular pouch, swimmers rather than flyers like the Longipennes. The cormorants (_Phalacrocorax_) inhabit rocky coasts and are green-eyed, large, heavy, black birds with greenish-purple and violet iridescence; they are among the most familiar of seashore birds. They feed chiefly on fish and dive and swim under water with great ability. Cormorants are rather gregarious, keeping together in small groups when fishing, migrating often in great flocks, and in the breeding season gathering in immense numbers on certain rocky cliffs or islets. They build their nests of sticks and sea-weed; the eggs are three or four, and usually bluish green with white, chalky covering substance.

The pelicans are large, long-winged, short-legged water-birds with enormous bill and large gular sac which is used as a dip-net to catch fish. There are three species in North America, the white pelican (_Pelecanus erythrorhynchus_) occurring over most of the United States, the brown pelican (_P. fuscus_) of the Gulf of Mexico, and the California brown pelican (_P. californicus_) of the Pacific coast.

An interesting member of this order is the famous frigate or man-of-war bird (_Fregata aquila_), with very long wings and tail and feet extraordinarily small. The frigates have the greatest command of wing of all the birds. They cannot dive and can scarcely swim or walk.

=The ducks, geese, and swans (Anseres).=--The familiar wild ducks, of which there are forty species in North American fresh and salt waters; the geese, of which there are sixteen species, and the three species of wild swans constitute the order Anseres. The bill in these birds is more or less flattened and is also lamellate, i.e. furnished along each cutting-edge with a regular series of tooth-like processes; the feet are webbed, and the body is heavy and flattened beneath. Of the fresh-water or inland ducks, the more familiar are the mallard (_Anas boschas_), a large duck with head (male) and upper neck rich glossy green; the blue-winged teal (_Querquedula discors_) and green-winged teal (_Nettion carolinense_); the shoveller (_Spatula clypeata_) with spoon-shaped bill; the beautiful crested wood-duck (_Aix sponsa_); the expert diver, the plump little ruddy duck (_Erismatura rubida_), and others. Of the coastwise ducks, the canvas-back (_Aythya vallisneria_) is famous because of its fine flavor, while among the strictly maritime ducks the eiders (_Somateria_), which live in Arctic regions, are well known for their fine down. Of the geese, the commonest is the well-known Canada goose (_Branta canadensis_), while the pure-white snow-goose (_Chen hyperborea_), with black wing-feathers and red bill, is not unfamiliar. The wild swans (_Olor_) are the largest birds of the order, and are less familiar than the ducks and geese.

=The ibises, herons, and bitterns (Herodiones).=--The tall, long-necked, long-legged, wading birds, known as herons and ibises, compose a small order, the Herodiones, of which but few representatives are at all familiar. Perhaps the most abundant species is the green heron (_Ardea virescens_) or "fly-up-the-creek," one of the smaller members of the order. The crown, back, and wings are green, the neck purplish cinnamon, and the throat and fore neck white-striped. This bird is commonly seen perching on an overhanging limb, or flying slowly up or down some small stream. The great blue heron (_Ardea herodias_) is common over the whole country. It is four feet long and grayish blue, marked with black and white. It may be seen standing alone in wet meadows or pastures, or flying heavily, with head drawn back and long legs outstretched. It breeds singly, but oftener in great heronries, in trees or bushes. Its large bulky nests contain three to six dull, greenish-blue eggs about two and one-half inches long. The white egrets of the Southern States are shot for their plumes and have been locally exterminated in some places. The night-herons (_Nycticorax_) differ from the other forms in having both the neck and legs short. The bittern (_Botaurus lentiginosus_), Indian hen, stake-driver, or thunder-pumper, as it is variously called, is a familiar member of the order, found in marshes and wet pastures, and known by its extraordinary call, sounding like the "strokes of a mallet on a stake." In color it is brownish, freckled and streaked with tawny whitish and blackish. Its nest is made on the ground; its eggs, from three to five in number, are brownish drab and about two inches long.

=The cranes, rails, and coots (Paludicolæ).=--The cranes, of which three species are known in North America, are large birds with long legs and neck, part of the head being naked or with hair-like feathers. The rare whooping crane (_Grus americana_) is pure white with black on the wings, and is fifty inches long from tip of bill to tip of tail. The sand-hill crane (_G. mexicana_) is slaty gray or brownish in color, never white, and although rare in the East is quite common in the South and West. Cranes build nests on the ground, and lay but two eggs, about four inches long, brownish drab in color with large irregular spots of dull chocolate-brown.

The rails are smaller than the cranes, with short wings and very short tail. They live in marshes and swamps, and in flying let the legs hang down. Their legs are strong, and for escape they trust more to speed in running than to flight. They are hunted for food. The most abundant rail is the "Carolina crake" or "sora" (_Porzana carolina_), small and olive-brown with numerous sharp white streaks and specks. Many of these birds are shot each year during migration in the reedy swamps of the Atlantic States. The American coot or mud-hen (_Fulica americana_), dark slate-color with white bill, is one of the most familiar pond-birds over all temperate North America. Its nest consists of a mass of broken reeds resting on the water; the eggs number about a dozen, and are clay-color with pin-head dots of dark brown.

=The snipes, sandpipers, plover, etc. (Limicolæ).=--The large order Limicolæ, the shore-birds, includes the slender-legged, slender-billed, round-headed, rather small wading birds of shores and marshes familiar to us as snipes, plovers, sandpipers, curlews, yellow-legs, sandpeeps, turnstones, etc. Most of them are game-birds, such forms as the woodcock and Wilson's or English snipe being much hunted. The food of these birds consists of worms and other small animals, which are chiefly obtained by probing with the rather flexible, sensitive, and usually long bill in the mud or sand. The killdeer (_Ægialitis vocifera_), familiar to all in its range by its peculiar call and handsome markings, the upland or field plover (_Bartramia longicauda_), with its long legs and melodious quavering whistle, the tall, yellow-shanked "telltale" or yellow-legs (_Totanus melanoleucus_) of the marshes and wet pastures, are among the most widespread and familiar species of the order. On the seashore the dense flocks of white-winged, whisking sandpipers and the quickly running groups of plump ring-necked plover are familiar sights. One of the largest birds of this order is the long-billed curlew (_Numenius longirostris_) of the upland pastures. The bill of the curlew is long and curved downwards. The nests of these shore-birds are made on the ground and are usually little more than shallow depressions in which the few spotted eggs (four is a common number) are laid. The young are precocial.

=The grouse, quail, pheasants, turkeys, etc. (Gallinæ).=--The Gallinæ include most of the domestic fowls, as the hen, turkey, peacock, guinea-fowls, and pheasants, and the grouse, quail, partridges, and wild turkeys. The chief game-birds of most countries belong to this order. They have the bill short, heavy, convex, and bony, adapted for picking up and crushing seeds and grains which compose their principal food. Their legs are strong and usually not long, and are often feathered very low down. The Gallinæ are mostly terrestrial in habit and are sometimes known as the Rasores or "scratchers." Among the more familiar wild gallinaceous birds are the quail or "Bob white" (_Colinus virginianus_), abundant in eastern and central United States, the ruffed grouse (_Bonasa umbellus_) of the Eastern woods, and the prairie-chicken (_Tympanuchus americanus_) of the Western prairies. The sage-hen (_Centrocercus urophasianus_), the largest of the American grouse, reaching a length of two and one-half feet, is an interesting inhabitant of the sterile sagebrush plains of the West. The ptarmigan (_Lagopus_) or snow-grouse, represented by several species, are found either among the rocks and snow-banks above timber line on high mountains, or in the Arctic regions. In summer their plumage is brown and white; in winter they turn pure white to harmonize with the uniform snow-covering. On the Pacific coast are several species of quail, all differing much from those of the East. These Western species have beautiful crests of a few or several long plume-feathers, the body-plumage being also unusually beautiful. The eggs of all the Gallinæ are numerous and are laid in a rude nest or simply in a depression on the ground. In many of the species polygamy is the rule. The young are precocial.

=The doves and pigeons (Columbæ).=--The doves and pigeons constitute a small order, the Columbæ, closely related to the Gallinæ. A distinguishing characteristic of the Columbæ lies in the bill, which is covered at the base with a soft swollen membrane or cere in which the nostrils open. The members of this order feed on fruits, seeds, and grains. Our most familiar wild species is the mourning-dove or turtle-dove (_Zenaidura macroura_) found abundantly all over the country. It lays two eggs in a loose slight nest in a low tree or on the ground. The beautiful wild or passenger pigeon (_Ectopistes migratorius_) was once extremely abundant in this country, moving about in tremendous flocks in the Eastern and Central States. But it has been so relentlessly hunted that the species is apparently becoming extinct. In the Rocky and Sierra Nevada mountains is a rather large dove, the band-tailed pigeon (_Columba fasciata_), which subsists chiefly on acorns. The domestic pigeon represented by numerous varieties, pouters, carriers, ruff-necks, fan-tails, etc., is the artificially selected descendant of the rock-dove (_Columba livia_). The young of all pigeons are altricial.

=The eagles, owls, and vultures (Raptores).=--The "birds of prey" compose one of the larger orders, the members of which are readily recognizable. In all the bill is heavy, powerful, and strongly hooked at the tip. The feet are strong, with long, curved claws (small in the vultures) and are fitted for seizing and holding living prey, such as smaller birds, fish, reptiles, and mammals which constitute the principal food of the true raptorial species. The vultures feed on carrion. The turkey buzzard (_Cathartes aura_) is the most familiar of the three species of carrion-feeding Raptores found in the United States. The buzzard nests on the ground or in hollow stumps or logs, and lays two white eggs (sometimes only one) blotched with brown and purplish. The largest North American vulture is the California condor (_Pseudogryphus californianus_), which attains a length of four and one-half feet, with a spread of wing of nine and one-half feet. Of the eagles, the most widespread and commonest is the bald eagle (_Haliætus leucocephalus_). It is three feet long and when adult has the head and neck white. The golden eagle (_Aquila chrysætos_) has the neck and head tawny brown. Of the many species of hawks, the marsh harrier (_Circus hudsonius_), abundant all over the country and readily known by its white rump, is one of the most familiar. The name "chicken-hawk" is given to two or three different species of large broad-winged hawks of the genus _Buteo_. The stout little sparrow-hawk (_Falco sparverius_), common over the whole country, is familiar and readily recognizable by its pronounced bluish and black wings and black-and-white banded chestnut tail. Altogether fifty species of hawks and eagles are found in this country. Of the owls, the barn-owl (_Strix pratincola_) with its long triangular face and handsome mottled and spotted tawny coat is more or less familiar; the great horned owl (_Bubo virginianus_), the snowy owl (_Nyctea nyctea_), and the great gray owl (_Scotiaptex cinerea_) are the common large species, while the red screech-owl (_Megascops asio_) (fig. 138), the most abundant owl in the country, and the strange burrowing owl (_Speotyto cunicularia_), which lives in the holes of prairie-dogs and ground-squirrels in the West, are familiar smaller ones. Thirty-two species of owls are recorded from North America.

=The parrots (Psittaci).=--The parrots, of which only one species is native in the United States, constitute an interesting order of birds, the Psittaci. They are abundant in tropical America. They have a very thick strongly hooked bill, with a thick and fleshy tongue. The feet have two toes pointing forward and two backward. The plumage is usually brightly and gaudily colored. The natural voice is harsh and discordant, but many of the species can imitate with surprising cleverness the speech of man. Parrots are long-lived and usually docile, and are much kept as pets. The single native species, the Carolina paroquet (_Conurus carolinensis_), is about a foot in length, is green, with yellow head and neck and orange-red face. Its range once extended from the Gulf of Mexico north to the Great Lakes, but it has been nearly exterminated in all the States but Florida.

=The cuckoos and kingfishers (Coccyges).=--The cuckoos and kingfishers are regarded as constituting an order, Coccyges, a small group whose members are without any definite bond of union. Only ten species of North American birds belong to this order. The yellow-billed and black-billed cuckoos (_Coccyzus_) or "rain-crows" are long-tailed, slender, lustrous drab birds, which lay their eggs in the nests of others. They are notable for their peculiar rolling call. On the plains and hills of California and the southwest lives the road-runner or chaparral cock (_Geococcyx californianus_), a strange bird belonging to the cuckoo family. It is nearly two feet long, of which length the tail makes half. These birds run so rapidly that a horse is little more than able to keep up with them. They feed on fruits, various reptiles, insects, etc. The one common kingfisher of this country, the belted kingfisher (_Ceryle alcyon_), a thick-set, heavy-billed, ashy blue-and-white bird, is familiar along streams. As it flies swiftly along it gives its rattling cry. It nests in deep holes in the stream-banks, and lays six or eight crystal-white spheroidal eggs.

=The woodpeckers (Pici).=--The familiar woodpeckers and sap-suckers compose a well-defined order, Pici, which is represented in North America by twenty-five species. The bill of the woodpecker is stout and strong, usually straight, fitted for driving or boring into wood; the tongue is long, sharp-pointed, and barbed, fitted for spearing insects. The feet have two toes turned forward and two backward; the tail-feathers are stiff and sharp-pointed and help support the bird as it clings to the vertical side of a tree-trunk or branch (fig. 139). The food of most woodpeckers consists chiefly of insects, usually wood-boring larvæ (grubs). These birds do much good by destroying many noxious insect pests of trees. A few species, the true sap-suckers, probably feed on the sap of trees. Their nests are made in holes in trees, and the eggs are pure white and rounded. The harsh and shrill cries of the woodpeckers are familiar to all.

The largest and one of the most interesting woodpeckers is the ivory-billed (_Campephilus principalis_), twenty inches long, glossy blue-black, with a high head-crest which is scarlet in the male. This bird lives in the heavily wooded swamps of the Southern States. Among the more abundant and widespread, and hence better known, woodpeckers are the yellow-hammers (fig. 139) or flickers (_Colaptes auratus_ in the East, _C. cafer_ in the West), the red-headed woodpecker (_Melanerpes erythrocephalus_), with its crimson head and neck and pure-white "vest"; and the black-and-white downy (_Dryobates pubescens_) and hairy (_D. villosus_) woodpeckers or "sap-suckers." The California woodpecker (_M. formicivorus_), a near relative of the red-headed woodpecker, has the curious habit of boring small holes in the bark of oak- or pine-trees and sticking acorns into these holes. Sometimes thousands of acorns are put into the bark of one tree, to which the birds come occasionally to break open some acorns and feed on the grubs inside.

=The whippoorwills, chimney-swifts and humming-birds (Macrochires).=--All the birds of this order are remarkable for their power of flight. They have long and pointed wings; their feet are small and weak and used only for perching or clinging. All feed on insects, which are caught on the wing by the short-beaked, wide-mouthed swifts and whippoorwills and extracted from flower-cups by the humming-birds with their long and slender bills. The whippoorwill (_Antrostomus vociferus_) is common in the woods of the East and is readily known by its call. Its two brown-blotched white eggs are laid loose on the ground or on a log or stump. The night-hawk (_Chordeiles virginianus_), common over the whole country, is seen at twilight flying vigorously about in its search for insects. Its nesting habits are like those of the whippoorwill. The sooty-brown chimney-swifts (_Chætura pelagica_), popularly confused with the swallows, are the common inhabitants of old chimneys, in which they build their curious saucer-shaped open-work nests. Their eggs are pure white and number four or five. Of the humming-birds but one species, the ruby-throat (_Trochilus colubris_), is to be found in the Eastern States, but in the western and especially southwestern parts of the country several other species occur. In all seventeen species have been found in the United States. The nests (fig. 140) of the hummers are very dainty little cups lined with hair or wool or plant-down. The ruby-throat lays two tiny pure-white eggs.

=The perchers (Passeres).=--Nearly one-half of the birds of North America belong to the great order Passeres, and of all the known birds of the world more than half are included in it. The Passeres or perching birds include the familiar song-birds and a great majority of the birds of the garden, the forest, the roadside, and the field. The feet of these birds always have four toes and are fitted for perching. The syrinx or musical apparatus is, in most, well developed. The nesting and other domestic habits are various, but the young are always hatched in a helpless condition and have to be fed and otherwise cared for by the parents for a longer or shorter time. The North American species of this order are grouped into eighteen families, as the fly-catcher family (Tyrannidæ), the crow family (Corvidæ), the sparrows and finches (Fringillidæ), the swallows (Hirundinidæ), the warblers (Mniotiltidæ), the wrens (Troglodytidæ), the thrushes, robins and bluebirds (Turdidæ), etc. In this book nothing can be said of the various species which belong to this order. However, as the passerine birds are those which most immediately surround us and which, by their familiar songs and nesting habits, most interest us, the out-door study of birds by beginning students will be devoted chiefly to the members of this order, and many species will soon be got acquainted with. The robin and bluebird will introduce us to the shyer and less familiar song-thrushes; the study of the kingbird or bee-martin will interest us in some of the other fly-catchers; from the familiar chipping sparrow and tree-sparrow we shall be led to look for their cousins the swamp-sparrows and song-sparrows, and the larger grosbeaks and cross-bills, and so on through the order.

=Determining and studying the birds of a locality.=--To identify the various species of birds in the locality of the school it will be necessary to have some book giving the descriptions of all or most of the species of the region, with tables and keys for tracing out the different forms. Such manuals or keys are numerous now; the study of birds is one of the most popular lines of nature study, and a host of bird books has been published in the last few years. The best general manual is Coues's "Key to the Birds of North America," which includes not only keys for tracing and descriptions of all the known species of birds on this continent, but also accounts of the distribution, of the nesting and eggs, and of the plumage of the young birds, besides a thorough introduction to the anatomy and physiology of birds, and directions for collecting and preserving them. Jordan's "Manual of Vertebrates" gives keys and short descriptions of the birds found east of the Missouri River; Chapman's "Handbook of the Birds of Eastern North America" is excellent. To be able to use these manuals it is necessary to have the bird's body in hand; and that means usually death for the bird. Recently there have been published several bird-keys which attempt to make it possible to determine species, the commoner ones at any rate, without such close examination. The birds in these books are usually grouped wholly artificially (without any reference to their natural relationships) according to such salient characteristics as color, markings, size, habit of perching, or running, or flying, etc. These characteristics are such as can presumably be made out in the living bird by aid of an opera-glass or often with the unaided eye. Such books make no pretence to be scientific manuals nor to include any but the more usual and strongly marked species. They are usually limited to the birds of a restricted region. Such books are readily obtainable. There are several popular illustrated "bird-magazines" devoted to accounts of the life and habits of birds. Of these "Bird-lore" is the organ of the Audubon Society for the Protection of Birds.

In trying to become acquainted with the birds of a locality it must be borne in mind that the bird-fauna of any region varies with the season. Some birds live in a certain region all the year through; these are called _residents_. Some spend only the summer or breeding season in the locality, coming up from the South in spring and flying back in autumn; these are _summer residents_. Some spend only the winter in the locality, coming down from the severer North at the beginning of winter and going back with the coming of spring; these are _winter residents_. Some are to be found in the locality only in spring and autumn as they are migrating north and south between their tropical winter quarters and their northern summer or breeding home; these are _migrants_. And finally an occasional representative of certain bird species whose normal habitat does not include the given locality at all will appear now and then blown aside from its regular path of migration or otherwise astray; these are _visitants_. As to the relative importance, numerically, of these various categories among the birds which may be found in a certain region and thus form its bird-fauna we may illustrate by reference to a definite region. Of the 351 species of birds which have been found in the State of Kansas (a region without distinct natural boundaries and fairly representative of any Mississippi valley region of similar extent), 51 are all-year residents; 125 are summer residents, 36 are winter residents, 104 are migrants, and 35 are rare visitants.

It must also be kept in mind in using bird-keys and descriptions to determine species that the descriptions and keys refer to adult birds and in ordinary plumage. Among numerous birds the young of the year, old enough to fly and as large as the adults, still differ considerably in plumage from the latter; males differ from females, and finally both males and females may change their plumage (hence color and markings) with the season. The seasonal changes of plumage accomplished by molting may be marked or hardly noticeable. "All birds get new suits at least once a year, changing in the fall. Some change in the spring also, either partially or wholly, while others have as many as three changes--perhaps, to a slight extent, a few more.... It is claimed by some that now all new colors are acquired by molt, and by others that in some instances (young hawks) an infusion or loss, as the case may be, of pigment takes place as the feather forms, and continues so long as it grows."

There is much lack and uncertainty of knowledge concerning the molting and change of plumage by birds, and careful observations by bird-students should be made on the subject.

In connection with learning the different kinds of birds in a locality, together with their names, observations should be made, and notes of them recorded, on their habits and on the relation or adaptation of structure and habit to the life of the bird. Some of the special subjects for such observation are pointed out in the following paragraphs. A suggestive book, treating of the adaptive structure and the life of birds is Baskett's "The Story of the Birds."

=Bills and feet.=--The interesting adaptation of structure to special use is admirably shown in the varying character of the bills and feet of birds. The various feeding habits and uses of the feet of different birds are readily observed, and the accompanying modification of bills and feet can be readily seen in birds either freshly killed or preserved as "bird-skins." Such skins may be made as directed on p. 467, or may be bought cheaply of taxidermists. A set of such skins, properly named, will be of great help in studying birds, and should be in the high-school collection. In some cases the general structure of feet and bills may be seen in the live birds by the use of an opera-glass. The characters of bills and feet are much used in the classification of birds, so that any knowledge of them gained primarily in the study of adaptations will have a secondary use in classification work.

Note the foot of the robin, bluebird, catbird, wrens, warblers and other passerine or perching birds. It has three unwebbed toes in front, and a long hind toe perfectly opposable to the middle front one. This is the _perching_ foot. Note the so-called _zygodactyl_ foot of the woodpecker, with two toes projecting in front and partly yoked together, and two similarly yoked projecting behind. Note the webbed swimming foot of the aquatic birds; note the different degrees of webbing, from the _totipalmate_, where all four toes are completely webbed, _palmate_, where the three front toes only are bound together but the web runs out to the claws, to the _semi-palmate_, where the web runs out only about half way. Note the _lobate_ foot of the coots and phalaropes. Note the long slender wading legs of the sandpipers, snipe and other shore birds; the short heavy strong leg of the divers; the small weak leg of the swifts and humming-birds, almost always on the wing; the stout heavily nailed foot of the scratchers, as the hens, grouse, and turkeys; and the strong grasping talons, with their sharp long curving nails, of the hawks and owls and other birds of prey. In all these cases the fitness of the structure of the foot to the special habits of the bird is apparent.

Similarly the shape and structural character of the bill should be noted, as related to its use, this being chiefly concerned of course with the feeding habits. Note the strong hooked and dentate bill of the birds of prey; they tear their prey. Note the long slender sensitive bill of the sandpipers; they probe the wet sand for worms. Note the short weak bill and wide mouth of the night-hawk and whippoorwill and of the swifts and swallows; they catch insects in this wide mouth while on the wing. Note the flat lamellate bill of the ducks; they scoop up mud and water and strain their food from it. Note the firm chisel-like bill of the woodpeckers; they bore into hard wood for insects. Note the peculiarly crossed mandibles of the cross-bills; they tear open pine-cones for seeds. Note the long sharp slender bill of the humming-birds; they get insects from the bottom of flower-cups. Note the bill and foot of any bird you examine, and see if they are specially adapted to the habits of the bird.

The tongues and tails of birds are two other structures the modifications and special uses of which may be readily observed and studied. Note the structure and special use of the tongue and tail of the woodpeckers; note the tongue of the humming-bird; the tail of the grackles.

=Flight and songs.=--The most casual observation of birds reveals differences in the flight of different kinds, so characteristic and distinctive as to give much aid in determining the identity of birds in nature. Note the flight of the woodpeckers; it identifies them unmistakably in the air. Note the rapid beating of the wings of quail and grouse; also of wild ducks; the slow heavy flapping of the larger hawks and owls and of the crows; and the splendid soaring of the turkey-buzzard and of the gulls. This soaring has been the subject of much observation and study but is still imperfectly understood. The soaring bird evidently takes advantage of horizontal air-currents, and some observers maintain that upward currents also must be present. The principal hopes for the invention of a successful flying-machine rest on the power of soaring possessed by birds. The speed of flight of some birds is enormous, the passenger-pigeon having been estimated to attain a speed of one hundred miles an hour. The long distances covered in a single continuous flight by certain birds are also extraordinary, as is also the total distance covered by some of the migrants. "It is said that some plovers that nest in Labrador winter in Patagonia, their long wings easily carrying them this great distance."

Varying even more than the manner and power of flight among different birds are the vocal utterances, the cries and calls and singing. By their calls and songs alone many birds may be identified although they remain unseen. The field-student of birds comes to know them by their songs; knows what birds they are; knows what they are doing or not doing; knows what time in their life-season it is, whether they are mating, or brooding, or preparing to migrate; knows whether they are frightened, or self-confident, whether in distress or happy. Little urging and suggestion are needed to induce the student to attend to the songs. But the naturalist should not only hear and enjoy them, but by observation and the recording of repeated observations, he should come to understand the significance of the calls and songs.

As to how these sounds are made, attention has already been called (see p. 338) to the voice-organ or syrinx. The condition of this organ varies much in birds, as would be expected from the differing character of vocal utterances. Dissections will make these differences apparent.

=Nesting and care of young.=--Among the birds' most interesting instincts and habits are those domestic ones which include mating, nest-building, and care of the young. Birds' eggs and birds' nests are always attractive objects of search and collection for boys, and most boys have a considerable personal knowledge of the domestic habits of the commoner summer birds of their region. With this interest and unsystematized knowledge as a basis the teacher should be able to get from the class much excellent field-work and personal observation. The first thing to undertake in this study is the gathering of data regarding the character of the nests of different species, their situation, the time of nesting, the participation or non-participation of the male in nest-building, etc.; also the number of eggs, their size and color markings, the length of incubation, the help or lack of help of the male in brooding, etc. In connection with this gathering of data in the field by note-taking, sketching, and photographing, nests and eggs can be collected (see directions on page 469). Let only one clutch of eggs of each species be taken for the common high-school collection, and if more than one nest is desired take used and deserted nests. When the nestlings are hatched, the bringing of food, the defence of the home, and the teaching of the young to fly should all be observed and noted.

Some attempt should be made to systematize the miscellaneous data obtained. Do all the members of a group have similar nesting habits? Note the early nesting of birds of prey; note the nests of the woodpeckers in holes in trees; note the nesting of the various swallows. Is there any significance in the colors and markings of eggs? Observe the protective coloration obvious in some (see Chap. XXXI). Are there differences in the condition of the newly hatched nestlings? Note the helpless altricial young of the robin; the independent precocial young of the quail.

The strong influence of the mating passion will be made plain by observations on the fighting, love-making, singing, and general behavior of the birds in the mating season. The expression of the mental and emotional traits, the psychic phenomena of birds, are most emphasized at this time, and reveal the possession among animals lower than man of many characteristics which are too commonly ascribed as the exclusive attributes of the human species.

=Local distribution and migration.=--As explained in Chapter XXXII, the geographical distribution of animals is a subject of much importance, and offers good opportunities in its more local features for student field-work. The field-study of the birds of a given locality will comprise much observation bearing directly on zoogeography or the distribution of animals. Certain birds will be found to be limited to certain parts of even a small region, the swimmers will be found in ponds and streams and the long-legged shore-birds on the pond- or stream-banks, or in the marshes and wet meadows, although a few like the upland plover, curlews, and godwits are common on the dry upland pastures. Distinguish the ground-birds from the birds of the shrubs and hedge-rows and these again from the strictly forest-birds. Find the special haunts of swallows and kingfishers. Which are the shy birds driven constantly deeper into the wild places or being exterminated by the advance of man; which birds do not retreat but even find an advantage in man's seizure of the land, obtaining food from his fields and gardens?

Make a map on large scale of the locality of the school, showing on it the topographic features of the region, such as streams, ponds, marshes, hills, woods, springs, wild pastures, etc., also roads and paths, and such landmarks as schoolhouses, county churches, etc. On this map indicate the local distribution of the birds, as determined by the data gradually gathered; mark favorite nesting-places of various species, roosting-places of crows and blackbirds, feeding-places, and bathing- and drinking-places of certain kinds, the exact spots of finding rare visitants, rare nests, etc., etc. The making of such a zoogeographical map will be a source of great interest and profit to the students.

As already mentioned, many of the birds of a locality are "migrants," that is, they breed farther north, but spend the winter in more southern latitudes. These migrants pass through the locality twice each year, going north in the spring and south in the autumn. They are much more likely to be observed during the spring migration than in the fall, as the flight south is usually more hurried. The observation of the migration of birds is very interesting, and much can be done by beginning students. Notes should be made recording the first time each spring a migrating species is seen, the time when it is most abundant and the last time it is seen the same spring. Similar records should be made showing the movements of the birds in the fall. A series of such records covering a few years will show which are the earliest species to appear, which the later, and which the last. Such records of appearance and disappearance should also be kept for the summer residents, those birds that come from the South in the spring, breed in the locality, and then depart for the South again in the autumn. Notes on the kinds of days, as stormy, clear, cold, warm, etc., on which the migration seems to be most active; on the greater prevalence of migratory flights by day or by night; on the height from the earth at which the migrants fly, etc., are all worth while. The Division of Biological Survey, U. S. Department of Agriculture, keeps records of notes on migration sent in by voluntary observers and furnishes blanks to be filled out by each observer. A suggestive book about migration, and one giving the records for many species at many points in the Mississippi valley is Cooke's "Bird Migration in the Mississippi Valley." Migration is discussed in most bird-books.

=Feeding habits, economics, and protection of birds.=--The feeding habits of birds are not only interesting, but their determination decides the economic relation of birds to man, that is, whether a particular bird species is harmful or beneficial to man. Casual observation shows that birds eat worms, grains, seeds, fruits, insects. A single species often is both fruit-eating and insect-eating. Do fruits or do insects compose the chief food-supply of the species? To determine this more than casual observation is necessary. The birds must be watched when feeding at different seasons. The most effective way of determining the kind of food which the bird takes is to examine the stomachs of many individuals taken at various times and localities. Much work of this kind has been done, especially by the investigators connected with the Division of Biological Survey of the U. S. Department of Agriculture, and pamphlets giving the results of these investigations can be had from the Division. It has been distinctly shown that a great majority of birds are chiefly beneficial to man by eating noxious insects and the seeds of weeds. Many birds commonly reputed to be harmful, and for that reason shot by farmers and fruit-growers, have been proved to do much more good than harm. Some few birds have been proved to be, on the whole, harmful. An investigation of the food habits of the crow, a bird of ill-repute among farmers, based on an examination of 909 stomachs shows that about 29 per cent of the food for the year consists of grain, of which corn constitutes something more than 21 per cent, the greatest quantity being eaten in the three winter months. All of this must be either waste grain picked up in fields and roads, or corn stolen from cribs and shocks. May, the month of sprouting corn, shows a slight increase over the other spring and summer months. On the other hand the loss of grain is offset by the destruction of insects. These constitute more than 23 per cent of the crow's yearly diet, and the larger part of them are noxious. The remainder of the crow's food consists of wild fruit, seeds and various animal substances which may on the whole be considered neutral.

The slaughter of birds for millinery purposes has become so fearful and apparent in recent years that a strong movement for their protection has been inaugurated. Rapacious egg-collecting, legislation against birds wrongly thought to be harmful to grains and fruit, and the selfish wholesale killing of birds by professional and amateur hunters, help in the work of destruction. Apart from the brutality of such slaughter, and the extermination of the most beautiful and enjoyable of our animal companions, this destruction[18] works strongly against our material interests. Birds are the natural enemies of insect pests, and the destroying of the birds means the rapid increase and spread, and the enhanced destructive power of the pests. It is asserted by investigators that during the past fifteen years the number of our common song-birds has been reduced to one-fourth. At the present rate, says one author, extermination of many species will occur during the lives of most of us. Already the passenger-pigeon and Carolina paroquet, only a few years ago abundant, are practically exterminated. Protect the birds!

FOOTNOTE:

[18] One of the most unfortunate and conspicuous examples of this slaughter is the partial extermination of the song-birds of Japan in the interests of European milliners. To meet their demands the country people used birdlime throughout the woods with disastrous effectiveness, as shown in the present exceeding scarcity of birds and the abundance of insect pests.