Down feather - the core is short, there is no second order beard. If the shaft of a down feather is so shortened that the barbs come off in a single bunch, this is actually down. Feathers moult regularly. Distributed unevenly.
3. Musculature: especially developed muscles of the chest (large pectorals - work - lowering the wings and subclavian - raising the wings) - in flying and the muscles of the hind limbs - in flightless.
4. Skeleton lightweight (due to pneumatics), durable (due to fusion). Skull without seams, thin-walled, huge eye sockets, toothless jaws.
Spine consists of the cervical, thoracic, lumbar, sacral, tail sections.
Cervical - up to 25 vertebrae, long, very mobile.
Pectoral - spliced, carry ribs, which are attached to the sternum at their ends and form the rib cage. Edge - consists of two parts - one is movable connected to the vertebra, the other to the sternum. Both parts are movably connected to each other. The upper part of the rib has a process overlapping the adjacent rib - additional strength of the chest is achieved, while maintaining mobility.
The chest has a high ridge - keel - the place of muscle attachment.
Lumbar (vertebrae are fused) the department fuses with sacral department (the vertebrae are fused), with the ilium, forming a characteristic for birds complex sacrum ... This also includes part of the caudal vertebrae. It has an important adaptive value in connection with the support of the body only on the hind limbs.
Tail the department ends with a bone plate - the coccygeal bone, which is the basis for attaching the tail feathers. The pelvis of birds is open - the bones of the pelvis are not connected at the bottom.
Front limb belt - 3 paired bones: crow, scapula, collarbone. The clavicles grow together with the lower ends and form fork .
Wing skeleton - the humerus, forearm and several bones of the hand, has three fingers, several small bones grow together into one and form a complex bone - sufficient strength of this section, since it bears a large load.
Hind limb belt - consists of 3 pairs of pelvic bones, which fuse with the lumbar, sacral and first caudal vertebrae.
Hind limb - thigh, lower leg, tarsus (consisting of the tarsus and metatarsus) and 4 toes (3 facing forward, 1 - back).
5. Body cavity - protected by the chest and wide pelvis, it contains all the internal organs.
6. Digestive system: oral cavity (no teeth), pharynx, esophagus with goiter (in some), stomach (glandular and muscular), intestines (thin and thick with blind outgrowths), cloaca. There is no rectum. High intensity of digestion - adaptation to flight.
7. Respiratory system: lungs - dense spongy bodies. Respiratory tract: larynx, trachea, bronchi, bronchioles. Part of the branching of the bronchi forms thin-walled bags - air bags - between the internal organs, muscles, under the skin, inside the long bones of the skeleton. There is voice apparatus .
Breathing in flight - carried out by lowering and raising the wings. When the wings are raised, the air sacs also expand, and air enters them through the lungs.
When the wings are lowered, the air sacs are compressed and air passes through the lungs again. Thus, gas exchange occurs both during inhalation and exhalation when passing through the lungs, this phenomenon is called - double breathing ... Provides continuous ventilation. Also air bags - reduce friction, reduce bird weight, cool.
8. Circulatory system: 4-chambered heart. The first aortic arch, two circles of blood circulation. Blood doesn't mix anywhere. High speed of blood circulation (pulse 400-600 bpm), which ensures a high level of metabolic processes. Temperature - constant high 42-43ºС.
also a useless remedy, since it does not delay the absorption of the poison. In most cases, serious consequences after a poisonous snake bite are not caused by the action of poison, but by cauterization, bloodletting, pulling limbs with a tourniquet above the bite site, etc. Snake venom is used to prepare medicinal serums against snake bites. Serum is prepared from the blood of a horse, injected with increasing doses of poison over a period of 16 months. As a result, the blood acquires such immunity that the animal can tolerate the injection of an 80-fold lethal dose. Produce monovalent sera, specific in relation to the venom of one species of snakes, and polyvalent, acting against the venom of several types of snakes. Medicinal preparations are also prepared from the venom of vipers, for example, vipratox, vipraxin, viprazide and others used in the treatment of sciatica, sciatica, rheumatism.
Hemostatic agents (lebetoks) are made from the venom of gyurza and shitomordnik, drugs that cure epilepsy are made from the venom of a rattlesnake, and cobra venom is used to make drugs used in the treatment of bronchial asthma and a number of other diseases. Snake venom is widely used in biochemistry. Snake nurseries are organized to obtain poison. The first such nursery - a serpentarium - was created in Brazil near the city of São Paulo (Butantan); it is still the largest in the world. There are similar nurseries in India, Indonesia, South Africa and other countries. In nurseries, they take poison from snakes all the time, without killing them.
Reptiles serve as a source of raw materials for industry. For a long time, the skin of a crocodile, large snakes and lizards is used for the manufacture of suitcases, briefcases, shoes, etc. Crocodile skin is especially appreciated. At the beginning of this century, crocodiles were harvested at 500 thousand copies per year. In some places their number was so reduced that they were taken under protection and attempts were made to artificially breed them. For example, Florida farms kept up to 12 thousand crocodiles, supplying the markets with up to 3,000 copies per year.
Among our species, monitor lizards and large snakes are important as raw materials for the leather industry. The shell of some sea turtles is used, especially the bisse, whose horn plates in hot water and pressed into a homogeneous mass under pressure. Combs, frames for spectacles, etc. are made of this beautiful mass of high quality in terms of plastic properties. Some reptiles are eaten by humans, most often the meat and eggs of turtles. There is a regular fishery for soft-skinned turtles and some species of sea turtles, especially green ones.
In North America, terrapines are hunted, which they began to breed and
on farms. Among our species, the meat of the Mediterranean, Central Asian and Far Eastern soft-skinned turtles is quite edible. You can eat the egg yolks of all our turtles. Turtle meat is also used to feed fur animals.
Class Birds (Aves).
It is generally accepted that birds are a progressive, specialized branch of reptiles adapted to flight. Their ancestors were Archosavria, a very diverse group of reptiles that dominated the Mesozoic era. It is assumed that the transition to an arboreal lifestyle (jumping from branch to branch) was accompanied by the growth and compaction of the structure of horny scales along the posterior edge of the limbs, sides of the body and tail, which made it possible to lengthen the jump due to planning, and then proceed to active flight (Fig. 96).
And at present, up to 90% of bird species are associated with trees and shrubs.
Birds are highly organized vertebrates, the body of which is covered with feathers, and the front limbs are turned into wings. The ability to move in the air, warm-bloodedness and other features of the structure and life gave them the opportunity to widely settle on Earth. The greatest species diversity of birds (according to Konstantinov et al.) Is recorded in tropical forests (85%), where the layered structure of the stand is clearly expressed.
In total, there are about 9 thousand bird species, of which 734-751 species are in Russia.
Similarities between birds and reptiles:
1) lack of skin glands;
2) strong development of horny formations on the body;
3) diapsid type skull (the upper arch is reduced);
4) rudiments of the cervical ribs are noticeable, the posterior cervical vertebrae have well-developed movable ribs that do not reach the sternum, large hook-shaped processes sit on the ribs;
5) open basin;
6) in the hind limb, a typical intertarsal joint, the bones of the metatarsus and the lower row of bones of the tarsus merge into a single bone - the tarsus;
7) similar composition of the forelimbs;
8) general plan of the peripheral circulatory system, the structure of the genitourinary system, the nature of embryonic development, etc.
Some of the progressive traits that distinguish them from reptiles include:
1) the ability to fly (feathers, forelimbs converted into wings, double breathing system, hollow bones)
2) a higher level of development of the central nervous system, which determines the adaptive behavior of birds;
3) high (41-42 degrees) and constant body temperature, supported by a complex thermoregulation system;
4) perfect reproductive organs (nest building, incubating eggs and feeding chicks);
External structure
The evolution of birds followed a single path associated with the development of the air environment. Flight as the main mode of their movement left an imprint on their external and internal structure (although they also retained the ability to move through trees, on the ground).
The body is dismembered into the head, neck, torso and tail. The small head has various senses. The jaws are devoid of teeth and are dressed with horny caps that form a beak. The shape of the beak is different, which is associated with the nature of the food consumed. The neck of different birds different lengths and is very mobile. The body is rounded. The forelimbs are turned into wings. The hind legs are of a different structure. it
associated with a variety of habitats. The legs have four toes ending in claws. Bottom part legs covered with horny shields. The shortened tail is equipped with a fan of tail feathers. It has a different structure in different birds. The skin is dry, devoid of glands (with the exception of the coccygeal), which serves to lubricate the feather cover and make it waterproof.
Feather cover (Fig. 97).
The feather cover helps to maintain a constant body temperature of birds. The basis is made up of contour feathers (they consist of a rod, a point, a fan) - they give the bird a streamlined shape. On the wings, they are called flywheels, and those forming the plane of the tail are called steering ones. Under the contour feathers are located with a thin rod - down feathers. They are devoid of second order barbs and, accordingly, do not form a closed fan. There is also down itself, which has a shortened shaft with a bunch of 1st order barbs extending from them.
Figure: 97. Types and structure of the pen
Features of the skeleton (Fig. 98).
The skeleton in birds is light (most bones are filled with air) and strong (many bones grow together in the early stages of embryonic development). The cervical region consists of 11 to 25 vertebrae (the head can be rotated almost 180 degrees). The thoracic vertebrae have grown together. With ribs and sternum, they form the ribcage. Most birds have an outgrowth on the sternum - a keel. It increases the area of \u200b\u200battachment of the pectoral muscles.
The last thoracic vertebra, all lumbar, sacral, and anterior caudal vertebrae have grown together into a complex sacrum. The tail section consists of several movably connected vertebrae and vertebrae, which form the coccygeal bone, which serves as the place of attachment of the tail feathers.
In the skeleton of the wing, 3 underdeveloped fingers have been preserved, the small bones of the hand have grown together into a single bone - a buckle. The belt of the forelimbs consists of paired shoulder blades, collarbones (fused with the lower ends) and crow bones. In the skeleton of the legs, several small bones of the foot have grown together into a single bone - the tarsus, which allows the bird to walk. Hind limb girdle - the pelvis is formed by two pelvic bones fused with a complex sacrum.
Musculature of birds. Muscles in birds have reached a high level of development, especially the pectoralis major muscles, which lower the wings. In good flyers, they make up 1/5 of their body weight. Among the muscles of the hind limbs (up to 35 individual muscles) there are muscles with long tendons. When the bird sits on a branch, the tendons stretch and squeeze the fingers.
Figure: 98. Bird skeleton
Digestive system (Fig. 99).
The structure of the digestive system is characterized by further complication and is closely related to the flight of birds. They have no teeth and are partially replaced by the sharp edges of the beak. The oral cavity is small and leads into the pharynx, which passes into the esophagus. In some, it forms an extension - goiter (in granivores). This is where food is stored and softened. The stomach consists of two sections: anterior - glandular and posterior - muscular. In the first, chemical processing of food takes place, and in the muscular one - mechanical. The intestine is short, on the border of the thin and thick sections there are blind outgrowths. The short colon does not store feces, and feces are excreted from the intestines very often, which lightens the weight of the bird. The rectum is absent - an adaptation to lighten the body. The process of digestion of food in birds is very active: in insectivores it does not exceed 1 hour, and in granivores - 4 hours. An intensive metabolism is associated with the consumption of significant
the amount of feed, especially increasing in small birds, which are characterized by large heat losses.
Figure: 99. Internal organs of birds
1 - esophagus; 2 - glandular stomach; 3 - spleen; 4 - gizzard; 5 - pancreas; 6 - duodenum; 7 - small intestine; 8 - rectum; 9 - cecum; 10 - cesspool; 11 - goiter; 12 - liver; thirteen -
trachea; 14 - lower larynx; 15 - light and air bags; 16 - testes; 17 - seed tubes; 18 - kidneys; 19 - ureters
Respiratory system (Fig. 98).
The respiratory system has a number of features associated with adaptation to flight. It begins with the nostrils located at the base of the beak. From the mouth, the laryngeal slit leads into the larynx, and from it into the trachea. In the lower part of the trachea and the initial sections of the bronchi is the vocal apparatus - the lower larynx. The source of sounds is the membranes vibrating during the passage of air between the last cartilaginous rings of the trachea and the half rings of the bronchi. The bronchi penetrate into the lungs, branch into small tubes - bronchioles - and very thin air capillaries, which form an air network in the lungs. Blood vessels are closely intertwined with it, gas exchange occurs through the walls of the capillaries. Some of the bronchial branches are not divided into bronchioles, they go beyond the lungs, forming thin-walled air sacs located between the internal organs, muscles and even inside the hollow bones. Volume
air sacs are almost 10 times the volume of the lungs. Paired lungs are small and not very extensible; they grow to the ribs on the sides of the spine. In a calm state and during movement on the ground, the act of breathing is carried out due to the movement of the chest. When inhaling, the sternum descends, moving away from the spine, and when exhaling, it rises, approaching it. During flight, the sternum is motionless. When the wings are raised, exhalation occurs, oxygen-rich air enters the lungs from the air sacs, where gas exchange takes place. Thus, oxygen-rich air passes through the lungs twice: both when you exhale and when you inhale (the so-called double breathing). Air bags prevent the body from overheating, as excess heat is removed with the air.
The vocal apparatus of birds has not one larynx, but two - the upper (larings) and the lower (sirings). The main role in the formation of sounds belongs to the lower, which is very complex. Its very presence is the difference between birds and other animals. It is located at the bottom of the trachea where the trachea branches into two main bronchi.
The lower larynx has two or four vibrators that work independently of each other, which allows the bird to pose as a duet or quartet. It also allows the trachea to be used as the strongest resonator. In many birds, the latter greatly increases in length and diameter, and the bronchi also increase, each having an independent sound source. The bird is able to significantly change the shape of the complex system of the vocal apparatus with the help of body movements and the tension of special muscles. This allows her to control the pitch and timbre of her voice.
The rhythmic characteristics of sound are determined by the reflex cooperation of the lower and upper larynx. The upper one acts as a stop valve in the path of the sound flow.
The circulatory system (Fig. 100).
The circulatory system of birds is represented by a four-chambered heart (two atria, two ventricles) and outgoing blood vessels. Venous blood is concentrated in the right side of the heart, and arterial blood in the left. Organs
and tissues receive pure arterial blood, which promotes enhanced metabolism and ensures a constant high body temperature (38-42 degrees). From the left ventricle, arterial blood flows into the right aortic arch (in birds only). Arteries depart from it, supplying oxygen to all parts of the body. Venous blood through the anterior and posterior vena cava returns to the right atrium. This movement of blood makes up a large circle of blood circulation. Through the pulmonary circulation, venous blood flows through the pulmonary artery from the right ventricle to the lungs. Oxidized blood from the lungs is directed through the pulmonary veins to the left atrium, in which the small circle ends. Blood circulates at a high speed, which is associated with the vigorous work of the heart, high blood pressure. The resting pulse of passerines is 400-600 strokes during flight -1000
Figure: 100. Circles of blood circulation and circulatory system
Excretory system (fig. 101)
Paired metanephric kidneys are very large, which is associated with increased metabolism in birds. The kidney is an elongated flat body, subdivided into three lobes. The kidneys are located under the dorsal walls of the pelvis. From each kidney, a ureter leaves, opening into the middle section of the cloaca. In the cloaca, water is reabsorbed from the urine.
No bladder. Thanks to this, the thick, mushy urine of birds, consisting, like in reptiles, mainly of uric acid, is not retained in the body, which contributes to the relief of the body, as well as the economical use of water in the body of the bird.
The adrenal glands, in the form of small paired yellowish bodies, are located near the anterior margin of the kidneys.
Figure: 101. Genitourinary organs of the male (A) and female (B) pigeons and their location schemes:
1 - aorta;
2 - adrenal gland,
3 - right kidney,
4 - left kidney,
5 - ureter,
6 - testes,
7 - seed channel,
8 - left ovary,
9 - left oviduct,
10 - rudiment of the right oviduct,
11 - the final section of the intestine,
12 - cloaca
Nervous system
The nervous system of birds has become much more complex than that of reptiles. The high development of the central nervous system is due to the more complex behavior of birds. It manifests itself in different forms taking care of the offspring (nesting, laying and incubating eggs, heating the chicks, feeding them), in seasonal movements, in the development of sound signaling. Represented by the brain, spinal cord and nerves. The brain is enclosed in a voluminous cerebral box. The cerebral hemispheres of the forebrain are large in size and formed by the striatum. The midbrain has developed visual lobes. The cerebellum ensures balance and precise coordination of the bird during flight. The olfactory lobes are poorly developed. Cranial nerves 12 pairs. Complex forms of caring for offspring in birds are progressive features that have developed in the process of their historical development.
"Class - birds"
Birds are highly organized vertebrates. The ability to fly for a long time, warm-bloodedness and other features of life gave them the opportunity to widely settle on Earth. The life of birds is associated with meadows, fields, swamps, banks of reservoirs, open areas of water. However, most of their species are forest dwellers. In the crowns of trees and shrubs, tits, kinglets, crossbills are common, on tree trunks - woodpeckers, nuthatches, pikas, on the ground - black grouse, hazel grouses, capercaillie. In terms of the number of species, the class of birds is the largest among terrestrial vertebrates (about 9 thousand species).
Features of the structure and life of birds
The ability to fly, along with other modes of movement, determined many specific features of the external and internal structure of birds.
External structure. Birds have a relatively small head, a long mobile neck, and a compact body. The head has a beak, which consists of bony jaws and horny sheaths. The nostrils are located on the beak. Large eyes have movable eyelids and a nictitating membrane. On the head (closer to the back of the head) there are auditory openings.
The body of birds is covered with feathers: contour, down, down. A contour feather consists of a core, a dense plate - a fan, a free part of the core - a point. The fan is formed by barbs of the first and second order, interlocking microscopic hooks of barbs of the second order. Down feather does not have a dense fan. Down - feathers with a very short shaft and a bunch of barbs extending from it. Contoured feathers give streamline to the bird's body, protect from the wind. The largest of them form the flying surface of the wings (flight feathers) and tail (tail feathers). Down feathers and down prevent heat release. Birds restore the integrity of the split fans with their beaks, lubricate them with fat. Worn feathers are replaced with new ones during the seasonal molting period.
The skin of birds is thin, dry. Most have only a coccygeal gland (produces an oily fluid that birds lubricate their feathers with). On the legs of birds there are horny scales.
Features of the skeleton. The skeleton in birds is light (most bones are filled with air) and strong (many bones grow together in the early stages of embryonic development). The cervical region consists of 11 to 25 vertebrae (the head can be rotated almost 180 degrees). The thoracic vertebrae are fused together. With ribs and sternum, they form the ribcage. Most birds have an outgrowth on the sternum - a keel. It increases the area of \u200b\u200battachment of the pectoral muscles.
The last thoracic vertebra, all lumbar, sacral, and anterior caudal vertebrae have grown together into a complex sacrum. The tail section consists of several movably connected vertebrae and vertebrae, which form the coccygeal bone, which serves as the place of attachment of the tail feathers.
In the skeleton of the wing, 3 underdeveloped fingers have been preserved, the small bones of the hand have grown together into a single bone - a buckle. The belt of the forelimbs consists of paired shoulder blades, collarbones (fused with the lower ends) and crow bones. In the skeleton of the legs, several small bones of the foot have grown together into a single bone - the tarsus, which allows the bird to walk. Hind limb girdle - the pelvis is formed by two pelvic bones fused with a complex sacrum.
Musculature of birds. Muscles in birds have reached a high level of development, especially the pectoralis major muscles, which lower the wings. In good flyers, they make up 1/5 of their body weight. Among the muscles of the hind limbs (up to 35 individual muscles) there are muscles with long tendons. When the bird sits on a branch, the tendons stretch and squeeze the fingers.
Features of the structure of the organs of the body cavity. The esophagus in many birds has an expansion - a goiter, where food accumulates, softens and is partially digested. The stomach consists of two sections: glandular and muscular. In the glandular, food is processed with digestive juices, in the muscular it is rubbed with small pebbles swallowed by birds. The large intestine is short and birds defecate frequently (an adaptation to weight loss). The birds have preserved a cloaca.
The lungs of birds are dense, spongy bodies. Air passes through the trachea, two bronchi, which branch out and end in thin-walled vesicles, braided by capillaries. Some of the branches of the bronchi extend beyond the lungs and form air sacs, the main role of which is participation in the respiratory mechanism during flight. When the wings are raised, the volume of the body cavity increases, which leads to stretching of the air sacs. In this case, air from the lungs passes into the front air sacs, and air from the external environment through the respiratory tract goes into the lungs and into the back bags. At this time, gas exchange occurs in the lungs. When the wings are lowered, the volume of the body cavity decreases and, under the pressure of internal organs, air containing a lot of oxygen passes from the posterior air sacs to the lungs, and the air from the anterior sacs to the trachea and is discharged outside. Thus, air passes through the lungs both during inhalation and exhalation. The more intense the flight, the better the lungs are ventilated. When moving on land and at rest, breathing in birds occurs without the participation of air sacs.
The heart in birds is four-chambered (two atria and two ventricles). The large and small circles of blood circulation are completely dissociated (arterial blood enters the systemic circulation from the heart, and venous blood into the small circle). The blood circulation rate in birds is extremely high, which is associated with a high frequency of heart contractions.
The excretory organs of birds are bean buds. The resulting urine flows down the ureters into the cloaca and is excreted with feces.
Metabolism. Perfect breathing, consumption a large number food and its rapid digestion, high heart rate and rapid tissue supply with nutrients and oxygen provided birds with a high level of metabolism. Thanks to the feather cover, the transfer of heat to the environment has significantly decreased and the temperature of the birds has become high (up to 43 ° C) and constant.
Nervous system. In birds, the forebrain hemispheres, midbrain, and cerebellum are highly developed. The development of the forebrain hemispheres is associated with the rapid formation of various conditioned reflexes, the improvement of vision with the midbrain, and the coordination of complex movements with the cerebellum, especially during flight. The behavior of birds is characterized by great complexity, which manifests itself in the choice of nesting sites, the construction of nests, the protection of nesting territories, the breeding and feeding of chicks, the relationship of adults with each other, etc.
Reproduction and development of birds
Features of the reproductive organs. In the females of most birds, the right ovary is underdeveloped and only the left is functioning. The eggs in the ovary do not ripen at the same time. The developed egg, passing through the oviduct, is fertilized with spermatozoa introduced by the male into the female's cloaca.
Egg structure. Most of the egg is occupied by the egg itself - the yolk with the embryonic disc (always facing upward). After fertilization, the yolk is covered with protein, a two-layer undershell membrane (at the blunt end of the egg it exfoliates and forms an air chamber), a calcareous shell with numerous pores, the thinnest overshell membrane that protects the egg from penetration of microbes.
The development of the embryo. The females of most birds lay their eggs in pre-built nests. The nest, even a hole in the soil, contributes to the compact arrangement of eggs, the retention of heat and air humidity under the incubating bird. The development of the embryo in the egg occurs at a high temperature (about 39 ° C) and a certain humidity. The formed chick pushes its beak into the air chamber and inhales air. There is a horny tooth on its beak. After breaking through the shell, the chick comes out.
Chick development types. According to the degree of development of chicks hatching from eggs, birds are divided into brood and chicks. In brood birds (black grouse, hazel grouse, chickens, ducks), chicks are born with sighted, covered with thick down. The brood hen leads them, warms them with the warmth of her body, gives danger signals, summons them to the found food, etc. In chicks (pigeons, starlings, tits), chicks hatch blind, naked or with sparse down.
Parents warm them in the nest with their warmth, bring them food, protect them from enemies.
Seasonal phenomena in the life of birds
Bird nesting. In the spring, birds choose nesting sites, build or repair nests, females lay eggs in them, and then incubate them. Most often, birds nest in separate pairs and protect the selected territory from the invasion of individuals of their own and similar species. With a limited choice of nesting sites and the ability to collect food from a large area, some birds (rooks, shore martins, black-headed gulls) nest in colonies. In some birds, colonial nesting arose as an adaptation to joint protection from enemies.
Post-nesting period. The second important seasonal phenomenon in bird life is molting. As a rule, it occurs gradually, and the birds do not lose their ability to fly. Only in some (geese, ducks, swans) all flight feathers fall out at once during molting, and birds cannot fly for several weeks. In the post-nesting period, birds gather in small flocks and roam in search of food. Some of them (nutcracker, jay) store food for the winter. At the end of summer and autumn, post-nesting migrations intensify and gradually, in some species of birds, they pass into autumn and winter migrations, and in others, into autumn migration. According to the development of seasonal movements of birds, they are divided into sedentary, nomadic and migratory.
Sedentary and nomadic birds. Resident birds (house sparrow, jackdaw, rock dove) live in the same area, have adapted to the transition from one type of food to another, the use of human kitchen waste. Magpies, black grouse, capercaillie, hazel grouse, tits are close to sedentary birds.
Wandering birds (woodpeckers, nuthatches, bullfinches) move away from summer places habitat for tens and even thousands of kilometers. They do not have permanent places of wintering and repeated routes of movement. By the end of winter, nomadic birds usually approach their former nesting sites.
Migratory birds (orioles, swifts, ducks, geese, cranes) fly to wintering grounds and to nesting sites by flyways that have been established for centuries. The main signal of the flight is the decrease in the day.
Methods for studying bird migrations. Knowledge about wintering places and flyways of birds was obtained by the ringing method. Recently, miniature sensors that are attached to the back of the bird have been used. Knowledge of bird migration is essential for their protection and rational fishing.
The emergence of bird migration. Scientists believe that bird migration originated several hundred thousand years ago, when the seasons began to be established on Earth with climate change in temperate latitudes. The main reason for the occurrence of flights is the lack or lack of food in nesting places during the cold season.
The origin and the most important orders of birds
Signs of similarity between modern birds and reptiles. Modern birds and reptiles have a number of similarities: dry skin, scaly cover (in birds on the legs), cloaca, eggs are rich in yolk and have parchment-like or calcareous shells, development without transformation. In modern tropical birds, the goatsin, chicks have fingers with which they cling to tree branches. All of this indicates that modern birds and reptiles are related groups of animals and have common ancestors.
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First birds. An important proof of the origin of birds from ancient reptiles is the found fossilized imprints of the skeleton and feathers of one of the ancient birds, called the first bird, or Archeopteryx. The first bird was about the size of a magpie. Jaws with teeth, a long tail with 20 vertebrae resembled reptiles. Their forelimbs had all the features of a bird's wings. On the hind limbs, the tarsus was developed, the fingers were located, like in birds, three fingers forward, and one back. The first birds evolved about 180 million years ago from ancient reptiles that ran on the ground on their hind legs, could climb trees, jump from branch to branch.
The most important orders of birds. In the class of birds, there are about 30 orders. The largest of them is a detachment of passerines. It includes different types larks, sparrows, swallows, wagtails, starlings, crows, magpies, blackbirds. Passerines are most numerous in forests. The legs of the birds of this order are four-toed (three toes are directed forward and one is directed backward). During the nesting period, they live in pairs, build skillful nests. Chicks are born naked, helpless.
Of the other orders of birds, the largest in terms of the number of species are Charadriiformes, Anseriformes, Chickens, Falconiformes, and Storkiformes. The order of Charadriiformes includes woodcock, lapwing, plover, carrier and other waders - small and medium-sized birds with long legs and a thin long beak. They live in wetlands, along the banks of rivers and other bodies of water. Sandpipers are brood birds. They feed mainly on invertebrates.
The order of anseriformes includes geese, ducks, swans. These waterfowl have dense plumage with developed down, a large coccygeal gland, swimming membranes between the toes. The edges of a wide beak with teeth or with transverse plates forming a filter apparatus. Many dive well, getting food from the bottom of the reservoir.
The order of chickens (hazel grouse, black grouse, capercaillie, quail, partridge, pheasants, wild bank and domestic chickens, turkeys) includes birds with strong legs adapted to raking the soil or forest litter when foraging, short and wide wings, providing a rapid takeoff and short flight. They lead mainly a sedentary or nomadic lifestyle. Gens are brood birds. Chicks feed mainly on insects, worms and other invertebrates, adults are mainly herbivorous.
The order of storks (storks, herons, bitterns) unites birds of medium and large size with a long neck and long legs. They feed on damp meadows, swamps or in the coastal parts of water bodies by amphibians, small fish, and molluscs. They usually nest in colonies.
The order of falconiformes includes falcons, hawks, kites, eagles. They have strong legs with sharp curved claws, a hook curved beak, and sharp eyesight. The wings are either narrow, sharp, facilitating fast flight, or wide, allowing them to float in the air in search of prey. The chicks of these birds hatch from the sighted eggs, covered with thick fluff.
The group of woodpeckers includes great and lesser spotted woodpeckers, green woodpeckers, black woodpeckers (gall), and twirls. They have a sharp chisel-like beak, a long, sharp tongue with jaggies, elastic ends of the tail feathers bent towards the support, legs with two toes pointing forward and two backward, which allows them to hold well on tree trunks. The exception is the whirlwind, which has a straight and weak beak, the rods of the tail are inelastic. Woodpeckers - chick birds, hollow-nests.
Ecological groups of birds
The main ecological groups of birds. Birds of different orders inhabit this or that habitat. In connection with adaptation to life in similar conditions, they developed similar features of structure and behavior, formed ecological groups of birds: birds of the forest, birds of swamps, fresh water bodies and their coasts, birds of open desert-steppe spaces, birds of open air spaces, daytime predators.
The birds of the forest live in spaces bounded by trees and shrubs. In such conditions, they developed adaptations for fast take-off and accurate landing on branches, maneuvering between trees (shortened wide wings, rather long tail).
Small birds, feeding mainly in the crowns of trees and shrubs (titmouse, kinglets), have thin and sharp beaks, tenacious toes with sharp claws. Woodpeckers and some passerines (pikas and nuthatches) have tough tail feathers with sharp tops, a fairly strong beak, short legs with tenacious toes that help to hold onto tree trunks when getting food. The birds of the lower forest layer (wood grouse, black grouse, hazel grouse) have developed adaptations to feeding on the ground.
Birds of swamps, coasts and open areas of fresh water bodies. Some of the birds of this group (egrets, bitters, storks) usually feed in swamps, damp meadows, in the coastal part of water bodies. They have a long neck, thin long legs. Birds foraging in open areas of water (ducks, teals, geese) have dense plumage, highly developed down and subcutaneous layer of fat, a developed coccygeal gland, short legs with swimming membranes, a wide beak with a filtering apparatus.
Birds of the steppes and deserts (African ostrich, bustard, little bustard) have keen eyesight, a long neck, well-developed legs, allowing them to notice danger in time and hide from enemies. The bustard living in the steppes of our country (body weight of males up to 16 kg) and little bustard (body weight up to 1 kg) are rare birds. The main reasons for this are the plowing of the steppes and poaching.
Birds of open air spaces - swallows (village, city, coastal), swifts - spend most of their active life in the air. The rapid flight of these birds is facilitated by long narrow wings, highly developed pectoral muscles, and a notched tail - the rudder during flight. On the fly, they catch insects with their wide mouths.
Daytime predators (eagles, falcons, hawks, kites) live in various habitats - in forests, mountains, on plains. Any daytime predator can be recognized by its strong hooked beak, powerful legs with strong toes and curved claws. Among them there are also scavengers, such as vultures and vultures.
Types of poultry. Poultry
The importance of birds in nature and human life. Birds restrain an increase in the number of insects - plant pests, carriers of pathogens of diseases of animals and humans, and small rodents. Many of them destroy the seeds of weeds, promote the spread of seeds of mountain ash, cedar pine, oak acorns, etc. They and the eggs they lay are included in the food chains of many animals, some reptiles.
A person is of great interest to ducks, geese, woodcocks, snipe, great snipe, quail, pheasants as objects of sport hunting, hazel grouses, black grouse, wood grouse and some other birds as objects of fishing.
Bird protection. In order to preserve the number of birds in our country, strictly defined hunting periods have been established; it is prohibited to hunt birds during their reproduction and molting. The places where rare birds are found have become protected. AT last years special attention is paid to the protection of such rare birds as the bustard, little bustard, white crane, white-tailed eagle.
Every person should take care of birds. The most affordable ways of caring are making and hanging artificial nests (nest boxes, cracks, titmouses), planting hedges of thorny bushes around the gardens, in which various insectivorous birds nest, feeding birds in winter.
Types of poultry. A small number of bird species have been domesticated by humans, primarily for the purpose of obtaining meat, eggs, feathers and down. Chickens, ducks, geese, turkeys, guinea fowls are of the greatest importance in the human economy. The first place among poultry is occupied by chickens. They have tender tasty meat, carry a lot of eggs, and can be kept in a limited area. The ancestor of domestic chickens is the wild bank chicken. She still lives in the forests of India, Burma and the Malay Archipelago.
Test work on the topic "Class Birds"
Option 1
1. Scientists suggest that birds evolved from:
2) reptiles;
3) amphibians;
4) mammals.
2. The place of attachment of the tail feathers is:
2) the sacral vertebra;
3) tailbone;
3. The spine of a bird consists of sections:
1) trunk, lumbar and tail;
2) cervical, thoracic, lumbar, sacral, caudal;
3) cervical, trunk, sacral, caudal;
4) cervical, thoracic and sacral.
4. Part of the respiratory system of birds are (are):
2) air bags;
3) flying muscles;
5. The group of nomadic birds includes:
1) sparrows;
2) pigeons;
3) crows;
4) bullfinches.
6. The night predator is:
1) sparrow's syllable;
2) tit;
3) mandarin duck;
7. Birds lack:
1) sternum;
2) cloaca;
3) the bladder;
6) skin glands.
8. Why are the flight feathers of the eagle owl fringed?
9. Name the ancestor of modern breeds of domestic turkeys.
10. Why do birds need a coccygeal gland?
11. What are the flying muscles attached to?
12. How many sacral vertebrae do birds have?
13. What is the peculiarity of the structure of the reproductive system of birds in females?
14. What bones are the skeleton of the hind limb of birds?
Verification work on the topic "Birds"
Option 2
1. The transitional form between reptiles and birds is:
1) coelacanth;
2) stegocephalus;
3) archeopteryx;
4) the platypus.
2. The organ of hearing in birds consists of them:
1) the inner ear;
2) the outer and middle ear;
3) inner and middle ear;
4) the outer ear.
3. Contour wing feathers are called:
1) threadlike;
2) flywheels;
3) covering;
4) steering.
4. The heart of birds consists of:
1) two ventricles and one atrium;
2) two atria and one ventricle;
3) two atria and two ventricles;
4) one ventricle and one atrium.
5. The sedentary birds of the European part of our country include:
1) black swift;
2) barn swallow;
3) house sparrow;
4) finch.
6. The night predator is:
2) gray owl;
3) mandarin duck;
7. Indicate the flight adaptations of birds:
1) hollow bones;
2) the presence of a cloaca;
3) the presence of a feather cover;
4) lack of skin glands;
5) the presence of a goiter;
6) the presence of a keel.
8. Name the ancestors of modern breeds of domestic chickens.
9. Why do geese and ducks sit shallow in the water?
10. How is the strength of the bird support system achieved?
11. What is the name of the lower legs of the bird?
12. How many vertebrae are cervical birds?
13. Why is the cerebellum very large in birds?
14. What bones does the skeleton of the forelimb of birds consist of?
Answers to the test work on the topic "Class Birds"
this is an adaptation for silent flight
north american turkey
its secret is used to lubricate the feathers and prevent them from getting wet
2 vertebrae
consists of one - left - ovary and left oviduct
one femur, fused bones of the lower leg, bones of the foot forming a tarsus and four toes
bank chickens
the thickness of the feather cover is large, and there is a lot of air between the feather and the down
due to the fusion of many bones in the early stages of individual development
9 - 25 vertebrae
due to complex bird movements that require coordination during flight
one humerus, two bones of the forearm (ulna and radius), several bones of the hand, and three underdeveloped fingers
The body is divided into head, neck, torso, limbs and tail. There is a beak on the head, consisting of beak and mandiblescovered with horny sheaths. At the base of the beak is wax - leathery thickening. The eyes are very large, behind them, hidden by feathers, there are auditory openings leading to the eardrum. The neck is mobile, the upper limbs have turned into wings, on the lower four fingers, three are directed forward, one is directed backward, the fingers end in horny claws. The lower part of the legs is covered with horny scales.
© Veils... The skin of birds is thin, consists of a multilayer epidermis and dermis, there are almost no skin glands, only at the base of the tail there is a coccygeal gland. The oil of the coccygeal gland is used to lubricate the plumage, and it is especially developed in waterfowl, so that their feathers do not get wet. Birds living in arid regions (the bustard) lack the coccygeal gland. Reptile scales have changed into a feather cover, light, durable and well retaining heat. Feathers are derived from the epidermis and contain a stable and durable keratin protein.
The part of the feather immersed in the skin is called a quill, and a hollow shaft and a fan are located above. The fan is formed by first-order horn barbs that extend from the shaft in both directions; they have barbs of the second order with small hooks that fix the barbs to each other, and a light and durable surface of the fan is formed (Fig. 159). This is the structure outline bird feather. Have downy feathers on a short shaft are long and thin beards not linked by hooks, fluff does not have a shaft; barbs extend from a common base.
There are very large feathers on the wings of the bird, which are called paramount and secondary flight feathers... Their outer fan is narrow, and the inner one is wider, this allows air to pass between the feathers when raising the wing, and when lowering under air pressure, a single wing plane is formed. On the tail are helmsmen contour feathers, the whole body is covered with contour feathers integumentary feathers.
During flight, the cover feathers give the pigeon a streamlined shape and regulate heat transfer. Active muscular work leads to heating of the body, and there is a need for additional heat transfer. For this they serve pharmacies - Areas of the body surface devoid of feathers. Feathered sections are called pterilia(fig. 158) .
The color of the plumage in birds is very different, it can be protective, it can be very bright and play a big role in sexual selection.
The feather cover is periodically replaced, molting occurs. Moulting usually occurs gradually, but in some species (for example, black grouses, wood grouses, ducks, geese and swans almost simultaneously lose feathers) it can occur so intensely that for some time they lose their ability to fly.
© Skeleton and musculature... The skeleton is light and strong due to the thinness of the bones and their pneumatic nature - there are large cavities in the bones. It consists of four sections: the skeleton of the head, the axial skeleton, the skeleton of the limbs and their belts.
The skeleton of the head (skull) has a cerebral and facial sections. Brain department large, articulated with the spine by one condyle, like in reptiles. AT facial department huge eye sockets and elongated jaws, modified into a beak.
The skeleton of the torso consists of spine and chest... The spine includes five sections: cervical, thoracic, lumbar, sacral and caudal. The cervical vertebrae are from eleven to twenty-five. The cervical vertebrae are characterized by saddle joints, which provide greater neck mobility (in owls, the head rotation angle reaches 270 degrees). The pigeon has five thoracic vertebrae, six lumbar vertebrae (fused into a solid bone plate), and two sacral vertebrae.
The posterior thoracic, lumbar, sacral, and anterior caudal are fused into a complex sacrum. There are only fifteen caudal vertebrae, the middle six remain free, the last four have fused to form the coccygeal bone, a vertical bony plate to which the tail feathers attach.
The rib cage is formed by ribs consisting of two bones connected by a joint at an angle to each other. Thanks to this structure of the ribs, the sternum can move in and out in relation to the spine during breathing movements. On the top of the ribs, there are flat outgrowths overlapping the back ribs, which increases the strength of the chest. Most birds have a keel on the sternum, to which the pectoral muscles are attached, which set the wings in motion.
The forelimbs consist of the humerus, the forearm is represented by the ulna and radius, the hand consists of fused bones of the wrist and metacarpus, which form a common bone - buckle, and three fingers: the second, third and fourth. The skeleton of the hind limbs is represented by the femurs, in the tibia, the tibia and fibula are fused, in the foot there is a tarsus and four fingers. The tarsus is formed by the fused bones of the tarsus and metatarsus.
The belt of the forelimbs consists of paired bones: powerful crow, saber-shaped shoulder blades lying on the ribs, and the collarbones, which have grown together in the lower part and formed a fork, characteristic of birds. The belt of the hind limbs is formed by paired fused bones: ilium, ischial and pubic. Moreover, the pelvis of birds is open, the ischial and pubic bones do not grow together, this is due to the laying of large eggs. Due to the fact that the main load during walking falls on the hind limbs, the pelvic bones are massive, firmly grow together with the posterior thoracic, lumbar, sacral vertebrae, as well as with part of the caudal vertebrae, forming a complex sacrum (Fig. 160).
The muscles of birds are more developed than that of reptiles. The muscles that lower and raise the wings (pectoral and subclavian, respectively) are especially strongly developed, the muscles of the legs are highly developed, especially in running birds.
© Digestive system... Birds are animals with a constant body temperature (homeothermal), a very high metabolic rate. All modern birds have no teeth, their jaws are covered with horny sheaths, and food cannot be chewed. The beak has a very different structure, depending on the nature of the food. In the mouth, the tongue, also adapted to various foods, opens the salivary glands into the oral cavity. Food is swallowed and sent through the esophagus to the stomach. The pigeon has a goiter, in which not only the swelling of the grains occurs, but during the period of feeding the chicks “bird's milk” is formed - a white nutritious curdled mass for feeding the chicks. From the goiter, the swollen grains are sent through the esophagus to the stomach, to its first, glandular section, where enzymes act on food. The absence of teeth is compensated for by the muscular part of the stomach, in which food is rubbed with the help of the horny walls of the stomach. In addition, granivorous birds ingest pebbles that help grind food. From the stomach, the food mass enters the duodenum, where pancreatic enzymes and liver bile act on it.
From the duodenum, food enters the small intestine, where the digestion of proteins, fats and carbohydrates is completed. The large intestine is short and ends in a cloaca. There is no rectum, feces do not accumulate, which reduces body weight. Digestion is very fast.
© Respiratory system... The development of airspace has led to an absolutely remarkable adaptation of the respiratory system to the most complete gas exchange and a number of other functions that the respiratory system performs. The long trachea begins with a laryngeal slit, at the place where the trachea is divided into two bronchi is an expansion - the lower larynx, in which the vocal membranes are located. The bronchi enter the lungs and branch out. The branches of the bronchi are connected by numerous thin channels, from which there are many protrusions - bronchioles, braided by capillaries, alveoli in birds are absent.
Part of the bronchi passes through the lungs and forms huge thin-walled air sacs. Distinguish between front and rear air sacs. Gas exchange in air bags does not occur, they perform the function of an "air pump", pumping air through the lungs.
The lungs themselves in birds are small and weakly stretchable. Unlike the saccular lungs of amphibians and the cellular lungs of reptiles, the lungs of birds are spongy and, most importantly, adapted for unidirectional air flow during inhalation and exhalation.
When inhaling, the sternum descends, the inhaled air passes into the rear air sacs, from there through the lungs, in which gas exchange occurs, into the anterior air sacs. When you exhale, air leaves the front air sacs to the outside, from the rear - passes through the lungs and is excreted from the body. Thus, a continuous, unidirectional flow of air through the lungs is carried out both during inhalation and exhalation. This phenomenon of gas exchange during inhalation and exhalation is called double breathing(fig. 161) .
In addition to the unidirectional movement of air, oxygen saturation of the blood is provided by the countercurrent movement of blood in relation to the movement of air. Due to this, an unusually high efficiency of gas exchange is achieved, at which the body receives a sufficient amount of oxygen even at high altitudes.
Another important function of air sacs is to protect the body from overheating: the air cools the internal organs and muscles (heat production in flight is 8 times more than at rest). Air sacs reduce the density of the body; some air sacs even grow into the cavities of the long bones. The total volume of air sacs is 10 times that of the lungs.
The frequency of respiratory movements in a pigeon at rest is on average 26, in flight - 400, this is also associated with the removal of excess heat through the respiratory organs. If necessary, the so-called thermal dyspnea occurs, this leads to an increase in heat transfer along with the exhaled air and a greater evaporation of moisture from the surface of the respiratory tract.
© Circulatory system... The high level of metabolism, warm-bloodedness led to a significant change in the circulatory system. The heart becomes four-chambered, the septum divides the heart into two parts - right and left. Each part of the heart is made up of an atrium and a ventricle. Venous blood returns to the right half of the heart through the vena cava (upper and lower) from the systemic circulation (Fig. 162).
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From the left ventricle, blood through right aortic arch goes into the systemic circulation. The carotid arteries, which carry blood to the head, are separated from it, and the subclavian arteries to the upper limbs. The right aortic arch merges into the dorsal aorta, providing blood to the internal organs. Then venous blood is collected in the vena cava and enters the right atrium.
Unlike the circulatory system of reptiles, in birds, blood from the heart to the organs in a large circle flows not through two arteries (left and right aortic arches), but only along the right. In avian embryos, both aortic arches are laid, but subsequently the left aortic arch is reduced.
The erythrocytes of birds are biconvex, the oxygen capacity of the blood is 2 times higher than that of reptiles. Thus, the circulatory system provides metabolic processes with a sufficient amount of oxygen, and the average body temperature in birds is about 42 degrees.
© Nervous system... Due to an active lifestyle, the nervous system, especially the brain, is further complicated. In the brain, the cerebral hemispheres are enlarged, but, like in reptiles, they are represented mainly by striatum - growths of the bottom of the forebrain.
The roof of the hemispheres is poorly developed and has a smooth surface. The olfactory lobes are poorly developed and adjoin the cerebral hemispheres in front. The diencephalon is covered by the large hemispheres. In the midbrain, visual hillocks have received a very strong development, which is associated with the paramount importance of vision in the life of birds. The cerebellum is very large; its development is associated with flight, which requires quick and precise coordination of movements. 12 pairs of cranial nerves depart from the brain. From the spinal cord are the spinal nerves that are part of the peripheral nervous system.
From the senses, vision is in the first place. Birds have very large eyeballs, an increase in the absolute size of the eyes makes it possible to obtain large image sizes on the retina, and it is better to distinguish its details.
Accommodation is carried out in several ways: firstly, by changing the curvature of the lens, secondly, due to the movement of the lens relative to the optical axis, and thirdly, the curvature of the cornea also changes. The retina contains visual receptors: sticks and cones, rods provide black and white vision, cones provide color.
In birds leading different lifestyles, the ratio of rods and cones is not the same, rods predominate in owls, and cones in chickens. To excite the latter, a great strength of light is needed, therefore chickens see very poorly in the dark.
The organ of hearing, like the organ of vision, is of great importance in the life of birds. A skin fold is formed around the auditory opening in a number of species, the external auditory canal leads to the large eardrum. The plumage along the edges of the ear canal not only covers the auditory opening, but also, when the position of the head changes, plays the role of a horn that directs sound waves into the auditory opening. In the middle ear cavity there is the only auditory ossicle (stapes), there is an Eustachian tube. The sense of smell in most birds is poorly developed.
© Excretory system... The kidneys in birds are pelvic (Fig. 163), ureters depart from the kidneys, opening into the cloaca. There is no bladder, this is also one of the devices for reducing body weight during flight. Isolation product - uric acid (up to 80% of all nitrogen in urine), which in the form of crystals precipitates into the solution, forming a white mushy mass.
© Reproductive organs... The male has bean-shaped testes in the abdomen next to the kidneys; spermatozoa through the vas deferens enter the seminal vesicles, which serve as a reservoir for semen, and then into the cloaca (Fig. 164).
Copulatory organs are present only in a few species (anseriformes, ostriches), in the rest, the introduction of spermatozoa is carried out by pressing the cloaca of the male to the cloaca of the female. In females, only one is formed, the left ovary. The reduction of the second ovary is probably due to the fact that birds lay large eggs, which are difficult to form simultaneously in two ovaries and oviducts. The oviduct funnel is located near the ovary, the opposite part of the oviduct (uterine) opens into the cloaca.
Is happening ovulation - rupture of the ovarian wall
and the release of the egg into the body cavity. The ovum must be fertilized in the initial part of the oviduct, then the ovum is covered with egg membranes: a albuminous membrane, in the next section - with two parchment-like undershell membranes, a calcareous shell, pigments, a thin supershell membrane is formed in the uterine section, which keeps the egg from penetrating bacteria.
The entire period of passage of the egg through the oviduct in a chicken is about a day. The shell consists of 90% calcium carbonate, penetrated with microscopic pores, which provide gas exchange of the developing embryo. There are more than 7 thousand pores in a chicken egg, more of them at the blunt end. The shell is the source of the salts necessary for the formation of the chick's skeleton. Unlike reptile eggs, water absorption from the environment does not occur; all the water required for the development of the embryo is contained in the protein and yolk. An additional source of water is metabolic water formed by the oxidation of nutrients.
The embryonic disc (the nucleus of the egg and a small part of the active cytoplasm) is on the top of the yolk; chalazes (cords) keep the yolk suspended in the center of the protein. This protects the embryo from jolts, in addition, in any position of the egg, the embryonic disk is on top, closer to the warmth.
In many species the birds do not form pairs, and mating of males occurs with many females; to polygamists include wood grouse, black grouse. Sexual dimorphism in polygams is especially clearly visible. But most species belong to monogamous, some form pairs only for the period of oviposition (ducks), some - for several years (eagles, swans).
While the egg is moving along the oviduct (15 - 20 hours), incomplete cleavage occurs and an embryonic disc is formed, consisting of two layers of cells. In chickens, hatching does not begin immediately, but after several eggs have been laid. Until hatching has begun and the temperature is below 40 degrees, the development of the embryo stops and resumes after the start of hatching. With the development of the embryo, embryonic membranes are formed, characteristic of amniotes: amnion with amniotic fluid, serosaand allantois.Allantois is formed as an outgrowth of the back of the intestine and serves for the accumulation of waste products, the embryonic bladder. Later, it adheres tightly to the shell and is a respiratory organ, because there are a lot of blood vessels in its walls. The yolk sac gradually decreases, in addition, on the 10th day, the embryo begins to swallow amniotic fluid in small portions, which serves as additional nutrition. Later, the protein from the protein coat is also consumed by the embryo.
By this time, an "egg tooth" is formed on the beak - a calcareous build-up, with the help of which the chick breaks through the shell membrane of the air chamber and switches to pulmonary respiration. Through not 
how many hours, with his help, the chick breaks the shell and frees itself from the embryonic and egg membranes.
Incubation lasts about 21 days in chickens. Bird chicks can be divided into two groups: brood and chicks (Fig. 165). The brood chicks are chickens of the order chickens, which are born pubescent, sighted, with open auditory canals. Having dried up, the chickens look for food on their own after a few hours. Chicks of chick birds hatch naked, blind, with closed auditory canals and need regular heating and feeding (Passerine order).
Manifold. Modern birds are subdivided into 3 superorders: Penguins, Ostrich (Keelless) and Typical birds (Cilegrud).
Superorder Kilegrudy.
The majority of birds belong to this group; they have well developed wings and, therefore, the keel of the sternum as the place of attachment of the muscles that set them in motion.
Chicken squad unites brood birds that feed mainly on the ground, run well, fly poorly. Most are sedentary. Most are polygamous, males are usually brightly colored, females who have to take care of their offspring have a protective coloration. This order includes wood grouses, black grouse, hazel grouses, pheasants.
Birds from detachment Day predators have a sharp curved beak and hooked claws. They have excellent eyesight and are all good flyers. Some fly very quickly and hunt mainly in the air, while others look out for their prey on the ground. Most feed on small rodents, regulating their numbers. This order includes eagles, hawks, kites, falcons.
AT squad owls nocturnal birds with large forward-facing eyes enter. The rods in the retina give them good vision even in the dark. In addition, they have excellent hearing, the head can rotate 270 degrees, the owl itself sits motionless, turning only its head, which allows you to accurately determine the location of the prey without drawing attention to itself. The flight is silent as the tips of the contour feathers are soft. Owls, eagle owls, owls, scops owls belong to this order. They feed mainly on rodents, large species can hunt hares, hedgehogs, birds and other small animals.
Detachment Anseriformes. Brood semi-aquatic animals, swim well, some dive. The legs are laid back, have a swimming membrane on the toes, the coccygeal gland is well developed. The beak is flat, with rows of transverse horny plates that help filter the water. Food - plants and invertebrates taken from the water. This order includes ducks, geese and swans. All types of swans are protected by law. The sea duck eider lines its nests with light and very warm down, which is of great economic importance.
Birds from of the Woodpecker squad... A chisel-like beak, a hard tail with which the woodpecker rests against the trunk, short legs with sharp claws allow these birds to catch both adult insects and their larvae living under the bark. All species of woodpeckers are very useful for the forest, they destroy insects and provide housing for other birds living in hollows. In the fall, they switch to seed nutrition conifers, there are always a lot of broken cones near the woodpecker's forge. The largest woodpecker is yellow, great and lesser spotted woodpeckers are often found.
Squad Passerines unites more than half of all bird species. Most are small, the largest belong to the corvids (magpie, rook, raven). Tits, flycatchers, orioles, nuthatches, pikas, wagtails bring huge benefitby feeding on insects and controlling their numbers. Even granivorous species (sparrows) feed their chicks with insects, and they themselves collect a huge amount of weed seeds.
In open spaces, in swamps and steppes, large birds live from detachment of Cranes. Long legs, long neck allow you to see danger from afar. They feed on small animals and plant food, nest in remote places on the ground, brood chicks. All cranes are migratory birds. A typical representative of the steppe regions of the south is the Demoiselle crane. Many species have become rare and need protection. The bustard (dudak), whose mass reaches 16 kg, belongs to the same order. It lives in a dry climate, so the coccygeal gland is not developed. During the rain, her plumage gets wet, she loses the ability to fly. Rare, protected species.