The main external anatomical differences between birds and animals. Origin of birds: features, interesting facts and description

The bird differs from other animals in the structure of the digestive system, greater intensity metabolic processes. This is due to its high precocity and productivity. During the first 50 days of life, the average weight of meat chickens and ducklings increases 40 times compared to birth weight, goslings - 35 times.
The bird has no teeth in the mouth, it captures food with its beak and swallows it whole. In ducks and geese, transverse skin plates are located along the edge of the beak, which help to tear off grass and separate solid particles from liquid food.
From the oral cavity, food, only slightly wetted by saliva, enters the esophagus. In granivorous birds, the esophagus expands before entering the chest cavity, forming a goiter. Geese and ducks have a slight dilatation of the esophagus in place of the goiter. Once in the crop, the food swells and softens under the influence of moisture and temperature, as a result, part of the nutrients passes into a soluble state. From the goiter, food gradually passes into a small glandular stomach and is exposed to the enzyme pepsin and hydrochloric acid. Then it enters the muscular stomach, where, with the help of a hard cornea and gravel, it is thoroughly ground and mixed with gastric juice from the glandular stomach. From the muscular stomach, food enters the intestines, where it is digested in a slightly acidic environment.
Digestion in birds is much faster than in other animals. For example, in chickens, food passes through the digestive canal in 4-5 hours, in an adult bird, in 7-8 hours. Whole and coarsely chopped grains stay longer in the digestive canal and are exposed to enzymes. Farinaceous feeds have a significantly higher passage speed and digestibility. This feature of bird digestion is taken into account when cooking combined feed, where all grain feed for better mixing is first crushed, and then the finished mixture is granulated. The diameter of the granules for an adult bird is approximately equal to the size of a grain of wheat. For young birds, the granules are pre-crushed and fed in the form of grits.
The bird digests fiber and organic matter of feed worse than other animal species. In chickens, the coefficients of digestibility of fiber of different feeds range from 0 to 20-25%. Nitrogen-free extractives from feeds with a low fiber content (3-5%) are digested by 80-90%, and with a high fiber content (20-30%) - only by 25-34%. Geese digest the fiber of oat grains only by 10-12%. According to current standards, the maximum fiber content in the diets of laying hens and chickens should not exceed 4-7%, and in the diets of turkeys and geese - 6-10%. With a lack of fiber in the diets, digestion is disturbed, productivity decreases, which can cause pecking and death of the bird.
In the digestive tract of birds, complex organic substances are broken down into simpler compounds: proteins to amino acids, carbohydrates to monosaccharides, fats to glycerol and fatty acids. Absorbed into the blood, these substances are carried to all organs and tissues of the body, used to create new and restore old cells, the formation of digestive juices, the synthesis of enzymes, hormones, vitamins. At the same time, the body is constantly breaking down and oxidizing complex organic substances. The released energy is used to maintain body temperature, muscle work, and the synthesis of new compounds.
The intensity of metabolism depends on the physiological state, age and productivity of the bird, as well as on the amount and ratio of nutrients entering the body. For the normal functioning of the body, it is necessary that the bird consumes a certain amount of water, protein, fat, carbohydrates, minerals and vitamins daily.
The metabolism in the bird's body proceeds using the energy that comes from the feed. The productivity of a bird by 40-50% depends on the availability of its energy. In poultry farming, the energy nutritional value of feed, feed mixtures is expressed in megajoules and kilocalories of exchangeable energy.
Metabolic energy is an indicator of the energy value of feed and the provision of energy to the bird due to the nutrients of the diet, depending on species differences and physiological state.
In poultry feeding, a certain relationship was found between the level of metabolic energy and crude protein in the diet. With a lack of metabolic energy, crude protein is used by the body for energy purposes, which is accompanied by an increase in consumption and feed consumption per unit of production. With an excess of metabolic energy in the bird's body, intensive fat deposition occurs. Especially undesirable is an excess of energy in feed for rearing young and meat line hens, as this leads to rapid obesity and a sharp decrease in egg production in adult birds.
The ratio of metabolizable energy to protein in the poultry diet - the energy protein ratio (EPO) indicates how much metabolizable energy is accounted for by each percent of crude protein. In 1 kg of feed, with an optimal energy-protein ratio, high egg production of chickens is ensured throughout the entire productive period and intensive growth of young animals.
Protein has a major impact on poultry health, productivity and product quality. The need for protein depends on the physiological state, feeding conditions and keeping of the bird. Both excess and lack of protein are undesirable.
The protein value of poultry feeding is determined not only by the level of crude protein, but also by the content of amino acids in the feed (see Appendix 10). It has been established that 40-45% of the bird's need for protein is satisfied by essential amino acids, and the rest is compensated by non-essential amino acids.
With an imbalance in the amino acid composition of the diet, there may be a violation of the absorption of individual amino acids. For example, methionine can inhibit the absorption of leucine and phenylalanine and vice versa. With an increase in the level of lysine in the diet by 20%, the growth rate of chickens is sharply reduced and feed costs increase.
In poultry diets, the content of lysine, methionine, methionine + cystine, tryptophan, arginine, histidine, leucine, isoleucine, phenylalanine, phenylalanine + tyrosine, threonine, valine and glycine is normalized. When balancing the nutritional value of feed mixtures according to the amino acid composition, it is necessary to accurately normalize the addition of synthetic amino acid preparations, since the need for amino acids depends on the level of crude protein in the diet.
In the current standards of poultry feeding, the need for metabolic energy and other substances is characterized by their content in 100 g of complete mixed feed (see Appendix 11).
The need for protein in poultry depends on the availability of feed nitrogen, their amino acid composition, balanced diet, ambient temperature and other factors. In diets that are full in amino acid composition, the protein level can be reduced by 5-10%. There is a close relationship between the use of amino acids in the body of poultry and the provision of diets with vitamins, especially group B. With a lack of vitamins, metabolism is disturbed, the growth of young animals slows down, egg production, the quality of eggs and poultry meat decrease. To ensure that the poultry need for vitamins is guaranteed, they are additionally introduced into mixed feed (see Appendix 12).
Of the minerals in compound feed, the amount and ratio of calcium and phosphorus are primarily taken into account. With a calcium deficiency, chalk, limestone, shell are introduced into the feed. The sources of phosphorus and calcium are bone meal, mono-, di- and tricalcium phosphate, defluorinated phosphate.
Balancing diets for sodium is carried out at the expense of table salt.
The need for poultry in trace elements is satisfied by guaranteed additions of manganese, zinc, iron, copper, cobalt and iodine in the form of salts, which are introduced into mixed feed, as a rule, as part of vitamin and mineral premixes. Special prophylactic preparations, enzymes and antioxidants are also added to bird feed mixtures.

Bird class (Aves)

general characteristics(G.P. Dementiev)

Birds are a class of vertebrates, whose representatives are well characterized by the fact that their body is covered with feathers and their forelimbs are modified into flight organs - wings. With rare exceptions, birds are flying animals, and those species that do not fly have underdeveloped wings. For movement on a solid substrate, the birds use their hind limbs - legs. Thus, birds, unlike all other terrestrial vertebrates, are bipedal animals. Birds have a very energetic metabolism, body temperature is constant and high, the heart is four-chambered, arterial blood is separated from venous. The cerebral hemispheres and sense organs are well developed, especially vision and hearing.

From a biological point of view, the most characteristic features birds are, on the one hand, the intensity of metabolism, the intensity of the course of life processes, and on the other - movement through the air by flight. These two main features of birds largely determine their biology. It is these properties of birds that fundamentally distinguish them from other groups of vertebrates. Despite the common evolutionary origin of birds and reptiles, the biological differences between these two groups of animals are enormous.

In terms of mobility and ability to overcome space, birds rank first among terrestrial vertebrates. Great mobility is associated with a great work of the muscles, with a large expenditure of energy, which require rapid and intense compensation. Despite the fact that the lungs of birds are inflexible and relatively small, the use of oxygen in them and the nutrition of the body with oxygen in birds is very intensive, which is explained by the action of the air sac system. The active part of the respiratory process in birds, unlike other vertebrates, occurs not only during inhalation, but also during exhalation. The significance of this for the intensification of metabolism in the body is obvious. Arterial blood is completely separated from venous blood, and the work of the heart is very energetic. In this regard, there is also an energetic work of the digestive organs: the bird consumes a large amount of food, and its assimilation proceeds quickly and very completely. All these features are closely connected with the presence of a constant body temperature in birds (and the latter with the development of a heat-insulating cover of feathers). The body temperature in birds is higher than in mammals, most often it is close to 42 ° C, in a few species it drops below 39 ° C, but often reaches 45 and 45.5 ° C.

Of the other very significant features of the biology and structure of birds, we must also mention the features of reproduction. Compared with reptiles, there is, firstly, a weak intensity of reproduction, and secondly, the complexity of the biological phenomena accompanying reproduction, and in particular the complexity of the phenomena of caring for offspring. The latter, as it were, compensates for the low fertility.

The whole evolution of birds went in close connection with their acquisition of the ability to fly. The appearance of the main biological and anatomical features of the bird's body had to go simultaneously with the appearance and development of their mobility, the improvement of their motor capabilities. Paleontological material shows that at a certain stage of evolutionary development the ancestors of birds were terrestrial running reptiles. The ancestors of the ancestors of birds, judging by our ideas about the general course of the evolution of the animal world, must have belonged to very ancient groups of primitive archeosaurs that lived in the Triassic, and perhaps in the Permian period. These were, of course, running ground forms and, apparently, medium-sized animals.

In the Jurassic, there was an intermediate tree form between reptiles and birds - archeopteryx, which already has some signs of modern birds, in particular feathers or feather-like formations. Thus, at this time, the transition of the ancestors of birds from a terrestrial lifestyle to an arboreal one took place and, obviously, a constant body temperature arose (the latter is indicated by the presence of plumage in Archeopteryx). The design of the Archeopteryx skeleton is still far from bird-like and lacks its most important functional features. The general trend of further stages in the development of birds (after the Jurassic) is associated with an improvement in their ability to move and with the acquisition of the ability to fly. Although non-flying species were also encountered later, most of them died out or are on the way to extinction, but relatively small, but well-flying groups have reached the greatest prosperity since the Tertiary period. The latter and among modern birds are the most numerous.

The speed and freedom of movement gave birds great advantages in the struggle for existence and in the history of their development and give now.

Birds are found all over the globe, with the exception of the interior of Antarctica, in a wide variety of localities and in a wide variety of climatic conditions. In 1937, employees of the Soviet polar station observed gulls, guillemots and a snow bunting near the North Pole. In Antarctica Amundsen observed a great skua in 1912 at 84°26" S. The vertical distribution of birds is also very wide, and various species inhabit the highest mountain systems of the world, such as the Himalayas and the Andes. m; Humboldt saw condors in the Andes at 6655 m.

The number of birds in different places is different. The largest number of bird species is found in the Central and South America: about 1700 species are found in Colombia, about 1440 in Brazil, 1357 in Ecuador, 1282 in Venezuela. The bird fauna of the Congo (Kinshasa) is also abundant, in which (together with Rwanda and Burundi) there are 1040 species of birds. The fauna of some tropical islands is also rich: 554 bird species in Kalimantan (Borneo), 650 in New Guinea.

In the African savannah and gallery forests, the bird population is also diverse: 627 species in Ghana, 670 in Cameroon, 674 in Zambia, 871 species in Sudan.

As you move away from the tropics, the composition of the bird population becomes poorer. So, in the taiga zone of Europe, Asia and North America, there are approximately 250 species of birds. The avifauna of some European countries is characterized by the following figures: Great Britain and Ireland - about 450 species (many stray), Greece - 339 species, Yugoslavia (Serbia - 288 species, Macedonia - 319 species), Finland - 327 species, Norway - 333 species, Portugal - 315 species. From Asian countries, 341 species of birds were found in Afghanistan, and 425 species in Japan. There are 775 bird species in the United States of America and Canada. In total, about 8600 species of birds are currently known.

Within the USSR there are more than 700 species of birds, which is about 8% of the entire world avifauna.

The number of individuals of individual species of birds is very different. Few accurate estimates are available. In recent years, the International Union for Conservation of Nature and Natural Resources has been evaluating the number of rare species of birds that are endangered. It was found that about 20 pairs of cahow petrel were preserved in Bermuda; white American cranes in North America in 1963, 39 individuals were counted; white-backed albatrosses on the island of Torishima in Japan in 1962, 47 birds were noted; white-billed American woodpeckers in Cuba found about 13 individuals; California condors in 1960 were 60-65 birds; Japanese ibis on the island of Hokkaido in 1962, approximately 10-15 individuals were counted; about 300 takahe shepherds on the South Island of New Zealand; Hawaiian geese in the Hawaiian Islands and in zoos in 1962, 432 individuals were counted. The conservation of all these species and a number of others is threatened. It can be added that from the end of the 17th century to the present, 76 species of birds have become extinct, and to a large extent under the influence of human activity.

What are the most numerous bird species? In the Arctic, apparently, a small auk is a little auk, in the Antarctic and Subantarctic - a small petrel Wilson's petrel, in tropical seas - a sooty tern (several tens of millions of individuals of each species).

Of the terrestrial birds, the most numerous, apparently, are the house sparrow and starlings. Bird numbers are, of course, approximate. conducted in England and Wales (Fischer, 1954). The total bird population there is estimated at 120 million individuals belonging to 426 species, but 75% of these 120 million belong to only 30 species, each of which is 3% of a million or more. The finch and blackbird are thought to be represented by about 10 million individuals (of each species); there are about 7 million starlings, the same number of robins; house sparrows, forest hawks, song thrushes, meadow pipits - 3 million of each species; rooks 1750 thousand; about 1 1/4 million each of common buntings, wrens, gray warblers, willow warblers, pigeons; 3/4 million each of jackdaws, field larks, titmouse, barn swallows, city swallows and linnets; about 350 thousand greenfinches, great tits, forest pipits, grasshopper warblers, black swifts, moorhens, lapwings, mallards, gray partridges. Of course, these figures are approximate. For relatively rare and less numerous birds of England and Wales, the following figures are given: black-headed gulls - about 150 thousand, barn owls - 25 thousand, gray herons - about 8 thousand, great grebes - about 2% of a thousand. The number of some birds in Britain is increasing. So, silly - there are about 200 thousand of them - it became 5 times more than it was at the beginning of this century; sharply increased - up to 1 / 4 million - the number of gannets.

In total, according to rough estimates, about 100 billion individuals of birds live on the globe, and this alone indicates their great and diverse importance in the life of our planet.

Reactions of the body of birds to adverse changes external environment have a completely different character than that of amphibians, reptiles and some mammals. In all the above groups (except birds), a decrease in temperature reduces the activity of the body, which leads to hibernation when adverse conditions occur in nature. In birds, the response to a decrease in temperature is increased movement - migrations or flights, transferring the body to more favorable conditions for its existence.

However, it should not be imagined that the bird, due to its freedom and speed of movement, is little dependent on the influence of the environment, on the situation and conditions of its habitat.

The way of life of a bird and its behavior depend on the climate in a broad sense (especially temperature and light; the absence of the latter limits the possibility of vigorous activity of the bird, in particular nutrition; a certain intensity and duration of illumination also determines - through the eye and pituitary gland - the development of the gonads of birds), and on food and the conditions for obtaining it, and on nesting conditions (in particular, on the availability of a suitable place for the nest and nesting territory), and on population density, on competition, etc.

It is remarkable that birds, paradoxical as it may seem at first glance, are very conservative in terms of habitats. Each species and subspecies lives in a strictly defined area. Observations by Howard and many other scientists, and in recent years as a result of ringing (marking caught birds with special rings) have established that the life of each bird is inextricably and closely connected with the "homeland" in the narrow sense, that is, with that relatively small area of ​​the earth's surface - groves, forests, fields, etc., where the bird was born. Bird nesting occurs annually (with rare exceptions) in this area or in its immediate vicinity. There is a struggle for this nesting territory in the spring. This does not apply only to birds that nest colonially and to species that do not form nesting pairs. Apparently, the very singing of passerine birds should be considered mainly as a signal warning other males of the same species that this nesting area is occupied. Migratory birds return in the spring to their nesting site, and the young (with some exceptions) settle somewhere nearby (but, of course, outside the nesting area of ​​the parents).

The attachment of birds to the place of their homeland is so great that usually the onset of unfavorable circumstances on it causes either a decrease in the rate of reproduction, or non-nesting, or death.

From a general biological point of view, such attachment of birds to their homeland can be explained in general view the fact that for each bird the optimal conditions for existence at a certain time of the year are available precisely at home. Indeed, for example, the far north, in addition to calm and comfortable places for nesting, low temperatures favorable for cold-loving forms, and an abundance of food, also provides advantages in rearing the brood. The non-setting summer sun allows birds to be active most of the day, and a large amount of light determines and stimulates the development of the sex glands. It has been established with sufficient certainty that the daily cycle of birds is closely dependent on lighting conditions: each species wakes up, behaves actively and rests at a certain lighting strength, which determines the daily activity of the bird. The conservation of habitats characteristic of birds is directly and closely related to their possibilities of movement, since only flight can bring a bird that has flown hundreds and thousands of kilometers from the nesting site in autumn back to that small piece of land where it nested last year (or in past years). This, moreover, is connected with the peculiarities of bird orientation, which will be discussed below.

Before turning to the consideration of individual issues of bird biology, let's say a few more words about plumage which performs various and very important functions. Bird feathers serve the purposes of thermoregulation, mainly to keep warm, create a "streamlined" surface of the body and protect the skin from damage.

Although the body of birds is usually completely covered feathers(with the exception of some bare areas - around the eyes, at the base of the beak, etc.), feathers do not grow on the entire surface of the bird's body, but on certain specific areas that are called pterylium, while the areas of skin between them that do not carry feathers are called apteria.

Distinguish usually contour feathers, down and some other varieties of feathers. The structure of the contour pen is as follows. There is a dense and elastic kernel, around which, usually symmetrically, is located fan, forming a dense, air-impermeable plate. The part of the rod that directly comes out of the skin and does not carry a fan is called the chin, the rest of it is called the trunk.

Often the feather also has a so-called side trunk, which has the form of a thin and soft rod with downy beards and in rare cases (for example, in emus and cassowaries) reaching a large development.

Contour feathers come in various sizes and shapes. Different groups of them, bearing different names, carry various functions. Among them, special mention should be made of primary and secondary flight feathers. The first, usually 9 or 10 in number, are attached to the back of the hand, they are stiffer than all the other feathers and create thrust (to a lesser extent lift) during flight, their fans are usually asymmetrical. Secondary flywheels are attached to the forearm (more precisely, to the ulna). Their number is variable and ranges from 6 (in hummingbirds) to 37-38 (in some tube-noses). They constitute the bearing surface of the wing. tail formed tail feathers(their number ranges from 8 to 28). The remaining coverts have special names according to their location on the body: upper and lower tail coverts, large, medium, small wing coverts, etc. (Fig. 5).

The fluff differs from the contour feather in that its core is soft, the fans are also soft and their beards are not interlocked. Down grows either only on pterylia, or on apteria, in some groups of birds - all over the body. Down serves to keep warm.

Let us now turn to the consideration of individual questions of bird biology. Let's start with flight. In the structure of the bird, from the point of view of adaptations to certain modes of movement, the following features attract attention. In the skeleton, which is distinguished by strength and lightness, the forelimbs are completely freed from supporting the body when walking, standing, and sitting. Their function is mainly reduced to movement through the air, i.e. flight, and in some aquatic forms (penguins) - to movement in the water. In this regard, the forelimbs do not carry grasping functions (although in hoatzin chicks, in which the fingers remain free for some time, the forelimb serves to climb branches). This, in turn, caused changes in the structure of the skeleton of the head and neck. Grasping functions are performed by the beak. This is associated with a significant mobility of the occipital articulation, a strong development of the muscles that rotate the head and the transfer of the center of gravity of the head back. The cervical spine in birds is very mobile, and the chest is, as it were, carried back. The mobility of the cervical spine is expressed both in the wide possibilities of flexion (both lateral and sagittal) and in the possibility of neck rotation, usually up to 180°, in owls up to 270°.

The body skeleton, which should serve as a strong support during flight, is inactive. The spine in its thoracic region can usually bend only in the lateral direction (with the exception of diving forms and shepherds living in shrubbery). In many forms, a number of thoracic vertebrae fuse into one so-called dorsal bone, a number of vertebrae (lumbar, sacral, caudal, sometimes chest) fuse together with the pelvic bones into complex sacrum. Free tail vertebrae are few, and the terminal tail vertebrae are fused into a bone that serves to support the tail feathers. pygostyle. The shoulder blades fit snugly to the ribs, being connected to them by a system of ligaments and muscles; the ribs bear hook-shaped processes directed backwards, strengthening the connection between the ribs along the longitudinal axis of the body. The articulation of the bones of the shoulder girdle is extremely strong. Finally, the large size of the sternum provides support during flight for internal organs, and its large crest (keel) serves as an attachment site for powerful muscles that control the movement of the wing. The trunk skeleton in birds is a strong and inactive box, reminiscent to some extent of the skeleton of an airplane. It can be added that the lungs of birds firmly adhere to the ribs, and the movement of the latter during flight automatically stimulates the work of the respiratory apparatus.

In the structure of the limbs, the most characteristic feature is the fusion of a number of bone elements. A complex sacrum and pelvis, formed by the fusion of a series of vertebrae and pelvic bones, give the hind limbs a strong support. The widest and most stable pelvis is characteristic of terrestrial (running) and climbing species, the narrowest - diving. The thigh of birds is short, but powerful. Unlike reptiles, the femoral neck is located at a right angle to its main part. The mobility of the thigh in birds is therefore limited, but the articulation of the thigh with the pelvis is extremely strong. The fibula is reduced and to some extent merges with the tibia, to which the upper (proximal) row of tarsal (tarsal) bones also grows. The lower (distal) row of these bones merges with the three metatarsal bones into one bone, the so-called tarsus. In birds, therefore, there is not an ankle, but an intertarsal (intertarsal) articulation. Such a device of the leg gives it greater strength and stability. In particular, the fusion of the metatarsals makes it easier to maintain balance when the bird is landing on the ground or on a branch. A strong and long tarsier facilitates repulsion during takeoff and makes the bird more stable. The toes of birds are well developed and represent the most diverse types of adaptation to the mode of movement. In forms that live in marshy places and move on soft surfaces, they are very long. In running ground forms, they are strong, but rather short, and in the most specialized groups for movement on the ground (ostriches, etc.), a reduction (decrease) in the number of fingers is observed, as in mammals. In tree forms, there are complex adaptations to the coverage of branches and certain correlations (dependencies) between the length of the fingers and the size of the knots on which certain species sit. Aquatic forms develop swimming membranes.

Birds have four or three toes on their feet. The first toe is usually turned back, often poorly developed and absent in the case of a three-toed foot. The African ostrich has only two fingers.

Forelimb of birds wing- extremely idiosyncratic. The final part of it is arranged very simply, since a significant number of bones grow together. The wing fingers of birds do not protrude and are covered by a common skin; only three fingers; the number of phalanges of the fingers is small (usually one or two phalanges in the first finger, two or three in the second and one in the third); distal carpal bones and metacarpal bones fuse to form one bone; only two proximal carpal bones are preserved. Separate elements of the carpal section of the wing are inactive, and the whole of it serves as a strong support for the flight feathers. At the same time, the first finger bears a winglet, the second finger - the first, second and third primary flywheels, the third finger - the fourth primary flywheel, the rest of the primary flywheels are attached to the wrist.

The strength of the parts of the skeleton that carry the primary feathers is of great importance for flight, since it is these feathers that are the tool for the bird to move forward (and simultaneously rise), while the secondary feathers, located along the direction of the air flow, perform only the task of maintaining the bird in the air and lifting it.

The strength of the bird skeleton, in addition to the fusion of its individual elements, is also determined by the composition (an abundance of mineral salts) and the structure of the bones; lightness is explained by the airiness (pneumaticity) of many bones associated with air sac systems - pulmonary and nasopharyngeal. The relative weight of the skeleton in birds is therefore low.

In connection with the energetic functioning of the limbs and the weak mobility of the body, the muscles of the wings and legs are strongly developed in birds, and the muscles of the body are relatively poorly developed. The cervical muscles are very complex and functionally diverse, which ensures the mobility of the neck. The pectoralis major muscle, which lowers the wing, which in birds of prey is approximately 1/14, in a goose 1/11 of the total body weight, is known to be located on the chest, between the humerus and the keel of the sternum. However, the size of the pectoral muscles is not directly dependent on the size of the wing. Birds with a large wing surface, in particular those that use predominantly soaring flight, have a relatively underdeveloped musculature of the wing. Birds with a small wing surface have strong muscles. Generally speaking, the muscles of birds are distinguished by their high density, mobility, and long tendons.

Of the features of the musculature of birds, one should also mention the peculiar arrangement of the tendons of the muscle - the deep flexor of the fingers, which creates an automatic clamping of the branch by the fingers of a sitting bird. The tendon of the deep flexor of the fingers has an uneven surface, covered, as it were, with notches, which correspond to protrusions, or ribs, on a wide and free tendon bag. In a bird sitting on a tree, under the influence of its weight, this clamping device is compressed and the fingers are fixed in a bent position. This adaptation is especially developed in passerines, but, apparently, all birds have it (only ratites and penguins do not have it).

Birds move on a variety of substrates; they generally move well on the ground, climb trees, many dive and swim in the water, but the most characteristic way of bird movement is still flight.

There are few flightless forms among modern birds. Some of them (ostriches, emus, cassowaries, rhea, kiwi, penguins) may never have flown, others have lost the ability to fly, no doubt secondary.

The aerodynamic picture of the movement of birds through the air is very complex. The nature of the flight of individual groups and species is very diverse and is directly related both to their ecological properties (marine, terrestrial, arboreal; catching perched or flying prey, etc.) and to their evolution. The structure of the wing (length and proportions, the length of the flight feathers, etc.), the ratio of body weight to the area of ​​\u200b\u200bthe wings (the so-called weight load), muscle development - these are the main factors that determine the properties of flight in birds.

Bird flight can be divided into two main categories: it is soaring, or passive, flight and waving, or active, flight.

When soaring, the bird moves in the air for a long time, without flapping its wings and using ascending air currents, which are formed due to uneven heating of the earth's surface by the sun. The speed of these air currents determines the height of the bird's flight. If the upward air current rises at a speed equal to the speed of the fall of the bird, then the bird can hover at the same level; if the air rises at a speed exceeding the speed of the fall of the bird, then the latter rises. Using the differences in the speed of two air streams, the uneven action of the wind - its strengthening and weakening, changes in the direction of the wind, pulsations, air - a soaring bird can not only stay in the air for hours without spending much effort, but also rise and fall. Land soaring species, such as carrion-eating vultures, etc., usually use only ascending air currents. Marine soaring forms - albatrosses, petrels, feeding on small invertebrates and often forced to descend to the water and rise - usually use the effect of the action of the wind, differences in the speed of air currents, air pulsations and turbulence. Soaring birds are characterized by large sizes, long wings, long shoulder and forearm (large development of the bearing surface of secondary flywheels, the number of which in vultures reaches 19-20, and even 37 in albatrosses), a rather short brush, relatively small heart sizes (since passive flight does not require increased muscle work). The wing is either wide (terrestrial species), or narrow (marine species).

Waving flight is more complex and varied than soaring. It is worth comparing the flight of a swift, the flight of a crow slowly moving its wings, a kestrel fluttering in the air and a peregrine falcon rapidly rushing to its prey, a fast-flying duck and a pheasant flapping its wings heavily, to make sure this remark is true. There are various and rather conflicting attempts to classify various types flapping flight, which we will not dwell on here.

The bird usually uses more than one type of flight, but combines them depending on the circumstances. At the same time, it must be borne in mind that flying movements consist of phases successively replacing one another. The flapping of the wings is followed by phases when the wing does not produce rowing movements: this is a gliding flight, or soaring. This flight is mainly used by birds of medium and large sizes, with sufficient weight. Small birds, on the other hand, usually work vigorously all the time with their wings, or at times they can fold their wings, pressing them to the body. The latter is especially characteristic of finches.

Acceleration in flight is achieved by a bird by increasing the weight load of the bearing surface, for which it is necessary to fold the wings somewhat. A slow flying bird with a fully extended tail and outstretched wings. As the movement accelerates, it somewhat folds the fly feathers, and in all well-flying birds they form a continuous surface (in the falcon, gull, swift, swallow, etc.).

The wind is of great importance for the speed of movement of birds. Generally speaking, a tail or slightly side wind is favorable for flight, but a head wind is favorable for takeoff and landing. Tailwind during flight increases the flight speed of the bird. This increase is quite significant: for example, according to observations of pelicans in California, it was found that an increase in air speed from actual calm to 90 km/h contributed to the change in the flight speed of pelicans from 25 to 40 km/h. However, a strong tailwind requires a lot of effort from the bird to maintain the ability to actively control the flight.

The duration and speed of the flight of birds is very great, although exaggerated ideas are usually widespread in this respect. The very phenomenon of migration shows that birds can make long movements. European swallows, for example, winter in tropical Africa, and some waders nesting in northeastern Siberia fly to New Zealand and Australia for the winter.

The speed and height of the flight of birds are significant, although they have long been surpassed by modern aircraft. However, the flapping wing of a bird gives it many advantages, primarily in maneuverability, compared to modern aircraft.

Modern technical means (observations from aircraft, high-speed photography, radars, etc.) made it possible to more accurately determine the flight speeds of birds. It turned out that on average birds use higher speeds when migrating than when moving outside the migration season.

Rooks on flights move at a speed of 65 km/h. The average speed of their flight outside the time of migration - during the nesting period and wintering - is approximately 48 km/h. Starlings on migrations fly at a speed of 70-80 km/h, at other times 45-48 km/h.

According to observations from aircraft, it has been established that the average speed of movement of birds during flights ranges between 50 and 90 km/h. So, gray cranes, herring gulls, large sea gulls fly at a speed of 50 km/h, finches, siskins - 55 km/h, killer whales - 55-60 km/h, wild geese (different types) - 70-90 km/h, wigeon - 75-85 km/h, sandpipers (various species) - on average about 90 km/h. The highest speed was noted in the black swift - 110-150 km/h.

These figures refer to spring migrations, which are the busiest and probably reflect the highest bird flight speeds. Autumn migrations are much slower, for example, the flight speed of storks on autumn migrations is hardly half the speed of their spring movement.

The question of the flight altitude of birds remained unclear for a long time. The old notion that the movement of birds takes place, as a rule, at high altitudes (500-1600 m above sea level) was questionable. However, astronomical observations have shown that, in all likelihood, the maximum flight altitude of birds reaches 2000 and even 3000 m. To some extent, this was confirmed by the use of radar.

It turned out that flights in spring proceed at higher altitudes than in autumn, that birds fly at higher altitudes at night than during the day. Passerine birds, such as finches, fly at altitudes somewhat less than 1500 m; larger passerines, such as thrushes, - at an altitude of 2000-2500 m. Sandpipers fly at an altitude of about 1500 m.

Although flight is the main and most characteristic way of movement of birds, they also have other very diverse ways of movement. The well-known divisions of birds into aquatic, terrestrial, and arboreal indicate the well-known differences between these groups in terms of movement. For land birds, running and walking are characteristic, for water birds - swimming and diving, for arboreal birds - jumping and climbing on the branches and trunks of trees. It is clear that this division is schematic and does not exhaust the complexity of bird movements.

Birds climbing trees have strongly developed claws on their paws, fingers can be widely spaced, often with the fourth finger moving far forward. An example of birds climbing trees are pikas, nuthatches, woodpeckers, parrots. In birds climbing a tree from the bottom up, a hard tail with pointed tail feathers serves as a support during climbing. The legs of climbing birds are short, the flexor muscles are strongly developed. The main phalanges of the fingers are short. In arboreal birds, jumping and climbing branches, the clamping devices of the tendon of the deep flexor of the fingers are strongly developed. In parrots, the paws are expanded, and their fingers can be widely spaced; when climbing, they are also helped by a beak, strong and mobile.

Birds with long wings usually move poorly on the ground. Swifts cannot, for example, walk at all. Grebes and loons do not walk well on the ground. They, like those living on the rocks, have a tarsus facing straight ahead, which increases the stability of the birds when sitting. A good adaptation to increase the supporting surface when walking is the elongated outgrowths on the fingers that develop by winter in most grouse, and in white partridges - claws (they are longer in winter) and plumage of fingers; this makes it easier for them to move through the snow. Many birds living on swampy soil have long fingers, for example, the fingers of jakans running along the leaves of aquatic vegetation are very long. In well-walking and running birds, the legs are long, and both the tarsus and lower leg are long (for example, in waders, shepherds, and partly in chickens). The ability to run reaches its greatest development in ostriches and rhea. Emu can run at a speed of 31 km/h. The earth cuckoo can reach speeds up to 20 km/h, quail - up to 15.5 km/h.

Many birds swim and dive: anseriformes, petrels, copepods, some sandpipers, terns, gulls, guillemots. Floating and diving birds have shortened legs widely spaced (the thigh and tarsus are shortened), so they waddle on land. They are characterized by a rigid and tightly fitting plumage to the body. In aquatic birds, the oil gland is usually well developed, but, judging by the latest data, its function is not directly related to the impermeability of plumage. The body of swimming birds is usually elongated, while that of diving birds is flattened. The proportion of floating, and especially diving birds, is significant, approaching one in cormorants and grebes. In diving birds, the legs are usually set far back, the pelvis is narrow, the wing bones are flattened, and the absolute and relative dimensions of the wings are insignificant. It can be said that good diving birds are, as it were, on the way to losing the ability to fly; in addition to reluctantly resorting to flight and hard-flying birds, there are also flightless birds among divers (Galapagos cormorant, recently extinct "wingless" auk, etc.). It is also characteristic of diving birds that the center of gravity of the body is carried back, which facilitates the immersion of the back of the body and legs in water and, in combination with the flattened shape of the body, makes it easier for the bird to maintain balance.

Swimming in the water, the bird acts with its legs, which are carried back and pulled up; at the same time, the shins lie almost horizontally, the hips are directed forward and down. Webbed fingers serve as a propeller or oar blade, swimming movements are reduced mainly to straightening and bending the bobbin. To speed up movement in the water, the bird raises and lowers the hip and moves the lower leg forward and backward. This work of the legs of a floating bird is provided by the strong development of the muscles that lower the thigh, extend the metatarsus and flex the fingers. Birds row either with one or with two legs at once, but for turning on the water, pushes or kicks of the leg of the opposite side serve (when turning right - left, when turning left - right).

Diving and snorkeling birds are of two types. Some birds swim under water with the help of wings (as if flying), others - with the help of their legs. There are also intermediate types. The first includes penguins, the second - diving ducks, cormorants, loons and grebes. Pigs use both wings and legs when diving. Dipper, running along the bottom of streams, spreads its wings to stay in the water (slight specific gravity dipper would otherwise contribute to pushing it out of the aquatic environment to the surface). A special way of diving, associated not with swimming under water, but only with diving, among diving petrels, gannets, terns, ospreys; these birds, rushing to their prey, descend into the water from a flight and then immediately get out to the surface.

Ducks, geese, coots, cormorants and other birds tirelessly move all day long in the aquatic environment. The energetic work of the motor apparatus, heart and lungs allows diving birds to stay under water for a long time. Razorbill can stay under water 1-2 min, polar loon - somewhat more than 3 min, black-throated diver - 2 min, cormorant - more than 1 min, turpan - up to 3 min, big merganser - up to 2 min, American coot - 3 min. These are the maximum numbers. Maximum diving depths for grebes - 7 m, polar loon - 10.2 m, black-throated diver - 6.1 m, red-throated diver - 8.8 m, great cormorant - 9.4 m, turpana - 7.2 m, mergansers - 4.1-5.6 m, tags - 4.8 m. Penguins swim under water for about 10 m/s, grebes - about 1 m/s.

For the existence of each species of animals, it is necessary to resolve three main tasks: nutrition, reproduction and protection from dangers in order to preserve individuals and species in the conditions of the struggle for existence. Movement in vertebrates, and in birds in particular, is one of the most essential elements of animal defense. Having considered the aspects of bird biology related to it, let's move on to considering their features related to nutrition.

Conditions nutrition largely determine the course of life phenomena in birds. They influence the geographic distribution of birds, seasonal movements, reproduction and mortality rates, conditions of intraspecific and interspecific competition. The need to eat a certain type of food determines the feeding stations of each species. Seasonal changes in the environment partially cause changes in nutritional conditions, partially change the rate of the body's need for food (in the cold season, with a large loss of heat by the body, more food is required). Migrations and migrations of birds are also in a certain connection with feeding conditions.

The feeding regime of individual species is very different. It changes with the seasons and with the age of the bird. Some species are highly specialized in terms of nutrition (stenophages), others do not show preference for a certain type of food (euryphages). Birds feed on both plant and animal food, the latter generally predominating.

Let us dwell on the most important features of the structure of birds associated with the conditions and methods of nutrition. With relatively few exceptions (in particular, these include owls and birds of prey), birds take food with their beaks. The shape of the beak is therefore very diverse (Table 3). Birds that get food from the water or from the ground (storks, herons, waders, etc.) have long beaks. In these birds, there is a correlation between the length of the beak and the length of the legs and neck. These are usually non-floating forms. On the other hand, a long beak is characteristic of some tropical forest birds that feed on the fruits of woody plants - toucans and hornbills. The large size of the beak in these birds is compensated by the highly developed pneumaticity of the skull. Finally, a long beak is found in many species sucking flower nectar (many hummingbirds, honeyeaters, etc.) or in birds looking for food in the folds and depressions of stones or bark (pikas, wall climbers). In birds, the beak of which serves to hold live and sometimes large prey, it is of moderate length or even short, but equipped with a steep hook at the end of the upper jaw (cormorants, owls, diurnal predators), and sometimes with a tooth (falcons). In birds grabbing large prey, the lower jaw is usually large and high (herons, storks, guillemots, gulls); but sometimes even in birds that feed on vertebrates, the lower jaw is small, short and low (predatory, owls), in the latter case, grasping prey is usually done with strong armed paws. In birds that catch insects on the fly - swallows, swifts, flycatchers - the beak is not long, but wide and, as it were, flattened, and the cut of the mouth goes far back. They, like other insectivorous birds, have hard bristles on the edges of their mouths, which make it easier to catch insects. In woodpeckers, hollowing a tree, the beak is very strong, straight and chisel-shaped; its action is complemented by a long tongue, the end of which is seated with sharp spike-like protrusions that firmly hold the insect. In crossbills, husking coniferous seeds from cones, the jaws are crossed and form a lever for raising cone scales. In granivorous passerines (finches, etc.), the beak is short, strong, wide and high; the palatine surface bears sharp furrows and ridges in them; all this is a device for cracking and crushing seeds and fruit pits.

Modern birds have no teeth. Among the early Tertiary species, there were still forms with teeth, but at least from the Middle Eocene, toothed birds were no longer encountered. The crushing of food is carried out in birds either by the beak (for example, in predators), or by combined movements of the beak and tongue (in granivorous), or by the stomach. Prey is often held on with one or two feet. Woodpeckers and nuthatches crush food items (cones, acorns, etc.), pinching them in a tree (the so-called "woodpecker forges"). Crows, gulls and, perhaps, a bearded man crush hard prey (crayfish, shells, bones, etc.), throwing it from a height to the ground. The diversity of the structure and functions of the tongue in birds also depends on the variety of methods for crushing and pre-treatment of food (Fig. 8). In many forms, the tongue is rudimentary and serves only to isolate the airways; such is the language of cormorants, pelicans, boobies, kingfishers, hornbills, hoopoes, ostriches, and some petrels. However, the tongue performs the same function in other species (the mechanism is as follows: when a bird holds food in its beak, the end of the tongue rests against a gap in the middle of the palate and makes it possible to use the nasal cavity for breathing). In other birds, the tongue serves as a “probe” (woodpeckers, nuthatches), a suction pump (hummingbirds, honeysuckers, sunbirds), a grasping organ (parrots), a brake to hold slippery prey (penguins), a grater (birds of prey), and finally, a complex sieve (flamingos, ducks, geese). There are no taste buds in birds on the tongue - they are located on the palate, under the tongue and in the pharynx. The sense of taste in birds is developed quite significantly: birds distinguish between sweet, salty, sour, and some species of birds and bitter.

Salivary and mucous glands in the oral cavity of birds are relatively poorly developed; they are completely absent in copepods that swallow slippery prey captured in the water.

Esophagus birds are rather extensible, especially in species that swallow large prey (pelicans, gulls, herons, cormorants); characteristic and frequent formation, the so-called goiter- Expansion of the esophagus rich in glands. In those birds that immediately absorb a large amount of food, but sometimes go hungry for a long time, the goiter serves as a reservoir for food that gradually enters the stomach. In others, such as chickens, parrots, pre-processing of food begins already in the goiter. In predators, undigested parts of food accumulate in the goiter - bones, wool, feathers, etc.

The anterior part of the stomach of birds - the so-called glandular stomach- performs the functions of chemical processing of incoming food, and the rear - gizzard- processes food mechanically. The posterior (lower) end of the stomach is separated from the intestines by a ring-shaped constrictor muscle (sphincter), which prevents the penetration of bone fragments and other hard or sharp parts of food into the small intestines. Fish-eating bird species (herons, cormorants, grebes, penguins) and some others have a third section, the so-called pyloric sac, at the posterior end of the stomach; its function is to prolong the presence of food in the stomach for better processing. The glandular stomach is most developed in birds that immediately swallow a large amount of food (in piscivores and predators).

The secret of the digestive glands in birds acts very vigorously: in marabou and many carnivores, it completely or to a large extent dissolves the bones, and in cormorants, herons and ducks - fish scales. But in owls and shrikes, the bones are not digested at all. For all types of birds, chitin, keratin and fiber are indigestible (the latter, perhaps, in chicken, duck and pigeons is partially absorbed due to the activity of intestinal bacteria).

The muscular stomach in some birds is distinguished by a strong development of muscles, which also form tendon discs. The walls of the stomach work in this case as millstones and grind hard and coarse food. This is how the muscular stomach is arranged in granivorous birds and birds that feed on solid arthropods and mollusks (chickens, anseriformes, ostriches, cranes, many passerines, many pigeons). In other birds, the musculature in the gizzard is slightly developed, and it continues mainly the chemical processing of food by enzymes flowing from the glandular stomach. This is how the muscular stomach is arranged in meat-eating, fish-eating and frugivorous birds.

In many species of birds, the tubular glands of the muscular stomach secrete a secret, which then forms a periodically changing hard keratin membrane, the so-called cuticle. It is also an apparatus for grinding food. Finally, in many birds, the mechanical effect of the muscular stomach on food is further enhanced by the fact that they swallow sand, pebbles, or hard seeds of plants.

Digested food travels from the stomach to the intestines, first to the duodenum, then to the small intestine. Most birds have blind guts. Sometimes they carry digestive functions, sometimes they are also a lympho-epithelial organ, sometimes only the last; in some species, the caecum is rudimentary or even completely absent. They reach their greatest development in herbivorous birds (however, there are exceptions). The rectum in birds serves to accumulate undigested food residues; its end goes to cloaca An organ common to birds and reptiles. The ducts of the urinary and reproductive systems also open in the cloaca, and on the dorsal side there is the so-called Fabrician bag, which undergoes reduction in adult birds (at the age of 8-9 months), but is well developed in young ones. The function of this bag is to form lymphatic cells and oxyphilic leukocytes.

Liver in birds it is relatively very large, its bile ducts flow into the duodenum. Most species have gallbladder, which is associated with the need to simultaneously supply the intestines with a large amount of bile (for processing watery and fatty foods). Pancreas in birds it has a rather varied shape, but is always well developed and relatively larger than in mammals. Its size and value are inversely proportional to the gallbladder: it is largest in granivorous birds, smaller in meat-eating birds. The relative total energy turnover in birds is very high, especially in small passerines, while in large species it approaches the magnitude of the energy turnover in mammals. In the gray crow, for example, at an ambient temperature of 20-22 ° C, the total energy turnover is 840 feces for 1 m 2 body surfaces per day, buzzard - 780 feces, in chicken (at a temperature of 23 ° C) - 580 feces; at the same time, at a neutral temperature (32-36 ° C), i.e., with minimal heat transfer, the goldfinch's energy turnover is 1534 feces, the gray shrike even 1775 feces for 1 m 2 surfaces per day. The turnover of energy and the need for nutrients, and in accordance with this, both cardiac activity and the work of the respiratory apparatus, change depending on external conditions and periodic changes in the internal state of the body. In males, energy consumption increases during the mating period, in females - during the laying of eggs. The increase in energy expenditure is associated with the molting period.

A decrease in energy turnover is observed in incubating birds, which can be considered as an adaptation to a long and immobile stay on the nest.

A decrease in external temperature below known limits causes an increase in energy expenditure to maintain body temperature. For example, a drop in external temperature from 32.6 to 9.8 ° causes a threefold increase in oxygen consumption in a sparrow. To keep warm, small birds are forced to expend more energy than large ones (the size of the body surface grows in the square, and the volume in the cube, therefore, large birds the ratio of body surface to volume is more advantageous). Small birds, with a significant decrease in temperature, spend more than half of the energy received from food for thermoregulation of the body.

In winter, for birds, due to cooling and shortening of the day, critical moments occur, and with a strong drop in temperature, death from exhaustion can occur: the onset of darkness stops the possibility of feeding, and the bird cannot receive sufficient sources of energy.

Plumage and its seasonal changes are essential for the thermoregulation of birds (Fig. 10). When molting in autumn, many species show an increase in the downy part of the feather or (with a double molt per year) an increase in the number of feathers compared to the warm season. Geographical forms (subspecies) living in the north differ from their southern relatives in denser and more lush plumage (three-toed woodpeckers, large spotted woodpeckers, chickadees, gyrfalcons). Of great importance for northern birds is the white color of their plumage, in which air bubbles form in the feather, creating a heat-insulating layer. The significance of the feather for keeping warm is clear in itself, but the concrete idea of ​​this is best seen from the experience of Giaya (1929): in the great gray shrike, when the temperature was lowered from 28 to 0.6 °, the energy expenditure increased by 50%, but when the bird was plucked, the same difference in temperature caused an increase in energy expenditure by a factor of three, i.e., by 200%. Other adaptations to cold temperatures: the deposition of subcutaneous fat (especially in water birds), the work of air sacs (retaining warm air), a slight increase in the size of birds in the northern forms of the same species compared to the southern ones, and finally, a relative increase in the size of the heart.

Starvation causes a drop in temperature in birds. Generally speaking, in those species that have a higher body temperature and a high need for oxygen and are more mobile, the need for food is higher and its assimilation is faster. Opposite readings indicate less need for food. Therefore, for example, songbird chicks die within a few hours after the start of starvation, while large species can live without food for about a month (white owl - 24 days, white-tailed eagle - 45 days, golden eagle - 21 days, domestic chickens - 26-31 days). Weight loss in this case can reach 30-40%.

The body's need for water is relatively small. This is explained by the insignificance of skin evaporation, and also by the fact that water is absorbed from the urine by the body of the bird back while the urine is in the upper part of the cloaca. Many carnivorous and frugivorous species therefore do not drink at all.

The digestive process in birds is very fast and energetic. At the same time, meat and fruits are digested and absorbed faster, seeds are slower. During the day, a bird can eat a lot, and the maximum in this case often greatly exceeds the required minimum. Small owls (house owls) digest a mouse in 4 hours, a gray shrike - in 3 hours; watery berries in passerines pass through the intestines in 8-10 minutes, chicken grains in 12-24 hours. Insectivorous birds fill their stomachs five or six times a day, granivorous birds fill their stomachs twice. Predators eat once or twice a day. Small birds eat about 1/4 of their weight per day of dry food substances, large birds - much less (about 1/10) - Chicks eat more. Accurate observations have established that swallows, tits, starlings and other small birds fly up to the nest with food hundreds of times a day while feeding their chicks. So, the great tit brings food 350-390 times, the nuthatch - 370-380 times, the redstart - 220-240 times, the great spotted woodpecker - 300 times, and the American wren even 600 times. At the same time, the weight gain in chicks per day is 20-60% of the initial weight. For the first seven to eight days, the weight of passerine chicks increases by 5-6 times. It is therefore understandable that the chick eats more food per day than it weighs itself. This circumstance determines the enormous importance of insectivorous birds in the life of nature and in the human economy. With a high intensity of bird growth and a fairly significant number of eggs in clutches (which, moreover, in many species it is normal for two per year, and for some three), one pair of passerine birds has to feed 10-15 young annually on average.

Finally, relatively recently, another remarkable biological property of birds has been established: the abundance of food and favorable feeding conditions cause them to increase reproduction. Thus, in many species in years with favorable nutritional conditions, the number of eggs in the clutch is greater than in less favorable years. Sometimes in the "productive" fodder years, additional clutches appear in birds. On the contrary, in years that are unfavorable in terms of feeding conditions, the intensity of reproduction decreases (the number of eggs in the clutch is less), and the mortality among young birds becomes very high.

One more feature deserves attention. With an abundance of food, birds eat more. For example, according to observations made in Western Europe, in "mouse" years one buzzard eats up to 14 mice and voles daily, and in ordinary average years - up to 5 pieces, the kestrel eats 9 and 2 mice, respectively, long-eared owls - 12 and 4, etc. It should be noted that one vole, according to our ecologists, destroys up to 2 kg grain per year.

Finally, the abundant appearance of some kind of food sometimes leads to the fact that those species of birds begin to feed on it, which usually neglect this kind of food. The results of A.N. Formozov's observations made in 1936 in North-Western Kazakhstan are interesting: when a large number of locusts appeared, even ducks began to feed on them.

Thus, it can be said that feeding conditions determine many aspects of the life of birds, and in the case of mass reproduction of one or another bird food object, it attracts special attention from them. Consequently, a certain kind of natural regulation of the number of massively multiplied animals takes place. It is well known that the appearance of harmful insects anywhere in large numbers usually attracts birds. In such cases, the usefulness of insectivorous birds is especially evident. When, for example, in 1893-1895. in the Volga region, the pest of forests, the gypsy moth, multiplied strongly, local observers noted an unusual raid of cuckoos. The reproduction of field crop pests - click beetles attracts rooks that dig out of the ground and eat the larvae of these beetles, the so-called wireworms. According to some estimates, the rook eats more than 8,000 wireworms a year. There are observations of how a flock of rooks in one day completely cleared an area of ​​6 ha. Locust reproduction causes increased reproduction and accumulation of various starlings, in particular pink ones. The wandering locust is followed by a wide variety of bird species. The reproduction of mice causes increased activity in the fields of birds of prey - owls, buzzards, small falcons. Wandering lemmings in the tundra and forest tundra are followed by numerous snowy owls, great gulls and skuas, buzzards and even peregrine falcons.

The food of many species of birds consists of animals that have a negative value for the human economy. These are insects and small mammals, primarily rodents. Reproduction of both of them goes and can go very quickly. And in the fight against these pests lies the main positive value of birds for the economy. Commercial and hunting birds and poultry bring direct benefits to humans, but its significance, in contrast to the widely held opinion even now, is small compared to the benefits that birds bring by exterminating voles, mice, harmful insects, their eggs and larvae. There is no doubt that from an economic point of view, it is this aspect of bird activity that seems to be the most important and significant.

The importance of the danger to agriculture from pests should by no means be underestimated. If in our time - the time of high technology - they cannot bring the situation to a catastrophe, they still cause very serious damage. In pre-revolutionary Russia, the losses of field crops from pests were determined (of course, with a certain approximation) at 900 million rubles. per year, losses in forestry - 300 million rubles, losses in horticulture and horticulture - 90 million rubles. In the United States of America, the loss of agriculture from pests in 1921 was estimated at a billion dollars, and the benefit from the extermination of insects by birds was 444 million dollars; consequently, the birds have reduced the damage by more than one-third in relative terms and by an enormous absolute value. All these calculations are, of course, approximate, but they give an idea of ​​the scale and general meaning this phenomenon.

There is one more important consideration. Of the known species of birds, the vast majority belong to the order of passerines, which combines, with rare exceptions, insectivorous birds, or birds that feed their chicks with insects. In addition, the number of individuals of these small and medium-sized species is immeasurably greater than the number of individuals of large species, so it is not an exaggeration to say that insectivorous birds make up about 90% of the total number of birds living today.

If so, then one can, perhaps, agree with one American author who expressed the idea that "if all birds were destroyed, then Agriculture in the United States would be impossible."

One should not imagine the matter in such a way that birds themselves can destroy pests during their mass reproduction, but their role in the extermination of rodents and insects in "normal" years is very large and can be characterized as "control" over the reproduction of pests, as a very significant tool for keeping the number of pests at a low level.

Other aspects of bird activity related to nutrition are also not indifferent to humans. Many granivorous birds contribute to the dispersal of seeds (the latter sometimes remain viable even after passing through the intestines of the bird), in southern countries many species actively contribute to the pollination of plants. Birds of prey, hunting for other birds and animals, play a certain positive role as an instrument of selection. A known number of predators contributes to the maintenance of the health of the species that are their prey, since in the first place they prey on sick or weak specimens. Carrion-eating birds bring certain health benefits.

From the point of view of human economic interests, the nutritional traits of birds can be reduced in general terms to the extermination of useful wild animals and wild plants, to competition with more useful animal species, to harming cultivated plants, to eating domestic animals. At the same time, it should be borne in mind that we have no reason to say that this or that bird should be considered absolutely beneficial or absolutely harmful. Birds do not bring any benefit or harm "in general". Therefore, the question of absolute protection or absolute destruction of any bird species cannot be raised. Both a useful and harmful bird, like any other animal, can only be in certain conditions and at certain times. The situation is changing - the economic importance of birds is also changing. Starlings, for example, which bring benefits in the spring and summer by exterminating insects, in some areas on migration and wintering can be definitely harmful to gardens, and more recently in Tunisia, the fight against starlings was carried out by the massive use of explosives. Ravens harm by destroying the nests of useful birds, in particular waterfowl, but at the same time exterminate insects, mice and voles. The great spotted woodpecker feeds on insects that are harmful to the forest, but at the same time destroys a certain number of tree seeds, and sometimes harms the trees themselves (so sometimes, in places, as, for example, in the Buzuluk forest, the harm from the great spotted woodpecker, which interferes with the normal renewal of pine, is more than good). Sparrow eats berries, displaces beneficial insectivorous birds from nesting places, but also feeds insects on nestlings. The peregrine falcon feeds on waterfowl and other useful birds, but at the same time, in the tundra near its nests, arctic foxes leave the nests of other birds alone, as the falcon vigorously attacks arctic foxes and drives them out of the vicinity of its nest, thereby providing significant assistance to the entire surrounding bird population. The goshawk feeds on useful birds, but promotes natural selection and is rightly valued in places as an excellent bird of prey. We will not touch here on the very important question of the aesthetic significance of birds.

It is useful to emphasize that in the fauna of the USSR, numbering more than 700 species of birds, at least less than a dozen species are essentially harmful. Borrowed from the Western European owners of hunting grounds and their rangers and, unfortunately, firmly rooted and widespread opinion about the "harm" of birds of prey must be decisively discarded. The vast majority of predators benefit from the extermination of rodents and insects; others, for example, large falcons - peregrine falcons, gyrfalcons, although they hunt mainly birds, are rare, and besides, they live in any noticeable number in such areas (north) where wild riches have not yet been sufficiently used by man. They are in no way competitors of the latter, but at the same time they serve as one of the best ornaments of our nature; and the reproduction of birds of prey is relatively slow. This does not mean that one should not fight against predators who are used to catching pigeons, poultry, or with a hawk that disperses currents of black grouse in an organized hunting economy, etc. Feeding conditions are reflected in the geographical and stationary distribution of birds. In particular, this applies to those species that are stenophages, i.e., highly specialized in nutrition.

The African vulture eagle is found only where the kind of palm grows, the fruits of which it feeds on. Many birds that feed on certain plants, or in which a certain type of plant predominates in the diet, are found only where these plants are available. So, for example, the Scottish grouse is closely related in its distribution to wild rosemary, crossbills - with certain types of coniferous trees, honeysuckers, hummingbirds, etc. - with the presence of those plants whose nectar they feed on.

There are, in fact, few omnivorous birds: crows can serve as an example of them. In general, for each species of birds, a certain specialization is characteristic both in the choice of food and in the methods of obtaining it. Unfortunately, these issues have not yet been studied enough. Meanwhile, some certain substances, absorbed by birds at least in small quantities and occasionally, are apparently very important for the normal functioning of the bird's body. For example, in young birds of prey that do not receive bones, rickets develop and the normal course of molting is disturbed. For grouse, it is necessary from time to time to swallow needles, which probably serve to cleanse the stomach of worms.

Changing the external conditions that determine the conditions of nutrition is of great importance for birds. These changes have a particular effect in those regions where climatic changes are significant according to the seasons or where various kinds of meteorological conditions (snow cover, humidity, temperature, etc.) fluctuate greatly. The effect of temperature on the body's need for food in birds and the effect of light on the ability to satisfy this need have already been discussed above. Snow cover is also of great importance for ground-feeding species. Therefore, for example, many granivorous birds winter in Mongolia, where winters are very severe, but there is little snow. On the other hand, for example, in Lapland beyond the Arctic Circle, one can also meet in winter a rather diverse composition of small passerines: chickadees, great tit, pika, etc. These birds get food from trees and are less dependent on snow cover. For the same reason, birds that get food from cracks and other shelters or on vertical tree trunks in the bark, etc., for example, wrens, nuthatches and pikas already mentioned, do not fly away for the winter, but remain in the cold and temperate zones at home. Even in the conditions of the Arctic polar night, birds hibernate, if only they have the opportunity to get their own food. For example, off the coast of Greenland, the polar guillemot hibernates near polynyas and breedings at 77 ° and even 78 ° 30 "north latitude, near Svalbard - even at 80 ° north latitude. In the tropics and subtropics, the main climatic reason for changing the feeding conditions of birds is the onset of the dry season.

The disappearance of insects, the decrease in the number of insects, periodic changes in plant life - all these factors determine the diet of birds and, accordingly, affect their distribution.

If in some species these changes cause movements, then in others they are associated with seasonal changes in the diet. Partridges, for example, feed mainly on berries and insects in summer, berries in autumn, and willow shoots in winter. The raven in northern Siberia is omnivorous in summer, and feeds mainly on pied beetles in winter. Starlings feed mainly on insects in summer, in autumn and wintering, in addition, on fruits and berries. Many such examples could be cited.

Harvest and crop failure of fodder greatly affect the life of birds. Periodic quantitative fluctuations in the animal population and in the vegetation cover cause periodic fluctuations in the conditions for the existence of birds, for which certain animals and plants serve as food. These phenomena include the harvest and crop failure of fruits and berries, the abundance or scarcity of insects, the mass reproduction or extinction of rodents, etc. The mass appearance of food objects also causes the mass appearance of the corresponding species of birds, and vice versa. For example, when there is a bad harvest of mountain ash, waxwings migrate from Northern Europe in masses, and when there is a bad harvest of cones, crossbills, nuts, etc. More or less long-term changes in nutritional conditions sometimes cause changes in the boundaries of the distribution area. So, the house sparrow gradually settled, following the man, but the replacement of horses by cars caused a decrease in the number of sparrows at the northern border of its distribution - in Scandinavia and a strong reduction in its numbers in North American cities.

The influence of nutritional conditions on reproduction and mortality has already been discussed. Here we present only some figures. In Lapland, in the "lemming" years, the hawk owl has 11-13 eggs, the gray owl has 7-9 eggs, the eagle owl has up to 6, the long-eared owl- 7-9, for a snowy owl - 11-12. Even in the Lapland gyrfalcon in an exceptionally abundant year with lemmings near the city of Kautokeino in the north-east of Norway, clutches of 7-9 eggs were found. Second clutches in years rich in food in those species that usually have only one clutch have already been discussed.

On the other hand, in lean years, with a decrease in the number of rodents, predators feeding on them have a smaller number of eggs in clutches, and mortality among chicks is higher. Apparently, the consequence of poor feeding conditions can explain the phenomenon of cannibalism among the chicks of many species of predators - hawks, eagles and other birds, when the youngest of the chicks becomes a victim of the older ones.

The influence of feeding conditions on the reproduction of birds is especially noticeable in the north, where, in connection with this, periodic non-nesting is observed. Such fluctuations in numbers and "refusals" from nesting have been established in the Arctic for birds of prey and some waterfowl, and in other latitudes for many chickens (grouse, partridge, quail, pheasant, etc.).

Nutritional conditions undoubtedly underlie the emergence of bird flights, although, of course, the modern picture of this phenomenon is very complex and is apparently determined by a whole combination of external and internal causes. We will return to the issue of flights below.

We pass to the description of the cycle of phenomena in the life of birds, connected with reproduction.

The reproductive system of birds is characterized by the fact that the period of its activity in the vast majority of species is limited to a strictly defined time in the year, and at rest the size of the gonads is literally tens of times smaller than during the period of activity.

In the structure of the reproductive system of females, its asymmetry is characteristic: the right ovary, as a rule, is absent, the right oviduct is always absent. During the breeding season, the volume of the ovary increases greatly, and since the eggs in it are at different stages of development, the entire organ takes on a kind of grape-like shape. At the end of the laying of eggs, the ovary rapidly decreases, and its size reaches the size of the ovary of the dormant period even at the time when the bird is incubating. In the same way, in connection with the onset of the breeding season, the oviduct also increases in volume. For example, in a domestic chicken, the oviduct during the dormant period has about 180 mm in length and 1.5 mm in the lumen, during the laying period - about 800 mm in length and about 10 mm in the light. All departments of the oviduct at this time become more isolated than at other times of the year.

After the laying period, the oviduct collapses, the tubules of its glands are reduced, its lumen remains uneven and expanded in places. In a bird that did not lay eggs, the oviduct has the appearance of a smooth and thin tubule throughout its entire length. These differences in the condition of the oviduct can serve as a reliable sign in determining the age of autumn and spring birds.

A very characteristic adaptation to the breeding of offspring in birds is the development of the so-called mounted(hatching) spots(Fig. 11). The presence of these spots facilitates the heating of the masonry. The skin in the area of ​​the sores is characterized by a special looseness of the connective tissue; the fat layer here usually disappears; down, and sometimes feathers and their rudiments fall out; skin muscle fibers are reduced; at the same time, the supply of these places with blood is enhanced. A fully developed brood spot is a patch of bare and slightly inflamed skin. Each species of birds is characterized by a certain arrangement of perched spots; they are sometimes paired, sometimes unpaired. Passerines, petrels, guillemots have one spot, pheasants, waders, gulls, predators have two abdominal and one chest. The size of the nest spots is in a certain correspondence with the size of the masonry. Geese and ducks do not have mosquito spots; they, however, during the period of laying eggs develop a special long fluff, which is pulled out by the bird; with this down the incubating bird surrounds the eggs in the nest, and it serves as an excellent means of protecting them from cooling. Gannets do not have brood spots, but they warm the eggs by covering them from above with their webbed paws; guillemots and penguins put their paws under the eggs. These birds, apparently, have special arteriovenous anastomoses in their paws, which provide enhanced blood supply to these parts of the body. In addition, penguins have a special leathery protrusion, or pocket, near the cloaca, which is arbitrarily stretchable and allows the incubating bird to cover the egg with skin.

In addition to the changes just mentioned in the body of birds in connection with the breeding season, there are others, in particular, in many species a bright breeding outfit develops. The difference in appearance between males and females is denoted as sexual dimorphism.

The external signs of sexual dimorphism cannot fit into any general scheme. Penguins, petrels, copepods, grebes, loons, wrynecks, swifts, many bee-eaters and kingfishers do not differ between the sexes either in color or in size. Males and females of small passerines, most birds of prey, owls, waders, gulls, guillemots, shepherds and other birds differ only in size.

In other species, males differ more or less sharply from females in coloration. Usually the color of the male is brighter in those species in which the male does not take part in caring for the offspring. In these cases (ducks, many chickens), females often have a pronounced protective coloration. In those species in which males take care of the offspring (colored snipes, waders, some kingfishers, three-fingered, etc.), females are somewhat brighter than males.

Differences in color usually appear after reaching puberty, but sometimes even earlier (woodpeckers, passerines, etc.). In many forms that have two molts per year, color dimorphism is noticeable only at certain times of the year, namely during the breeding season.

The brightness of the color of males is especially characteristic of northern ducks (but not geese), many chickens (pheasants, francolins, capercaillie, black grouse), many passerines (the so-called birds of paradise, orioles, finches, redstarts, etc.). In related groups, the differences in coloration of the sexes are generally similar even in different species (in orioles, males are bright yellow or red, females are dull greenish with a longitudinally mottled ventral side of the body; in many finches, males have red colors that are absent in females, for example, in smurfs, crossbills, bullfinches, especially in lentils, etc.). Sometimes females develop a color similar to that of males (the so-called cock-feather color in grouse, in some passerines - redstarts, zhulans, etc.). In addition, with age, in females with functioning gonads, the appearance of features similar to the color of the male is sometimes observed; this happens, for example, in birds of prey (merlins, etc.).

Sexual differences in coloration are expressed not only in the color of plumage, but also in the color of other parts of the body (beak, iris, bare parts of the skin, even the tongue). In cuckoos, the color of males is of the same type (gray), females are dimorphic (in addition to gray color, there is also a red one).

Sex differences are expressed, in addition, in the presence of outgrowths and appendages of the skin on the head (for example, in chickens), in the development of individual feathers (Khokhlov, long tail coverts in peacocks, feathers on the wing and tail of birds of paradise, long tail feathers in pheasants, etc.), in the proportions, sizes and shapes of individual parts of the body, in the arrangement of internal organs (the vocal apparatus of many species, the throat sac of the male bustard, etc.), in general.

Males of gallinaceous birds develop spurs on their legs; males and females of many species have different beak sizes (for hornbills, ducks, scourges, some passerines, etc.).

As a rule, males are larger than females. This is especially pronounced in chicks and bustards. Other groups have more females than males. This is observed in those species in which males take care of the offspring (in phalaropes, colored snipes from waders, three-fingered, tinamous, some cuckoos, kiwi and cassowaries). A large size of females, however, is also found in those species in which the main part of the care for the offspring lies with the females (in most diurnal predators, owls, many waders).

We now turn to the description of reproduction in birds.

With the onset of spring, when revival begins everywhere in nature, the behavior of birds also changes. migratory species leave winter quarters and go to their distant homeland. Nomadic non-migratory birds also begin to approach their nesting sites. Sedentary species appear at nests. Not in all places and not in all species of birds this spring revival occurs simultaneously. The further south the territory is, the earlier, of course, the spring revival of nature occurs there.

For each bird species, spring revival is associated with the onset of special, favorable circumstances for this species. Sometimes it is even difficult to understand why one bird arrives early to the nesting place, and the other late. The bearded vulture, or lamb, living high in the mountains, begins to nest in the Caucasus and Central Asia as early as February, when everything around is covered with snow; such an early start of nesting is explained by the slow development of chicks. They appear in April, by July they only reach the size of adults, and until September they still remain with their parents and use their help. Consequently, the first months of life of young bearded vultures fall at the most favorable time in terms of temperature, nutritional conditions, etc. If bearded vultures started nesting later, then the rearing of chicks would end only in winter. For the same reasons, the gyrfalcons nesting in our far north sit on their eggs in the snow in early spring, otherwise they would not have had time to hatch the young before the onset of severe autumn weather.

The desert saxaul jay starts nesting in the Karakum desert very early, even before the appearance of a large number of insects and before the development of vegetation. This early date gives the desert jay an opportunity to bring out its young in relative safety. Its nest is easily accessible to the main enemies of the birds of the Central Asian deserts - various snakes and monitor lizards, but early nesting allows the jay chicks to learn to fly before the revival of reptile activity begins with the onset of heat.

The last example is the swift and the swallow. Both birds are excellent fliers and feed on insects, but the swift arrives late and leaves early, and the swallow stays with us much longer. The late arrival of the swift is explained by the fact that favorable conditions for feeding and rearing chicks for it come later than for the swallow. The difference in the device of the eyes allows the swallow to see well both in front of itself and on the sides, while the swift sees well only in front of itself. Therefore, the swift can only catch flying insects, and the swallow, in addition, can peck out or grab on the fly those insects that sit on buildings, trees, etc. The mass summer of insects falls on the warmest time, while sitting insects in large numbers can be found earlier and later. That is why the swift appears with us later than the swallow and flies away earlier.

Many birds form pairs for life; this includes large predators, owls, herons, storks, etc. Others form seasonal pairs (songbirds). There are, however, also such species which do not form pairs at all and in which all care for the offspring falls to the lot of sex alone. Most often, this sex is the female. This is how the summer life goes on for most of our chicken birds - capercaillie, black grouse, pheasant, as well as for the turukhtan sandpiper. However, among the phalaropes living in the north and among the three-fingered waders found in the USSR in the Far East, the male takes care of the brood. In the mentioned chicks and turukhtans, the males are brighter than the females. The opposite is true for phalaropes and three-fingered birds: in them, the female is taller and more elegantly feathered than the male. Birds that form pairs are called monogamous, not forming a pair - polygamous.

The behavior of birds during the mating season, which usually falls in the spring months and early summer, is distinguished by a number of features. Many birds also change their appearance at this time. A number of birds change part of their plumage by spring and put on their mating attire, which usually differs from the autumn one in bright colors.

In some species, males lek, that is, they take special poses that are conspicuous from a distance, and make special calls. Such display is especially well expressed in chicken birds - black grouse, capercaillie, white partridge, and some waders. Other birds in the spring make peculiar movements in the air - soar high up, fall down, soar again, while uttering loud cries. Such a courtship flight is performed, for example, by birds of prey; the spring draft of woodcocks and the spring "bleating" of snipes have the same meaning. In small passerine birds, males sing during the mating season, enlivening with their singing both inhospitable deserts, harsh tundras, and human settlements. The spring "dances" of cranes, and the cuckoos' cuckooing, and the spring drumming of woodpeckers, and the cooing of pigeons belong to the same phenomena.

Each species of bird is characterized by a certain and different behavior in spring - voice, posture, etc. Each songbird - nightingale, starling, chaffinch - sings in its own way. Showing, therefore, applies only to other individuals of the same species and serves as a certain signal for them. These signals are by no means always directed to individuals of the opposite sex. For a long time it was thought that the singing of male birds refers only to females and attracts them. In fact, this is not so. The meaning of singing is primarily to show other males of the same species and possible competitors that the nesting territory is occupied. Birds in the spring, as you know, jealously guard the places they occupy (nesting sites) and expel all other individuals of the same species from them. The nesting area is especially zealously protected during the most "responsible" periods, immediately before laying eggs in the nest and during incubation.

Interesting observations were made in England. A weasel appeared near the nest of the reed bunting. The male and female bunting began to fly around her screaming and tried to drive her away. Another reed bunting flew up to the noise, and the disturbed couple, leaving their caress, began to chase the bunting. This scene was repeated three times in a row.

The value of displaying also lies in the fact that it expresses and enhances the excitation of the displaying bird and individuals of the opposite sex. This is the only meaning of mating in those species that do not form mating pairs (grouse, black grouse, turukhtans).

The center of the bird's nesting area is nest- the place where the female lays her eggs. However, not all birds build nests for themselves. In the north of the USSR, for example, on islands in the White Sea, on Novaya Zemlya, as well as on the Chukotka Peninsula, on Kamchatka, on the Commander Islands, sea birds (guillemots, guillemots, auks) nest in huge numbers, forming clusters of many thousands, the so-called " bird markets"But they don't actually make nests, and each female lays her egg right on the ledge of a rock. The nightjar and the avdotka don't make nests: they lay their eggs right on the ground. Some birds only clear a place for laying and sometimes still make a simple litter of dry grass, moss, feathers, etc. This is what pheasants, capercaillie, hazel grouses, white partridges, black grouse, waders, most owls, some predators, and also those birds that breed chicks in hollows - woodpeckers, wrynecks. Most birds, however, build nests, while each species is characterized by a certain manner of arranging a nest and choosing certain materials for its construction. Young birds, who have never seen how a nest is built, arrange it in the same way as their parents.

Most often, nests are made of branches, grass or moss; these nests are either folded or woven, and special additional materials are often used to fasten them and lining them. Thrushes weave a nest of stems and coat it with clay. The finch makes a nest of moss, masking it with lichen. The Remez tit skillfully weaves a nest of wool in the form of a purse with a long side corridor. Small birds nesting on the ground (larks, wagtails) build grass nests or line a depression in the ground with grass.

Birds of medium and large size build nests from large twigs and branches. Some birds have several nests, in one of which they nest, while others serve as spares. In large birds of prey (eagles, eagles), the nest serves for many years in a row and, as a result of amendments and add-ons, turns over the years into a huge structure up to 2 m in height and across. Such nests usually eventually fall to the ground during storms, because the bitches that serve as their support cannot withstand their weight.

The inside of the nest is usually deepened, and the edges are raised; recessed part of the nest tray, or tray, serves to place eggs and chicks.

Some birds make stucco nests. Flamingos make their nests out of silt in shallow water. Rocky nuthatches living in the mountains build their nests out of clay. The barn swallow builds a saucer-shaped nest of clay and mud glued together with saliva under the roofs. The city swallow, or funnel, arranges a nest closed from above with a roof made of the same materials.

Some birds nest in burrows. In kingfishers, a zigzag path breaks through between roots in earthen cliffs on the banks of rivers; this passage leads to a cave, the bottom of which is lined with fish scales. Sand martins nest in colonies along river banks. Their nests are difficult to access, as a narrow passage leads to them, sometimes reaching a length of 3 m. Pink starlings, shelducks, rollers and bee-eaters nest in minks.

Finally, the oystercatcher found along the sandbanks of rivers in Turkmenistan simply buries its eggs in the hot sand. This method of nesting is somewhat reminiscent of the weed-hens, or big-legs, living in Australia and on the islands southeast of Asia. Weed chickens lay their eggs in huge heaps of sand or rotting plants, these heaps sometimes reach 1.5 m in height and 7-8 m in a circle. The eggs here are well protected from cooling, and the embryo's own heat is enough for its development.

A place for building a nest in those birds that actively defend their nesting site, that is, in passerines, nightjars, some waders, etc., is found by the male, who, moreover, usually returns from wintering or migration earlier than the female.

The number of eggs in a clutch for each bird species varies within certain limits. More or less of them depends on various reasons. In many species, in years that are favorable in terms of temperature, and especially in terms of nutrition, the number of eggs in the clutch is greater than in bad years. This has been established for many owls, gallinaceous owls, and others. In especially unfavorable years, such birds do not nest at all. The age of the bird is also of some importance. In predators, ravens, old females apparently lay fewer eggs than young ones. In chickens, the opposite is true: in the first year, females lay fewer eggs; fewer eggs are laid by young females of some passerines, such as starlings. Due to different nesting conditions in the same species of birds, the number of eggs in the clutch in the north and in the temperate zone is greater than in the south. For example, in an ordinary wheatear in Greenland, the number of eggs in a clutch is 7-8, in the European part of our country - 6, and in the Sahara - 5. A large number of eggs in a clutch in the north is, as it were, insurance against adverse climatic conditions, and also corresponds to the great opportunities for feeding chicks in the north (long day and almost round-the-clock activity of insects).

Always one egg in a clutch occurs in some predators (for example, in the short-toed eagle), in the oystercatcher, in the tube-nosed, and in many guillemots. Nightjars, pigeons, cranes, flamingos, pelicans, gulls, terns have 2 eggs in a clutch. In waders and quails, the usual and maximum number of eggs in a clutch is 4. In small passerines, the number of eggs in a clutch is 5, often 4, 6, and 7; it happens even more, for example, the great tit has up to 15, the long-tailed tit has up to 16. Of the ducks, the largest number of eggs in the teal is 16, of the chickens in the gray partridge - 25. The usual number of eggs in a clutch of chickens and ducks is 8-10.

The color and shape of bird eggs are very diverse (Tables 1 and 2). In some, such as owls, the eggs are almost round, in others they are elongated. One end of the egg is usually wide, the other narrower. The narrowing of one end of the egg and the expansion of the other are especially pronounced in various guillemots nesting in colonies in the north. In those birds that lay their eggs in closed nests, in hollows and burrows, or cover their eggs, the color of the shell is white. White eggs in owls, kingfishers, rollers, woodpeckers, many passerines. In birds nesting in open nests, and even more so on the ground, the eggs are variegated, and their coloring is very reminiscent of the color of the surrounding landscape. You can go two or three steps to a laying of some sandpiper or partridge lying on the ground and not notice it. Shell thickness varies greatly. Birds nesting on the ground have the relatively thickest shells; this is understandable, since their eggs are at greater risk (of course, this refers to the relative thickness of the shell in accordance with the size of the egg). Of our birds, the francolins belonging to the chicken birds have the thickest shells.

Table 2. Bird eggs: 1-8 - common cuckoo(1, 3, 5, 7) and small passerines - "host" birds (2 - thrush-like, reed warbler, 4 - red-eared bunting, 6 - common redstart, 8 - garden warbler); 9 - small cuckoo; 10 - short-tailed warbler; 11 - ordinary oatmeal; 12 - black-headed warbler; 13 - remeza oatmeal; 14 - polar bunting; 15 - snow bunting; 16 - field lark; 17 - white wagtail; 18 - grosbeak; 19 - common starling; 20 - fieldfare; 21 - messes; 22, 23 - shrike; 24 - thick-billed warbler; 25 - hawk warbler; 26 - blue stone thrush; 27 - song thrush; 28- common remez; 29 - great tit; 30 - jackdaws; 31 - crows; 32 - crow; 33 - magpies; 34 - jays; 35 - common pika; 36 - yellow-headed beetle; 37 - chaffinch; 38 - barn swallow; 39 - wren; 40 - field sparrow; 41 - deaf cuckoo; 42 - house sparrow; 43, 44 - forest horse; 45 - common tap dance; 46 - meadow coinage; 47 - willow warblers; 48 - chiffchaff-shade-forging; 49 - common nightingale; 50 - saxaul jay; 51 - rocky nuthatch; 52 - common lentils; 53 - carduelis; 54 - hawks; 55 - gray flycatcher; 56 - long-tailed flycatcher; 57 - broad-tailed warbler; 58 - bullfinch; 59 - waxwing; 60 - scura; 61 - spruce crossbill; 62 - African black-headed oriole; 63 - common oriole; 64 - woodcock; 65 - a large curlew; 66 - brown-winged plover; 67 - common turtledove; 68 - rock dove; 69 - oystercatcher; 70 - forest snipe; 71 - blue magpie; 72 - lapwing; 73 - small plover; 74 - Khrustan; 75 - blackie

The size of the eggs depends on a number of reasons. Small birds in comparison with their own weight carry rather large eggs, large birds - small ones. The more eggs in a clutch, the smaller the relative size of an individual egg. Finally, those birds in which the chicks leave the nest well developed and capable of independent movement and foraging lay relatively larger eggs compared to those in which the chicks are born helpless. Very small eggs are laid by the cuckoo, this is probably due to the fact that she does not incubate them herself, but throws them into the nests of small birds. Both cuckoo and snipe weigh about 100 G, but a snipe egg weighs about 17 G, cuckoo egg - only about 3 G.

Interesting data on the ratio of the bird's body weight, the weight of an individual egg and the weight of the entire masonry.

In some birds, the weight of the clutch even exceeds the weight of the body of an adult bird: in a chauffeur, when laying 12 eggs, it is 125% of the bird's weight, in a carrier oystercatcher, 117%, in a kinglet, when laying 11 eggs, 120%, and in a goldeneye duck, when laying 12 eggs, 110%.

Both parents sometimes participate in incubation of eggs - male and female (for example, in many predators), sometimes only the female. The latter refers to those species in which the male and female already live separately during incubation, such as capercaillie, black grouse, pheasants, ducks. Both sexes usually incubate when their coloration is similar, however, there are exceptions. In most passerines, only the female incubates. Finally, in the three-fingered and phalaropes, only males bear all the worries about the offspring.

Hatching is a very dangerous time in the life of birds. A bird sitting on a nest can easily be attacked by various enemies. Birds nesting on the ground can be especially easily affected. Therefore, females, on whom most of the worries about laying and chicks fall, in many species are painted to match the color of the surrounding area. The females of the white partridge, pheasant, little bustard, sitting on their eggs, completely merge with the soil and vegetation surrounding them. At the same time, it must be borne in mind that the incubating bird is less cautious and, especially at the end of incubation, flies off the nest very reluctantly - only at the very last minute, so the value of such a color in harmony with the landscape is very great. The incubating bird feeds less than usual, especially in those cases when the male lives separately at this time. Therefore, the incubating bird usually grows thin and loses a lot of weight.

The duration of incubation in individual species of birds is very different. It depends on the temperature of the environment, the body and the duration of breaks when the nest is left by the incubating bird, partly on the size of the egg compared to the size of the bird. A longer period of incubation occurs in those species that nest closed - in minks, hollows, etc. Small passerines incubate on average about 15 days. Large predators sit on their eggs for a very long time - about one and a half months.

Birds begin to incubate in different ways, some immediately after laying the first egg (predators, owls, storks, gulls, swifts, hoopoes, loons, grebes, from passerines - crows and crossbills). In such birds, there are great differences in the development of individual chicks, and in the "mouse" years in the nest of a snowy owl in the tundra you can find an egg, a newly hatched chick and large owls putting on a transitional outfit. Chickens, ducks, geese, and most passerines incubate the clutch only after all the eggs have been laid, and their chicks develop more evenly. Finally, there are birds in which incubation begins after more than half of the eggs have been laid (woodpeckers and shepherds). When one egg is removed from the clutch, some species of birds (for example, gulls, skuas, waders) supplement the clutch. With the death of the entire clutch, many birds make a second, additional clutch, unless incubation has gone too far. The use of chickens in poultry farming is based on this property of birds (the egg-laying of domestic chickens reaches 350 eggs per year). By taking eggs away from a bird, it is possible to force it to lay very intensively (in such experiments, the little bird was forced to carry up to 62 eggs).

Many small birds normally have two or even three clutches in summer. Additional and second clutches, if they occur towards the end of summer, contain fewer eggs than the first clutches. But in those birds in which the first clutch is very early, when spring is just beginning and the conditions for growing and feeding the young are less favorable than for the chicks that hatch later, there are fewer eggs in the first clutch than in the second (thrushes, Muscovy tit, larks, common bunting).

According to the methods of development of chicks, all birds can be divided into two categories: some are called brood, other - chicks(Fig. 14).

Nestlings of brood birds immediately or after a very short time after leaving the egg leave the nest and can move independently. They leave the nest with open eyes and ears, in a well-developed downy outfit. This group includes those birds that stay mainly on the ground or near the water, but not on trees: ducks, geese, shepherds, bustards, cranes, loons, grebes, gulls, sandpipers, sandgrouse, flamingos, three-fingered.

Young chicks emerge from the egg with underdeveloped limb musculature, naked or slightly pubescent, often blind and deaf. They do not yet have a constant body temperature, and in this respect they resemble the lower vertebrates. These chicks are thus completely helpless and spend the first days or weeks of life in the nest until they develop plumage and can move independently. It can be said that the chicks of brood birds emerging from the eggs correspond in their development to the chicks of the period when the latter are ready to fly out of the nest. Nestling birds include, for example, passerines, woodpeckers, cuckoos, hoopoes, swifts, pigeons, rakshas, ​​kingfishers, copepods (pelicans and cormorants), as well as raptors, owls and tube-nosed birds.

In young chicks, the color of the mouth and its edges is very characteristic - usually bright (yellow or pink).

Brood care in brood and nestling birds also has a different character. Brood adult bird, in which the young are composed (in some species, the male, in the majority - the female, less often part of the brood is with the male and part with the female, as is the case with grebes and cranes), leads the brood, guards it, covers it with its body when unfavorable weather occurs (cold, rain), finds and indicates food to the chicks. However, little ducklings immediately begin to find their own food on their own. In some waterfowl chicks in the first days of life, when tired, they sit on their mother's back, and grebes keep the chicks under their wings when swimming and even diving.

The relationship between parents and offspring in nestling birds is more complicated. In cases where both sexes participate in incubation, or when the male feeds the incubating female, both parents feed the chicks together, but the nature of their participation in feeding is not the same. At first, in birds of prey, the prey is caught mainly by the male, and the female feeds the chicks, tearing the prey into pieces. When the chicks grow up and begin to tear their prey themselves, both parents carry food to them. It has already been noted that rearing chicks requires great effort from old birds.

Feeding chicks with food in different species occurs in different ways. Insectivorous birds give food to only one chick upon arrival at the nest (with rare exceptions), meat-eating and granivorous birds give food to the entire brood. The sequence and uniformity of feeding of chicks in granivorous is ensured by the movement of "fed" and "hungry" chicks in the nest. Fed chicks usually move to the edge of the nest and defecate, raising their tail high; in their place, hungry ones move into the middle of the tray.

Adult birds clean the nest of all impurities (only pigeons and hoopoes do not do this) and warm the chicks, covering them with their bodies. Since overheating is no less dangerous for chicks than cold, the parents shade the nest at hours when the direct rays of the sun fall on the brood; an adult bird stands above the nest and slightly opens its wings. Many predators shade their chicks with green tree branches.

In nesting birds, the chicks usually leave the nest after they have learned to fly.

In different species of birds, the timing of the stay of chicks in the nest is different. In small passerine birds, the period of a chick in the nest from leaving the egg to emergence is about two weeks or more (for the blue tit 18 days, for the kinglet 18-19 days, for the robin 15 days, for the wren 17 days), i.e. approximately coincides with the period of incubation. In large species, development is slower and not only absolutely, but also relatively. The raven incubates for 21-22 days, and the chick sits in the nest for 50 days. The red-throated loon incubates for 38-40 days, and the ability to fly occurs only in a 60-day-old chick. In passerine birds, nestlings of forms nesting on the ground most likely develop (the lark flies out of the nest on the 9th day after hatching, the nightingale - on the 11th), while the chicks of the nuthatch nesting in hollows sit in the nest for 25-26 days, the great tit chicks - 23 days, starling chicks - 21-22 days. Species nesting in the north also develop rapidly: the Lapland plantain flies out of the nest after 10 days.

Parents continue to feed the chicks for some time after they leave the nest. Departure from the nest is also associated with the complete development of the plumage, which replaces the nestling's downy clothing.

Chicks reach full growth in the first autumn of life. The vast majority of birds, with the exception of some large species, begin to nest already at the age of about a year, that is, in the next spring. Even those birds nest, which by this time wear plumage that differs in color from the plumage of adults (for example, a falcon, a hawk). Interestingly, the weight of the chicks immediately before leaving the nest is often greater than the weight of young birds in the following months. This is because exercise in motion and solo flight sometimes cause a young bird to shed fat stores.

How many years do birds live? There is relatively little information about their lifespan in natural, natural conditions. A well-known idea of ​​the longevity of birds is given by the results of their marking and ringing, as well as observations of the life of birds kept in captivity. At the same time, it is necessary to distinguish between the maximum possible from a physiological point of view, the potential life expectancy and the real, average, existing in nature, where there are various reasons that limit the life of a bird: adverse weather (meteorological) and food conditions, the activity of all kinds of predators, and finally, diseases.

Generally speaking, large-sized birds have a longer lifespan than small ones. A definite relationship between life expectancy and reproduction characteristics (fertility, type of development - nestling or brood) in birds could not be established. Finally, there are differences in life expectancy among different systematic groups of birds. It can be noted that small passerine birds live relatively longer than small mammalian species.

The English zoologist Flower calculated (1925-1938) the average life expectancy of birds living in the London and Cairo Zoological Gardens, and came to the conclusion that within the same order it varies relatively slightly. According to his calculations, average duration the life of crows and cockatoo parrots is 20 years, owls 15 years, diurnal birds of prey 21-24 years, copepods 20 years, ducks 21 years, herons 19 years, waders 10 years, gulls 17 years, ratites 15 years, pigeons 12 years, chicken 13 years.

For domestic chickens, life expectancy is noted, of course, as an exception, 24, 25 and even 30 years. (However, signs of aging - a decrease in fertility - are noted in Leghorn layers already after 3 years of life.)

A few figures on the potential lifespan of birds kept in captivity. From the order of passerines, the age of 60 and even 69 years was noted for the raven, from small passerines for the garden warbler - 24 years, for the blackbird and robin - 20 years, for the skylark - more than 20 years. From the detachment of owls, eagle owls lived to 34, 53 and 68 years. Parrots are also long-lived: for the red macaw, the age of 64 years is noted, for the cockatoo - more than 56 years, for the Jaco parrot - more than 49 years. For diurnal predators, the following data are known: the buffoon eagle lived 55 years, the condor 52 and more than 65 years, the golden eagle 46 years, and according to other, but not very reliable information, more than 80 years, griffon vulture more than 38 years. Of the Anseriformes, Canada Goose lived for more than 33 years, Lesser Swan 24 1/2 years. Of the cranes, the Australian crane lived for 47 years, the gray crane for 43 years, the antigone crane for 42 years. African heron shoebill lived 36 years. Herring gulls lived to over 20 years of age, and one even to 49 years. The pink pelican lived to be 51 years old. Some pigeons have lived for about 30 years. Ostriches milked up to 40, emus up to 28 years.

Other data on the age of birds are obtained as a result of ringing. A few numbers related to Soviet Union, are. Turukhtan, ringed as an adult, was taken at the age of 9, oystercatcher - at 14 years old, black-headed gull - at the age of 16 years, sea dove gull - at the age of 20 1/2 and 21 1/2 years, common tern - at the age of 16, 17 and 18 years, arctic tern - at the age of 13 and 14 years, black-throated loon - aged 17 1/2 and 22 years. Despite the significant mortality of ducks as a result of hunting for them, there are cases when mallards ringed by adults lived to 18 and 20 years; broad-nosed duck - up to 20 years. The lifespan of an eider is set at 12 years. The loaf heron lived to be 20 years old, the bittern - up to 9 years, the stork - up to 11 years. Ringed by chicks, kites lived to be 12 and 15 years old. The field harrier was caught at the age of 13. The gray crow, marked with a chick, lived to be 14 1/2 years old, the starling - up to 12 years, the pink starling - up to 11 years, the thrush warbler - up to 8 years, the black swift - even up to 9 years. In other countries, ringed small passerines were caught at this age: house sparrow - 11 1/2 years, robin - 10 1/2 years, gray flycatcher - 12 1/2 years, killer whale - 9 years. These figures are, of course, not limiting.

However, in a natural environment, the natural mortality of birds significantly limits life expectancy and they can reach the "limiting" age only as an exception. The mortality of young birds during the first year of life is especially significant. In particular, in passerines it apparently exceeds 50% (naturally, with fluctuations by year and by species). For example, in the pied flycatcher, the mortality rate of first-year-olds is 60% of their total number, and in the redstart - even up to 79%. Of the 77 killer whale chicks ringed in the same area in the GDR, 51 disappeared in the first year, 17 in the second, 6 in the third, 2 in the fourth, and only one survived to the age of five. In the American wren, up to 70% of adults and up to 74% of young first-year birds die during the winter.

Similar phenomena occur in other birds. For example, among emperor penguins in harsh Antarctica, the mortality rate of young in unfavorable years reaches 77%. Of the peregrine falcons ringed in the GDR, 44 were killed at the age of one year, 10 at the age of 2 years, 4 at the age of 3 years and only 2 at the age of four. Of the 669 ringed common buzzards taken in the GDR, 465 were taken in the first year of life, 111 in the second, and only 93 were older. Wilson's storm petrel on Graham Land in Antarctica kills up to 65% of chicks in nesting burrows, mainly due to snow blockages. In the common tern, up to 95% of young die in the first year of life, but the average mortality rate of terns that survive the first year of life in all ages is only 17.2%. At the same time, the average age of birds in the nesting colony (excluding young ones) is 3-5 years.

Water birds, especially colonial ones, have a higher average age than passerines, and the natural mortality of adults is relatively lower.

Of the other general questions of the biology of birds, which are in a certain connection with the phenomena of reproduction, it remains for us to dwell on molting and migration.

Necessity molting, i.e., the periodic change of plumage, is explained by wearing and fading of the feather. Under the influence of the sun, moisture, dryness, the color of the feather changes: black becomes brownish, dark brown - pale brown, gray - brownish-gray, etc. Even more important is the erasure of the edges of the feather, accompanied by a violation of its structure, since small cohesive beards are partially destroyed. The weakly pigmented or non-pigmented parts of the feather are especially worn. These changes are also more significant in the most important elements of the plumage during flight - fly and tail feathers. Feather wear adversely affects the flying properties of the bird.

The most intense molting in adult birds occurs after the end of the breeding season. The alternation of the processes of reproduction and molting can be partially explained by the fact that both of them require the expenditure of a large amount of energy and therefore can hardly occur simultaneously in the body of a bird. The normal course of molting requires good nutrition of the body, a weakening of nutrition causes a slowdown in the course of molting and irregularities in the structure of the feather (transverse impressions appear on large feathers that go along the fan and make the feather fragile).

While the feather has not yet reached half of its normal length, its growth is rapid, and then slows down. In small birds, feathers grow more slowly than in large ones. In a sparrow, the secondary primaries grow at a rate slightly greater than 4 mm per day, in the saker falcon the daily increase in primaries in the last period of growth is 6-7 mm in a day.

Each species of bird molts at a very specific time and in a specific sequence. Birds belonging to the same family, order, usually have the same course of molting, and it thus serves as one of the systematic characters of groups.

With regard to the change of flight and tail feathers, there are known general patterns. The tail feathers change either centripetally, i.e. from the extreme pair to the middle one, or centrifugally, that is, from the middle pair to the extreme one, or, finally, as is the case with woodpeckers, the molt starts from the pair adjacent to the middle tail ones, goes to the edge of the tail, and ends with the central steering ones. The secondaries usually molt concentrically, i.e., the molt begins with the outermost feather and ends with the middle feathers, or centrifugally. The molting of the primary flight feathers ends with the change of the front (second and first) feathers; it begins in some species from the middle feathers (from the seventh) and goes to the inner (proximal) edge of the row, i.e., the eighth, ninth, tenth, and then the sixth, fifth, fourth, third, etc .; in other species, the primary fly feathers are replaced in a row - the tenth, ninth, etc. In some species - loons, ducks, geese, swans, flamingos, cranes, shepherds, guillemots - fly feathers fall out simultaneously or almost simultaneously, and the bird for some time (ducks for 21-35 days, swans - up to 49 days) loses the ability to fly. In some birds, molting begins with small feathers, in others - with large ones, although in general the change of small and large plumage coincides, but the change of the anterior primary feathers, as the most important feathers in flight, usually occurs at the very end of the molt, after the other parts of the plumage are fully developed.

The various types of molting in birds can be broadly described as follows. When emerging from the egg, the young bird is dressed fetal down, which is replaced by the first outfit of contour (definitive) feathers. This (first) outfit of contour feathers is called nesting. Often it is distinguished by a special color (often similar to the color of females), softness and less density of the feather, as well as a greater width, and sometimes the length of the tail and flight feathers. The nesting outfit of the birds is worn for a different time - from several weeks to 16-18 months. For many passerines, its change is post-nesting molt takes place at the end of summer. In pigeons, rollers and owls, it occurs in the first autumn. Birds of prey begin to molt at the age of about one year - sparrowhawks around May, golden eagles - in April, peregrine falcons - in March and May; their molting ends in late autumn or early winter, so that they nest while still in their nest plumage with a small admixture of feathers from the next plumage. Many waders, as well as shepherds, hens and grebes molt, changing their nesting outfit, in autumn or winter at the age of 5-8 months; herons molt later, in spring; at the age of 8-10 months, tube-nosed birds replace their nesting outfit. In ducks, post-nesting molting begins in September and ends in winter or even by spring.

Post-nesting molting sometimes leads to a change in the entire plumage and is then called complete, or with it only part of the plumage (small feathers) is replaced, and then it is called partial. An example of a partial post-nesting molt in passerines is the molt of the families of crows, finches, wagtails, titmouses, flycatchers, warblers, and thrushes. For example, in a white wagtail at the age of about 2% of the month, coverts of the head, body, lesser and middle wing coverts, part of the greater wing coverts, inner secondary flight feathers, and sometimes the middle pair of tail feathers are replaced. However, the volume of such partial molting is different in different genera. In other passerines (larks, starlings, etc.), the post-nesting molt is complete. After a complete post-nesting molt, the bird puts on an outfit that will be worn for a year and changed or once a year and completely - this is the so-called annual outfit(falcons, hawks, starlings, larks), or (which is rare) will be replaced twice a year (the so-called premarital attire common black grouse, city swallow).

With a partial post-nesting molt, subsequent molts can cover the entire plumage. Then the outfit worn by the bird as a result of post-nesting molting is called combined annual outfit(since in it large plumage, in particular flywheels and rudders, remains from the nesting plumage); such an outfit is worn, for example, by crows, tits, common bunting, mountain bunting (but not all buntings). If the outfit, worn as a result of partial post-nesting molting, will then be replaced twice a year, then it is called combined premarital attire(flycatchers, wagtails, many warblers).

Further molts go like this. The annual outfit is replaced as a result of molting, which usually occurs in late summer - early autumn. This line is called annual molt. In the event that the color of the annual plumage put on as a result of the post-breeding molt differs from the final coloration of adult birds (this happens, for example, in large gulls, eagles and sea eagles), the corresponding annual plumage is marked as transition. If three or four years pass before the final attire is obtained, then we have with the corresponding bird first transitional annual outfit, second transitional annual outfit etc.

The change of the wedding attire, as well as the change of the annual attire, takes place in late summer - early autumn. Subsequent molts are already regularly following this pattern. Birds wearing an annual outfit change it once a year as a result of an annual molt. In forms that molt twice a year, the intermarital or post-nuptial attire, as a result of the mating molt, is replaced by the combined mating, then the post-nuptial molt occurs, etc.

In many cases, molting brings with it a change in color. Sometimes, by spring, a change in color in birds is obtained even without molting, as a result of fraying of the edges of the feathers and the protrusion of bright flowers that were covered by the edges of the feathers (for example, in small finches, buntings, etc.). But no repainting of the grown pen - a physiologically dead formation, contrary to the opinion of the old authors, does not occur and cannot occur. The marriage attire is usually brighter than the intermarital attire, and the sex differences in it are more pronounced. The process of molting reaches the greatest complexity in the white partridge, in which four outfits can be distinguished per year: two of them (spring and winter) correspond to mating and intermarital, and summer and autumn have no analogies among other groups of birds.

Different animals react differently to adverse environmental changes, such as a decrease or increase in temperature, snow cover, and a decrease in the amount of food. With such changes, many animals reduce their vital activity, become inactive, hide in various kinds of shelters, and finally fall into a state of stupor, the so-called hibernation. This happens in reptiles and even in many mammals.

Birds are another matter. Their body reacts to the above changes in the environment by increasing activity. This specificity of the activity of the avian organism finds its most striking expression in seasonal flights, or migrations(Fig. 15). Many hypotheses, often contradictory, have been put forward about the origin of flights. In general, based on the data of the modern picture of flights, our information about the climates of past geological times, etc., it can be assumed that the origin of this phenomenon cannot be associated only with the events of the so-called ice age, when glaciers that spread widely on the continent of Europe and Asia made the northern hemisphere unsuitable for the habitation of many species of birds (and other animals).

Flights arose as a result of periodic changes in climatic conditions associated with the change of seasons. They apparently also existed in Tertiary times, before the onset of the great glaciation. This is indirectly indicated by the existence of regular flights of many bird species in tropical and subtropical zone. The Quaternary glaciation, of course, influenced the pattern of bird migration in the northern hemisphere, but it was not the cause of their occurrence. At the same time, it must be remembered that the unevenness of glaciation, the movement of centers of glaciation in the meridional direction (which caused a difference in climate not only along the north-south line, but also along the west-east line) had a very difficult effect on changes in the nesting areas and wintering areas of birds and created in many places an environment convenient for nesting, but not for a settled way of life. The long northern day was, of course, always favorable for rearing offspring, and the intensity of lighting in the north for local bird species was necessary condition normal development of the genital organs during the breeding season. The general retreat of the glaciers, which created a more favorable climatic situation and thus stimulated reproduction, caused the birds in the northern hemisphere to occupy new nesting territories, which, however, had to be periodically vacated due to large differences between the seasons. It can be assumed that the territory and directions of migration in most cases reflect the path of introduction of the bird into a given nesting area. The general scheme of the phenomenon of flights in the historical perspective is reduced to the adaptation of the bird organism to cover large distances in order to find the most favorable territories for its existence, and in spring the incentives associated with reproduction predominate, and in the autumn - incentives associated with nutrition. The immediate causes of flights have to be considered a complex interaction of both external and internal factors. It is impossible to reduce all phenomena to only one of these causes, as many do. Feeding conditions (associated with the deterioration of conditions for obtaining food, a decrease in the number of prey, a reduction in the daylight hours, etc.) can undoubtedly explain the autumn departure to a certain extent. However, this phenomenon stands in connection with the onset of certain physiological changes in the body, accompanying the end of the reproduction period.

The influence of external conditions on the state of the organism of birds has been repeatedly mentioned above. Here it is useful to recall that the birds living all year round in monotonous and rather favorable conditions, they lead a settled way of life. It can be considered that the stimuli for flights are fluctuations in the nutrition of the body periodically caused by changes in external conditions, inextricably linked with certain phases of the annual activity of the gonads. Since the frequency of nesting cycles for birds is hereditary, the very desire to fly must be innate in some forms. Of great importance here is the question of "attachment" of birds to the nesting territory and competition.

The specific phenological situation does not determine the beginning of flights, although, of course, it affects their course. Wind, for example, matters, especially strong winds in the opposite direction of the flight. In general, however, the autumn departure of birds coincides with the end of the breeding season, but does not always immediately follow it. An intermediate stage for many species is the formation of flocks and migration. As a rule, areas with a cold climate are occupied later in the spring and left earlier by birds in the fall than warmer ones. In some species, females fly earlier than males; others have the opposite; in most species, both sexes fly at the same time. Often in autumn, young birds fly away earlier than old ones. The order of bird migration is also different; some species fly during the day, others at night, some silently, others emit characteristic cries (crowling of cranes, cackling of geese, etc.). At night, usually those species that are forced to expend a lot of energy during the flight fly, this requires enhanced feeding during the day. During the day, well-flying forms fly, which can largely make do with the energy reserves accumulated in the body during flights. It is known that before the flight, the birds are usually very well-fed. The autumn formation of reserve energy sources (fats, glycogen, protein) is associated not only with increased nutrition, but also with the extinction of the activity of the gonads.

The study of bird migration by ringing has conclusively proven that for every bird and for every bird population in a given area, flights occur between the nesting site and the wintering site, and, as a rule, the bird returns in the spring to the same place where it hatched or nested in the previous year. This is closely related to the repeatedly observed conservatism of birds with regard to the choice of habitat. Wintering places are strictly defined in the same way. Of course, there are individual deviations from this general scheme, but these are exceptions.

The ecological situation of a particular area determines, of course, its suitability as a wintering place, but the wintering place will not always be the closest ecologically favorable area to the nesting place. Probably, competition in the form of occupation of the nearest areas convenient for wintering by other populations of this species is also important here. For example, perhaps this is precisely why the northern forms of one species often winter to the south than the subspecies of the same species nesting in the middle zone, etc. To explain the occurrence of distant winterings, one has to involve historical reasons as well. This can be seen, for example, in the course of flights of dispersing species. The green warbler, which has spread westwards in recent decades, still winters in Southeast Asia; so does lentils; the warbler from Scandinavia flies to India for the winter; on the other hand, the horned lark, which has recently settled in the northern part of Scandinavia, began to winter in England.

Favorable climatic conditions largely determine the suitability of a particular area for wintering. Therefore, for example, in Europe, many migratory birds fly not only in the south, but also in the west. England, with its mild winters and light snowfalls, for example, provides shelter for many Central European and North European birds - passerines, woodcocks, lapwings, etc. Southwestern Europe and especially the Mediterranean attract even more birds. Huge concentration of birds in the Nile Valley. African wintering areas are generally very plentiful, with 76 European bird species reaching the Cape. Some Siberian and Arctic birds also fly here.

In Western Europe and North Africa, many of our game birds winter - waterfowl and quail (which, unfortunately, suffer greatly from the disorder of hunting in the Mediterranean countries).

In India, in the south of China, on the islands of the Indo-Australian archipelago, there are massive wintering grounds for many northern and arctic birds. On the territory of the USSR, masses of waterfowl winter in the South Caspian, where the Kyzyl-Agach named after A.I. S. M. Kirov and Gasan-Kuli nature reserves (the first in Lankaran, the second in the lower reaches of the Atrek in Turkmenistan). In the form of a scheme, it can be assumed that most of the northern birds nesting west of the Yenisei fly southwest in autumn (many of them winter in India); birds from Trans-Yenisei Siberia fly mainly to Southeast Asia, skirting the inhospitable Central Asian deserts and mountains. Some birds go even further, reaching, as East Siberian godwit and Icelandic sandpiper do, New Zealand. In America, unlike in Europe, the influence of the Gulf Stream does not cause fly-by traffic to be deflected, and the birds fly more or less due south. It should be added that the wintering grounds of different subspecies of the same species are usually well demarcated.

The direction of migration is determined, of course, by the location of nesting and wintering grounds. At the same time, with a certain number of exceptions, movement proceeds along paths that are possibly favorable in an ecological sense (convenience of orientation, food, rest, etc.), which are very significant factors here; in particular, water birds tend to stick to rivers, lakes, etc. The general directions of flights (autumn) in Europe are west, southwest, less often south and southeast; in North America, as already mentioned, the predominant direction is south and southeast; in Asia - south, southwest, less often southeast and east.

The directions of departure and arrival do not always coincide, and the speeds of spring arrival and autumn departure often do not coincide (arrival usually goes "friendlier" and faster). The movement of birds along ecologically favorable habitats was the reason for the emergence, until recently, of the widespread theory of flyways. According to the theory developed by Palmen, birds on flights supposedly move only along relatively narrow and strictly fixed "paths", and do not fly outside them. In fact, the movement of birds is different.

Landscape factors, as well as the conditions of nutrition, rest, etc., determine the movement of flocks of migratory birds. Vast mountain ranges can therefore cause a bypass direction of flight (for example, this explains the insignificance of the flight through high Central Asia). Water basins favor aquatic birds, but land birds avoid the ocean as far as possible and fly over it (with rare exceptions) near the coast and over the shortest distances. Continental water basins do not serve as an obstacle for land birds flying through the North, and through the Baltic, and through the Mediterranean, and through the Black Sea. Birds of the sea coasts, for example, many shorebirds, keep to the coasts when migrating. Thus, some waders from northeastern Siberia move south along the coast of the Pacific Ocean, and waders from Northern Europe move along the coasts of Scandinavia, the Baltic, and the Atlantic Ocean. Accumulations of waterfowl migratory birds attract migratory predators.

It should be noted that some birds are more flocking on migration (for example, storks, cranes), in others the relationship between individuals and groups of individuals is less pronounced.

Migration, undertaken by many species in connection with the onset of unfavorable conditions, and irregular and random evictions from the nesting area, examples of which we see in the saji, should be distinguished from flights. Mountain forms undertake more or less regular vertical migrations.

The complex functioning of the locomotive apparatus of birds, especially during flight, requires a complex orientation mechanism. Let's stop a little on this question. The sense of smell in birds, unlike mammals, is poorly developed. Hearing in birds functions excellently, but the first place among the sense organs belongs to vision. In this regard, birds occupy the first place among other animals. It is characteristic that among birds there are no forms with underdeveloped eyes, and even more so blind ones. The very size of the eyes is very large, and the volume of the eye, for example, of a buzzard is approximately equal to the volume of a human eye.

The field of vision in birds is large, but vision is predominantly monocular and lateral (lateral) (Fig. 16). The total field of view in birds with a pronounced lateral (lateral) arrangement of the eyes (for example, in passerines) is 300 ° (in humans, only about 200 °), the lateral field of view of each eye is 150 ° (i.e., 50 ° more than in humans). But the field of binocular vision, i.e., the area of ​​​​the coincidence of the fields of vision of both eyes in front of the bird, is only 30 ° (in humans - 150 °). In birds with a wider head and with eyes turned more or less forward (lateral-frontally), the general field of view is the same, but the field of binocular vision is wider - about 50 ° (this includes nightjars, birds of prey and some others). In owls, finally, whose eyes are forward-facing (frontal), the lateral field of view of each eye is only 80° (smaller than in humans); this is partly due to the fact that their eyes are completely motionless; the immobility of the eyes in owls is compensated by the mobility of the neck, in particular, the great freedom of its rotation (up to 270). The maximum value of the field of binocular vision in birds. is 60°. As a rule, the movement of each eye and its visual perceptions in birds are independent; the visual fields of both eyes are also independent; in connection with the movements of the bird's head, they can diverge, approach and partially coincide.

Visual acuity in birds is very high, and the minimum of perception significantly exceeds that of a person (in a buzzard, for example, 4 times): a peregrine falcon sees turtledoves at a distance of more than 1000 m. There is reason to believe that in relation to the perception of space and distance, birds occupy the first place among all animals. This, of course, is directly related to the speed of movement of birds in the air.

It is possible that birds have a sense of position in space, or geographical position, which is undoubtedly present, but the mechanism of which remains unclear until recently. This feeling is the most interesting side of orientation in birds. In a number of cases, the finding by the bird of the goal of movement cannot be explained either by optical stimuli or by visual memory. So, for example, among the Salangan swifts that nest colonially in deep dark caves (near the city of Padang in Sumatra there is a cave with a depth of 2 km where the salangan colony is located), each bird unmistakably finds its nest among others in complete darkness. South American guajaro nightjars also nest colonially in deep, dark caves. In this case, orientation occurs with the help of echolocation.

The impossibility of explaining the finding of a target by migratory birds (place of nest or wintering) by visual stimuli or motor memory alone is indicated by the fact that many species fly at night, that in many migratory birds young birds born in summer fly off in autumn earlier than old ones (and, consequently, independently of them and without any experience and example, make their first journey to wintering). Many species that breed in the Canary Islands, such as some swifts, winter on the African mainland and therefore fly over the open ocean 50 km to the first islands lying on their way (Palma and Tenerife). Finally, numerous experiments have been carried out on the importation of birds from nests, and the birds accurately returned back from distances of tens, hundreds, and even more than a thousand kilometers. Kluiver (1936) in Holland drove starlings from nests at a distance of 150 km, and the birds were under anesthesia, and 60% of them still returned. This ability to determine the geographical position is especially developed in migratory birds. The sense of geographical position not only guides birds in a certain direction at a certain time, but also stimulates the flight of birds in a certain direction. In the development of this feeling, as we see in the example of carrier pigeons, both heredity and exercise are of a certain importance, and the appearance and consolidation of it in birds is associated with natural selection (those individuals survived that unmistakably found the purpose of movement).

Of the existing explanations, the most probable seems to be the connection of the sense of geographical position with certain magnetic phenomena, since it is difficult to imagine any other universal stimulus that changes in connection with changes in geographical position.

In the field of bird classification, there is still no generally accepted system. Different researchers allocate either a larger or a smaller number of units. IN this book we, based on the features of the structure, lifestyle, as well as the probable origin and family ties, distinguish the following groups of birds, to which we attach the importance of orders. Such a division of orders is very close to the system of orders proposed at one time by the famous ornithologist E. Stresemann, and to the system of orders adopted in the book by G.P. Dementiev "Birds" (Guide to Zoology, volume six, 1940). Many ornithologists distinguish larger groups of birds into orders, in such systems the orders named below acquire the meaning of suborders.

The class of birds in its modern form does not break up into subclasses (the extinct Archeopteryx is allocated into a special subclass), but 2 superorders can be distinguished in it: penguins(Impennes) and typical, or neopalates, birds(Neognathae). Perhaps, ratites should be singled out as a special superorder; the latter should be called running birds(Ratidae). We follow the order of orders recommended as the standard for faunistic publications by the XI International Ornithological Congress in Basel in 1954 (Wetmer system).

Classification of modern birds

Superorder Penguins (Impennes)

1. Detachment Penguins (Sphenisciformes)

Superorder New-palatine, or Typical, birds (Neognathae)

2. Order Ostriches (Struthioniformes)

3. Detachment Nandu (Rheiformes)

4. Order Emu and Cassowaries (Casuariiformes)

5. Order Kiwi (Apterygiformes)

6. Detachment Tinamou (Tinamiformes)

7. Detachment Gagara (Gaviae, or Gaviiformes)

8. Toadstool squad (Podicipedes, or Podicipediformes)

9. Squad Procellariiformes

10. Detachment Copepods (Steganopodes, or Pelecaniformes)

11. Detachment Ankle (Gressores)

12. Flamingo Squad (Phoehicopteri)

13. Detachment Anseriformes (Anseres, or Anseriformes)

14. Order Diurnal birds of prey (Accipitres, or Falconiformes)

15. Order Chicken (Galliformes)

16. Order Shepherd partridges (Mesoenades)

17. Detachment of the Three-Fingers (Turniceps)

18. Squad Cranes (Grues, or Gruiformes)

19. Detachment Shepherds (Ralli, or Ralliformes)

20. Order Pawfoot (Heliornithes)

21. Kagu Squad (Rhinocheti)

22. Order Solar herons (Eurypygae)

23. Squad Seriema (Cariamae)

24. Detachment Bustards (Otides) *

* (Detachments from shepherd partridges to Bustards inclusive are sometimes combined into one detachment called crane-like. )

25. Detachment Sandpipers (Limicolae)

26. Squad of Seagulls (Lari, or Lariformes)

27. Detachment of Chistika (Alcae, or Alciformes) *

* (Detachments of shorebirds, gulls and guillemots are sometimes combined into one detachment called charadriiformes. )

28. Detachment Ryabki (Pterocletes, or Pterocletiformes)

29. Detachment Pigeons (Columbae, or Columbiformes)

30. Order Parrots (Psittaci)

31. Squad Cuckoo (Cuculiformes)

32. Squad Owl (Striges, or Strigiformes)

33. Detachment Kozodoi (Caprimulgi)

34. Detachment Long-winged (Macrochires)

35. Detachment of bird-mouse (Colii)

36. Detachment Trogons (Trogones)

37. Detachment Rakshi (Coraciae)

38. Detachment of Hoopoe (Upupae)

39. Detachment of Woodpeckers (Picariae)

40. Order Passeriformes (Passeriformes)

To the question, what external signs distinguish a bird from other animals? given by the author Olka) the best answer is Characteristics of the BIRDS class
Birds are a class of vertebrates, whose representatives are well characterized by the fact that their body is covered with feathers and their forelimbs are modified into flight organs - wings. With rare exceptions, birds are flying animals, and those species that do not fly have underdeveloped wings. For movement on a solid substrate, the birds use their hind limbs - legs. Thus, birds, unlike all other terrestrial vertebrates, are bipedal animals. Birds have a very energetic metabolism, body temperature is constant and high, the heart is four-chambered, arterial blood is separated from venous. The cerebral hemispheres and sense organs are well developed, especially vision and hearing.
From a biological point of view, the most characteristic features of birds are, on the one hand, the intensity of metabolism, the intensity of the course of life processes, and on the other hand, movement through the air by flight. These two main features of birds largely determine their biology. It is these properties of birds that fundamentally distinguish them from other groups of vertebrates. Despite the common evolutionary origin of birds and reptiles, the biological differences between these two groups of animals are enormous.
In terms of mobility and ability to overcome space, birds rank first among terrestrial vertebrates. Great mobility is associated with a great work of the muscles, with a large expenditure of energy, which require rapid and intense compensation. Despite the fact that the lungs of birds are inflexible and relatively small. the use of oxygen in them and the nutrition of the body with oxygen in birds is very intensive, which is explained by the action of the air sac system. The active part of the respiratory process in birds, unlike other vertebrates, occurs not only during inhalation, but also during exhalation. The significance of this for the intensification of metabolism in the body is obvious. Arterial blood is completely separated from venous blood, and the work of the heart is very energetic. In this regard, there is also an energetic work of the digestive organs: the bird consumes a large amount of food, and its assimilation proceeds quickly and very completely. All these features are closely related to the presence of a constant body temperature in birds (and the latter - with the development of a heat-insulating cover of feathers). The body temperature in birds is higher than in mammals, most often it is close to 42 ° C, in a few species it drops below 39 ° C, but often reaches 45 and 45.5 ° C.
Of the other very significant features of the biology and structure of birds, we should also mention the features of reproduction. Compared with reptiles, there is, firstly, a weak intensity of reproduction, and secondly, the complexity of the biological phenomena accompanying reproduction, and in particular the complexity of the phenomena of caring for offspring. The latter, as it were, compensates for the low fertility. The whole evolution of birds went in close connection with their acquisition of the ability to fly. The appearance of the main biological and anatomical features of the bird's body had to go simultaneously with the appearance and development of their mobility, the improvement of their motor capabilities. Paleontological material shows that at a certain stage of evolutionary development the ancestors of birds were terrestrial running reptiles.

1-2-3, look at the teacher!

II . The stage of preparing students for the active and conscious perception of new material. Message about the topic and purpose of the lesson

– You can determine the topic of our lesson by guessing the riddle:

Dreaming of a spider at night
Miracle - Yudo on a bitch.
Long beak and two wings.
Arrives - things are bad.
And who is the spider afraid of?
Guessed? This …(bird ) (slide 1)"So what are we going to talk about?"That's right, it is this group of animals that we will study today.- The purpose of our lesson is to repeat and generalize knowledge about birds, their structure, habits, habitat; come to understand the importance of caring for nature, in particular about birds. - As an epigraph for today's conversation, I took the lines of M.M. Prishvin and I. Druzhinin (slide 2)For a fish - water, for a bird - air, for a beast - forest, steppes and mountains. And a man needs a homeland. And to protect nature means to protect the Motherland. ( M. Prishvin)

In the forest and on the river bend,
In native fields, where the distance is bright,
You with kindness do not be apart.
Do no harm to nature.
…Go to the ground as a good friend ,
Be her protector.
So that only the singing of birds over the meadow,
So that the world and the sun are ahead. (I. Druzhinin )

III . Statement of problem questions. 1. How are birds different from other animals?2. What makes a bird fly?3. What birds are called migratory, sedentary, nomadic?

IV . The stage of updating knowledge.

Birds. What do we know about them?The owl has been a symbol of wisdom since ancient Greece.
The double-headed eagle in the coat of arms of Russia is a symbol of courage and strength.
Birds inhabit all continents and islands of the globe. Currently, about 9,000 species of birds are known in the world fauna, and there are approximately 100 billion birds in total on the globe.
The oldest known bird fossil is about 150 million years old. Scientists in the layers of the earth's crust found the fossilized bones of the skeleton of an unknown creature, and next to it are the prints of its feathers. They called this bird Archeopteryx, which translated into Russian meant "ancient wing".Teacher: In the modern world, scientists who study the life and habits of birds are calledornithologists. Ornithology is the science that studies the life and habits of birds.(slide 3)How are birds different from other animals? By what signs of body structure and lifestyle do we define a bird?

V . The stage of learning new knowledge. Practical work students A) practical work. (slide 4)Teacher: You have feathers on your tables. How do they differ?(By shape, by color, by size)
- Every pen has a nib. Consider it.
- Put the feathers in your palm. Blow. What happened?(Feathers fly, they are light )
- Dip the feather into a glass of water. Did it get wet?(Water dripping down)
- What conclusion do we draw?(Feathers protect the bird from water and dampness)
Why do birds need big feathers?(To fly)
- And the little ones? (for warmth) Now close your eyes and imagine the flight of a bird. Here the bird flapped its wings, begins to lower them, the wings are repelled from the air, lower again, and flap again. The body of the bird has a streamlined shape, convenient for flight. Feather cover retains heat and does not allow the bird to freeze even in extreme cold.(Slide 5) Conclusion : Birds are animals whose body is covered with feathers. It consists of a head, neck, torso, limbs (two wings and a pair of legs). Only birds have hard beaks. B) Identification of birds by their voicesTeacher: Let's try to answer the second question of our lesson: What are they?What sounds do birds make! They can sing, shout, crow, cackle, roar, hoot, cackle, coo, chirp( Sounds like birdsong.) (Slide 6)What birds did you hear now?(Children's answers are heard: owl, woodpecker, eagle, sparrow, crane, goose)
What do you know about birds, their habits, habitats? (slide 7) Birds according to the method of nutrition are divided into groups:predatory (eagle, owl, hawk), granivorous (crossbill, oatmeal, nutcracker), omnivorous (crow, lark, jackdaw); insectivorous (titmouse, cuckoo, swallow); by habitat in environment: wild and domestic (chickens, ducks, geese) according to the method of flights: migratory, nomadic, settledWhat means migratory birds? namemigratory birds. (Lark, rook, starling, swift, nightingale, swallow)What birds come to us for the winter? (Bullfinch, waxwing) These are wintering birds.Nomads (nuthatch, bullfinch, waxwing, siskin)What does settled birds mean? (Permanently live with us, settled in certain place) What do you knowsettled birds? (Crow, sparrow, goldfinch, woodpecker, nuthatch, magpie, dove, crossbill, tit, jackdaw). Fizminutka. Swans fly, flap their wings, Bent over the water, shake their heads. Proudly able to stand straight, They sit very quietly on the water.

VI . Stage of application of the studied.

Guys, where can I meet birds? (Children's answers: on the street, in the forest, by the river ...) (slides 8, 9, 10)

Very often, birds are the heroes of works (in fairy tales, stories, poems, fables ..) Remember some of them.

Nightingale - Andersen "The Nightingale"

Goose - S. Lagerlöf "Niels' wonderful journey with wild geese"

Cockerel - A.S. Pushkin "The Tale of the Golden Cockerel"

Swallow - G. Andersen "Thumbelina"

Owl - A. Milne "Winnie the Pooh and Everything, Everything, Everything"

Swan - G. Andersen "The Ugly Duckling"

Duck - D.N. Mamin - Siberian "Grey Neck"

Sparrow - K. Paustovsky "Disheveled Sparrow"

Swift - V. Astafiev "Strizhonok Squeak"

Crow - A. Krylov "Crow and Fox"

VII . Stage of control and self-control

Let's check how you learned the topic of the lesson. Open the notebook to p.. Exchange notebooks with a neighbor. Use a pencil to mark your agreement or disagreement with your friend's answer (+ or -). (Mutual check)

Take your notebook. Who has questions about the assignment?

VIII . Correction stage

Guys, take a look at the photos of the next slide. What unites them?

(People should help the birds in winter, feed them).

Reading A. Yashin's poem "Feed the birds in winter." ( slide 11)

Feed the birds in winter.

Let from all over

They will flock to you, like home,

Stakes on the porch.

Their food is not rich.

Need a handful of grain

One handful -

And they will not be afraid of winter.

How many of them die - do not count,

It's hard to see.

But in our heart there is

And the birds are warm.

Is it possible to forget:

Could fly away

And stayed for the winter

Along with people.

Train the birds in the cold

To your window

So that without songs it was not necessary

We welcome spring.

What does this poem make you think about? Which important questions affects? (Children express their thoughts.) How can you help the birds? (Make a feeder, don't forget to feed the birds...)

We made feeders

We opened a canteen.

Sparrow, bullfinch - neighbor,

You will have lunch in the winter!

Visit on the first day of the week

The tits have come to us.

And on Tuesday, we looked

The snowmen have arrived.

Three crows were on Wednesday.

We didn't expect them for dinner.

And on Thursday from all over -

A flock of greedy sparrows.

And on Friday in our dining room

The dove ate porridge.

And on Saturday for pie

It's seven forty.

Sunday, Sunday

The messenger of spring has arrived -

The traveler is a starling...

Here comes the end of winter. Let's do a good deed. At home, together with your parents, make a feeder and bring it to school. With the advent of cold weather, we will hang them on the school grounds and take care of our little brothers together.People were wasteful with nature. They plucked plants, plowed up, burned the land. Many different animals and birds were exterminated by people. Some were diligently hunted, others did not leave a patch of forest or steppe, others were caught by predators. In the end, people realized that if you do not help nature, even more animals will die. To prevent this from happening, they compiled an official Red Book. The idea of ​​this book is to save the whole animal and vegetable world. The Red Book consists of color illustrated pages.(showing the Red Book)

IX . Wrap-up stage. Let's summarize our work. Tell me, who are these birds?Conclusion : Birds are animals whose body is covered with feathers. It consists of a head, neck, torso, limbs (two wings and a pair of legs). Only birds have hard beaks.) Which distinguishing feature in these animals? (there are feathers) Teacher: Guys, and now, before summing up the main result of the lesson, let's listen to Gnetova Dasha. In the morning the sun rises
He invites everyone to the street.
I leave the house.
Hello my homeland!
Live on our planet
wonderful creatures,
They fly and sing
And keep the earth sacred.
Tell me children
Is it possible to live without birds in the world? - Why do we need birds? What is the importance of birds in human life? (hunting object: meat, egg, down, feather; crop protectors: eat insects, destroy rodents; songbirds and decorative birds: give pleasure.) - What will happen if the birds on the ground suddenly disappear?(Children's answers are heard) - Why do we need to take care of the birds? (Birds are our friends)

Additional material. And did you know that…

The swan brings out the chicks in the rain.

The woodpecker has the longest tongue.

The penguin's wings are not covered with feathers, but with scales.

The eagle flies above all.

A hummingbird can fly with its tail forward

Hummingbird is the smallest bird.

Birds ostrich, kiwi, penguin - fly.

The largest bird is the African ostrich.

Used Books :

1. Zhirenko O.E., Lapina E.V., Kiseleva T.V. I am a citizen of Russia! Class hours for civil and patriotic education: grades 1-4.– M.: VAKO, 2006.– 160s
2. Class hours 1-4 grade / comp. G.P. Popova. - Volgograd: Teacher, 2008. - 287 p.
3. What? For what? Why? The Big Book of Questions and Answers \ Per. K. Mishina, A. Zykova. - M.: Eksmo, 2006. - 512p.

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

Birds: general characteristics

Birds are highly organized warm-blooded animals. In nature, there are nine thousand species of modern birds. Characteristic features class are the following features:

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

Birds, the general characteristics of which are presented above, are able to fly due to the listed features. This distinguishes them from other classes of animal vertebrates.

Appearance on earth

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

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

The origin of birds from reptiles

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

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

Ancestors - waterfowl

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

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

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

• The toes and tarsus of many birds are covered with corneal scales and scutes, like those of reptiles. So the scales on the legs can replace feathers. It is characteristic that the rudiments of feathers in birds and reptiles do not differ. Only birds then develop feathers, and reptiles develop scales.
• Investigating the origin of birds, the features of which are incredible in resemblance to reptiles, scientists have determined that the jaw apparatus is more noticeable. Only in birds it turned into a beak, and in reptiles it remained the same, like in turtles.
• Another sign of the similarity of birds and reptiles is the skeletal structure. The skull and spine are articulated by only one tubercle located in the occipital region. Whereas in mammals and amphibians, two tubercles are involved in this process.
• The location of the pelvic girdle of birds and dinosaurs is the same. This can be seen from the skeleton of the fossil. This arrangement is associated with the load on the pelvic bones when walking, since only the hind limbs are involved in holding the body.
• Birds and reptiles have a four-chambered heart. In some reptiles, the septum of the chambers is incomplete, and then arterial and venous blood mix. Such reptiles are called cold-blooded. Birds have a higher organization than reptiles, they are warm-blooded. This is achieved by eliminating the vessel that carries blood from the vein to the aorta. In birds, it does not mix with arterial.
• Another similar feature is incubation of eggs. This is typical for pythons. They lay about fifteen eggs. The snakes curl up over them, forming a kind of canopy.
• Most of all, birds are similar to reptile embryos, which in the first stage of their development look like fish-like creatures with tails and gills. This makes the future chick look like other vertebrates in the early stages of development.

Differences between birds and reptiles

When paleontologists study the origins of birds, they compare facts and pieces of evidence to find out how birds are similar to reptiles.

What are their differences, read below:

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

firstbirds

Fossil remains of ancient birds have now been found. After a thorough study, scientists came to the conclusion that they all belong to the same species that lived one hundred and fifty million years ago. These are Archeopteryx, which means "ancient feathers" in translation. Their difference from today's birds is so obvious that the Archeopteryx was singled out in a separate subclass - lizard-tailed birds.

The ancient birds have been little studied. The general characteristic is reduced to the definition of the appearance and some features of the internal skeleton. The first bird was distinguished by its small size, approximately like a modern magpie. Her forelimbs had wings, the ends of which ended in three long fingers with claws. The weight of the bones is large, so the ancient bird did not fly, but only crawled.

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

Importance and protection of birds

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

Different birds play different roles. Grain-eating - eat seeds and fruits, certain types- store them, transferring them over long distances. On the way to the storage place, the seeds are lost. This is how plants spread. Some birds have the ability to pollinate them.

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

Man, as far as possible, protects the birds and helps them survive in harsh winters. People are putting up temporary nests everywhere. Titmouse, flycatchers, blue titmouse settle in them. Winter periods characterized by a lack of natural bird food. Therefore, birds should be fed, filling the nesting place with small fruits, seeds, bread crumbs. Some birds are commercial species: geese, ducks, hazel grouses, capercaillie, black grouse. Their value to humans is great. Of sporting interest are woodcocks, waders, snipe.

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

Today: when filling the bird nests with food, you need to make sure that salt does not get there. She is a white poison for birds.