Bird class, general characteristics of the class

Birds are highly organized vertebrates whose bodies are covered with feathers and whose forelimbs are turned into wings. The ability to move in the air, warm-bloodedness and other features of their structure and life activity gave them the opportunity to spread widely on Earth. Bird species are especially diverse in tropical forests. There are about 9,000 species in total.

This is a highly specialized and widespread class of higher vertebrates, representing a progressive branch of reptiles that have adapted to flight.

The similarity of birds with reptiles is evidenced by common characteristics:

1) thin, gland-poor skin;

2) strong development of horny formations on the body;

3) the presence of a cloaca and others.

The progressive features that distinguish them from reptiles include:

a) a higher level of development of the central nervous system, which determines the adaptive behavior of birds;

b) high (41-42 degrees) and constant body temperature, maintained by a complex thermoregulation system;

c) perfect reproductive organs (nest building, incubation of eggs and feeding of chicks).

Structural features

The evolution of birds followed a single path associated with the development of the air environment. Flight as their main method of movement left an imprint on their external and internal structure (although they also retained the ability to move through trees and on the ground).

1) Their body is divided into a head, neck, torso and tail. The small head contains various sensory organs. The jaws are devoid of teeth and covered with horny sheaths 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 is of different lengths and is characterized by great mobility. The body has a rounded shape. The forelimbs are transformed into wings. The hind legs are of different structure. This is due to the diversity of habitats. The feet have four toes ending in claws. The lower part of the legs is covered with horny scutes. The shortened tail is equipped with a fan of tail feathers. It has different structures in different birds.

2) The skin is dry, devoid of glands (with the exception of the coccygeal gland), which serves to lubricate the feather cover and make it waterproof. The body is covered with feathers. The basis is made up of contour ones (consisting of a rod, an edge, a fan) - they give the bird’s body a streamlined shape. On the wings they are called flight wings, and those forming the plane of the tail are called tail wings. Below the contour feathers there are down feathers with a thin shaft. They are devoid of second-order beards and, accordingly, do not form a closed fan. There is also the fluff itself, which has a shortened shaft with a bunch of 1st order barbs extending from them. Feather cover helps maintain a constant body temperature of birds.

3) The skeleton of birds, due to their adaptation to flight, is light and durable. Lightness is due to pneumaticity, and strength is due to the fusion of individual bones at an early age (skull, trunk spine, tarsus, hand bones and others). Tubular bones are hollow, contain air, so they are light. The skeleton has six sections: skull, spine, forelimb girdle, forelimb skeleton, hind limb girdle, hind limb skeleton. The skull is characterized by a large size of the braincase and eye sockets, and toothless jaws. The thin bones of the skull grow together without forming sutures. A single condyle serves to articulate the skull with the spine. The spine consists of the cervical, thoracic, lumbar, sacral and caudal sections. Only the cervical region is mobile, all the rest are inactive or fused together (the terminal caudal sections are fused into the coccygeal bone). There is a rib cage formed by the thoracic vertebrae, radiating ribs and sternum. In flying birds and penguins, the sternum bears a high crest - the keel, to which strong muscles are attached that provide movement of the wings (or flippers). The shoulder girdle consists of the scapula, poracoid and clavicle - it creates support for the wings. The pelvic girdle consists of three paired bones: the ilium, the ischium and the pubis. Below, the pelvic bones are not connected, which is associated with the laying of large eggs.

Bird skeleton

4) Muscles are important in movement, both in the air and on land and water. The muscles of the chest, which raise and lower the wing, reach great development. Birds that have lost the ability to fly have well-developed muscles in their hind limbs (ostriches, chickens, geese).

5) The structure of the digestive organs is characterized by further complication and is closely related to the flight of birds. They have no teeth; they are partially replaced by 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 - a crop (in granivores). This is where food is stored and softened. The stomach consists of two sections: the anterior - glandular and the posterior - muscular. In the first, chemical processing of food occurs, and in the muscular one, mechanical processing occurs. The intestine is short, at the border of the thin and thick sections there are blind outgrowths. The short colon does not accumulate feces, and feces are passed out of the intestines very often, which makes the bird lighter in weight. The rectum is absent - an adaptation to lighten the body. The process of digesting food in birds is very active: for insectivores it does not exceed 1 hour, and for granivores - 4 hours. Intensive metabolism is associated with the consumption of a significant amount of food, especially increasing in small birds, which are characterized by large heat losses.

Internal organs of birds:

1-esophagus; 2-glandular stomach; 3-spleen; 4-muscular stomach;

5- pancreas; 6 duodenum; 7-small intestine;

14-lower larynx; 15-light and air bags; 16- testes;

17-vas deferens; 18-buds; 19-ureters

6) 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 fissure leads into the larynx, and from it into the trachea. In the lower part of the trachea and the initial sections of the bronchi there is a voice apparatus - the lower larynx. The source of sounds is the membranes that vibrate as air passes between the last cartilaginous rings of the trachea and the semi-rings of the bronchi. The bronchi penetrate into the lungs, branching into small tubes - bronchioles - and very thin air capillaries, which form an air-carrying 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 and extend beyond the lungs, forming thin-walled air sacs located between internal organs, muscles and even inside hollow bones. The volume of the air sacs is almost 10 times the volume of the lungs. The paired lungs are small and have little extensibility; they grow to the ribs on the sides of the spine. In a calm state and while moving on the ground, the act of breathing is carried out due to the movement of the chest. When you inhale, the chest bone lowers, moving away from the spine, and when you exhale, it rises, moving closer to it. During flight, the sternum is motionless. When the wings are raised, exhalation occurs, oxygen-rich air passes from the air sacs into the lungs, where gas exchange takes place. Thus, oxygen-saturated air passes through the lungs twice: both when exhaling and when inhaling (the so-called double breathing). Air sacs prevent the body from overheating, as excess heat is removed with air.

7) 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 is concentrated in the left. Organs and tissues receive clean arterial blood, which promotes increased metabolism and ensures a constant high body temperature (38-42 degrees). From the left ventricle, arterial blood enters the right aortic arch (only in birds). Arteries branch out from it, supplying oxygen to all parts of the body. Venous blood returns through the anterior and posterior vena cava to the right atrium. This movement of blood constitutes the systemic 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 sent through the pulmonary veins to the left atrium, where the pulmonary circle ends. Blood circulates at high speed, which is associated with vigorous heart function and high blood pressure. The pulse of passerines at rest is 400-600 beats, and during flight - 1000.

Circulatory system and heart

Circulation circles

1-heart; 2-vessels of the systemic circulation; 3-vessels of the pulmonary circulation; venous blood is shown in blue, arterial blood is shown in red, mixed blood is shown in purple

8) The excretory organs are represented by two large kidneys lying deep in the pelvis. Their weight is 1-2% of body weight. Through two ureters, uric acid flows into the cloaca and is excreted along with excrement. There is no bladder, which makes the bird lighter.

9) Birds are warm-blooded animals, they have a constant body temperature (on average 42 ° C). Warm-bloodedness is due to an increase in the level of metabolism through the intensification of digestion, respiration, blood circulation, excretion and the presence of heat-insulating covers. The constancy of the ambient temperature is an important progressive feature of birds compared to previous classes of animals.

10) The nervous system of birds compared to the nervous system of reptiles has become significantly more complex. The high development of the central nervous system is due to the more complex behavior of birds. It manifests itself in various forms of care for offspring (nest building, laying and incubating eggs, warming chicks, feeding them), in seasonal movements, and in the development of sound signaling. Represented by the brain, spinal cord and outgoing nerves. The brain is enclosed in a voluminous braincase. The large 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. There are 12 pairs of cranial nerves.

Complex forms of caring for offspring in birds are progressive features that have developed in the process of their historical development.

Nervous system and brain

11) The most important sense organs are the organs of vision and hearing. Their eyes are large, equipped with upper and lower eyelids and a third eyelid, or nictitating membrane. All birds have color vision. Visual acuity is several times higher than that of a human. The organ of hearing, like that of reptiles, is represented by the inner and middle ear. In the inner ear, the cochlea is better developed, and the number of sensitive cells in it is increased. The middle ear cavity is large - the only auditory bone - the stapes - is of a more complex shape. The eardrum is located deeper than the surface of the skin; a canal leads to it - the external auditory canal. Hearing is very acute. Compared to reptiles, birds have an increased surface area of ​​the nasal cavity and olfactory epithelium. Some birds (ducks, waders, carrion-eating predators) have a well-developed sense of smell and are used when searching for food. In other birds it is poorly developed. The taste organs are represented by taste buds in the mucous membrane of the oral cavity, on the tongue and at its base. Many birds distinguish between salty, sweet and bitter.

12) Birds are dioecious, their fertilization is internal. In the female, only the left ovary and left oviduct are functional; the right ovary and right oviduct are reduced. This is due to the large size of the eggs: if there were two ovaries, their large mass and hard shell would make it difficult for the eggs to fly and move through the oviduct. In males, the testes are paired, their ducts open into the cloaca. Bird eggs are large in size due to the large amount of nutrients they contain. The actual egg (or egg) of birds is called the yolk. On its surface there is a germinal disc from which the embryo develops. The bulk of the yolk serves as a reserve of nutrients and water. Passing through the oviduct, the egg is first surrounded by a layer of protein, which protects it from mechanical damage and serves as a source of water for the development of the embryo, then it is covered with a subshell membrane and, finally, with a durable calcareous shell. The shell is permeated with tiny pores that ensure gas exchange between the embryo and the external environment. The shell membrane protects the egg from the penetration of bacteria. When the egg enters the oviduct, the development of the embryo in it is just beginning. To continue development outside the body, the egg needs to be warmed. Birds have developed an incubation instinct, during which embryonic development occurs in the egg. At the earliest stages of development, the bird embryo is very similar to the embryos of its ancestors - the notochord, gill slits and gill arteries are formed, a long tail appears - evidence that the distant ancestors of birds were aquatic animals. Paleontological finds indicate that the immediate ancestors of birds were reptiles.

13) According to the degree of physiological maturity of the chicks at the time of hatching, all birds are divided into two groups - brood and nestling. In brood chicks, immediately after hatching, they are covered with down, sighted, and can move around and find food. Adult birds protect their brood, periodically warm the chicks (especially in the first days of life), and help in searching for food. This includes all galliformes (grouse, hazel grouse, partridges, pheasants and others), anseriformes (geese, ducks, swans, eiders), cranes, bustards, ostriches. In nestling birds, the chicks are initially blind, deaf, naked or slightly pubescent, cannot move, and remain in the nest for a long time (in passerines - 10-12 days, in some - up to two months). At this time, their parents warm them and feed them. This includes pigeons, parrots, passerines, woodpeckers and many others. The chicks leave the nest feathered, almost reaching the size of adult birds, but with uncertain flight - one to two weeks after departure, the parents continue to feed and train them to find food. Thanks to various forms of caring for offspring, the fertility of birds is much lower than that of reptiles, fish, and amphibians.

Chicks

1-chick bird (field pipit);

2-brood bird (grey partridge)

Seasonal phenomena in the life of birds, nesting,

migrations and flights

Adaptation of birds to seasonal phenomena

The life of birds is carried out rhythmically and is associated with changes in their metabolism, behavior, and population organization. The lifespan of birds varies. In captivity they live longer than in nature. Biological rhythm is determined by seasonal changes in living conditions and the nature of hereditary adaptations of birds to the environment. A change in the light regime serves as a signal that influences the hormonal system, which determines the annual state of the bird’s body. In the tropics, this signal is humidity - alternating dry and wet periods. Additional signals may be the amount and types of feed. Thus, the annual life rhythm consists of a number of biological periods, in each of which one or another biological phenomenon predominates: mating, egg laying, molting, migration, and so on.

Main periods of the annual cycle:

1) Preparation for reproduction (enlargement of the gonads, migration of birds to nesting sites, formation of pairs). After the silent winter months, the bird world begins to revive in early spring. On clear days, the trills of great tits and nuthatches that winter in our forests are heard more and more often, and the drumming of woodpeckers is heard. The snow is gradually melting, grass shoots are emerging. The first insects fly out and crawl out. Birds that spent the winter in warmer climes are returning to their homeland. They usually nest in the same area of ​​forest or meadow where they raised their chicks in previous years. In this area in the spring the male begins to sing. By singing, he invites the female and notifies the males of his species that the place is occupied. Sometimes he fights with rivals, not allowing them to settle in the occupied territory. Here the male and female feed, and later build a nest. Many birds pair up for only one season. This is how geese and most small passerine species behave. In ducks and pheasants, the male and female stay together only until the eggs are incubated. Predators, as well as storks, herons and some other birds live in pairs for many years, but wood grouse and black grouse do not form permanent pairs.

2) Reproduction and hatching of juveniles (development of nesting sites, maturation of the egg, construction of nests, laying eggs, incubating them, feeding the juveniles). Most birds lay eggs in a nest, which is often built by the female, sometimes by the male, and often they work together: the male brings the material, and the female lays it down and fastens it. Simple cup-shaped nests are built by large birds of prey, rooks, and pigeons. Their main material is twigs and branches. Finches and goldfinches have hemispherical nests. Covered on the outside with moss and lichen. They are invisible from the ground, as they blend in with the pattern of bark and lichens on the branches of the tree. A spherical structure of moss, stems and twigs, held together by hair, is made by a tiny wren. Many forest birds - woodpeckers, nuthatches, tits, flycatchers - lay eggs at the bottom of a hollow or in a nest built here. Shore swallows nest in burrows on coastal cliffs, usually located above or near the body of water. The male and female dig a hole with their finger claws. In the depths of the hole. At a distance of about a meter from the entrance, they make an extension - a nesting chamber. The nest is made from grass stems lined with feathers. City swallows stick their structures, made from clumps of moist clay soil, to the wall of a house under the eaves, holding the material together with saliva. Thus, the nest has a finished roof and a small entrance under it. Many birds (for example, ducks, cranes, chickens) make nests directly on the ground. Some birds, such as auks and guillemots, lay a single egg, without any bedding, directly on a bare rock above the sea. The well-known cuckoo does not build its own nest. The female lays 10-12 eggs, one at a time, in different nests of other birds, which incubate them. The hatched cuckoo throws the rest of the chicks out of the nest, and the orphaned parents feed the stranger. The fledgling cuckoo chick is for the most part much larger than its adult caregivers. The number of eggs in a clutch varies. Large birds of prey (eagles), emperor penguins and some other birds incubate only one egg. Tits can have up to 15 eggs in a clutch, and partridges can have up to 20 eggs. Both parents are often busy with incubation, replacing each other on the nest; In chickens and ducks, one female incubates. In small birds, incubation lasts about 14 days, in large birds longer. So, a chicken incubates for 21 days, and swans and large birds of prey - about 1.5 months. Typically, brooding birds turn the eggs in the nest from time to time. This ensures their more uniform heating, which contributes to the rapid development of the embryo. Some birds do not incubate their eggs at all. For example, weed chickens in Australia and the islands of the Malay Archipelago bury their clutches in the ground, where the embryo in the egg develops under the influence of the heat of the surrounding soil. During the nesting period - one of the most important periods in the life of birds - they should not be disturbed. Frightened birds may leave the nest, and then the chicks will die. The first and second periods are determined by innate instincts. They manifest themselves under the influence of the laws of a complex set of living conditions of birds. The behavior of the male, the nesting landscape, the nest itself, heat and other phenomena have a “signaling” character. During the breeding season, birds lead a more sedentary lifestyle and are closely associated with nesting sites. Caring for chicks, especially those that do not leave the nest for a long time, is quite difficult. The parents not only warm and feed them, flying in with food up to 400 times during the day, but also save them from overheating by the sun's rays: if there is no natural shade around, the bird often stands over the chicks with their wings slightly open during the hot part of the day. Parents regularly carry chicks' droppings in their beaks away from the nest. Maintain cleanliness. When an enemy appears, adult birds jealously protect their offspring. If a predator passes or flies near the brood, the parents raise alarming cries, neighboring nesting pairs of different species join them and all together rush at the newcomer so that he is forced to retreat. Sometimes the mother bird tries to distract the attention of a person or dog from her nest by appearing injured. When the enemy tries to grab her, she flies further and further and disappears. All the actions of birds associated with caring for their offspring are instinctive, just like the actions of bees, burying beetles, stickleback fish and other animals. When removing droppings from the nest, adult birds, of course, do not know that this is necessary for the proper development of the chicks’ plumage and maintaining their health. No bird teaches its young to pretend to be wounded.

Bird's nests

3) After nesting molt occurs after reproduction. In black grouse, hazel grouse, ducks, geese, swans, as well as in poultry, chicks are born covered in down. With their eyes open, they can leave the nest a few hours or the next day after hatching and even run after their mother. Such birds are called brood birds. Despite their independence, these chicks still need heating during the first days of life and often hide under their mother’s wings, since their body temperature does not immediately become constant. In birds of prey, crows, rooks, pigeons, woodpeckers, parrots, sparrows, tits and many others, the chicks hatch helpless, with fused eyelids and closed ear openings. Their body is naked or covered with separate tufts of thin, sparse down. They cannot stand on their feet and do not leave the nest for a long time. Such birds are nesting birds. Their parents feed them for a long time, even after they jump out of the nest and begin to flutter from tree to tree. When the young become airborne, feeding stops. Most birds form flocks in secluded places, many lose the ability to fly (Anseriformes).

Birds nests

4) Preparing for winter. Birds migrate in search of food, feed intensively, which intensifies metabolic processes and accumulates fat. Some people harvest seeds, fruits, insects and their larvae (passerines), and the corpses of mouse-like rodents (owls).

5) Wintering. During this period, daylight hours are greatly shortened, temperatures drop, snow cover and ice form on reservoirs. Birds move in search of food and make complex flights. Residents (jackdaws, sparrows, pigeons, partridges, black grouse, hazel grouse, wood grouse) migrate within the same area where they lived in the warm season. Some (bullfinches, waxwings, rooks, bee-eaters) gather in flocks and roam, but do not have permanent wintering grounds. Others migrate long distances from their nesting sites. They are called migratory birds. Some leave their nesting grounds at the end of summer (nightingales, swifts), others - in late autumn (ducks, swans, geese). An important role in the orientation of birds during migration is played by the organs of vision and visual perception, landscape, sun, starry sky and more. The migratory instinct is one of the forms of adaptation of birds to changing environmental conditions. It manifests itself under the complex influence of the environment, a decrease in the amount of feed, the onset of leaf fall, the formation of snow cover, and a decrease in day length. Migration began in pre-glacial times, but the last glaciation played a decisive role: after the glacier melted, the birds moved north and mastered ecologically new conditions. The postglacial dispersal routes of the species often coincide with the migration routes.

Adaptation of birds to different habitats

Bird ecology

There are 28 orders in the class of birds. The main ones are: penguins, ostriches, kiwis, ghagras, grebes, tubenoses, copepods, wading birds, anseriformes, birds of prey, gallinidae, crane-like birds, waders, pigeon-like birds, parrots, owls, swift-winged birds (swifts), woodpeckers, passerines. More than half - about 5 thousand species - are passerine birds.

Birds are adapted to different habitats, which determines the emergence of ecological groups among them. Each group is attached to its habitats, uses its own food and has certain adaptations for obtaining it.

The following ecological groups are distinguished:

1) Birds of parks and gardens live near human habitation, destroying harmful insects. These are numerous representatives of the passerine order: tits, sparrows, swallows, flycatchers, starlings and others. Most passerines are insectivorous birds, but even those that eat seeds feed their offspring with insects. These are usually small to medium sized birds. The great tit is a beautiful, agile bird the size of a sparrow. It is easily distinguished by its greenish coloration on the back, yellow chest with a black stripe and black cap on the head. She is one of the first to sing a short, sonorous song at the end of February - beginning of March, as if notifying everyone about the imminent arrival of spring and warmth. The great tit is very prolific. She nests early and lays up to 12 eggs. After two weeks, the chicks hatch, and after another three weeks the brood leaves the nest. Soon the adult birds begin their second clutch, sometimes in the same nest. Great tits are found in mixed forests; there are many of them in parks, gardens, and near human habitations. In autumn and winter they gather in small flocks. Flapping from branch to branch, tits carefully examine the cracks in the bark in search of hidden insects. City, village and shore swallows spend most of the day in flight, catching insects (small flies, mosquitoes, midges) in the air. They pursue their prey both above the ground and high in the air. The flight of swallows is fast, easy and agile thanks to their long sharp wings. All day long, swallows hunt tirelessly in the air. They can even drink on the fly, flying low over the water and scooping it up with their open beak. Catching prey is facilitated by a very wide mouth opening and a small flattened beak. Swallows have short legs, they walk awkwardly and rarely land on the ground.

2) Birds of meadows and fields nest and feed on the ground. They unite representatives of many orders: larks, wagtails (passeriformes order), lapwings (wader order), cranes (crane-like order), partridges and quails (gallinaceae order), corncrakes (Granaceae order). In early spring, over a field or steppe, the silvery ringing trills of a skylark are heard high in the sky. Larks arrive as soon as thawed patches appear in the fields. These birds are common in meadows and steppes, and willingly settle on cultivated lands. Here they find abundant food and shelter for their nest, which they build right on the ground. The lark is clearly visible when it flutters in the air to its iridescent song. It's not easy to spot it on the ground. Modest, grayish-brown plumage with dark speckles makes the lark inconspicuous among grasses and field plants. The lark feeds only on the ground; it does not catch prey in the air. The lark quickly runs among the plants, looking for prey, grabbing it from the ground and from blades of grass. Insects are the main food of chicks and adult birds.

3) Birds of swamps and coasts obtain food from the surface of the earth, from the bottom or wet soil, due to which some of them have ankle legs and thin, unwebbed fingers (herons and storks - the order Acioriformes), others have webbed feet ( swans, geese, geese, ducks, teals, pochards - order Anseriformes). In the swamps and coasts, curlews, sandpipers, plovers, and snipes are found from the order Waders; pelicans and cormorants from the order Copepods are found. Most representatives of this group are of commercial importance. The life of many birds is closely connected with the bodies of water in which they forage. Waterfowl, as the name suggests, are capable of swimming, and many of them also dive. Due to adaptations for swimming and diving, waterfowl have webs between their toes, and the legs themselves are set far back. On land, most waterfowl move slowly and clumsily. The plumage of waterfowl is protected from getting wet mainly by the structure of the feather cover. The dense interweaving of feather and downy barbs forms a thick layer with a water-repellent outer surface. In addition, water resistance is facilitated by countless air bubbles contained in the thinnest cavities of the plumage layers. Lubricating the feathers with secretions from the coccygeal gland is also important for protection from water: it preserves the natural structure, shape and elasticity of the feathers, forming a waterproof layer. Waterfowl include many birds of different orders. Penguin squad. They live on the coasts of continents and islands in the southern hemisphere. The emperor penguin is found only in Antarctica. Penguins come ashore during the breeding season and stay in the open sea the rest of the time. These birds swim and dive beautifully in search of fish, shellfish and small crustaceans, but do not fly at all. Penguin wings are small and shaped like narrow, flat flippers. The muscles of the wings, and with them the entire chest bone to which they are attached, are developed no worse than those of good flyers. Short legs with membranes between the toes stretch back when swimming and serve as a rudder. Penguins walk on ice and snow, holding their bodies vertically and relying on their legs and tail. Emperor penguins go out onto the ice to breed. They do not build nests, but keep their only egg on the webs of their feet, hiding it under a large fold of skin on the stomach, and incubate while standing. Penguin colonies are full of noise and shouting. The chicks that are born are dressed in thick down and are very fat, but they are helpless and develop slowly. The parents feed them by regurgitating food into the chicks' mouths, or the chicks themselves stick their beaks down their parents' throats and pull out the prey. During a storm or blizzard, grown-up down jackets gather together in a dense crowd and, to make it warmer, stand huddled close to each other. Order Stork-like. The white stork is a large bird with large black wings and long, red legs. Storks live among open spaces with sparsely located groups of trees, in places where there are extensive low-lying meadows, swamps, and ponds. Thanks to its long legs, the stork can go far into the water. With the help of long fingers with a small membrane between their bases, the stork confidently walks through swampy places. Storks are migratory birds and winter far from their nesting sites - in Central and Southern Africa, in some areas of South Asia.

4) Birds of deserts and steppes are inhabitants of vast open spaces with sparse vegetation. It is difficult to find shelter here, and therefore many birds living in the steppes and deserts have long legs and necks. This allows them to scan the area far away and see approaching predators in advance. Birds of steppes and deserts find their food on the ground, among vegetation. They have to walk a lot in search of food, and therefore the legs of these birds are usually well developed. Some species save themselves not by flying away, but by running away from danger.

In these environmental conditions, 2 groups are distinguished:

a) running birds: ostriches, bustards, little bustards. They live in flocks: they move with the help of their legs (ostriches do not fly at all). They nest and feed on the ground and are of commercial importance;

b) fast-flying birds - sajja, group of hazel grouse. These also include the eagle that lives in the steppes (an order of diurnal predators), which destroys mouse-like rodents. Due to overfishing and plowing of lands, their numbers have greatly decreased. The bustard, little bustard, white crane, demoiselle crane are listed in the Red Book of Russia. Squad of cranes. In April, they fly high in the sky accompanied by loud purring. The cranes lined up in triangles. They return from Africa and South Asia to their breeding grounds. Most cranes live in wetlands, but the demoiselle crane nests in the steppe zone. Immediately after arrival, the mating games of the cranes begin. They gather in a large circle, in the center of which several couples “dance” to the sound of loud trumpets. After some time, the “dancers” stand in the circle of “spectators”, giving way to other birds. Demoiselles nest directly on the ground: in the steppe or on arable land. The nest is a shallow hole covered with grass stems. There are two eggs in the clutch. Belladonnas feed mainly on plant foods, and to a lesser extent on insects. Demoiselles are now rare and need protection. Ostrich squad. Of the inhabitants of the steppes and deserts, ostriches must be considered the most remarkable. These are very large flightless birds with a heavy body on long strong legs. The African ostrich has only two toes on its feet with large claws. African ostriches live in groups, sometimes in herds of large mammals. Tall growth, sharp eyesight and caution allow the ostrich to be the first to notice danger and scare away the entire herd. He flees from enemies (predator or hunter). An ostrich's step while running reaches 4 m, and its speed reaches 70 km per hour. In a close encounter with an enemy, the ostrich defends itself with its legs, causing serious injuries. Bustard squad. The bustard is one of the largest and rarest birds. Its weight reaches 16 kg. Bustards settle in the steppes. Thanks to their good eyesight, they already notice danger from a distance and fly away or run away on their powerful legs. Sometimes a bustard hides among sun-bleached grass and then becomes completely invisible thanks to the protective coloring of its plumage. Bustards are omnivorous birds: they eat leaves, seeds and shoots of plants, as well as beetles, locusts, lizards, and small mouse-like rodents. The chicks feed mainly on insects. In case of danger, the female pretends to be wounded and distracts the enemy’s attention from the chicks by running to the side and dragging her wings. The chicks hide on the ground.

5) Birds of the forest are the most numerous group. Its representatives have various forms of communication with the forest environment.

There are 3 groups:

a) arboreal birds that climb trees. They feed and make nests in trees, have short but strong legs, a thin chisel-shaped beak and a long or inward beak (parrots). By the nature of their diet they can be both granivorous and insectivorous: woodpeckers (order Woodpeckers), redpolls, siskin, goldfinch, nuthatches, crossbills, grosbeaks (order Passeriformes);

b) A group of forest birds. They nest in trees or in thickets of bushes, and catch prey in the air: kestrel, hawk, falcon (order diurnal predators), common cuckoo (order cuckoo), which eats harmful hairy caterpillars, common nightjar (order nightjar), owl, tawny owl, barn owl ( owl squad);

c) A group of forest birds that nest only on the ground. Food is obtained both on the ground and in trees. These numerous representatives of the gallinaceous order (pheasant, black grouse, wood grouse, hazel grouse and others) constitute the subject of the fishery.

The role of birds in nature and their importance in human life

No bird can be absolutely harmful or beneficial. They, like other animals, can be harmful or beneficial in certain circumstances and at certain times. For example, rooks in summer feed on insects and their larvae (chafer beetle, turtle bug, caterpillars of meadow moth and weevils, and others). However, in the spring they can peck out the sown seeds of cereals and garden crops, and in the fall they spoil corn and sunflowers, melons and watermelons, and so on. The pink starling is considered a very useful bird, since its main food is locusts and other orthoptera, but in summer and autumn, flocks of pink starlings can eat juicy fruits (cherries, mulberries, grapes) in gardens and thereby cause significant harm. The tree sparrow and other granivorous birds feed on the seeds of cultivated plants, but they feed their chicks on insects, including many pests. Cuckoos, feeding on forest pests, can suppress the outbreak of their reproduction, while at the same time, by laying eggs in the nests of insectivorous birds (warblers, pipit, redstarts, wagtails and others), they cause the death of part of their broods. The goshawk, useful in the wild, like most predators, having settled near a populated area, can destroy poultry.

All these examples indicate that the same bird under different conditions can be both beneficial and harmful. However, the vast majority can be considered useful. Birds such as diurnal raptors, owls, and many passerines are especially valuable. Many birds are important for humans from an economic point of view, these include commercial and hunting species, and numerous breeds of poultry.

Attracting and protecting birds - the cheapest and most effective method of controlling garden pests. Reliable gardener assistants in the fight against pests of fruit and berry crops are swallows, starlings, tits, flycatchers, redstarts, wagtails, nuthatches, pikas and other small insectivorous birds. Birds destroy especially many insects while feeding their chicks. Not only insectivores, but also most granivorous birds (sparrows, buntings, siskins, goldfinches) feed their chicks with insects, collecting them on branches and tree trunks, catching them in flight and on the ground.

THE IMPORTANCE OF BIRDS
IN NATURE:	FOR PERSON:
1. Limit plant growth. 2. Birds are one of the important components of wildlife. 3. Their role in the cycle of substances is great. 4. Promotes pollination of flowering plants. 5. Promotes the distribution of fruits and seeds, and therefore the dispersal of plants. 6. They are the orderlies of the planet - they exterminate sick and weakened animals. 7. Limit the number of other animals (invertebrates, rodents) 8. Serve as food for other animals (birds, reptiles, mammals).	1. Limit the number of insect pests and mouse-like rodents (insectivores and birds of prey). 2. Involving birds in the implementation of a biological method of protecting cultivated plants. 3. Game and poultry - suppliers of meat, down, eggs. 4. Bird droppings are a valuable organic fertilizer. 5. Aesthetic and scientific significance.

The importance of birds in nature and for humans is diverse: pollination of plants and distribution of their seeds and fruits (and thus regulation of numbers) of insects, arachnids, rodents and others; some birds harm gardens and grain crops. Birds have long been the subject of hunting; a number of species have been domesticated. Some birds carry infectious agents. The aesthetic significance of birds is great; they enliven forests and parks with their presence and singing. Birds are an essential component of any biogeocenosis. Birds are a source of food.

With the advent of high-speed jet aircraft, cases of collisions with birds have become more frequent, sometimes leading to serious accidents. This damage is prevented by scaring birds away from the airfield area and choosing flight routes that bypass areas of seasonal bird concentrations.

Now the numbers of many species have greatly decreased, and they may disappear completely if people do not actively protect them.

Used Books

1) Animal life. Encyclopedia in 6 volumes. T-5. Birds. Ed. prof. ON THE. Gladkova, A.V. Mikheeva. M.: “Enlightenment”, 1970. – 612 p.

2) Biology: Reference. materials. Textbook manual for students / D.I. Traitak, N.I. Klinkovskaya, V.A. Karyenov, S.I. Baluev; Ed. DI. Traitaka. – M.: “Enlightenment”, 1983. 208 p.

3) Encyclopedic Dictionary of a Young Biologist / Comp. M.E. Aspiz. – M.: “Pedagogy”, 1986. – 352 p.

4) Kovshar A.F. Songbirds. – Alma-Ata: “Kainar”, 1983. – 280 p.

5) Kovshar A.F. World of birds of Kazakhstan. – Alma-Ata: “Mektep”, 1988. – 272 p.

6) Children's encyclopedia in 12 volumes. Ch. ed. A.I. Markushevich. T-4. Plants and animals. Scientific ed. volumes: Bannikov A.G., Genkel P.A. –M.: “Pedagogy”, 1973. – 448 p.

7) Encyclopedic Dictionary of a Young Naturalist / Comp. A.G. Rogozhin. – M.: “Pedagogy”, 1981. – 406 p.

8) Biological encyclopedic dictionary / Ch. ed. M.S. Gilyarov; Editorial team: A.A. Baev, G.G. Vinberg, G.A. Zavarin et al. – M.: “Sov. encyclopedia", 1986. – 831 p.

9) Belyakova G.A. and others. Biology: A Handbook for High School Students and Applicants. – M.: “EXMO-Press”, 2000. – 352 p.

10) Naumov N.P., Kartashev N.N. Zoology of vertebrates. – Part 2. – Reptiles, birds, mammals: A textbook for biologists. Specialist. univ. – M.: “Higher School”, 1979. 272 ​​p.

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 steps;
   - 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. 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. Locomotor 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. Respiratory organs of birds- 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 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.

"Bird Class"

1 option

1. The body shape of birds has the shape:

a) streamlined;

b) flat,

c) spherical.

2. The beak of birds consists of:

a) horny jaws;

b) ridge scales; c) bone jaws.

3. The contour feather of birds consists of:

a) core, edge;

b) rod, fan, beard;

c) rod, fan, edge, beard.

4. What forms the chest of birds:

a) thoracic vertebrae;

b) thoracic vertebrae, ribs, sternum;

c) thoracic vertebrae, keel, ribs.

5. What bone forms the tail section of a bird:

a) pelvic;

b) coccygeal; c) crow.

6. The belt of the forelimbs of a bird consists of:

a) two elongated shoulder blades, two fused pelvic bones; two crow bones;

b) two coccygeal bones, two elongated shoulder blades; two crow bones;

c) two crow bones, two elongated shoulder blades, two clavicles fused at the bottom.

7. The most developed fingers of a bird:

a) 2 front;

b) average;

c) rear.

8. The skeleton of the hind limbs consists of:

a) femur, 2 fused bones of the lower leg, tarsus, finger bones;

b) femur, tarsus, finger bones, crow bone;

c) femur, tarsus, finger bones.

9. Goiter is:

a) dilation of the esophagus;

b) expansion of the pharynx;

c) dilatation of the intestine.

10. When the sternum lowers in birds, air passes from the lungs:

a) into the lungs and posterior air sacs;

b) into the anterior air sacs;

c) into the lungs.

11. The lungs of birds receive:

a) arterial blood;

b) mixed blood;

c) venous blood.

12. In birds only:

a) right ovary;

c) left ovary.

13. Birds have:

a) coccygeal gland;

b) sacral;

c) mammary gland.

14. Heart of birds;

a) 4-chamber;

15. The lungs of birds look like:

a) bags;

b) meshes;

c) spongy bodies.

16. Bird excretory organs:

b) kidneys and ureters;

c) cloaca.

17. Bird testes have:

a) bean-shaped;

b) pisiform;

c) curved.

18. What is the reason for the higher level of metabolism in birds (compared to reptiles):

a) with perfect breathing, rapid digestion of food;

b) with perfect breathing, rapid digestion of food, perfect blood circulation, improvement of the digestive system;

c) with perfect breathing, blood circulation, and rapid digestion of food.

19. What is the development of the midbrain associated with:

a) with coordination of complex movements;

b) with perfection of the visual organs.

20. What is the significance of poultry protein:

a) Protection from mechanical damage;

b) Protection from mechanical damage and water source;

c) Source of water.

Option 2

1. The bony jaws of the bird are covered with:

a) horny sheath;

b) bone cover,

c) keratinized cover.

2. Outside the bird’s body is located:

a) flight feathers;

b) helmsmen,

c) contour.

3. Large contour tail feathers are:

a) helmsmen;

b) flywheels,

c) downy.

4. What kind of liquid accumulates in the coccygeal gland: a) watery;

b) oily,

c) coccygeal.

5. What forms the rump of a bird:

a) the last thoracic vertebra, all lumbar, sacral and anterior caudal vertebrae;

b) all lumbar, sacral, anterior caudal, femoral,

c) last thoracic vertebra, sacral and anterior caudal.

6. What is the girdle of the hind limbs formed by:

a) 2 pairs of pelvic bones;

b) 3 pairs of pelvic bones;

c) pelvic and sacral bones.

7. The skeleton of the hind limbs consists of:

a) femur, 3 fused bones of the tibia, tarsus, finger bones;

b) femur, 2 fused shin bones, finger bones,

c) femur, 2 fused bones of the lower leg, tarsus, bones of the foot and fingers.

8. In the glandular section of the stomach there are:

a) glandular juices;

b) digestive juices,

c) enzymes.

9. The importance of bird air sacs:

a) participation in breathing;

b) decrease in body density, breathing,

c) protection of internal organs from overheating during flight, reduction of body density, participation in breathing.

10. When the sternum is raised, air containing CO2 passes:

a) into the trachea;

b) into the artery,

c) into the lungs.

11. The following open into the small intestine:

a) ducts of the pancreas, bile ducts of the liver and gallbladder;

b) ducts of the pancreas, bile ducts of the liver and gallbladder, duodenum;

c) ducts of the liver and gall bladder.

12. The high level of metabolism of birds is associated with:

a) with better breathing, blood circulation, faster digestion of food;

b) with more perfect breathing, faster digestion of food;

c) with more perfect breathing, with a more developed digestive system.

13. Reproductive organs of birds:

a) testes;

b) testes and ovaries,

c) ovaries.

14. Why is the germinal disc facing upward:

a) because the upper part of the yolk is heavier;

b) the lower part of the yolk is heavier,

c) the yolk is in the center.

15. The cords consist of:

c) nutrients.

16. The development of the cerebellum in birds is associated with:

a) perfection of the visual organs;

b) with the coordination of complex movements of the bird.

17. Bird excretory organs:

b) kidneys and ureters,

c) ureters.

18. When the sternum is lowered, air from the external environment enters:

a) posterior air sacs;

b) posterior air sacs and lungs,

c) lungs.

19. Birds’ body organs receive:

a) venous blood;

b) arterial,

c) mixed.

20. What ensures a constant temperature for birds:

a) high level of metabolism;

b) feather cover,

c) high level of metabolism and feather cover.

Thematic test

Test "Bird Class"

OPTION #1

1. Features of the integument of mammals:

a) the skin is damp. naked. there are many glands in it;

b) dry skin. covered with feathers;

c) most people have hairy skin;

d) the skin is covered with bone scales.

2. The circulatory system of mammals is characterized by:

a) three-chambered heart and 2 circles of blood circulation;

b) four-chambered heart and 2 circles of blood circulation;

c) two-chamber heart and one circulation;

d) a three-chambered heart with an incomplete septum and 2 circles of blood circulation.

3. The safety of offspring in mammals does not depend on:

a) live births;

b) habitat;

c) bearing babies;

d) feeding with milk.

4. The characteristics of equids do not include:

a) single-chamber stomach:

b) development of the 3rd finger;

c) multi-chamber stomach;

d) the terminal phalanges are covered with hooves.

5. The equids include:

b) rhinoceros;

c) pig;

6. The order Chiroptera belongs to

a) flying squirrel:

b) evening party:

c) echidna;

d) gopher.

b) platypus:

c) common hedgehog;

Additional questions.

1. What parts does the stomach of ruminant artiodactyls consist of?

2. What structural features are common to all mammals?

3. 3. What conclusions can be drawn from the following facts: a whale breathes with its lungs: the embryo of a blue whale develops teeth (then they disappear); The skeleton of the blue whale contains remains of pelvic bones.

OPTION #2

1. Warm-bloodedness in mammals is ensured by:

a) sweat glands;

b) wool cover;

c) feather cover:

d) dry skin without glands.

2. A higher level of organization of mammals compared to reptiles is achieved by the structure:

a) respiratory system:

b) nervous system;

c) digestive system;

d) musculoskeletal system.

3. Proof of the origin of mammals from reptiles is:

a) the structure of the nervous system:

b) the presence of chambers in the heart;

c) similarity in the development of embryos;

d) presence of teeth.

4. The signs of artiodactyls do not include:

a) an even number of fingers;

b) the terminal phalanges are covered with horny sheaths;

c) strong development of the 3rd finger.

5. Artiodactyls include:

a) rhinoceros;

d) musk deer.

6. The order of insectivores includes:

a) echidna;

c) muskrat:

d) evening party.

7. The order Rodents includes:

a) rabbit;

b) chipmunk:

Additional questions.

1. Why are monotremes considered ancient mammals?

2. What biological characteristics of rodents allowed them to become the largest order of mammals?

3. Why are mammals considered the highest among chordates?

General characteristics. Birds are warm-blooded vertebrates from the group Amniota, adapted for flight. The forelimbs are modified into wings. The body is covered with feathers, which also form the supporting plane of the wings and tail. Part of the bones of the metatarsus and tarsus, merging, formed a single bone - the tarsus. The skull articulates with the spine at one condyle. The cerebral hemispheres have a cortex, but their surface is smooth. The cerebellum is well developed. The lungs are spongy, connected to a system of air sacs. The heart is four chambered. There is only the right aortic arch; the left one atrophies during embryonic development. The excretory organs are the pelvic kidneys. Fertilization is internal. They reproduce by laying eggs.

Currently, about 9 thousand species of birds live on Earth, inhabiting all continents and islands. The USSR is home to approximately 750 species of birds.

Modern birds are divided into three separate super-orders: Keel-breasted birds (Carlnatae) , Ratites (Ra- titae), Penguins { linpennes).

Structure and vital functions. The appearance of birds reflects their adaptability to flight (Fig. 247). The body is streamlined, egg-shaped, and compact. The neck of most birds is thin and flexible. On the head, a beak protrudes forward, consisting of a mandible and a mandible. Modified forelimbs - wings - are used for flight. Most of their supporting plane is formed by large elastic flight feathers. The legs of birds bear the entire weight of the body when moving on the ground, climbing trees, taking off and landing. The legs have four sections: thigh, tibia, tarsus and toes. Usually the bird's legs are four-toed, but sometimes their number is reduced to three or even two (African ostrich). Of the four fingers, in most cases three are directed forward and one is directed backward.

Rice. 247. External (harrier)

Veils. The skin of birds is thin and dry. There are no skin glands. Only above the base of the tail in most birds is a special coccygeal gland located, the secretion of which is used to lubricate the feathers, which prevents them from getting wet. Birds are characterized by feather cover. Feathers are common to all bird species and are not found in other animals. Bird feathers evolved from the horny scales of reptiles.

Feather is a derivative of the epidermis of the skin (Fig. 248). It is formed by a horny substance - keratin. An individual feather consists of a feather (the part immersed in the skin), a shaft and a fan.

Rice. 248. Structure of bird nerves:

/ - rod; 2 - outer fan; 3 internal fan; ■/ - trunk; 5 - ochip; 6" -- hole is full; 7 bow

Rice. 249. Structure of a bird's wing:

/ - brachial bone; 2 - elbow bone; 3 ...... radius;

4 - is a wrist bone; 5 ......... part of the wrist; 6", 7

phalanges of fingers; 8 - wing; {.) wing membrane; 10 - bases of flight feathers; // - primary flight feathers; 12 -- secondary flight feathers

The rod is a dense horny tube with a loose horny core. The fan is formed by first-order beards extending from the shaft in both directions, from which, in turn, extend short second-order beards. The beards of the second order bear small hooks that connect the beards to each other, resulting in the formation of an elastic, light plate of the feather fan. In delicate down feathers, the shaft is shortened and bears thin, delicate beards not connected by hooks. In down, the shaft is not developed and the beards extend in a tuft from a common base.

Large elastic feathers that form the main part of the supporting plane of the wing are called flight feathers. Their fan is asymmetrical - the front side is narrow and the back side is wide. This structure allows the passage of air between the feathers when the wing is raised, and when the wing is lowered under air pressure it causes a tight connection of the feathers. Larger flight feathers, resting on the bones of the hand of the wing, are called primary flight feathers, and smaller and less elastic feathers connected to the bones of the forearm are called secondary flight feathers (Fig. 249). Tail feathers, which make up the tail and guide the flight of birds, are distinguished by their large size, elasticity and asymmetry of the webs. Smaller feathers covering the body of birds are called contour feathers, they give the body a streamlined shape. The areas in which they are located are called pteriliae, and the areas of skin devoid of them are called apteria (Fig. 250). The apteria are located along the midline of the chest, in the axillary region, along the shoulder blades, i.e., in those places of the body where the skin over the muscles tenses during flight. The apteria are covered by adjacent contour feathers. In many birds, especially aquatic ones, between the contour feathers There are downy feathers and fluff that warm the body.

The role of feathers in the life of birds is great and varied. Flight and tail feathers form most of the load-bearing surface of the wings and tail, hence they are essential for flight. The feather cover gives the bird's body a streamlined shape, which makes it easier for them to fly. Due to the high heat-protective properties of feathers and the air layers between them, the feather cover helps preserve body heat in birds and, therefore, participates in the thermoregulation of the body. It also protects the bird from various mechanical influences. Various feather pigments give birds one or another color, which is often protective in nature.

Periodically, usually once or twice a year, the feather cover of birds is completely or partially renewed by molting; in this case, old feathers fall out, and new ones (sometimes of a different color) develop in their place. In most birds, the molting of plumage occurs slowly and gradually, thanks to which they retain the ability to fly, but in waterfowl it occurs so quickly that they are temporarily unable to fly.

Rice. 250. Ptershzhi and aptsria birds (pigeon)

Rice. 251. Skeleton of a bird (pigeon):

/ - cervical vertebrae; 2 - thoracic vertebrae; 3 - caudal vertebrae; 4
- coccygeal bone; 5, in-ribs; 7 - sternum; S -- keel; .V--blades; 10 - coracoid; //-clavicle (fork); 12
-- brachial bone; 13 - radius bone; 14- elbow bone; 15 -

metacarpus; 16 .....18 - phalanges of fingers;

19 -21- pelvic bones; 22 - femur; 23 - shin bone; 24 - shank; 25, 26 - phalanges of fingers

The skeleton of birds is light and at the same time strong, which is important for flight (Fig. 251). Its lightness is achieved by the thinness of its constituent bones and the presence of cavities in the tubular bones of the forelimbs. The strength of the skeleton is largely due to the fusion of many bones.

The skull of birds is distinguished by a large thin-walled braincase, huge eye sockets, and toothless jaws. In adult birds, the bones of the skull are completely fused, which ensures its strength. The skull articulates with the first cervical vertebra with one condyle.

The cervical vertebrae, the number of which varies in different birds, articulate with each other by saddle-shaped articular surfaces, which gives the neck greater flexibility. The thoracic vertebrae in adult birds are fused to each other. The ribs are attached to the sternum at their lower ends; on the posterior edge they have hook-shaped processes, which overlap the ends of the ribs of the next pair; this gives the rib cage strength. The sternum of birds, with the exception of those that have lost the ability to fly, bears a high bony keel on the anterior surface, to which powerful pectoral and subclavian muscles are attached on both sides, driving the wing.

The posterior thoracic, lumbar, sacral and anterior caudal vertebrae in adult birds fuse with each other and with the thin iliac bones of the pelvis into a single sacrum, which serves as a solid base for the legs. The posterior caudal vertebrae fuse to form the coccygeal bone, which looks like a vertical plate. It serves as a support for the tail feathers.

The shoulder girdle consists of three pairs of bones: saber-shaped shoulder blades lying along the spine; thin clavicles, which grow together at their lower ends into a fork, spreading out the bases of the wings; coracoids - massive bones connected at one end to the shoulder blades and bases of the humerus, and at the other to the sternum.

The wing skeleton consists of a large, hollow inside bone of the shoulder, two bones (ulna and radius) of the forearm, a number of fused bones of the wrist and metacarpus and greatly reduced and modified phalanges of the II, III and IV fingers, I and V fingers are atrophied, II has only one phalanx , serving as a support for a separate bunch of feathers on the outer edge of the wing, the so-called winglet.

The pelvic girdle of the skeleton is formed by thin ilium, pubis and ischium bones, which in adult birds fuse into a single bone. The posterior ends of the pubic and ischial bones in most birds (except some ostriches) do not meet, so the pelvis remains open from below.

The skeleton of each hind limb consists of a large femoral bone, two tibia bones (tibia and fibula), a tarsus and phalanges of the fingers. The fibula is greatly reduced and fused to the tibia. During ontogenesis, the bones of the main row of tarsus grow to the lower end of the tibia. The remaining tarsal bones and the three metatarsal bones merge into a single elongated bone - the tarsus. The phalanges of the fingers are attached to the lower end of the tarsus.

Musculature. The pectoral and subclavian muscles, which move the wings, are especially developed. The leg muscles are also powerful, doing a lot of work when the bird walks and moves along tree branches, during takeoff and landing.

The nervous system, especially the central section, in birds has a more complex structure than in reptiles, which corresponds to a higher level of vital activity. The bird brain is distinguished by the large size of the forebrain hemispheres, the strong development of the visual thalamus of the midbrain and the huge folded cerebellum (Fig. 252). The roof of the hemispheres has a smooth surface, and the gray medulla in it is weakly expressed. The strong development of the visual thalamus of the midbrain, which carries visual function, is due to the importance of vision in the life of birds. The cerebellum is large and has a complex structure. Its middle part - the worm - with its front edge almost touches the hemispheres, and with its back end it covers the medulla oblongata. The worm is covered with characteristic transverse grooves. The development of the cerebellum is associated with flight, which requires precisely coordinated movements. Birds have 12 pairs of head nerves.

Digestive organs begin in the oral cavity. Modern birds have no teeth - they are partially replaced by the sharp edges of the horny sheath of the beak, with which the bird captures, holds and sometimes crushes food (Fig. 253). The long esophagus in many birds expands into a crop; here the beggar, being treated with saliva, swells and softens. From the esophagus, food enters the glandular stomach, where it is mixed with digestive juices. From the glandular stomach, food passes into the muscular stomach. Its walls are composed of powerful muscles, and in the cavity lined with a hard shell, there are usually small pebbles swallowed by the bird. These pebbles and folds The walls of the stomach, when the muscles of the walls contract, grind food.

The intestines of birds are relatively short. It has a longer thin section and a shorter thick section. At the border of these sections, two blind outgrowths extend from the intestine. The rectum is not developed, so feces do not accumulate in the intestines, which makes the bird lighter. The intestine ends with an extension - the cloaca, into which the ureters and ducts of the gonads open. The secretions of the large two-lobed liver and pancreas entering the duodenum help digest food.

The expenditure of enormous amounts of energy by birds during flight and the high level of metabolism necessitate the absorption of large amounts of food. Thus, the small bird of our forests, the wren, consumes an amount of food per day that exceeds "/4 of its body weight. Digestion processes in birds proceed very quickly: in a waxwing, rowan berries pass through the entire intestine in 8-10 minutes, and in a duck, opened 30 minutes after After she swallowed a 6 cm long crucian carp, its remains could no longer be detected in the intestines.

Rice. 253. Internal structure of a bird (pigeon):

/ - dissected pigeon; //- section of the pigeon’s stomach;

/ - trachea; 2 - esophagus; 3 - goiter; 4 - lung; 5 - air bags;

6 - heart; 7 - glandular stomach; 8 - muscular stomach

The respiratory organs of birds also show signs of adaptation to flight, during which the body needs increased gas exchange (Fig. 254). A long trachea extends from the bird’s throat, which in the chest cavity is divided into two bronchi. At the site of the division of the trachea into the bronchi there is an extension - the lower larynx, in which the vocal cords are located; its walls have bone rings. The lower larynx plays the role of a vocal apparatus and is especially strongly developed in birds that sing or make loud sounds.

Bird lungs have a spongy structure. The bronchi, entering the lungs, break up into smaller and smaller branches. The latter end in the thinnest blind tubules - bronchioles, in the walls of which there are capillaries of blood vessels.

Some of the branches of the bronchi extend beyond the lungs, continuing into thin-walled air sacs located between the muscles, among the internal organs and in the cavities of the tubular bones of the wings. These bags play a big role in the bird's breathing during flight. In a sitting bird, breathing is carried out by expanding and contracting the chest. In flight, when the moving wings need solid support, the chest remains almost motionless and the passage of air through the lungs is determined mainly by the expansion and contraction of the air sacs. This process is called double breathing, since the release of oxygen into the blood occurs both during inhalation and exhalation. The faster the flapping flight, the more intense the breathing. When the wings rise, they stretch and air is sucked into the lungs and further into the bags. When the wings lower, exhalation occurs, and air passes through the lungs silt bags, which contributes to the oxidation of blood in the lungs.

/ trachea;
2-- lungs; 3-11
- air bags

Rice. 255. Circulatory system of a bird (pigeon):

/ spicy atrium; 2 - right ventricle of the heart; 3 -left pulmonary artery; 4 right pulmonary artery; 5 - left atrium; 6 - left ventricle of the heart; 7 - right aortic arch; N, 9 - innominate arteries; 10 -12 - carotid arteries; 13 - subclavian artery; 14-- left thoracic artery; 15 - aorta; 16 - right femoral artery; 17 renal artery; 18 -sciatic artery; 19 -- iodine artery; 20 posterior mesenteric artery;
21 - caudal artery; 22 tail vein; 23 - renal portal vein; 24 - femoral vein; 25 - iodine-I! tire yen; 2 in posterior vena cava; 27 - intestinal vein; 28
- supraintestinal vein; 29 renal vein; 30 - jugular vein; 31
- subclavian vein; 32 - anterior vena cava

The circulatory system of birds has two circles of blood circulation (Fig. 255). The large heart is completely divided into right and left halves and has left and right atria and left and right ventricles. This achieves complete separation of arterial and venous blood flows. Arterial blood coming from the lungs through the pulmonary vein enters the left atrium, and from there into the left ventricle, from which it goes into the aorta. Venous blood from all over the body enters the right atrium, and from it into the right ventricle, in order to then travel through the pulmonary artery to the lungs.

In bird embryos, like reptiles, both the left and right aortic arches are formed, but during the embryonic development of the animal, the left one atrophies. Starting from the left ventricle of the heart, the right aortic arch bends to the right (which is why it is called right), turns back and continues with the aortic trunk, which extends under the spine. From the aortic arch depart large paired innominate arteries, which soon divide into the carotid arteries, carrying blood to the head, and the powerful thoracic and subclavian arteries, going to the pectoral muscles and wings. Arteries branch from the dorsal aorta to various parts of the bird's body and to the legs. The venous system of birds is basically similar to that of reptiles.

The high activity of the metabolic process in birds makes it necessary for rapid and abundant delivery of nutrients and oxygen to all parts of the body. Therefore, their blood circulation occurs very quickly, which is ensured by the energetic work of the heart. Thus, in many small birds the heart beats more than 1 thousand times per minute (in humans 60-80 times).

The excretory organs of birds are also adapted to intensive metabolism in the body, as a result of which the volume of decay products to be removed increases. The kidneys of birds are large in size and lie in the recesses of the pelvic bones. The ureters depart from them and open into the cloaca. Thick urine enters the cloaca, from where it is excreted along with feces.

Reproductive organs. The two testes lying in the abdominal cavity are bean-shaped. Vas deferens extend from them, opening into the cloaca. In some birds (geese), males have a copulatory organ. Females usually have only one, left, ovary, located near the kidney. The egg released from the ovary enters the unpaired oviduct, in the upper part of which fertilization occurs. Having passed through the oviduct, the egg acquires a protein shell, and once it enters the wider uterus, it is covered with a calcareous shell. Through the final section of the female genital tract - the vagina - the egg enters the cloaca, and from there it is excreted.

Rice. 256. Structure of a bird's egg:

/ ...... shell; 2-.....nodshell shell; ,4 -

air chamber; *"/ protein; L vitelline membrane; V yolk; 7 - germinal disc;
N~ white yolk; 9 -yellow yolk; 10 --chalazy

A bird egg is (relative to the size of the animal) very large in size, as it contains many nutrients in the form of yolk and white (Fig. 256). The embryo develops from a small germinal disc located on the surface of the yolk.

At the blunt end of the egg, between the shell and subshell membrane, there is a cavity filled with air; it helps the embryo breathe. The development of the chick in the egg is shown in Fig. 257.

Rice. 257. Development of the bird embryo:

/- IV - successive stages of development of the embryo; / - embryo; 2 - yolk; 3 -protein; 4-- amchutic fold; 5 cervical cavity; 6" - air chamber; 7 -~ shell; N-
serosa; 10 - amnion cavity; // -- allantois; 12 ■- yolk sac

Ecology of birds. The main form of movement for most birds is flight. Adaptation to flight caused a number of described changes in the structure of the body of these animals, and also left an imprint on all types of their life activities. Thanks to their ability to fly, birds have enormous capabilities for long-distance migrations and settlement: it was flight that allowed them to populate all oceanic islands, often located hundreds of kilometers from the mainland. Flight helps birds avoid enemies. Many birds forage for food during flight or look for it on the ground.

The flight pattern of different species of birds is far from the same - it is always in accordance with their way of life. There are two main types of bird flight: soaring and rowing flight. Soaring is the flight of birds on more or less motionless, outstretched wings. This flight can be carried out with the bird gradually descending in the air. But often, by soaring, a bird can maintain its gained height above the ground or even rise upward (this is achieved through the bird’s use of rising air currents). Rowing flight is accomplished by flapping the wings. In many birds, this active form of flight alternates with soaring in the air. During a calm rowing flight, a crow makes on average 2.9, and a seagull makes 2.2 wing beats per second. The maximum possible flight speed of a swallow is 28 m, a wood grouse is 16 m, and a swan is 14 m per second. Some birds can fly for more than 3 thousand km without stopping to rest.

The ability for active flight, warm-bloodedness and a high level of development of the central nervous system provided birds with the opportunity to become widespread on Earth. The adaptation of birds during evolution to life in various conditions (forests, open spaces, reservoirs) is associated with the formation of different ecological groups, differing in appearance and specific structural features.

Tree birds - inhabitants of various forests and bushes. This group includes woodpeckers, parrots, nuthatches, pikas, cuckoos, starlings, thrushes, pigeons, wood grouse, hazel grouse, etc. They usually forage and nest in trees, less often on the ground. The most specialized birds adapted for climbing trees (parrots, woodpeckers, nuthatches) have strong paws, armed with curved claws. Woodpeckers have two fingers pointing forward and two pointing back, which allows them to deftly climb tree trunks while relying on hard and elastic tail feathers. When moving along tree branches, parrots use not only their hind limbs, but also their beak.

Land birds - inhabitants of open spaces - meadows, steppes and deserts. This group includes ostriches, bustards, little bustards, and some waders. They feed and nest on the ground. In search of food, they move mainly by walking and running, rather than flying. These are large and medium-sized birds with a massive and wide body and a long neck. The legs are long and strong, with short and thick fingers, the number of which can be reduced to three, and in the African ostrich - up to two.

wading birds inhabit marshy meadows, swamps, and thickets along the coasts of water bodies. Typical representatives: herons, storks, cranes, many waders. Food is usually collected on the ground. Nests are made on the ground or in trees. These are large or medium-sized birds. Most have long, thin legs with elongated toes, with which they easily move through sticky soil or shallow water. The head is small, with a long hard beak. The wings are well developed. The tail is short. The plumage is loose, with poorly developed down.

Waterfowl They spend a significant part of their life on bodies of water. This group includes loons, grebes, guillemots, guillemots, penguins, cormorants, pelicans, ducks, geese, and swans. They swim well, and many dive, but they walk on land and usually fly poorly, and some do not fly at all (penguins). Many birds forage for food (fish, shellfish, crustaceans) in the water, while others feed on land on vegetative parts of plants and seeds. They nest along the banks of reservoirs, on the ground, in trees, in reed thickets, on rocks and in their crevices, in burrows. These are large and medium-sized birds with a somewhat flattened body on the ventral side and a short tail. The legs are set far back, which ensures an almost vertical body position when walking. They have dense plumage with well-developed down, membranes on their feet, and most have a developed coccygeal gland.

Air-water birds unlike the previous group, they are less associated with water bodies. The group includes gulls, terns, and petrels. They usually fly and swim well, but dive poorly. Soaring flight using air turbulence over waves or different speeds of air currents. They feed mainly on fish, which they look out for during the flight, then quickly rush at it and pull it out of the water with their strong and long beak, curved at the end. They often nest on the banks of rivers, lakes, seas, and on rocky ledges of sea shores. These are large and medium-sized birds with an elongated body, long, sharp wings and short legs, on which the three front toes are connected by a swimming membrane. The plumage is thick, with a lot of fluff.

Air-ground birds They spend a significant part of the daylight hours in the air, where they catch insects with their short, wide-opening beaks. Typical representatives: swifts, swallows, nightjars. These are excellent flyers with fast and maneuverable flight. They usually nest in buildings, in burrows along river banks, and on the ground. Their body is elongated, the neck is short, and the wings are long and narrow. The legs are short, making it difficult to walk on the ground.

Bird feeding. Most birds are carnivores, others are herbivores or omnivores. There are species that feed mainly on vegetative parts of plants (geese), berries (thrushes, waxwings), seeds (sparrows, crossbills), nectar (hummingbirds), insects (cuckoos, woodpeckers, many passerines), fish (gulls, cormorants, pelicans), frogs (ducks, storks, herons), lizards and snakes (storks, some diurnal predators), birds (hawks), rodents (owls, many diurnal predators). Some predators prefer to eat carrion (vultures, vultures, vultures). The nature of food may vary depending on age: most granivorous birds feed their chicks with insects. The composition of the beggar also varies according to the seasons of the year. For example, in the summer the black grouse feeds on green parts of plants, berries and insects, and in the winter - mainly on pine needles, buds, shoots and catkins of birch and alder.

Annual periodicity in the life of birds. In birds, as in other animals, the annual periodicity of life activity is closely related to seasonal changes in living conditions and has great adaptive significance. It allows you to time the most crucial moment in the life of each species - reproduction - to a specific season, when the conditions for feeding the chicks will be most favorable. The following stages of the annual cycle of birds can be distinguished: preparation for reproduction, reproduction, molting, preparation for winter, wintering.

Preparation for reproduction is expressed in the formation of pairs. Uniting in nests during mating time (monogamy) is characteristic of most bird species. However, the duration of existence of pairs varies significantly among different birds. Swans, storks, and eagles form pairs for several years or perhaps even for life. Other birds form pairs for the breeding season, and many ducks remain in pairs only until egg laying begins. In a smaller number of bird species, pairs do not form and during the breeding season the male fertilizes several females, who take full care of the offspring. This phenomenon is called ln-gamy (polygamy). It is characteristic of black grouse, pheasants, wood grouse, and domestic chickens. These birds have especially pronounced sexual dimorphism.

Pairing in birds is accompanied by mating: birds take various poses, hold their plumage unusually, make special sounds, and in some polygamous species, fights occur between males. The mating behavior of birds facilitates the meeting of individuals of different sexes and the formation of pairs, and stimulates the synchronous maturation of the reproductive products of both partners.

The fertility of birds is significantly lower than that of reptiles, which is due to the presence of various forms of care for offspring in birds (nest building, incubation and feeding of chicks). The number of eggs in a clutch ranges from 1 (penguins, guillemots) to 22 (gray partridge). Most birds incubate their clutch. In polygamous species, incubation is carried out only by the female (Culiformes, Anseriformes), in monogamous species, incubation is carried out alternately by a male and a female (pigeons, gulls, many passerines) or only by the female, and the male feeds her and guards the nesting site (owls, diurnal raptors, some passerines).

The duration of incubation varies for different birds and depends on the size of the egg and the bird, the type of nest and the intensity of incubation. Small passerines incubate for 11-12 days, crows - 17, swans - 35-40. Duration of incubation in poultry: 21 days for chicken, 28 days for duck, 30 days for goose, 28, 29 days for turkey.

Depending on the degree of development of the chicks that have just hatched from the eggs, birds are divided into brood, semi-brood and nestling birds (Fig. 258). The chicks of brood birds are pubescent, sighted, and are able to feed independently after a short time (Gulliformes, Anseriformes, ostriches). The chicks of half-brood birds hatch sighted and pubescent, but are raised by their parents until they acquire the ability to fly (gulls, guillemots, petrels). In nestling birds, the chicks are naked, blind, and remain in the nest for a long time (passerines, woodpeckers, pigeons), where they are intensively fed by their parents. Thus, a pair of flycatchers, tits or warblers brings food to their chicks up to 450-500 times a day.

After finishing feeding the chicks, the family usually breaks up and the birds unite in flocks. The highest mortality rate is observed in the first year of life of birds. Sometimes it can reach more than 50 % number of individuals flying out of the nest. Birds reach sexual maturity at different ages. Most small and medium-sized birds (many passerines) begin to breed in the next year of life, larger birds (hooded crows, ducks, small raptors and gulls) - in the 2nd year, and loons, eagles, petrels - in the 3rd-4th year -m, ostriches - in the 4th-5th year.

Rice. 258. Chicks of various birds at the same age:

/ - chicks (pipit); // - semibrood (eagle); ///-brood (partridge)

The average lifespan of small passerine birds is 1 - 1.5 years, and the maximum lifespan is 8-10 years. Larger bird species can live 40 years or more.

Shedding occurs differently in different birds. In some species (passerines) it is gradual, in others (Gulliformes, Anseriformes) it is rapid. Moulting anseriformes lose the ability to fly for 2-5 weeks. Shedding usually begins immediately after breeding. In males of many bird species that do not participate in breeding, molting occurs earlier than in females. Molting males of wood grouse and black grouse stay alone in remote areas of the forest, and duck drakes accumulate in large numbers in hard-to-reach wetlands during the molting period.

Preparing for winter . During this period, birds begin to wander in search of food. Intensive nutrition ensures fat accumulation. Some birds tend to store food, which makes their wintering easier. Jays collect acorns and bury them in the soil or under the forest floor, and nutcrackers collect nuts. In winter, birds use these reserves only partially. The other part of the seeds is eaten by mouse-like rodents and insects or, preserved until spring, germinates. Nuthatches and tits hide seeds of various trees in cracks in the bark, providing themselves with food by 50-60%. Small owls (passerine and great-footed owls) prepare the carcasses of mouse-like rodents for the winter and place them in tree hollows. Birds find their storerooms, apparently, thanks to memory and smell.

Zimovk A. In winter, birds face great difficulties in obtaining the required amount of food. In search of habitats that can most fully provide a particular species with food and protective conditions, many birds begin to make directed movements (nomads and migrations). Only sedentary birds remain in the places where they reproduced, and if they change their habitats, they fly no further than a few tens of kilometers (grouse grouse, hazel grouse, woodpeckers, sparrows, tits). Migratory birds can fly hundreds of kilometers, but usually stay within one natural zone (waxwings, tap dancers, bullfinches). The longest migrations are made by migratory birds that winter in other natural areas located thousands of kilometers from their nesting sites.

The division of birds into sedentary, nomadic and migratory is complicated by the fact that the same species in different parts of its range can behave differently. Thus, the gray crow in the south of the European part of the USSR is a sedentary species, in the south it is a migratory species. Changes in weather and feeding conditions from year to year also affect the nature of bird mobility. In warm winters, with a sufficient supply of food, some migratory species for a given area remain to spend the winter in their breeding grounds (ducks, rooks, blackbirds). This indicates that the main reason for bird migration is seasonal changes in living conditions. In areas where these seasonal changes are more pronounced, the number of migratory species is greater. Thus, in the USSR, out of 750 bird species, 600 are migratory, wintering mainly in the British Isles, Southern Europe, the Mediterranean, Africa and Asia.

The migratory routes of birds are enormous. The flight path of our warblers and swallows wintering in Africa is 9-K) thousand km, and the arctic tern from the coasts of the Barents Sea to the coasts of Africa is 16-18 thousand km. The flyways of waterfowl and marsh birds are confined to river valleys and sea coasts, where there are conditions suitable for their resting and feeding. Many birds fly in a wide front. Small passerines cover a distance of 50.....100 km per day, ducks - 100-

500, storks - ~ 250, woodcocks 500 km. Birds usually spend 1-2 hours per day flying, using the rest of the time to stop for rest and feeding. Crossing waters, they fly thousands of kilometers without rest. In spring, bird stops are more rare and short-lived than in autumn, so spring migrations usually occur at a faster rate than autumn ones.

Bird migration is one of the most interesting and poorly studied issues in bird biology. The mechanism that determines the orientation of birds during migration has not yet been fully studied. Based on observations in nature and experiments, it was possible to reveal that migrating birds can navigate by the position of the sun, moon, stars, and by landscape features. The innate migratory instinct plays an important role in the migratory behavior of birds and the choice of general direction during flight. However, it manifests itself in the presence of a certain amount of environmental factors. Under the influence of environmental conditions, it is possible to change this innate instinct.

Bird migration has evolved over thousands of years. The influence of the Ice Age on the formation of bird migration routes in the Northern Hemisphere is undeniable. The modern flyways of some birds follow the historical path of their settlement in post-glacial times.

Of great importance for the study of bird migration is the method of ringing, when chicks or adult birds are put on a metal ring with the number and designation of the institution carrying out the tagging on their paw before leaving the nest. In our country, all information about banding and harvesting of banded birds is sent to the Banding Center of the USSR Academy of Sciences (Moscow). Every year, about 1 million birds are ringed in the world, of which more than 100 thousand are ringed in the USSR. Ringing makes it possible to trace migration routes, flight speed, life expectancy and other important issues of bird ecology.

Economic importance of birds. The role of birds in human economic activity is great and diverse. Birds domesticated by humans (chickens, geese, ducks, turkeys, guinea fowl, pigeons) have long been used to obtain meat, eggs, down, feathers and other valuable products and industrial raw materials. In our country, poultry farming is the most important and rapidly developing branch of livestock farming. Many species of wild birds (Culiformes, Anseriformes, some waders) serve as objects of sport and commercial hunting, which makes it possible to additionally involve a significant amount of tasty meat into economic circulation.

The role of birds in the extermination of insects and mouse-like rodents - agricultural pests - is great. The importance of tits, flycatchers, nuthatches, starlings, thrushes and many other birds as regulators of the number of harmful insects especially increases during the period of feeding chicks. Thus, during the nesting period, a family of a common starling destroys 8-10 thousand May beetles and their larvae or over 15 thousand winter moth caterpillars. Many birds of prey, owls, seagulls, storks and a number of others exterminate mice, voles, gophers, rats, hamsters and other harmful rodents. The usefulness of birds is associated with their ability to quickly find and concentrate in areas of mass reproduction of pests, and for many species of birds - to switch to abundant, although often unusual, food. Thus, during the years of mass reproduction of mouse-like rodents, rooks, seagulls, etc. begin to feed on them.

Some birds act as plant distributors. Thus, in the taiga of Eastern Siberia in burnt areas, the restoration of cedar is often associated with the activity of the nutcracker. Jays participate in the dispersal of oak trees. Waxwings, thrushes, hazel grouse and many others spread the seeds of rowan, bird cherry, thorn, elderberry, viburnum, euonymus, blueberry, raspberry, lingonberry, etc.

Rice. 259. Various types of crowbars for giezdonapiya useful insectivorous BIRDS

To increase the number and attract useful birds, create favorable conditions for their nesting, hang artificial nesting boxes: birdhouses, nest boxes (Fig. 259),

carry out winter feeding it. d. When artificial nests are hung, the number of bluebirds (flycatchers, tits, starlings) increases sharply.

In some cases, birds can cause some damage. Rooks, useful for destroying soil insects, sometimes damage agricultural crops (especially corn), pecking out seeds and pulling out seedlings. Nomadic starlings peck at ripe cherry and grape fruits. In the southern regions of our country, in some places sparrows cause serious damage to the grain harvest. The bee-eater, which destroys bees, can be harmful to beekeeping. In some places, the hunting area is damaged by the reed harrier and the hooded crow. When colliding in the air with high-speed aircraft, birds sometimes cause serious accidents, which necessitates the creation of a system to scare birds away from airfields. It is also necessary to take into account the role of birds in the spread of certain diseases dangerous to humans and farm animals (ornithosis, influenza, encephalitis, etc.).