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Birds are a class of vertebrate animals, whose representatives are well characterized by the fact that their body is covered with feathers and the forelimbs are modified into flight organs - wings. With rare exceptions, birds are flying animals, and those species that do not fly have underdeveloped wings. To move on hard substrate, birds use their hind limbs - legs. Thus, birds, unlike all other terrestrial vertebrates, are bipedal animals.

Birds have a very energetic metabolism, their body temperature is constant and high, their heart is four-chambered, and arterial blood is separated from venous blood.

The cerebral hemispheres and sense organs, especially vision and hearing, are well developed. The special characteristics of signals provide individual, family, group and population camouflage, species identification of adult individuals, their contacts with young birds, education and training of the latter as a vital guide to environmental situations. Birds are found throughout the globe, with the exception of the interior of Antarctica, in a wide variety of locations and climates.

In the aisles of Russia there are more than 750 species of birds, which is about 8.5% of the world's avifauna.

The strength of the bird skeleton, in addition to the fusion of its individual elements, is also determined by the composition (abundance of mineral salts) and structural bones. Lightness is explained by the airiness of the light bones associated with the systems of air sacs - pulmonary and nasopharyngeal. The relative mass of the skeleton in birds is therefore small.

In the central zone of the European part of Russia, there are two types of sparrows: house (urban) and field (village).

It is not at all difficult to distinguish a house sparrow from a field sparrow. The house sparrow (male) has a dark gray cap on the crown, while the field sparrow has a brown cap; The brownie has one light stripe on its wings, and the field has two. In addition, the tree sparrow has black brackets on its cheeks on a light background, and a white collar around its neck. The house sparrow is larger and rougher in build than the field sparrow.

Both species have much in common in their lifestyle, diet, behavior and the sounds they make - chirping.

Sparrows are sociable birds and tend to live in colonies. They form flocks, sparrows notice danger more easily and find food more quickly. They lead a sedentary lifestyle, as they are adapted to living near humans and can obtain food for themselves all year round.

In central Russia, sparrows can be seen and observed in all seasons.

Sparrows are usually small in size. The head is small. The shape of the beak is varied, the lower limbs are four-fingered. The fingers end in sharp claws. The plumage is rigid, the length of the wings is moderate. The color of the male is usually brighter than that of the females.

All sparrows build nests. Building them in different places. Sparrow chicks appear naked, blind, and helpless. In the first days, parents warm the chicks and take care of the cleanliness of the nest. Small sparrows usually feed on insects.

Sparrows' nests are of a closed type and represent a rather rough pile of various materials obtained from the environment during the construction of the nest. Sparrows carefully line the tray in the nest with horsehair or the hairs of other animals. In this cavity, females lay 4 to 10 small eggs, white or gray with small dark specks.

It should be borne in mind that sparrows have sworn enemies - stray cats. At night, owls hunt sparrows. During the day, hawks - sparrowhawks - attack. In winter, when there is ice and after heavy snowfalls, sparrows cannot get food for themselves and, if they are not fed, they freeze to death. In some cases, sparrows do more harm than good, in others the harm compared to the benefit is small. Despite the damage sparrows cause to the economy, in some rural areas and large cities of Russia they are subject to protection as our assistants in protecting green spaces. In winter, it is advisable to feed sparrows by arranging feeding tables.

Bullfinches

The homeland of bullfinches is the coniferous forests of the northern taiga. Here they make nests and hatch chicks. In September, bullfinches form flocks, and in October they migrate to the forests of the central zone of our country for the winter. At this time, they appear in villages and cities, standing out sharply against the background of the fallen snow. Hence, probably, the name of these birds - bullfinches.

The bullfinch is larger than the sparrow. It has bright plumage: red on the chest and gray - bluish on the back. Females are similar in appearance to males, but differ in more modest gray plumage. Bullfinches of both sexes have a black cap on the crown and a thick, short black beak. Unlike many other birds, bullfinches sing not only males, but also females. The birds constantly call to each other with melodious whistles, and when they have eaten, they sit on branches and sing simple, creaky songs. The flight of bullfinches is beautiful and undulating, although, in general, these birds are not agile and slow. Their sluggish behavior makes it easier to organize children's observations of these birds.

In winter, bullfinches stay in mixed and deciduous forests, where they feed on seeds of alder, ash, maple, linden and other trees, as well as shrubs (lilac, etc.). In gardens and parks they eat tree buds, and on the outskirts of fields they look for seeds of quinoa, horse chestnut and other weeds in ravines and wastelands. Bullfinches are especially attracted to wild game, viburnum, which they readily eat.

There are 6 species of bullfinches in total, of which only the common bullfinch lives in Russia, including the one that flies in the winter as a nomadic bird to the village of Ochur.

Magpies

The magpie is slightly larger in size than the jackdaw, with elegant plumage. The head, wings and tail of a magpie are black with a greenish tint, and the belly, shoulders and individual places on the wings (sides) are white. The tail is long, stepped, and serves as a rudder during sudden movements on the ground and in flight.

At the end of February, before breeding, they behave noisily, chase each other, spreading their tails like a fan, and dance. However, magpies do not fly very well, preferring to jump from place to place.

Their nest is usually located in dense thickets at a height of 2 - 3 meters from the ground. It is well hidden from prying eyes, made up of large twigs on the outside and thinner twigs on the inside, intertwined with blades of grass and held together with clay. The tray is also cemented with clay and is a hard deep bowl - a bed for eggs, covered with moss, soft grass, and wool.

The top and sides of the tray are covered with a layer of thorny twigs, which form a roof, giving the nest a spherical shape. The entrance to the nest is located on the side. This arrangement of the nest protects the female sitting on the eggs.

Magpies are omnivores. During the period of feeding the chicks, they exterminate many forest and field pests.

However, in the spring, magpies destroy many bird nests, drinking eggs and eating chicks. This causes harm to arboreal insectivorous birds.

In autumn, especially in winter, magpies stay near housing. They can often be found on the outskirts of cities and towns. They gracefully move along the ground in small steps, lifting their tail up and wagging their heads with each step. Sometimes magpies begin to jump with long strides. The magpie also produces a loud chirping sound, which expresses the bird's anxiety when a person or animal approaches.

People have a lot of sayings about magpies, reflecting one or another of its features. Of these, “magpie is white-sided,” “magpie is a thief,” etc.

Despite the harm caused by magpies, we must not forget about the benefits, which are sometimes significant. So, for example, in addition to exterminating many harmful insects and rodents, magpies eat juicy fruits, throwing out seeds that have not lost their germination from the intestines with feces. By doing this, they contribute to the dispersal of many plants to new places.

Finally, in our monotonous northern nature, magpies serve as a real decoration, so they should not be destroyed.

tits

In our forests you can find tits of several species. Tits of different species have much in common; they generally lead a sedentary lifestyle, only partially migrating over short distances. However, tits living in the northern regions of the taiga migrate to more southern places in winter. Flocks of tits attract attention not only in the forest, but also in the vicinity of human habitation, when the onset of winter forces them to look for food everywhere. Some Sins are not afraid to look into the windows of houses and peck food stored there between the window frames. Wherever there are feeding tables and feeders, tits visit them. Tits roam in the forest all winter together with nuthatches.

Possessing strong, thick legs with strong toes and curved claws, tits deftly cling to any branch of spruce, pine or other tree. Carefully examining all the crevices of the bark, removing insects numb from the cold from it. This activity of tits is especially useful because they will destroy pests not only in summer, but also in winter. In addition, tits obtain insects from such shelters that are inaccessible to other, larger ones.

Tit nests are usually made in the hollows of small woodpeckers, recesses and crevices of rotten trunks. The nest of a tit is built by joint efforts (male and female) from thin twigs, dry stems, grasses, moss and lichens; the tray is lined with bast fibers, horsehair, and hairs.

In autumn and winter, tits of some species store food in reserve, hiding insects and seeds in cracks in the bark and crevices between conifers. Tits are perhaps the most useful of the birds living in Russia. The extermination of harmful insects at all times of the year is the main benefit that tits bring to humans.

In summer, tits are little noticeable: they stay in forests and parks, and their presence is revealed only by a ringing song, similar to the ringing of a bell, characteristic of all tits: “tsi-tsi”, or “si-si”. Tits become noticeable in the fall, when they gather in flocks and constantly wander in search of food.

Crow

Everyone knows the gray crow. She lives in cities and villages and is closely connected with man everywhere. Until about the end of the 50s. 20th century spring crows, breaking into pairs. They left the cities.

The nest is built from thick branches and is lined with wool inside.

Such nests absorb sunlight better and, when heated, help incubate the eggs.

Crows, like most crows, are omnivores. By destroying harmful insects and mice, the crow benefits humans. Crows prefer not to peck stolen eggs in a hurry on the spot, but carry them in their beak to a secluded place.

The damage caused by crows to nature reserves is especially great. To get the egg of a large bird, crows sometimes work in pairs: one crow teases the female who is sitting on the eggs, and the other crow drags the egg away.

Crows are very smart birds: they can, for example, count to five. In captivity, a crow can learn to talk like a parrot, and in freedom it often imitates the calls of birds. So you shouldn’t be surprised to hear from a crow, for example, the drumming characteristic of a woodpecker.

Having a high organization and capable (with rare exceptions) of flying. Birds are ubiquitous on earth, therefore they play an important role in the formation of many ecosystems, and are also part of human economic activities. Modern science knows about 9,000 species of birds existing today. At different periods of the past there were significantly more of them.

The following can be distinguished are common for birds characteristics:

1. Streamlined body shape. The forelimbs are adapted for flight, not walking, and therefore have a special structure and are called wings. Hind limbs of birds serve for walking and as a support for the body.
2. Backbone of birds has a small thickness, the tubular bones have cavities with air, which lighten the weight of the birds and contribute to less weight. This allows the birds to stay in the air longer. Bird skull has no seams, it is formed from fused bones. The spine is not highly mobile - only the cervical region is mobile.
   There are two skeletal structural features characteristic only of birds:

   - Shank- a special bone that helps birds increase the width of their stride;
   - Keel- the bony protrusion of the sternum of birds, to which the flight muscles are attached.

3. Bird skin have almost no glands, dry and thin. There is only coccygeal gland, which is located in the tail section. They grow from the skin feathers- these are horny formations that create and maintain a microclimate in birds, and also help them fly.
4. The muscular system of birds includes many different types of muscles. The largest muscle group is flight pectoral muscles. These muscles are responsible for lowering the wing, that is, for the flight process itself. The cervical, subclavian, subcutaneous, intercostal and leg muscles are also well developed. Motor activity in birds is differentiated: they can walk, run, jump, swim, and climb.
   There is also two types of bird flights: soaring And waving. Most bird species can fly great distances ( bird migration).
5. Birds' respiratory organs- lungs. In birds double breathing- this is when, in flight, a bird can breathe both at the entrance and at the exhalation, without suffocating in this way. When a bird inhales, air enters not only the lungs, but also air bags. From the air sacs it enters the lungs when you exhale.
6. Birds have a heart four-chambered, capable of completely separating blood into arterial And venous. The heart beats quickly, washing the body with pure arterial blood. High motor intensity is inextricably linked with high body temperature, which is maintained at a level of about +42 o C. Birds are already warm-blooded animals with a constant body temperature.
7. Digestive system of birds has its own characteristics, which are associated with the digestion of large volumes of often rough food (grains, vegetables, fruits, insects, etc.), as well as with lightening the mass of the gastrointestinal tract. It is the latter circumstance that is associated with the absence of teeth in birds, the presence of a goiter and the muscular part of the stomach, as well as the shortening of the hindgut. So, birds have no teeth, so their beak and tongue are involved in getting food. Goiter in birds served to mix the food entering it, after which it is sent to the stomach. IN muscular part of the stomach food is ground and mixed with each other and with gastric juices.
8. Excretory organs in birds, as well as the products of the final breakdown of urea in birds coincide with those in reptiles, with the difference that birds don't have a bladder to reduce body weight.
9. Bird brain divided into 5 departments. The greatest mass, respectively, the best development, have two forebrain hemispheres, which have a smooth bark. The cerebellum is also well developed, which is associated with the need to have excellent coordination and complex behaviors. Birds navigate in space using vision and hearing.
10. Birds are dioecious animals, in which it is already possible to observe sexual dimorphism. Females have a left ovary. Fertilization occurs internally bird development- direct. Most bird species build nests in which they lay eggs. The female incubates the eggs until the chicks hatch, which are then fed and taught to fly. Chicks can be brood or nesting, depending on how well developed the chicks hatching from the eggs are.

TOPIC: “Type chordates. Classes of poultry."

PLAN

1. General characteristics of the class of birds. Origin of birds

2. External structure in connection with lifestyle

3. Internal structure of birds

4. The meaning of birds

General characteristics of the class of birds

Pseudosuchia originated from archosaurs; they occupied all land areas, but even they cannot be considered the direct ancestors of birds. The immediate ancestors of birds have not yet been established. In the last century, namely in Jurassic deposits, first a feather imprint was found, and then two relatively complete skeletons. According to one of them, in 1861, the German paleontologist G. Meyer made a description of an “animal covered with feathers,” the imprint of the skeleton of which was found in lithographic shales in Bavaria. The first bird received the scientific name Archeopteryx. Analysis of the structure of Archeopteryx provides evidence of their lifestyle. They were arboreal climbing animals that could glide but not fly. This is evidenced by the weak skeleton of the forelimbs, a weak sternum without a keel, and the smooth surface of the wing bones. Judging by the structure of the pelvis, they laid small eggs, the size of 1/4 chicken eggs. Weak teeth indicate a diet of insects and fruits. One way or another, real birds appeared 170 million years ago. In birds, the nervous system and sensory organs are improved under the influence of behavioral adaptations. Redox processes accelerate - all systems change, the level of metabolism increases. As a result, warm-bloodedness appears and, as a result, integuments appear that protect against hypothermia.

Ornithology- a science that studies the life and structure of birds. The modern fauna consists of approximately 8 thousand 600 species of birds. Ours is 750 or 8.5%. These are flying terrestrial vertebrates, the whole organization is connected with flight - forelimbs - wings, with the exception of ostriches - up to 80-90 km/h.

Basic characteristics of birds

1. The body is covered with feathers, which perform a thermal insulation function and ensure streamlining of the body.

2. Transformation of the forelimbs into wings, which was accompanied by a restructuring of the skeleton and muscles of the limbs and shoulder girdle.

3. Transformation of the skeleton and muscles of the hind limbs and pelvic girdle provided the possibility of bipedal walking on a solid substrate and swimming.

4. Complete separation of the systemic and pulmonary circulation contributed to a better supply of tissues with oxygen and nutrients. A 4-chambered heart emerged. The right aortic arch is preserved, and the left one is reduced.

5. Pneumatization of the bones occurred, which increased their strength.

6. Intensification of breathing occurred due to the system of air sacs connected to the lungs.

7. Increased but constant body temperature allowed birds to master zones with cold climates.

8. In females, reduction of the right ovary and oviduct occurred.

9. In many ways they are similar to reptiles (a horny covering was found - the tarsus, an almost complete absence of skin glands, 1 condyle, a dioxide-type skull, arterial blood in the right aortic arch, embryonic development and the structure of the genitourinary system).

In 1679 The Italian scientist G. Boreli, in his work “The Life of Animals,” noted the most important features of the anatomy of birds associated with flight.

Features of adaptation of birds to flight:

· Transformation of forelimbs into wings;

· Streamlined body covered with feathers, tiled-like overlapping in the wing;

· Formation of the sternum in the form of a keel, with powerful muscles that control the wings;

Double breathing for intense metabolism

Lightweight skeleton (hollow bones)

· Reduced body weight due to the absence of a bladder, one ovary, teeth, and rectum

· The presence of high visual acuity and progressive development of the brain, in particular the cerebellum. Among birds there are no purely aquatic or purely terrestrial species. Due to flight in a certain environment, the size of birds also varies.

The number of individuals of individual bird species varies. There are birds that are very numerous. Since 1600, 90 species of birds have become extinct, 1/4 of these birds became extinct due to their natural biological reasons.

General characteristics of the class. Birds - first in the evolutionary series warm-blooded (homeothermic) animals. Their body temperature is constant and relatively independent of the ambient temperature. Another feature of this class is that it forms a special branch of evolution, the representatives of which acquired ability to fly. Most birds are flying species. The noted features allowed the birds to master the terrestrial, air and (partially) aquatic habitats, settle in almost all climatic zones and even change them, migrating as necessary to more favorable living conditions (migratory and nomadic species - see below).

Significant anatomical and physiological changes have occurred in the body of birds compared to their evolutionary predecessors - reptiles. At the same time, being “direct descendants” of reptiles, birds retained many of their characteristic features: the absence of skin glands, the presence of horny formations in the integument (scutes on the legs, the horny sheath of the beak, claws), a similar structure of the excretory and reproductive systems (it should, however, note that, unlike female reptiles, female birds have single ovary And oviduct- left), almost identical egg structure and embryo development.

Maintaining a constant body temperature of birds and a new method of movement required an increase in the level of metabolic processes, primarily due to the high intensity of all physiological functions: digestion, respiration, blood circulation, excretion. Food in the gastrointestinal tract of birds is digested very quickly due to the effectiveness of digestive enzymes, and after digestion, nutrients are actively absorbed due to an increase in the absorptive surface of the intestine: the intestinal mucosa forms numerous villi. Due to the absence of teeth, the function of grinding food is taken over by a powerful muscular stomach; The beak and claws (in birds of prey) may be involved in the primary mechanical processing of food. Undigested food remains are not retained in the rectum (this significantly lightens the body weight) and are removed through cloaca. Intense gas exchange in the lungs is achieved by "double breathing" in which atmospheric air enters the lungs not only during inhalation, but also during exhalation. This becomes possible thanks to the participation of inhalation of special air bags(Fig.III.31). Productive gas exchange in tissues is ensured by the fact that oxygen-enriched arterial blood comes to them. Arterial and venous blood in birds does not mix, since they have a heart four-chamber: solid interventricular septum completely separates the venous and arterial blood of the right and left ventricles. The systemic circulation (see Fig. III.34, E) begins from the left ventricle with one vessel - right aortic arch. Arterial blood is carried through the arteries extending from the aortic arch to all organs. The small circle begins from the right ventricle with the pulmonary artery, which carries venous blood to the lungs, where it gives off carbon dioxide and is saturated with oxygen. Birds have a high heart rate and therefore a high blood flow rate. The main end product of metabolism in most birds - uric acid - is excreted from the body through the body kidneys in the form of crystals (one of the ways to save fluid in the body). The bladder as a storage organ is absent in birds (lightening body weight).

Birds, unlike other animals, have feather cover (plumage). Feathers are horny formations of a complex structure that cover the skin. By their origin, they are derivatives of reptile scales. The main role of the feather cover is related to thermoregulation: it prevents the dissipation of heat from the surface of the body. Feather cover is no less important for flight. Feathers give the body a streamlined shape; The flight properties of the wings and tail largely depend on them. Feathers are varied in their purpose and structure. Those that define the contours of the body are called accordingly contour. They give the body a streamlined shape, which is very important for flight. Located under the contour downy feathers and fluff provide thermal insulation. The flight properties of the wing are associated with two rows of large flight feathers feathers and the upper and lower ones above them covering wing feathers. The tail feathers are called helmsmen. The pen consists of rod, the lower end of which (start) immersed in the skin. Special muscles are attached to it that raise and lower the feather. They extend from the rod in both directions beards of the first order, on which are located beards of the second order with hooks. Interlocking with each other, the barbs form fan pen. Down feathers and down have no second-order barbs; the shaft of real down is greatly shortened.

The development of the air environment by birds was facilitated by changes in the structure of the musculoskeletal system: the axial skeleton, the skeleton of the skull and paired limbs. The overall weight of the skeleton in birds is lightened by the presence of air cavities in many bones. The skull is formed by thin fused bones. Jaws turned into beak: upper jaw - beak, lower - mandible. The absence of teeth also greatly reduces the weight of the skull. In the axial skeleton, almost all vertebrae are fused; the cervical and part of the caudal vertebrae remain mobile. The fusion of the sections of the axial skeleton is very important, since to give the body stability on land and in the air, birds need a “rigid supporting structure.” The sternum has an outgrowth (keel) - the attachment point for the powerful pectoral muscles that move the wings during flight. When moving on the ground, birds rely only on their hind limbs, and in flight they use modified forelimbs - wings. Strong attachment of the hind limbs to the spine is achieved through the formation complex sacrum. It consists of the bones of the pelvic girdle, the vertebrae of the sacral and lumbar sections, part of the vertebrae of the caudal section and the last thoracic vertebra. In the skeleton of both pairs of limbs, the number of fingers decreases, the bones of the wrist and metacarpus lengthen and merge (forming buckle), tarsus and metatarsus (with formation tarsus).

In the brain, the largest section is the forebrain (see Fig. III.35, D). It consists of two hemispheres with a smooth surface. The olfactory lobes of the forebrain occupy a smaller volume compared to reptiles, which indicates the insignificant role of smell in the life of birds. The leading sensory organ is the organ of vision, and the development of the visual hillocks is associated with this; primary visual information enters the well-developed visual lobes of the midbrain. The cerebellum, the center of regulation and coordination of movements, reaches significant sizes. The progressive development of the brain is associated with elements of higher nervous activity (in particular, memory, learning, rational activity), as well as complex forms of bird behavior (nest building, caring for offspring, migration, etc.).

In addition to vision, birds have well-developed hearing, a sense of balance, and muscle sensitivity. The eyes are large. The retina of the eye has a high density of photoreceptors, which makes it possible to obtain a detailed image of an object, including in flight. Many birds have color vision. Accommodation of the eye is carried out by changing the shape of the lens with its simultaneous movement relative to the retina. The organ of hearing includes three sections: the inner ear, the middle ear and the rudiments. outer ear. Birds are characterized by a subtle discrimination of sounds in a wide range of frequencies; sound communication plays one of the main roles in their life (danger signals, marking the boundaries of the territory, attracting a mating partner, etc.). The organ of balance is vestibular apparatus. Together with muscle receptors, it is involved in the coordination of movements, which is especially important during flight.

Origin of birds. The ancestors of birds - saurischian dinosaurs- reptiles from the group of archosaurs (see Fig. III.30). For a long time, the only fossil animal known that vaguely resembled modern birds in appearance was Archeopteryx. In the Jurassic deposits of Germany, archaeologists found 5 prints of this “first bird”. Archeopteryx combined the characteristics of both reptiles (the presence of teeth, a long tail of 20 vertebrae, free fingers in the forelimb, the absence of a keel) and birds (feather cover, the characteristic structure of the shoulder girdle and hind limb). Currently, Archeopteryx is not considered the direct ancestor of birds. He represented a parallel line of development that developed adaptations for flight. There is still no consensus on how reptiles “learned to fly.” According to one version, the ancestors of birds led an arboreal lifestyle and gradually moved from jumping from branch to branch to gliding, and then to flapping flight. According to another hypothesis, they, like many reptiles, moved on the ground only on their hind limbs. Elongation of the scales on the forelimbs allowed them to “flip” while running quickly, and then switch to flapping flight.

Bird class system. Modern birds are represented by three superorders: Ratites, Penguins And Keeled. TO ratite include African and South American ostriches, as well as cassowaries and kiwis. All of them are deprived of the ability to fly, the wings are poorly developed, and there is no keel on the sternum; They move exclusively on the ground on their hind limbs, which have highly developed muscles. Distinctive feature penguins, which also do not fly - the ability to swim and dive. In the water they move using their wings, and not their hind limbs, like other swimming birds. Penguins are widespread in the Southern Hemisphere. Most modern birds belong to the superorder keel Let's look at their anatomical and physiological features using one of the representatives - the rock pigeon, which belongs to the order Pigeonidae.

Rock pigeon. Pigeonids live in forests (clint, wood pigeon, turtle dove) and mountains (rock pigeon). These are granivorous birds. The homeland of rock pigeons is the foothills, but they have adapted to close proximity to humans and currently inhabit many cities, using attics and niches of stone buildings for nesting. Abundant feeding makes the number of this species in cities very high.

The small rounded head of a rock pigeon ends beak, consisting of upper beaks And mandible. The beak is covered with a horny sheath. At the base of the beak are the openings of the nostrils, adjacent to them is an area of ​​soft bare skin - cere. On the sides of the head are large eyes, protected by the upper and lower eyelids and nictitating membrane. Behind the eyes are external auditory openings, covered with eardrum and covered with feathers. The neck is relatively long and mobile. In a pigeon standing on the ground, the thigh and lower leg are hidden by plumage and only the tarsus, covered with horny scales, is visible. Four fingers end in claws.

The pigeon's body is covered with feathers. The upper feathers are contour feathers. Beneath them are down feathers and real down, providing thermal insulation. Areas covered with contour feathers alternate with areas of bare skin. By giving off excess heat, non-feathered areas protect the body from overheating. The plane of the wing is formed by two rows of large flight feathers, partially covered by the upper and lower wing coverts. The tail feathers perform the function corresponding to their name.

Leather the pigeon's is thin and dry. The only skin gland located at the base of the tail (coccygeal), secretes a fat-like secretion to lubricate the feathers. This gives them elasticity and water-repellent properties.

IN spine The pigeon is distinguished into cervical, thoracic, lumbar, sacral and caudal sections, but due to adaptation to flight they have undergone significant changes.

The pigeon's skull is large (relative to the body), which is associated with an increase in the size of the brain located in it. The bones of the skull are thin and grow together without sutures. Large eye sockets create conditions for eye mobility. The jaw section is represented by a beak, covered with a horny sheath and devoid of teeth.

Forelimb belt of the dove, transformed into wings, includes saber-shaped shoulder blades, powerful downward coracoids (crow bones) and clavicles fused into fork. The sternum is connected to the spine using ribs. A growth extends from the lower surface of the sternum - keel(hence the name of the superorder) - the place of attachment of powerful “flight” muscles. Free forelimb consists of the shoulder, forearm and hand, extended by the formation of a buckle. Of the five fingers, three remain, with a reduced number of phalanges (Fig. III.32).

Pelvic girdle open, i.e. its left and right halves do not fuse on the ventral side; this allows females to lay relatively large eggs. In the skeleton free hind limb, In addition to the thigh and lower leg, there is a third link - the tarsus. In the skeleton of the lower leg, the fibula is greatly reduced in size and grows onto the tibia. The hind limb of the pigeon has four fingers with claws: three of them are directed forward, one is directed backward. This arrangement creates reliable support and fixation on any surface (Fig. III.33).

Musculature The pigeon is divided into the muscles of the head, neck, trunk and limbs. The long neck muscles provide complex head movements. Most of the muscles of the trunk are involved in flight, raising and lowering the wings - this subclavian And large pecs muscles that attach to the sternum and carina. The muscles of the hind limbs are highly developed, intended only for movement on the ground.

Peculiarities digestion associated with the need to intensify life processes. The process of digesting food in a pigeon, like in all birds, is accelerated. The stomach is divided into two sections: glandular And muscular. In the glandular stomach, food is digested (chemically processed) with the help of enzymes secreted by numerous digestive glands. Mechanical processing of food (grinding grain) occurs due to contractions of the powerful muscles of the walls of the second section of the stomach - the muscular one. Its inner surface has a dense horny lining and is devoid of glands. To more effectively grind food, pigeons, like many other herbivorous birds, swallow small pebbles, which linger in the stomach and act as millstones. The stomach cavity is small, and it cannot play the role of food storage. This function proceeds to a special expansion of the esophagus - goiter It also performs another function: in the first days after the chicks hatch, pigeons feed them the so-called "goiter milk" formed as a result of desquamation of epithelial cells lining the goiter. The ducts of the pancreas and liver open into the anterior section of the small intestine - the duodenum. At the border of the small and large intestines there are paired cecums. The rectum is very short, undigested food remains do not accumulate in it and are quickly eliminated through the cloaca.

Process breathing pigeon is very intense (ensuring thermoregulation and flight function). Air enters through the nostrils into the oral cavity, from there into the larynx and long trachea, which is divided into two bronchi. At the junction of the trachea, thin membranes are stretched - vocal cords. Due to the vibration of the membranes caused by the flow of air, pigeons, like other birds, produce a variety of sounds. In the lungs the bronchi depart secondary bronchi, and from them - parabronchi. This determines the spongy structure of the pigeon’s lungs, which are practically incapable of expansion. Thin-walled tubes are used to force air into and out of the lungs. air bags. They are located between all the internal organs, and some even extend into the tubular bones of the forelimbs. By expanding and contracting as the sternum lowers and rises, the sacs pump air through the lungs (see Fig. III.31). When you inhale, most of the air enters the bronchus into the posterior air sacs, and a smaller portion enters the lungs. When you exhale, air from the rear air sacs is directed into the lungs, from them into the anterior air sacs, from where it is discharged out through the trachea. Thus, atmospheric air enters the lungs and when inhaling, And when exhaling (double breathing).

The pigeon has a four-chambered heart: the ventricles are completely separated by a vertical septum. The resting heart rate is very high: 200-300 beats per minute, and during flight reaches up to 500 beats per minute. The pulmonary circulation begins with the pulmonary artery, which carries blood from the right ventricle to the lungs. Oxygen-enriched blood from the lungs flows through paired pulmonary veins into the left atrium. The remaining vessels belong to the systemic circulation. The single right aortic arch carries arterial blood from the left ventricle. Paired vessels (starting with one trunk) depart from it to the head (carotid arteries) and very large arteries that supply blood to the forelimbs and powerful pectoral muscles. Turning to the dorsal side, the right arch passes into the dorsal aorta, which supplies vessels to all organs. From organs located in the front part of the body, blood collects in the paired anterior vena cava. The veins carrying blood from all other organs merge into the posterior vena cava. Two anterior and one posterior vena cava empty into the right atrium. From it, venous blood flows into the right ventricle and from there into the pulmonary circulation (see Fig. III.34, E).

For brain The pigeon, like other birds, is characterized by an increase in the size of the forebrain hemispheres. Their surface, covered with a layer of gray matter, has no grooves or convolutions. The olfactory lobes occupy a small volume; the visual lobes of the midbrain are developed. Adjacent to the forebrain hemispheres at the back is a large cerebellum, covering the midbrain and a significant part of the medulla oblongata (Fig. III.35, D).

Presenters sense organs pigeon - organs of vision and hearing. Large eyes are protected by movable eyelids and a nictitating membrane. Accommodation of the eye is carried out both by changing the shape of the lens and by its simultaneous movement relative to the retina. The retina has a high density of photoreceptors. The ear includes three sections: the inner ear, the middle ear and the rudiments of the outer ear.

Organs discharge - pelvic kidneys - consist of three lobes. The kidneys are located on the dorsal side of the body and fit tightly to the bones of the complex sacrum. The ureters depart from the kidneys and empty into the cloaca; the bladder is absent. Uric acid, the end product of metabolism, is excreted from the cloaca along with the droppings.

Organs reproduction in males they are represented by paired testes, from which vas deferens extend into the cloaca; females have a single, left, ovary. A mature egg enters the oviduct from the ovary and, moving along it into the cloaca, gets dressed albumen, subshell And shell shells. The substances that form these membranes are secreted by the glands of the walls of the oviduct. Fertilization is internal: it occurs in the upper parts of the oviduct, since the sperm must merge with the egg before the formation of dense egg shells.

The female pigeon lays 2 eggs in a nest built from small twigs and devoid of special lining. During incubation, which lasts 16-19 days, the nest maintains temperature and humidity that are optimal for the development of the embryo. Development occurs due to the large amount of nutrients contained in the yolk of the egg. Hatched pigeon chicks are naked, blind and completely dependent on their parents (they need heating and frequent feeding). In the first days of life, pigeons feed their chicks with “crop milk” (see above), then regurgitate partially digested food for them. Almost fully fledged chicks leaving the nests (fledglings) switch to feeding on grain.

Features of bird reproduction and development. The breeding season for most birds begins with the onset of spring. Increasing the length of daylight hours stimulates the production of germ cells by the ovaries and testes of birds; An increase in air temperature, along with other factors, determines the beginning of nest construction. The timing of egg laying is related to natural conditions (mainly the availability and abundance of food) not only at the time it begins, but also throughout the entire period of hatching and feeding the chicks.

Most birds live in pairs during breeding. Some of them change partners every year (small passerine birds); in other species, pairs remain for several years, and sometimes even throughout their lives (geese, large birds of prey, herons, storks). For nesting, pairs, as a rule, occupy areas that vary greatly in size among birds of different species, and protect them from competitors. Attachment to certain nesting sites is due to the presence of optimal breeding conditions. Some birds nest in colonies (guillemots, cormorants, some gulls).

The methods of nest construction, types of building materials and locations of nests among representatives of the class are very diverse. Some species make nests on the ground (geese, many ducks, larks, wagtails, etc.), laying eggs in small depressions in the ground (many waders) or on stones (guillemots) without litter. Birds can nest on tree branches (rooks, thrushes, many other passerine birds), in hollows (tits, woodpeckers, flycatchers, owls, goldeneyes, etc.), on rocks (guillemots, gulls, birds of prey) and in burrows ( shore swallows, rollers, kingfishers, firebuckets). Grebes make floating nests from grass and reeds. The nests of some birds are heaps of grass (gulls, loons) or twigs (pigeons, crows, herons, birds of prey). Most small passerine birds build cup-shaped nests using a wide variety of materials: fresh and dry grass, twigs, leaves, feathers, wool, clay, etc. Weaver birds and some other birds make complex nests in the form of bags with entrance corridors, sometimes with lids, and hang them on branches. Both partners (pigeons, gulls), only the female (tits, nightingales, nuthatches) or only the male (warblers, wrens, many weaver birds) can take part in the construction of the nest. The laid eggs - the clutch - are incubated by either one of the parents (in most passerine birds, owls, geese, gulls and birds of prey - only the female, in many waders, kiwis, rheas and cassowaries - only the male), or both alternately. Weed chickens living in Australia do not incubate eggs at all. They bury them in sand or piles of rotting leaves and, periodically raking or filling these piles, maintain in them the temperature optimal for the development of embryos.

In some birds (passerines, woodpeckers, cuckoos, swifts, pigeons, etc.), eggs hatch into almost completely naked, blind chicks with weak limbs and poorly developed sense organs; They need not only feeding, but also heating and protection from overheating. These types are called chicks. In other species of birds, chicks are able to move and feed independently within a few hours after hatching. They have relatively strong legs, their body is covered with thick down, and their sense organs are well developed. Such chicks leave the nest soon after hatching and never return to it. The role of the parents in this case comes down to bringing the chicks to places with the most abundant and accessible food for them, protecting them from predators and warning them of danger. Birds with this type of development nest primarily on the ground and are called brood. These include gallinaceae, lamellar-billed birds (geese, ducks and swans), cranes, bustards, loons, and waders. The chicks of gulls, nightjars, owls and daytime raptors hatch in a dense downy plumage; they can move around, but are not able to obtain food themselves.

Only chicks of weed chickens can fly on the first day of life. Chicks of all other species are capable of flight only after their downy outfit is replaced by feathers. In most passerines this occurs one and a half to three weeks after hatching, in falcons - after one and a half, and in geese - after two months. Fledglings of chick species are still unable to feed on their own for some time, so their parents continue to feed them.

Some young birds lead a solitary lifestyle (predators), others keep broods until next spring (finches, tits, nuthatches). Chicks of swans and many geese can maintain contact with their parents until the next breeding season, flying with them for the winter and returning to their nesting sites.

Seasonal phenomena in the life of birds. All birds can be divided into migratory, nomadic And sedentary. TO migratory These include those species that annually leave their nesting areas and fly to certain wintering areas, sometimes over considerable distances. Many birds that fly from Europe to Africa in winter must fly about 9-10 thousand km one way. Birds migrating from the north-eastern regions of Russia to Western Europe (for example, turukhtan) have to overcome approximately the same distance. The farthest journey is made by Arctic terns, flying about 17.5 thousand km from nesting sites (in the Arctic) to wintering areas (in Antarctica, i.e. at the other pole of the globe). Nomadic birds (bullfinches, waxwings, woodpeckers, tits) do not make regular flights in strictly defined directions. Their wintering place is the area closest to the nesting site with the most optimal conditions for the winter season. Birds that winter in the same places where they breed are called sedentary. These include sparrows, wood grouse, and black grouse. Some birds of the same species living in different regions can be both migratory and sedentary. For example, peregrine falcons of the northern tundra are migratory, those living in the middle zone make only seasonal migrations, and Caucasian and Crimean peregrine falcons lead a sedentary lifestyle.

Birds are man's feathered friends. Their role in nature is invaluable. Read about them and their protection in the article.

Birds: general characteristics

Birds are highly organized warm-blooded animals. There are nine thousand species of modern birds in nature. The characteristic features of the class are the following:

• Feathers.
• Hard beak made of cornea.
• No teeth.
• A pair of forelimbs are transformed into wings.
• The chest, pelvic girdle and second pair of limbs have a special structure.
• The heart consists of four chambers.
• There is an air bag.
• The bird incubates the eggs.

Birds, the general characteristics of which are presented above, are capable of flying thanks to the listed features. This distinguishes them from other classes of vertebrate animals.

Appearance on earth

The origin of birds is explained by several theories. According to one of them, birds live in trees. At first they jumped from branch to branch. Then they glided, then made short flights within the same tree, and finally learned to fly in open space.

Another theory suggests that the origin of birds is related to the ancestors of birds, which were reptiles with four legs. Evolving, the scales became feathers, which allowed reptiles to jump while flying a short distance. Later the animals learned to fly.

The origin of birds from reptiles

Based on this theory, we can say that the ancestors of birds were also crawling reptiles. At first their nests were on the ground. This attracted predators who constantly destroyed the nests along with the chicks. Taking care of their offspring, the reptiles settled in the thicket of tree branches. At the same time, a hard shell began to form on the eggs. Before this they were covered with film. Instead of scales, feathers appeared, which served as a source of heat for the eggs. The limbs became longer and covered with feathers.

The origin of birds from ancient reptiles is obvious, according to scientists. The ancestors of birds begin to take care of their offspring: they feed the chicks in the nest. To do this, solid food was crushed into small pieces and placed in the beaks of the babies. With the ability to fly, the primitive birds of ancient times could better defend themselves against the attacks of their enemies.

Ancestors - waterfowl

The origin of birds, according to another theory, is connected with their aquatic counterparts. This version owes its existence to the remains of ancient birds that were found in China. According to scientists, they were waterfowl and lived more than a hundred million years ago.

According to the theory, birds and dinosaurs lived together for sixty million years. Among the finds were feathers, muscles, and membranes. Examining the remains, paleontologists came to the following conclusion: the ancestors of ancient birds swam. To get food from the water, they dived.

If you study the origin of birds, it is not difficult to find similarities between them and representatives of other classes. Plumage is the most noticeable feature of a bird's appearance. Other animals do not have feathers. This is the difference between birds and other animals. the following:

• The toes and tarsus of many birds are covered with corneal scales and scutes, like those of reptiles. This means that scales on the legs can replace feathers. It is characteristic that the rudiments of feathers in birds and reptiles are no different. Only birds then develop feathers, and reptiles develop scales.
• Investigating the origin of birds, whose similarities with reptiles are incredible, scientists have determined that the jaw apparatus is more noticeable. Only in birds it turned into a beak, but in reptiles it remained the same, like in turtles.
• Another sign of similarity between birds and reptiles is their skeletal structure. The skull and spine are articulated by only one tubercle located in the occipital region. Whereas in mammals and amphibians, two tubercles are involved in this process.
• The location of the pelvic girdle of birds and dinosaurs is the same. This can be seen from the skeleton of the fossil. This arrangement is associated with the load on the pelvic bones when walking, since only the hind limbs are involved in supporting the body.
• Birds and reptiles have a four-chambered heart. In some reptiles, the chamber septum is incomplete, and then arterial and venous blood mix. Such reptiles are called cold-blooded. Birds have a higher organization than reptiles; they are warm-blooded. This is achieved by eliminating the vessel that carries blood from the vein to the aorta. In birds it does not mix with the arterial one.
• Another similar feature is egg incubation. This is typical for pythons. They lay about fifteen eggs. The snakes curl up above them, forming a kind of canopy.
• Birds are most similar to reptile embryos, which in the first stage of their development resemble fish-like creatures with tails and gills. This makes the future chick similar to other vertebrates in the early stages of development.

Differences between birds and reptiles

When paleontologists study the origins of birds, they compare the facts and findings collected bit by bit and find out how birds are similar to reptiles.

What are their differences, read below:

• When the birds got their first wing, they began to fly.
• The body temperature of birds does not depend on external conditions; it is always constant and high, while reptiles fall asleep during cold weather.
• In birds, many bones are fused; they are distinguished by the presence of a tarsus.
• Birds have air sacs.
• Birds build nests, hatch eggs and feed chicks.

First Birds

Fossil remains of ancient birds have now been found. After careful study, scientists came to the conclusion that they all belong to the same species that lived one hundred and fifty million years ago. These are Archeopteryx, which means “ancient feathers.” Their difference from today's birds is so obvious that Archeopteryxes were separated into a separate subclass - lizard-tailed birds.

Ancient birds have been little studied. The general characteristics come down to determining the appearance and some features of the internal skeleton. The first bird was small in size, about the size of a modern magpie. Her forelimbs had wings, the ends of which ended in three long fingers with claws. The weight of the bones is large, so the ancient bird did not fly, but only crawled.

Habitat: coastal areas of sea lagoons with dense vegetation. The jaws had teeth, and the tail had vertebrae. No connections have been established between Archeopteryx and modern birds. The first birds were not the direct ancestors of our birds.

The importance and protection of birds

The origin of birds is of great importance in biogeocenoses. Birds are an integral part of the biological chain and participate in the circulation of living matter. Herbivorous birds feed on fruits, seeds and green vegetation.

Different birds play different roles. Granivores - eat seeds and fruits, some species - store them, transporting them over long distances. On the way to the storage location, the seeds are lost. This is how plants spread. Some birds have the ability to pollinate them.

Great role in nature. They control the number of insect populations by eating them. If there were no birds, the destructive activity of insects would be irreparable.

Man, to the best of his ability, protects birds and helps them survive in harsh winters. People are hanging temporary nesting boxes all over the place. Tits, flycatchers, and blue tits settle in them. Winter periods are characterized by a lack of natural food for birds. Therefore, birds should be fed by filling the nesting box with small fruits, seeds, and bread crumbs. Some birds belong to commercial species: geese, ducks, hazel grouse, wood grouse, black grouse. Their value for humans is great. Woodcocks, waders, and snipe are of sporting interest.

From time immemorial: the body and legs of Archeopteryx were covered with long feathers, three and a half centimeters. It can be assumed that the bird did not swing its legs. Feathers were inherited from ancestors who lived in more ancient times and used all four wings when flying.

Today: when filling bird nesting areas with food, you need to make sure that no salt gets in there. It is white poison for birds.