A story about birds of prey. Birds (brief description) Brief message about the bird

Birds - report for children. General characteristics and beautiful photographs of birds(20 photos)

Birds- These are warm-blooded animals. Their characteristic features are a body covered with feathers and forelimbs transformed into wings, which in most cases are used for flight. In addition, they do not have teeth, but instead have a beak with a keratinized covering. Birds appeared on Earth approximately 130 million years ago. Nowadays they can be found in all corners of the Earth, from the poles to deserts.

Kestrel (Agnes Kiss)

Appearance of the bird

The entire body, except for the limbs and beak, is covered with feathers. They serve to ensure flight and to protect the animal from heat and cold.

Feather

Feathers, like hair, are structures formed by the skin.

Bird skeleton

Bones bird skeleton have characteristic features. One of them is the development of the sternum into a special protrusion - the keel. The flight power depends on its value. Other structural features of birds are that many of their bones are hollow, and they also have a system of air sacs - these are outgrowths of the lungs that fill the space between the internal organs. All this greatly lightens the overall weight of the bird.

Structure of internal organs

Goiter- This is an expansion of the esophagus, where the digestive processes begin.

Some bird beak shapes

Beak shape depends on the nature of food and the method of obtaining it in different species of birds.

Blue Jay (Daniel Cedras, Nature’s Best Photography)

Nutrition and lifestyle.

Bird food very diverse: food can be fruits and grains, insects, rodents, other birds, as well as carrion. Some eat both plants and small animals, but there are others who only eat certain foods.
As for the lifestyle, there are birds that do not fly and spend their entire lives on the ground, for example, ostriches; Penguins cannot fly either, but they swim beautifully. Most birds fly, and some are better at it, and some are worse at it. Albatrosses, for example, spend almost their entire lives flying. And some fly only in case of imminent danger, as partridges do. Many birds from areas with cold climates fly thousands of kilometers to warmer regions with the onset of cold weather, since where they live they would not be able to find food at this time. They return to their home as soon as the conditions they need for life and procreation again appear there. These birds are called migratory; examples include storks and geese.

Sea Plover (Jonathan Kirk, Nature’s Best Photography)

Reproduction.

Birds have internal fertilization. They build nests of varying degrees of complexity, lay eggs, which, as a rule, hatch themselves, and then care for the offspring. Many species perform mating dances on the ground or in the air before mating. In some species, chicks are born blind and naked, receive food from their parents and remain in the nest until they can live on their own. These are chicks of nesting birds. An example would be eagles. In other species, the chicks are fully developed and within a few hours after birth they are able to follow their parents and get food on their own. These are chicks of brood birds. An example would be ducks.

Golden Wood Warbler (Charles W. Mc Rae, Nature’s Best Photography)

Many bird species They produce sounds that are very pleasant to the human ear. Singing serves birds to communicate with each other (in order to form a pair, mark their territory, etc.)

White-tailed eagle (Tarmo Syvapuro)

Flight.
Birds move through the air in two ways: active flight, which is constantly flapping their wings, and passive flight, hovering in the air. For the former, they have powerful muscles that converge at the keel. For the second, they use rising air currents to rise upward and then move smoothly with their wings spread wide.

Forest Kestrels (Bill Coster)

White-headed Bunting (Howard B. Cheek, Nature’s Best Photography)

Royal Tern (Mark B. Bartosik, Nature’s Best Photography)

Chilean pink flamingo (AP Photo/WCS, Julie Larsen Maher)

Crowned Lapwing (Jan Forseth, Nature’s Best Photography)

Common kingfisher (MANFRED DELPHO/AFP/Getty Images)

Carolina Duck (Diana E. Whiting, Nature’s Best Photography)

Each of us watched birds and thought about the sensations of freedom and weightlessness. Information about birds for children is summarized in this article.

Brief message about birds

Birds are warm-blooded animals. They have some features - a body that is covered with feathers, forelimbs that turn into wings. It is distinctive that birds do not have teeth. Instead, they have a beak with a keratinized covering. Birds appeared on Earth about 130 million years ago. They are found in all corners of the planet, from the cold poles to hot deserts.

General characteristics of birds

The body of birds, except for the beak and limbs, is covered with feathers. Feathers perform two main functions - they provide the animal with flight and protect it from cold and heat.

The bones of the skeleton also have some features. One of them is the keel - a special protrusion that has developed in the sternum. The strength and power of flight depends on the size of the keel. Another feature of the structure of birds is that most of their bones are hollow. There are also outgrowths of the lungs - this is a system of air sacs that fills the space between the organs. All these listed features greatly lighten the overall weight of the bird.

Feeding characteristics and lifestyle of birds

Animal nutrition is quite varied. Food includes grain, fruits, rodents, insects, other birds, and carrion. There are birds that eat both plant and animal food, and there are species that eat only one type of food.

Regarding lifestyle: birds that cannot fly spend their entire lives on solid ground (ostriches) or swimming (penguins). But most birds can fly and, for example, the albatross spends its entire life in flight. But partridges rise into the sky only when they are in some kind of danger.

Birds that live in areas with a cold, frosty climate, with the onset of winter, fly thousands of kilometers to warmer climes in search of food and warmth. They return home in the spring. Such birds are called migratory. We all know geese, storks and cranes, whose calls can be heard in the sky in the spring.

Bird breeding system

Birds have an internal fertilization system. They build nests of various designs, lay and incubate eggs, and also carefully care for their offspring. Some species of birds, before forming a pair, perform mating dances in the air or on the ground. Some birds have chicks that are blind and naked at birth. They receive food only from their parents and remain in the nest until they can live on their own. These include chicks of nesting birds, such as eagles. In other birds, chicks are born as fully developed babies and after a couple of hours from birth they follow their parents and get their own food. These include chicks of ducks and chickens.

How do birds move in the air?

Birds move through the air in 2 ways - active and passive. An active method of movement is when a bird, while in the air, actively flaps its wings. The passive method is when she floats in the air. For active flight, they have powerful muscles in the keel.

We hope that this brief information about birds has helped you. You can leave your story about birds using the comment form.

In our article we want to talk about the extraordinary diversity of birds on Earth. Depending on the classification, there are from 9,800 to 10,050 modern species of birds. If you think about it, this is an impressive figure.

Origin of birds

Modern science believes that birds descended from ancient reptiles. This is indicated by some common structural features with reptiles: dry skin, feathers like reptile scales, similarity of embryos, eggs.

It must be said that already in the Jurassic period there was an intermediate form between birds and reptiles called Archeopteryx. And at the end of the Mesozoic, real birds appeared. Modern birds have characteristic progressive features that distinguish them from reptiles. These are developed organs of hearing, vision, coordination of movements with certain centers in the cerebral cortex, the emergence of warm-bloodedness as a result of changes in the nervous and respiratory systems, the presence of a four-chambered heart and spongy lungs.

Variety of birds

Nowadays the bird world is very diverse. It is customary to divide all birds into three superorders:

1. Ratites. Most of the representatives of this group have poorly developed wings. Such birds do not fly, but they can run fast and well. A striking example is the African ostrich, which lives in savannas, semi-deserts and steppes of Africa, Australia and South America.
2. Penguins. This group is quite small. Its representatives live mainly in the Southern Hemisphere on the shores of Antarctica. These birds also cannot fly, but they swim beautifully. Their forelimbs are modified into flippers. On ice, penguins move in a vertical position, sliding and leaning on their tail. An interesting fact is that they do not build nests. They store the egg on the membranes of the limbs, hiding them under the folds of fat on the tummy. In general, a large fat layer protects penguins from the cold.
3. Keeled. This group is very numerous. It includes more than twenty units. These are passerines, gallinaceae, anseriformes, falconiformes, woodpeckers, etc.

As part of the article, we want to show the diversity of birds using specific examples of some representatives of the feathered world, since it is simply impossible to talk about everyone.

Ostrich

The African ostrich is the largest bird on Earth. Previously, these included other related species, rhea and emu. However, modern researchers classify them as separate orders. Therefore, from a scientific point of view, there is now only one true ostrich - the African one.

The first thing that surprises you about the bird is its enormous size. She is no less tall than a large horse. The height of the ostrich ranges from 1.8 to 2.7 meters, and the weight reaches 75 kg. There are also large males that weigh up to 131 kilograms. Naturally, most of the growth occurs in the neck and legs. But the bird’s head, on the contrary, is very small, which is even less reflected in the birds’ intelligence.

Bird feathers grow evenly throughout the body, but in most birds they are located along special lines called pterilia. African ostriches lack a keel, and therefore are not adapted to flight at all. But their legs cope well with running. The bird has very long legs and highly developed leg muscles. There are only two toes on each foot. One is huge with a claw, the other is smaller. The second finger helps maintain balance while running.

There are a lot of feathers on the body, tail and wings of the bird, but the head, neck and legs have only short fluff, giving the impression that they are naked. Females and males of the African ostrich differ in the color of their plumage. In addition, different species may have different colors of legs and beaks.

Habitat of the African ostrich

The African ostrich lives almost throughout Africa; it cannot be found only in the Sahara and North Africa. There was also a time when this bird lived in the lands adjacent to the African continent, in Syria and on the Arabian Peninsula.

In general, ostriches prefer open plains. They inhabit dry woodlands, grassy savannas, and semi-deserts. But dense thickets, swampy areas, and quicksand deserts are not to their taste. This is explained by the fact that there they cannot develop high speed while running. They lead in small groups. Very rarely, a pack can include up to 50 individuals, and they can graze together with antelopes and zebras. There is no constancy in the pack, but there is a clear hierarchy. High-ranking individuals hold their tail and neck vertically, while weaker representatives hold their tail and neck obliquely. The birds are active at dusk, and rest at night and during the heat of the day.

Ostriches, on the one hand, are stupid, but on the other hand, they are extremely cautious. While eating, they constantly look around, inspecting their surroundings. Having noticed an enemy, they quickly move away, not wanting to encounter a predator. They have very good eyesight. They can spot the enemy a kilometer away. Many animals monitor the behavior of the ostrich if they themselves do not have such good eyesight. The ostrich is capable of reaching speeds of up to 70 kilometers per hour, and in very rare cases, up to 90 kilometers per hour.

Sparrow

Speaking about the diversity of birds on the planet, let's move from the largest representative to one of the smallest - the sparrow. This bird has been familiar to us since childhood. The sparrow is a bird that is widespread in cities and towns. It is small in size, weighing from 20 to 35 grams. The bird is part of the passerine order, which, in addition to it, includes more than 5,000 species. The largest representative of this group is the raven, and the smallest is the wren.

The sparrow is a bird that got its name back in ancient times. This is due to the fact that birds love to raid farmers’ fields. Driving them away, people shouted “beat the thief.”

There are two species of sparrows in Russia: house sparrow (urban) and village sparrow. An interesting fact is that this species of birds has a special eye structure, and these birds see the whole world in pink. During the day, the sparrow consumes a significant amount of energy, and therefore cannot starve for more than two days.

House Sparrow

The birds have brown plumage with longitudinal black stripes. They do not exceed seventeen centimeters in length and weigh no more than 35 grams. Imagine, the world of birds is so diverse and rich that there are more than 16 species alone. This bird once lived only in Northern Europe. But then gradually the sparrows settled on almost all continents except the Arctic. Now they can be seen even in South Africa, America, Australia, where they were brought at the beginning of the twentieth century.

It should be noted that sparrows always settle near humans and lead a sedentary existence. And only birds living in more northern regions fly to warmer climes for the winter.

Sparrows are man's eternal companions. They are highly fertile. The basis of their diet is plant foods. But birds catch insects for their chicks. In villages, birds fly to the fields to pick up grains. Sometimes sparrows peck fruits and berries in gardens, thereby causing damage to people.

In one summer, two or even three generations of offspring can be born.

Stork

The stork is an extraordinary bird. She has long become a symbol of peace on earth. The white bird is so beautiful and graceful that many songs and poems have been written about it. The stork family is represented by twelve species. These are quite large individuals. As adults, they reach a meter in height and a wingspan of two meters. All storks have long legs, necks and beaks.

They are distributed on almost all continents. They live not only in the tropics, but also in temperate latitudes. Those individuals that live in warm climates do not fly away for the winter, while the rest fly to Africa and India. Birds live up to twenty years.

The most famous species is the white stork. Birds have lived on Earth since ancient times, as evidenced by archaeological finds. This species is considered practically mute, since its vocal cords are completely undeveloped.

Storks are famous for their endurance, as they are able to make very long flights.

The bird's lifestyle and diet depend on its habitat. prefers low-lying areas with meadows and swamps. Sometimes they settle on the roofs of houses, making nests there. They feed on food of animal origin: lizards, frogs, insects, small mice. The stork is a beautiful and noble bird.

Swans

The swan is a white bird that has captivated everyone with its beauty and grandeur. A small group of famous birds includes 7 species. In general, swans belong to and their closest relatives are geese and geese.

Swans are the largest wild waterfowl. Weight reaches eight kilograms. Birds have a very long and flexible neck, and each species is characterized by its special position. Birds' legs are quite short and equipped with special swimming membranes. On land, their gait seems very clumsy. The coccygeal gland of birds secretes a special lubricant, thanks to which the feathers do not get wet in the water.

All swans have the same coloring - white, and only the black swan differs from them.

They live in South and North America, Eurasia and Australia. They usually settle on the shores of water bodies, and these can be small lakes or huge bodies of water, such as estuaries or bays.

All swans can be conditionally divided into southern and northern. The southern ones lead a sedentary life, while the northern ones have to fly away for the winter. Eurasian individuals spend the winter in South and Central Asia, while American individuals spend the winter in California and Florida.

Birds usually live in pairs. They have a quiet and calm disposition. The birds' voices are quite clear, but they make sounds extremely rarely, but the mute swan can only hiss in case of danger.

Birds use buds, seeds, roots of aquatic plants, grass and small aquatic invertebrates as food. They find food in the water, diving their heads deep. But birds don’t know how to dive.

hummingbird bee

We talked about the fact that the African ostrich is the smallest and the smallest is the bee hummingbird. This Cuban bird is not only the smallest in the world, but also the smallest warm-blooded creature on Earth. The male is no more than five centimeters long and weighs no more than two paper clips. But females are slightly larger. The name itself suggests that these birds themselves are no larger than a bee.

The smallest bird is a very fast and strong creature. Shiny wings make her look like a precious stone. However, its multi-colored color is not always visible; it all depends on the viewing angle.

Despite its tiny size, the bird plays an important role in plant reproduction. She flies from flower to flower and collects nectar with her thin proboscis, while simultaneously transferring pollen from flower to flower. In one day, a small bee visits up to one and a half thousand flowers.

Hummingbirds build cup-shaped nests no more than 2.5 centimeters in diameter. They are woven from bark, lichens and cobwebs. In them the bird lays two small eggs the size of a pea.

Forest birds

Here, where you can appreciate the real diversity of birds, is in the forest. After all, it is home to many birds. At any time of the year you can find an extraordinary number of them here. Here wild birds build their nests, find food and raise their chicks. Dense greenery reliably protects birds from enemies and bad weather. Walking through the forest, you can hear a variety of bird voices; we don’t see them, but we hear their beautiful singing or the “peek-a-boo” familiar from childhood.

What birds live in our forests? The world of birds there is so rich that it is difficult to count all the species. Let's remember only the most famous: hazel grouse, woodpeckers, nutcrackers, swifts, owls, nightingales, black grouse, eagle owls, cuckoos, golden eagles, lentils, nutcrackers, wrens, flycatchers, tits, hawks, crossbills, siskins and many others. Forest birds have adapted to living in forest thickets. Each species lives in certain areas of the country, in its own characteristic places. An interesting fact is that absolutely all the birds of the forest coexist in the same territory, and among them there are formidable predators, and completely harmless, and very small birds. Simply an amazing combination.

Common kingfisher

The common kingfisher is a small bird with brightly colored feathers. The color of the plumage goes from a dark blue back to a bright orange belly. The beak of the kingfisher is the most ordinary: long and straight. Females are smaller in size than males. Birds settle along the coasts of rivers and streams. In general, in those places where there is quiet, running water.

But nests are made on steep banks among thickets of bushes. Kingfishers feel quite good in the mountains, sometimes settling there.

Birds pair up only during the mating season. In Russia, this is approximately the second half of April, just after returning from warm countries. Females and males dig out nests with their beaks, throwing away the soil with their paws. The mink, as a rule, is located near the water and is well camouflaged by branches.

It is surprising that kingfishers return to their home for several seasons. There is no nest inside as such; eggs are laid directly on the ground. Rarely is there any litter present. Usually the female lays five to seven eggs, and sometimes ten. The female and the male incubate in turn, replacing each other.

Among kingfishers there are both migratory and sedentary populations. They are widespread in Eurasia, Indonesia and northwest Africa, and New Zealand.

Kingfishers settle only near clean bodies of water, so their degree of cleanliness can be judged from them.

Using the examples of these birds, one can judge their diversity. They all differ from each other not only in appearance, but also in their lifestyle and habits, nevertheless they all belong to the same suborder.

General characteristics

Birds have a very energetic metabolism, their body temperature is constant and high, their heart is four-chambered, and arterial blood is separated from venous blood. The cerebral hemispheres and sensory organs, especially vision and hearing, are well developed. From a biological point of view, the most characteristic features of birds are, on the one hand, the intensity of metabolism, the intensity of life processes, and, on the other, movement through the air by flight. These two basic traits 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 occupy first place among terrestrial vertebrates. Greater mobility is associated with great muscle work, with high energy expenditures, which require quick and intense compensation. Despite the fact that the lungs of birds are poorly extensible 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 intensifying metabolism in the body is obvious. Arterial blood is completely separated from venous, and the work of the heart is very energetic. In connection with this, the energetic work of the digestive organs is also important: the bird consumes a large amount of food, and its absorption 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 of birds is higher than that of 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. Other very significant features of the biology and structure of birds should be mentioned more about the characteristics of reproduction. Compared to reptiles, birds have, firstly, a weak intensity of reproduction, and secondly, the complexity of the biological phenomena accompanying reproduction, and especially the complexity of the phenomena of caring for offspring. The latter seems to compensate for low fertility.

The entire evolution of birds was closely related to their acquisition of the ability to fly. The appearance of the main biological and anatomical features of the avian body should have occurred simultaneously with the appearance and development of their mobility, and 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 should, judging by our ideas about the general course of evolution of the animal world, belong to very ancient groups of primitive archaeosaurs that lived in the Triassic, and perhaps even in the Permian period. These were, of course, running terrestrial forms and, apparently, small animals. In Jurassic times, there was an arboreal form intermediate between reptiles and birds - Archeopteryx, which already had some signs of modern birds, in particular feathers or feather-like formations. Thus, at this time, the ancestors of birds transitioned from a terrestrial to an arboreal lifestyle 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 avian and lacks its most important functional features. The general trend of further stages in the development of birds (after the Jurassic period) is associated with an improvement in their ability to move and with the acquisition of the ability to fly. Although flightless species were encountered later, most of them became extinct or are on the way to extinction; starting from the Tertiary period, relatively small but well-flying groups reached their greatest prosperity. The latter are the most numerous among modern birds. Speed ​​and freedom of movement gave birds great advantages in the struggle for existence and in the history of their development, and they still do.

Birds are found throughout the globe, with the exception of the interior of Antarctica, in a wide range of locations and climates. In 1937, employees of the Soviet polar station observed gulls, guillemots and buntings at the North Pole. In Antarctica, Amundsen observed a great skua in 1912 at 84°26" south latitude. The vertical distribution of birds is also very wide, and various species inhabit the highest mountain systems of the world, for example the Himalayas and the Andes. Bearded vultures, for example, have been observed in Central Asia at altitudes slightly exceeding 7000 m; Humboldt saw condors in the Andes at an altitude of 6655 m. The number of birds varies in different places. The largest number of bird species is found in Central and South America: about 17.00 species were found in Colombia, about 1440 in Brazil, 1357 in Ecuador , in Venezuela - 1282 species. The bird fauna of 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 species of birds on Kalimantan (Borneo), 650 on New Guinea. In the area of ​​African savannas and gallery forests, the bird population is also diverse: 627 species in Ghana, 670 in Cameroon, 674 in Zambia, 871 species in Sudan. The composition of the bird population becomes poorer with distance from the tropics. Thus, 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 vagrants), 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 8,600 species of birds are currently known.

Within Russia there are more than 750 species of birds, which is about 8% of the world's avifauna. The number of individuals of individual bird species is very different. There are few accurate estimates yet. In recent years, the International Union for Conservation of Nature and Natural Resources has been determining the number of rare bird species that are in danger of extinction. It was found that the kahou shearwater survived in Bermuda in numbers of about 20 pairs; 39 individuals of white whooping cranes were counted in North America in 1963; white-mantled albatrosses were recorded on Torishima Island in Japan in 1962; 47 birds were recorded; About 13 individuals of Ivory-billed Woodpeckers were found in Cuba; California condors numbered 60-65 birds in 1960; Japanese ibises on the island of Hokkaido in 1962, approximately 10-15 individuals were counted; About 300 Takahe rails were counted on the South Island of New Zealand; Hawaiian geese on the Hawaiian Islands and in zoos in 1962, 432 individuals were counted. The conservation of all of these species and a number of others is in danger. It can be added that from the end of the 17th century to the present, 76 species of birds have become extinct, largely under the influence of human activity. What are the most numerous bird species? In the Arctic, apparently, a small auk bird, the auk, in the Antarctic and Subantarctic - a small petrel, the Wilson's petrel, in the tropical seas - a sooty tern (several tens of millions of individuals of each species).

Of the land birds, the most numerous are, apparently, the house sparrow and starlings. Counts of the number of birds, of course approximate, were carried out in England and Wales (Fisher, 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 numbers 354 million or more. The finch and blackbird are believed to be represented by approximately 10 million individuals (of each species); there are about 7 million starlings, the same number of robins; house sparrows, wood accentors, song thrushes, meadow pipits - 3 million of each species; rooks 1750 thousand; approximately 1/4 million each of common buntings, wrens, gray warblers, willow warblers, wood pigeons; 3/4 million each of jackdaws, skylarks, blue tits, barn swallows, city swallows and linnets; about 350 thousand greenfinches, great tits, tree pipits, grasshopper warblers, black swifts, moorhens, lapwings, mallards, and gray partridges. Of course, these numbers are approximate. For the 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, grebes - about 20 thousand. The numbers of some birds in Britain are increasing. So, fulmars - there are about 200 thousand of them - have become 5 times more than there were at the beginning of this century; increased sharply - up to? million - the number of gannets. In total, according to rough estimates, about 100 billion birds live on the globe, and this alone indicates their great and diverse importance in the life of our planet.

The reactions of the bird's body to unfavorable changes in the external environment are of a completely different nature than those of amphibians, reptiles and some mammals. In all of the groups listed above (except birds), a decrease in temperature reduces the activity of the body, which leads to hibernation when unfavorable conditions occur in nature. In birds, the response to a decrease in temperature is increased movement - migrations or flights, transferring the organism to conditions more favorable for its existence. However, one should not imagine the matter as if 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 bird’s lifestyle and behavior also depend on the climate in a broad sense (especially temperature and light; the absence of the latter limits the bird’s ability to be active, in particular feeding; a certain intensity and duration of lighting also determines, through the eye and pituitary gland, the development of the bird’s gonads) , and from food and the conditions for obtaining it, and from nesting conditions (in particular, from the availability of a suitable place for a nest and nesting territory), and from population density, from competition, etc. It is remarkable that birds, no matter how it seems At first glance, paradoxical, they are very conservative in terms of habitats. Each species and subspecies lives in a strictly defined area. Through the observations of Howard and many other scientists, and in recent years as a result of ringing (marking caught birds with special rings), it has been established that the life of each individual bird is inextricably and closely connected with the “homeland” in the narrow sense, i.e. with that relatively small area the earth's surface - groves, forests, fields, etc., where the bird was born.

Bird nesting occurs annually (with rare exceptions) on this site 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 breeding 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 site 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 ​​their parents). The attachment of birds to the place of their homeland is so great that usually the occurrence of unfavorable circumstances in it causes either a decrease in the rate of reproduction, or non-breeding, or death. From a general biological point of view, such an attachment of birds to their homeland can be explained in general by the fact that for each bird, optimal living conditions at a certain time of the year are found precisely in their homeland. Indeed, for example, the far north, in addition to calm and convenient places for nesting, low temperatures favorable for cold-loving forms, and an abundance of food, also provides advantages when feeding the brood. The never-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 gonads. It has been established with a fair degree of certainty that the daily cycle of birds is closely dependent on lighting conditions: each species wakes up, behaves actively and rests under a certain lighting intensity, which determines the bird’s daily activity. The conservatism characteristic of birds in their habitats is in direct and close connection with their possibilities of movement, since only flight can bring a bird that has flown hundreds and thousands of kilometers from its nesting site in the fall back to that small piece of land where it nested last year (or in previous years). This, in addition, is connected with the peculiarities of the birds’ orientation, which will be discussed below. Before moving on to consideration of individual issues of bird biology, a few words regarding plumage, which performs various and very important functions. Bird feathers serve the purpose of thermoregulation, mainly to preserve heat, create a “streamlined” surface of the body and protect the skin from damage.

Although the body of birds is usually completely covered with 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 some specific areas, which are called pterilia, while those located between them, the areas of skin that do not bear feathers are called apteria. There are usually contour feathers, down and some other types of feathers. The structure of a contour pen is as follows. There is a dense and elastic rod, around which, usually symmetrically, a fan is located, forming a dense plate impenetrable to air. The part of the rod that directly comes out of the skin and does not carry a fan is called the edge, the rest of it is called the trunk. Often the feather also has a so-called side trunk, which looks like a thin and soft rod with downy barbs and in rare cases (for example, in emus and cassowaries) reaches great development. Contour feathers come in different sizes and shapes. Different groups of them, bearing different names, have different functions. Among them, primary and secondary flight feathers should be highlighted. The first, usually 9 or 10 in number, are attached to the back of the hand, they are stiffer than all other feathers and during flight they create thrust (to a lesser extent lifting force), their feathers are usually asymmetrical. The secondaries 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 tubenoses). They make up the load-bearing surface of the wing. The tail is formed by tail feathers (their number ranges from 8 to 28). The rest of the covert feathers have special names according to their location on the body: upper coverts and lower coverts of the tail, large, medium, small wing coverts, etc. The down differs from the contour feather in that its shaft is soft, the webs are also soft and their beards are not linked together. Down grows either only on the pterilia, or on the apteria; in some groups of birds, it grows all over the body. Down serves to retain heat. In the structure of the bird, from the point of view of adaptation to certain methods of movement, the following features attract attention. In a skeleton characterized 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 water. In this regard, the forelimbs do not have grasping functions (although in hoatzin chicks, whose fingers also remain free for some time, the forelimb is used for climbing branches). This, in turn, caused changes in the structure of the head and neck skeleton. The beak performs grasping functions. This is associated with significant mobility of the occipital joint, strong development of the muscles rotating the head and transfer of the center of gravity of the head back. The cervical spine in birds is very mobile, and the chest seems to be pushed back. The mobility of the cervical spine is expressed in both 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 skeleton of the body, 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 rails living in bushes). In many forms, a number of thoracic vertebrae fuse into one so-called dorsal bone, a number of vertebrae (lumbar, sacral, caudal, and sometimes thoracic) fuse together with the pelvic bones into a complex sacrum. Free tail vertebrates are few in number, and the terminal caudal vertebrae are fused into the pygostyle bone, which serves to support the tail feathers. The shoulder blades fit tightly 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 creates support for the internal organs during flight, and its large crest (keel) serves as the attachment point for powerful muscles that control the movement of the wing. The trunk skeleton of birds is strong and inactive, somewhat reminiscent of the skeleton of an airplane. It can be added that birds are firmly attached to the ribs, and the movement of the latter during flight automatically stimulates the functioning of the respiratory apparatus. In the structure of the limbs, the most characteristic feature is the fusion of a number of bone elements. The complex sacrum and pelvis, formed by the fusion of a number of vertebrae and pelvic bones, give the hind limbs strong support. The widest and most stable pelvis is characteristic of terrestrial (running) and climbing species, the narrowest - diving. The bird's thigh is short but powerful. Unlike reptiles, the femoral neck is located at a right angle to the main part. The mobility of the hip in birds is therefore limited, but the articulation of the hip with the pelvis is extremely strong. The tibia is reduced and, to one degree or another, 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. Birds therefore have not an ankle joint, but an intertarsal (intertarsal) joint. This arrangement of the leg gives it greater strength and stability. In particular, the fusion of the metatarsal bones makes it easier to maintain balance when the bird lands on the ground or on a branch. A strong and long tarsus makes it easier to push off during takeoff and makes the bird more stable. Birds' toes are well developed and represent a wide variety of adaptations to their method of locomotion. In forms that live in swampy places and move on soft surfaces, they are very long. In running terrestrial forms they are strong, but rather short, and in the groups most specialized for movement on land (ostriches, etc.), like mammals, a reduction (decrease) in the number of fingers is observed. In tree forms, complex adaptations to the coverage of branches and certain correlations (dependencies) between the length of the fingers and the size of the branches on which certain species sit are observed. Aquatic forms develop swimming membranes.

Birds have four or three toes on their feet. The first toe is usually turned backward, often poorly developed and, in the case of a three-toed foot, absent. The African ostrich has only two toes. The forelimb of birds - the wing - is extremely unique. The final part of it is structured very simply, since a significant number of bones grow together. The wing toes of birds do not protrude outward and are covered by a common skin covering; 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); the distal carpal bones and metacarpus bones fuse to form one bone; Only two proximal carpal bones are preserved. The individual elements of the carpal section of the wing are inactive, and the whole of it serves as a strong support for the flight feathers. In this case, the first finger carries the wing, the second finger carries the first, second and third primary flight muscles, the third finger carries the fourth primary flight muscle, the remaining primary flight muscles are attached to the wrist. The strength of the parts of the skeleton that bear the primary flight feathers is of great importance for flight, since these feathers are the bird’s means of moving forward (and at the same time lifting), while the secondary flight feathers, located along the direction of the air flow, perform only the task of maintaining the bird in the air and her rise. The strength of the bird skeleton, in addition to the fusion of its individual elements, is also determined by the composition (abundance of mineral salts) and the structure of the bones; the lightness is explained by the airiness (pneumaticity) of many bones associated with the systems of air sacs - pulmonary and nasopharyngeal. The relative weight of the skeleton in birds is therefore small.

Due to the vigorous functioning of the limbs and poor mobility of the body, birds have highly developed muscles of the wing and legs and relatively weakly developed muscles of the trunk. The cervical muscles are very complex and functionally diverse, this ensures neck mobility. The pectoralis major muscle, which lowers the wing, making up approximately 1/14 in birds of prey and 1/11 of the total body weight in goose, 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 primarily use soaring flight, have relatively underdeveloped wing muscles. Birds with a small wing surface have strong muscles. Generally speaking, the muscles of birds are characterized by high density, mobility, and long tendons. Among the features of the muscles of birds, it is also worth mentioning the peculiar structure of the tendons of the muscle - the deep flexor of the fingers, which creates an automatic clamping of the branch with the fingers of a sitting bird. The tendon of the deep flexor digitorum has an uneven surface, covered with notches, which correspond to protrusions or ribs on the wide and free tendon bursa. For 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 is apparently present in all birds (only ratites and penguins do not have it). Birds move on a wide variety of substrates; They, in general, move well on the ground, climb trees, many dive and swim in the water, but the most characteristic method of bird movement is still flight. There are few flightless forms among modern birds. Some of them (ostriches, emus, cassowaries, rheas, kiwis, penguins) may have never flown, others have lost the ability to fly, undoubtedly for the second time.

The aerodynamic picture of bird movement through the air is very complex. The flight patterns of individual groups and species are very diverse and are directly related to both their ecological properties (sea, terrestrial, arboreal; catching sitting or flying prey, etc.) and 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 ​​the wings (the so-called weight load), and the development of muscles are the main factors that determine the flight properties of birds. Bird flight can be divided into two main categories: soaring, or passive, flight and flapping, or active, flight. When soaring, a bird moves in the air for a long time, without flapping its wings and using rising air currents that are formed due to uneven heating of the earth's surface by the sun. The speed of these air currents determines the bird's flight altitude. If the upward moving air flow rises at a speed equal to the speed of the bird's fall, then the bird can float at the same level; if the air rises at a speed exceeding the speed of the bird’s fall, then the latter rises upward. Using differences in the speed of two air flows, the uneven action of the wind - its strengthening and weakening, changes in wind direction, air pulsations - 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 and others, usually use only rising 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 wind, differences in the speed of air flows, air pulsations and turbulence. Soaring birds are characterized by large sizes, long wings, long shoulders and forearm (great development of the supporting surface of the secondary flight feathers, the number of which in vultures reaches 19-20, and in albatrosses even 37), a rather short hand, relatively small heart sizes (since passive flight does not require intense muscle work). The wing can be either wide (terrestrial species) or narrow (marine species). Flapping flight is more complex and varied than soaring flight. 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 swiftly rushing at its prey, a quickly flying duck and a pheasant heavily flapping its wings to be convinced of the validity of this remark. There are various and rather controversial attempts to classify the different types of flapping flight, which we will not dwell on here. A bird usually does not use one type of flight, but combines them depending on the circumstances. It should also be borne in mind that flight movements consist of phases that successively replace one another. The flapping of the wings is followed by phases when the wing does not produce rowing movements: this is gliding flight, or soaring. This flight is used mainly by birds of medium and large sizes, with sufficient weight. Small birds usually work energetically with their wings all the time or at times can fold their wings, pressing them to the body. The latter is especially typical for finches. Acceleration in flight is achieved by the bird by increasing the weight load of the supporting surface, for which it is necessary to fold the wings slightly. The slow-flying bird has a fully unfurled tail and outstretched wings. As the movement accelerates, it slightly folds the flight feathers, and in all well-flying birds they form a continuous surface (in the falcon, gull, swift, swallow, etc.). Wind is of great importance for the speed of movement of birds. Generally speaking, a tailwind or somewhat crosswind is favorable for flight, but a headwind is favorable for takeoff and landing. A tailwind during flight helps to increase the bird's flight speed. This increase is quite significant: for example, based on observations of pelicans in California, it was established that an increase in air speed from actual calm to 90 km/h contributed to a 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 active flight control. The duration and speed of flight of birds is very great, although exaggerated ideas are usually common in this regard. The very phenomenon of flights shows that birds can make long movements. European swallows, for example, winter in tropical Africa, and some waders nesting in North-Eastern Siberia fly to New Zealand and Australia for the winter. The speed and altitude of birds' flight are significant, although they have long been surpassed by modern flying machines. 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.) d.) made it possible to more accurately determine the flight speeds of birds. It turned out that when migrating birds, on average, they use higher speeds than when moving outside the migration season. When migrating, rooks move at a speed of 65 km/h. The average speed of their flight outside of migration time - during the nesting period and wintering - is approximately 48 km/h. During migration, starlings fly at a speed of 70-80 km/h, at other times 45-48 km/h. Based on observations from airplanes, it has been established that the average speed of movement of birds during migration ranges between 50 and 90 km/h. Thus, gray cranes, herring gulls, large sea gulls fly at a speed of 50 km/h, finches, siskins - 55 km/h, killer whale swallows - 55-60 km/h, wild geese (different species) - 70-90 km /hour, wigeons - 75-85 km/hour, waders (different species) - on average about 90 km/hour. The highest speed was observed for the black swift - 110-150 km/h. These figures refer to spring migrations, which are the most intense and probably reflect the highest flight speeds of birds. Autumn migrations proceed much more slowly, for example, the flight speed of storks during 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 idea that bird movements usually take place 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 has been confirmed by the use of radar. It turned out that migrations in spring take place at higher altitudes than in autumn, and that birds fly at higher altitudes at night than during the day. Passerine birds, such as finches, fly at altitudes somewhat lower than 1500 m; larger passerines, such as blackbirds, are at an altitude of 2000-2500 m. Waders fly at an altitude of about 1500 m.

Although flight is the main and most characteristic method of movement of birds, they also have other very diverse modes of movement. The well-known divisions of birds into aquatic, terrestrial, and arboreal indicate known differences between these groups in relation to movement. Land birds are characterized by running and walking, aquatic birds are characterized by swimming and diving, and arboreal birds are characterized by jumping and climbing on branches and tree trunks. It is clear that this division is schematic and does not exhaust the entire complexity of bird movements. Tree-climbing birds have highly developed claws on their paws, their toes can be spread wide apart, often with the fourth toe moving far forward. Examples of tree-climbing birds include pikas, nuthatches, woodpeckers, and parrots. In birds that climb trees from bottom to top, a rigid tail with pointed tails serves as a support for climbing. The legs of climbing birds are short, and the flexor muscles are highly developed. The main phalanges of the fingers are short. Arboreal birds that jump and climb branches have highly developed clamping devices for the flexor digitorum profundus tendon. Parrots have widened paws, and their fingers can be extended widely; When climbing, they are also helped by their beak, which is strong and mobile. Birds with long wings tend to move poorly on the ground. Swifts cannot, for example, walk at all. Grebes and loons walk poorly on the ground. In them, like in the guillemots living on the rocks, the tarsus faces straight forward, which increases the stability of the birds when sitting. A good adaptation for increasing the supporting surface when walking is the elongated outgrowths on the fingers that develop in the winter in most grouse, and in ptarmigans - claws (they are longer in winter) and the feathering of the fingers, which makes it easier for them to move through the snow. Many birds living on marshy soil have long fingers, for example, the fingers of jacanas running on the leaves of aquatic vegetation are very long. Birds that walk and run well have long legs, and both the tarsus and shin are long (for example, in waders, rails, and partly in chickens). The ability to run reaches its greatest development in ostriches and rheas. An emu can run at a speed of 31 km/hour. The ground cuckoo can reach speeds of up to 20 km/h, and the quail - up to 15.5 km/h. Many birds swim and dive: Anseriformes, petrels, copepods, some waders, terns, gulls, guillemots. Swimming and diving birds have widely spaced, shortened legs (the thigh and tarsus are shortened), so on land they waddle! They are characterized by rigid plumage that fits tightly to the body. In aquatic birds, the coccygeal gland is usually well developed, but, judging by the latest data, its function is not directly related to the waterproofness of plumage. The body of swimming birds is usually elongated, while that of diving birds is flattened. The specific gravity of swimming, and especially diving, birds is significant, approaching unity for 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 sizes of the wings are insignificant. It can be said that birds that dive well are on the way to losing the ability to fly; In addition to birds that are reluctant to fly and fly heavily, among the divers there are also flightless ones (the Galapagos cormorant, the recently extinct “wingless” auk, etc.). Diving birds are also characterized by moving the center of gravity of the body backward, which makes it easier for the rear part of the body and legs to submerge in the 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 moved back and pulled up; The shins lie almost horizontally, the hips are directed forward and down. The webbed fingers serve as a kind of blade of a propeller or oar; swimming movements are reduced mainly to straightening and bending with the tarsus. To speed up movement in the water, the bird raises and lowers its thigh and moves its lower leg back and forth. This work of the legs of a swimming bird is ensured by the strong development of the muscles that lower the femur, extend the metatarsus and flex the toes. Birds row either with one or two legs at once, and to turn on the water they use pushes or blows from the opposite side of the leg (when turning right - with the left, when turning left - with the right). Bird diving and snorkeling are of two types. Some birds swim underwater using their wings (as if flying); others - with the help of their legs. There are also intermediate types. The first includes penguins, the second includes diving ducks, cormorants, loons and grebes. When diving, guillemots use both wings and legs. A dipper running along the bottom of streams spreads its wings to stay in the water (the insignificant specific gravity of the dipper would otherwise contribute to pushing it out of the aquatic environment to the surface). A special method of diving, associated not with swimming under water, but only with immersion, in diving petrels, gannets, terns, ospreys; These birds, rushing at their prey, fall into the water from a flight and then immediately climb to the surface. Ducks, geese, coots, cormorants and other birds move tirelessly in the aquatic environment all day long. The energetic work of the locomotor system, heart and lungs allows diving birds to stay under water for a long time. The auk can stay under water for 1-2 minutes, the arctic loon - slightly more than 3 minutes, the black-throated loon - 2 minutes, the cormorant - more than 1 minute, the scoter - up to 3 minutes, the great merganser - up to 2 minutes, the American coot - 3 minutes. These are the maximum numbers. Maximum diving depths for great grebe - 7 m, loon - 10.2 m, black-throated loon - 6.1 m, red-throated loon - 8.8 m, great cormorant - 9.4 m, scoter - 7.2 m, mergansers - 4.1-5.6 m, eiders - 4.8 m. Penguins swim under water about 10 m/sec, grebes - about 1 m/sec.

For the existence of each animal species, it is necessary to resolve three main tasks: nutrition, reproduction and protection from dangers in order to preserve individuals and the species in the conditions of the struggle for existence. Movement in vertebrates, and in particular in birds, is one of the most essential elements of animal defense. Having examined the related aspects of bird biology, let us move on to consider their features related to nutrition. Nutritional conditions largely determine the course of life events in birds. They influence the geographic distribution of birds, seasonal movements, rates of reproduction and mortality, and the 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 partly cause changes in nutritional conditions, partly change the body's norm of need for food (in the cold season, when the body loses a lot of heat, more food is required). The movements 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 particular type of food (euryphages). Birds feed on both plant and animal food, and the latter, in general, predominates. Let us dwell on the most important structural features of birds associated with feeding conditions and methods. With relatively few exceptions (notably owls and birds of prey), birds take food with their beaks. The shape of the beak is therefore very diverse. 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 of these birds is compensated by the highly developed pneumaticity of the skull. Finally, a long beak is found in many species that suck flower nectar (many hummingbirds, honey suckers, etc.) or in birds that look for food in the folds and recesses of stones or bark (pikas, wall climbers). In birds whose beak serves to hold live and sometimes large prey, it is of moderate length or even short, but is equipped with a steep hook at the end of the upper jaw (cormorants, owls, diurnal raptors), and sometimes with a tooth (falcon). In birds that grab 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 (carnivores, owls); in the latter case, grabbing prey is usually done with force with armed paws. In birds that grab insects in flight - swallows, swifts, flycatchers - the beak is not long, rather 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, making it easier to catch insects. Woodpeckers chiseling a tree have a very strong, straight and chisel-shaped beak; its action is complemented by a long tongue, the end of which is seated with sharp spike-like protrusions. Holding the insect tightly. In crossbills that remove coniferous seeds from cones, the jaws cross crosswise and form a lever for lifting the cone scales. Granivorous passerines (finches and others) have a short, strong, wide and high beak; their palatal surface bears sharp grooves and ridges; all this is a device for biting and crushing seeds and fruit seeds.

The esophagus of birds is quite distensible, especially in species that swallow large prey (pelicans, gulls, herons, cormorants); A characteristic and common formation is the so-called goiter - a gland-rich expansion of the esophagus. In those birds that immediately absorb a large amount of food, but sometimes starve for a long time, the crop serves as a reservoir for food that gradually enters the stomach. In others, for example, chickens and parrots, pre-processing of food begins already in the crop. In predators, undigested parts of food accumulate in the crop - bones, wool, feathers, etc. The anterior section of the stomach of birds - the so-called glandular stomach - performs the functions of chemical processing of incoming food, and the posterior section - the muscular stomach - processes food mechanically. The posterior (lower) end of the stomach is separated from the intestine by a ring-shaped constrictor muscle (sphincter), which prevents bone fragments and other hard or sharp parts of food from entering the small intestines. In fish-eating species of birds (herons, cormorants, grebes, penguins) and some others, in the posterior horse of the stomach there is a third section - the so-called pyloric sac; its function is to prolong the stay of food in the stomach for better processing. The glandular stomach is most developed in birds that immediately swallow larger amounts of food (in piscivores and carnivores). The secretion of the digestive glands in birds acts very energetically: in marabou and many raptors it completely or significantly dissolves bones, and in cormorants, herons and ducks, fish scales in owls and shrikes are not digested at all. For all types of birds, chitin, keratin and fiber are indigestible (the latter, perhaps, in chickens, ducks and pigeons is partially digested due to the activity of intestinal bacteria). The muscular stomach of some birds is distinguished by the strong development of muscles, which also form tendon discs. In this case, the walls of the stomach work like a millstone and grind hard and rough food. This is how the muscular stomach is structured in granivores and birds that harbor hard arthropods (chickens, anseriformes, ostriches, cranes, many passerines, many pigeons). In other birds, the muscles in the muscular stomach are slightly developed, and it continues mainly the chemical processing of food with enzymes flowing from the glandular stomach. This is how the muscular stomach works in meat-eating, fish-eating and frugivorous birds. In many species of birds, the tubular glands of the muscular stomach secrete a secretion, which then forms a periodically changing hard keratin shell, the so-called cuticle. This 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 plant seeds. Digested food passes from the stomach to the intestines, first into the duodenum, then into the small intestines. Most birds have cecums. Sometimes they carry digestive functions, sometimes they are also a lymphatic-epithelial organ, sometimes only the latter; in some species the cecum is rudimentary or even completely absent. They reach their greatest development in herbivorous birds (however, there are exceptions). The rectum in birds serves for the accumulation of undigested food debris; its end passes into the cloaca - an organ common to birds and reptiles. The ducts of the urinary and reproductive systems also open into the cloaca, and on its dorsal side there is the so-called bursa of Fabricius, which undergoes reduction in adult birds (at the age of 8-9 months), but is well developed in young birds. The function of this bag is the formation of lymphatic cells and oxyphilic leukocytes. The liver of birds is relatively very large, its bile ducts empty into the duodenum. Most species have a gall bladder, which is due to the need to simultaneously supply the intestines with a large amount of bile (for processing watery and fatty foods). The pancreas in birds has a rather varied shape, but is always well developed and relatively larger than in mammals. Its size and significance are inversely proportional to the gall bladder: it is largest in granivores, smaller in meat-eating birds. The relative total energy turnover in birds is very high, especially in small passerines; in large species it approaches the value of the energy turnover of mammals. In a hooded crow, for example, at an ambient temperature of 20-22°C, the total energy turnover is 840 cal per 1 m2 of body surface per day, in a buzzard - 780 cal, in a chicken (at a temperature of 23°C) -580 cal; at the same time, at a neutral temperature (32-36 ° C), i.e., with minimal heat transfer, the energy turnover of the goldfinch is 1534 cal, and for the gray shrike even 1775 cal per 1 m2 of surface per day. Energy turnover and the need for nutrients, and in accordance with this, cardiac activity and the functioning of the respiratory apparatus change, depending on external conditions and periodic changes in the internal state of the body. In males, energy expenditure increases during the mating period, in females - during the period of egg laying. An increase in energy expenditure is associated with the molting period. A decrease in energy turnover is observed in brooding birds, which can be considered as an adaptation to a long and motionless 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 the sparrow to increase its oxygen consumption threefold. Small, birds; to preserve heat they are forced to spend; more energy than large ones (the size of the body surface increases in the 5th square, and the volume in the cube, therefore, in large birds; the ratio of body surface to volume is more favorable in birds). Small birds, when the temperature drops significantly, spend more than half of the energy received from feeding on thermoregulation of the body. In winter, due to colder weather and shorter days, critical moments come for birds, 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 obtain sufficient sources of energy.

Plumage and its seasonal changes are essential for the thermoregulation of birds. When molting in the fall, many species experience an increase in the downy part of the feather or (with double molting 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 having thicker and more magnificent plumage (three-toed woodpeckers, great spotted woodpeckers, chickadees, gyrfalcons). Of great importance for northern birds is the white color of their plumage, in which air bubbles form in the feathers, creating a heat-insulating layer. The importance of a feather for preserving heat is clear in itself, but a concrete idea of ​​this is best seen from the experiment of Giaia (1929): in the great gray shrike, when the temperature dropped from 28 to 0.6 °, energy expenditure increased by 50%, but when the bird was plucked, then the same difference in temperature caused an increase in energy consumption three times, i.e. by 200%. Other adaptations to cold temperatures: deposition of subcutaneous fat (especially in aquatic 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 . Fasting 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 absorption is faster. Opposite indicators indicate a lower 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 (snowy owl - 24 days, white-tailed eagle - 45 days, golden eagle - 21 days, domestic chickens - 26- 31 days). Weight loss can reach 30-40%. The bird's body's need for water is relatively small. This is explained by the insignificance of skin evaporation, as well as by the fact that water from urine is absorbed back by the bird’s body while the urine is in the upper part of the cloaca. Many meat-eating and frugivorous species 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, and seeds slower. A bird can eat a lot in a day, and the maximum in this case often greatly exceeds the required minimum. Small owls (little 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, grains in chickens - in 12-24 hours. Insectivorous birds fill their stomachs five to six times a day, granivorous birds - twice. Carnivores eat once or twice a day. Small birds eat about ? their weight, large ones are 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. Thus, 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. In this case, the weight gain in chicks per day is 20-60% of the initial weight. During the first seven to eight days, the weight of passerine chicks increases 5-6 times. It is therefore clear that the chick eats more food per day than it weighs. This circumstance determines the enormous importance of insectivorous birds in the life of nature and in the human economy. With a high growth rate of birds and a fairly significant number of eggs in clutches (of which, in many species, it is normal to have two per year, and for some, three), one pair of passerine birds has to feed on average 10-15 young annually.

Finally, another remarkable biological property of birds has been established relatively recently: the abundance of food and favorable feeding conditions cause them to increase their reproduction. Thus, in many species, in years with favorable nutritional conditions, the number of eggs in a clutch is greater than in less favorable years. Sometimes, in years that are rich in food, birds have additional clutches. On the contrary, in years with unfavorable feeding conditions, the intensity of reproduction decreases (the number of eggs in a clutch is smaller), and mortality among young birds becomes very high. One more feature deserves attention. When there is 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 normal average years - up to 5 pieces, the kestrel eats 9 and 2 mice, respectively, long-eared owls - 12 and 4, etc. etc. It should be taken into account that one vole, according to our ecologists, destroys up to 2 kg of grain per year. Finally, the abundant appearance of some kind of food sometimes leads to the fact that those species of birds that usually neglect this type of food begin to feed on it. The results of observations made by A. N. Formozov in 1936 in North-West Kazakhstan are interesting: when a large number of locusts appeared, even ducks began to feed on them. Thus, we can say that feeding conditions determine many aspects of the life of birds, and in the event of mass reproduction of a particular food item for birds, it attracts special attention from them. Consequently, a certain kind of natural regulation of the number of massively multiplied animals occurs. 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 clear. When, for example, in 1893-1895. In the Volga region, a forest pest - the gypsy moth - multiplied greatly, local observers noted an unusual raid of cuckoos. The reproduction of field crop pests - click beetles - attracts rooks, which 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 per year. There are observations of how a flock of rooks completely cleared an area of ​​6 hectares of these pests in one day. The breeding of locusts causes increased reproduction and accumulation of various starlings, in particular pink ones. The wandering locusts are followed by a wide variety of bird species. The breeding 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, ruffed buzzards and even peregrine falcons. The food of many bird species consists of animals that have a negative meaning for the human economy. These are insects and small mammals, primarily rodents. Reproduction of both occurs and can proceed very quickly. And the main positive significance of birds for the economy lies in the fight against these pests. Game birds and poultry bring direct benefits to humans, but their significance, contrary to what is still widely believed today, 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 threat to agriculture from pests should in no way be downplayed. 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, field crop losses from pests were determined (with a certain approximation, of course) at 900 million rubles. per year, losses in forestry - 300 million rubles, losses in gardening and horticulture - 90 million rubles. In the United States of America, agricultural losses from animal pests in 1921 were estimated at a billion dollars, and the benefits from the extermination of insects by birds were 444 million dollars; consequently, the birds reduced the damage by more than one-third in relative terms and by an enormous absolute amount. All these calculations are, of course, approximate, but they give an idea of ​​the scale and general significance of this phenomenon.

One more consideration is important. Of the known species of birds, the vast majority belong to the passerine order, which unites, 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 believe that insectivorous birds make up about 90% of the total number of individuals of currently living birds. If so, then we can perhaps agree with one American author who said; the idea that "if all birds were destroyed, agriculture in the United States would become 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 great and can be characterized as “control” over the proliferation of pests, as a very significant tool for keeping the number of pests at a low level. Other aspects of bird activity related to feeding are also of concern to humans. Many granivorous birds contribute to the dissemination of seeds (the latter sometimes remain viable even after passing through the bird’s intestines); in southern countries, many species actively contribute to the pollination of plants. Birds of prey that hunt other birds and animals play a certain positive role as an instrument of selection. A certain number of predators helps maintain the health of the species that are their prey, since they primarily prey on sick or weak specimens. Birds that feed on carrion bring certain health benefits.

From the point of view of human economic interests, the negative traits of birds associated with nutrition can be summarized in general terms as the extermination of useful wild animals and wild plants, competition with more useful species of animals, harm to cultivated plants, and 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 useful 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. A bird, like any other animal, can be both beneficial and harmful only under certain conditions and at a certain time. As the situation changes, the economic importance of birds also changes. Starlings, for example, which are beneficial in the spring and summer by exterminating insects, in some areas during migration and wintering can be definitely harmful to gardens, and until quite recently in Tunisia, the fight against starlings was carried out with the massive use of explosives. Crows cause harm by destroying the nests of beneficial birds, in particular waterfowl, but at the same time they exterminate insects, mice and voles. The Great Spotted Woodpecker feeds on insects 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 Buzuluksky Forest, damage from the Great Spotted Woodpecker interferes with the normal regeneration of pine trees, more than good). The sparrow eats berries, displaces beneficial insectivorous birds from nesting sites, but also feeds the chicks with insects. 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, since the falcon energetically attacks the arctic foxes and drives them away from the vicinity of its nest, thereby providing significant assistance to the entire surrounding bird population . The goshawk feeds on beneficial birds, but contributes to natural selection and in places is justly valued as an excellent bird of prey. We will not touch here on the very important issue of the aesthetic significance of birds. It is useful to emphasize that in the fauna of Russia, which numbers more than 750 species of birds, at least less than a dozen species are significantly harmful. Borrowed from Western European owners of hunting grounds and their rangers and, unfortunately, a firmly rooted and widespread opinion about the “harm” of birds of prey must be decisively discarded. The vast majority of predators benefit by exterminating 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 numbers in areas (north) where wild resources have not yet been sufficiently used by humans. They are in no way competitors of the latter, but at the same time they serve as one of the best decorations of our nature; and the reproduction of birds of prey proceeds at a relatively slow pace. This does not mean that one should not fight against predators who have gotten into the habit of catching pigeons, poultry, or against a hawk that disperses black grouse currents in an organized hunting area, etc.

Feeding conditions affect the geographic and stationary distribution of birds. This especially applies to those species that are stenophages, i.e., highly specialized in nutrition. The African vulture eagle is found only where the type of palm tree from which it feeds grows. Many birds that feed on certain plants or have a certain type of plant predominant in their diet are found only where these plants are available. For example, Scottish grouse is closely related in its distribution to wild rosemary, crossbills - to certain species of coniferous trees, honey suckers, hummingbirds, etc. - to the presence of those plants whose nectar they feed on. There are, in fact, few omnivorous birds: ravens can serve as an example. In general, each species of bird is characterized by a certain specialization both in the choice of food and in the methods of obtaining it. Unfortunately, these issues have not yet been sufficiently studied. 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, young birds of prey that do not receive bones develop rickets and the normal course of molting is disrupted. For grouse it is necessary, from time to time, to swallow pine needles, which probably serve to cleanse the stomach of worms. Changing external conditions that determine feeding conditions is of great importance for birds. These changes are especially affected in those areas where climatic changes between seasons are significant or where various types of meteorological conditions (snow cover, humidity, temperature, etc.) fluctuate greatly. The effect of temperature on the bird’s body’s need for food and the effect of light on the ability to satisfy this need has already been discussed above. Snow cover is also of great importance for ground-feeding species. Therefore, for example, many granivorous birds spend the winter in Mongolia, where winters are very harsh but there is little snow. On the other hand, for example, in. In Lapland beyond the Arctic Circle, even in winter you can find a fairly diverse composition of small passerines: chickadees, great tits, pikas, etc. These birds obtain food from trees and are less dependent on snow cover. For the same reason, birds that obtain food from cracks and other shelters or on vertical tree trunks in the bark, etc., for example, wrens, nuthatches and the already mentioned pikas, do not fly away for the winter, but remain in the cold and temperate zones of their homeland. Even in the conditions of the Arctic polar night, birds winter, as long as they have the opportunity to get their own food. For example, off the coast of Greenland, the Arctic guillemot winters near wormwood and clearings at 77° and even 78°30" north latitude, off Spitsbergen - even at 80° north latitude. In the tropics and subtropics, the main climatic reason for changes in the feeding conditions of birds is the onset of dry times reptiles. The disappearance of insects, a decrease in the number of insects, periodic changes in the life of plants - all these factors determine the food regime 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 food regime. Whites partridges, for example, feed mainly on berries and insects in the summer, berries in the fall, and willow shoots in the winter. The raven in Northern Siberia is omnivorous in the summer and feeds mainly on pieds in the winter. Starlings feed mainly on insects in the summer, and also on fruits and berries in the fall and wintering grounds. There are many such examples that could be given: The harvest and failure of food harvests have an enormous impact on the life of birds. Periodic quantitative fluctuations in the animal population and in plant cover cause periodic fluctuations in the living conditions of birds, for which certain animals and plants serve as food. These phenomena include the harvest and failure of fruits and berries, the abundance or scarcity of insects, the mass reproduction or extinction of rodents, etc. The mass appearance of food items also causes the mass appearance of the corresponding species of birds, and vice versa. For example, when the mountain ash crop fails, waxwings migrate in droves from Northern Europe, and when the cone harvest fails, crossbills, nuts, etc. More or less long-term changes in nutritional conditions sometimes cause changes in the boundaries of the distribution area. Thus, the house sparrow gradually spread, following humans, but the replacement of horses with 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 numbers. In Lapland, in “lemming” years, the hawk owl has 11-13 eggs, the great gray owl has 7-9 eggs, the eagle owl has up to 6, the long-eared owl has 7-9, and the snowy owl has 11-12. Even in the Lapland gyrfalcon, in an exceptionally abundant year with lemmings, clutches of 7-9 eggs were found near the city of Kautokeino in northeastern Norway. Second clutches in food-rich years in species that usually have only one clutch have already been discussed. On the other hand, in lean years, when the number of rodents decreases, the predators that feed on them have fewer eggs in their clutches, and the mortality rate among chicks is higher. Apparently, the phenomenon of cannibalism among the chicks of many species of raptors - hawks, eagles and other birds, when the youngest of the chicks becomes a victim of the older ones, can be explained as a consequence of poor feeding conditions. The influence of feeding conditions on the reproduction of birds is especially noticeable in the north, where, in connection with this, periodic non-breeding 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 (hazel grouse, partridges, quails, pheasants, 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 set of external and internal reasons. We will return to the issue of flights below.

The cycle of phenomena in the life of birds associated 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 of the year, and at rest the size of the gonads is literally tens of times smaller than during the period of activity. The structure of the female reproductive system is characterized by its asymmetry: the right ovary is usually absent, the right oviduct is always absent. During the breeding season, the volume of the ovary increases significantly, and since the eggs in it are at different stages of development, the entire organ takes on a grape-like shape. After laying eggs, the ovary quickly decreases, and its size reaches the size of the ovary of the resting period while the bird is incubating. In the same way, due to the onset of the breeding season, the oviduct also increases in volume. For example, in a domestic chicken, the oviduct during the resting period is about 180 mm in length and 1.5 mm in the lumen; during the laying period, it is about 800 mm in length and about 10 mm in the lumen. All sections of the oviduct at this time become more isolated than at other times of the year. After the laying period, the oviduct collapses, the canaliculi of its glands are reduced, its lumen remains uneven and in some places expanded. In a bird that did not lay eggs, the oviduct has the appearance of a smooth and thin tubule throughout. These differences in the condition of the oviduct can serve as a reliable indicator for determining the age of autumn and spring birds. A very characteristic adaptation to the hatching of offspring in birds is the development of so-called brooding spots. The presence of these spots makes it easier to heat the masonry. The skin in the area of ​​the brood spots is characterized by particularly loose connective tissue; the fat layer usually disappears here; down, and sometimes feathers and their rudiments fall out; skin muscle fibers are reduced; at the same time, blood supply to these places is enhanced. A fully developed brood spot is an area of ​​bare and slightly inflamed skin. Each bird species is characterized by a specific arrangement of brood spots; They are either paired or unpaired. Passerines, petrels, and guillemots have one spot; pheasants, waders, gulls, and raptors have two abdominal spots and one chest spot. The size of the brood spots is in a certain correspondence with the size of the clutch. Geese and ducks do not have brood spots; However, during the period of laying eggs, they develop a special long fluff, which is pulled out by the bird; The incubating bird surrounds the eggs in the nest with this down, and it serves as an excellent means of protecting them from chilling. Gannets do not have brood spots, but warm the eggs by covering them on top with their webbed feet; guillemots and penguins put their paws under their 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 extensible 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, many species develop a bright mating plumage. The difference in appearance between males and females is referred to as sexual dimorphism. External signs of sexual dimorphism cannot be placed into any general scheme. Penguins, petrels, copepods, grebes, loons, whirligigs, swifts, many bee-eaters and kingfishers have no differences between the sexes in either color or size. Males and females of small passerines, most raptors, owls, waders, gulls, guillemots, rails and other birds differ only in size. In other species, males differ more or less sharply from females in color. Typically, 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) the females often have a pronounced protective coloration. In the same species in which males take care of the offspring (colored snipe, waders, some kingfishers, threefingers, etc.), the females are somewhat brighter than the males. Differences in color usually appear after reaching sexual maturity, but sometimes earlier (woodpeckers, passerines, etc.). In many forms that have two molts per year, color dimorphism is noticeable only at a certain time of the year, namely during the breeding season. The brightness of the coloring of males is especially characteristic of northern ducks (but not geese), many gallinaceans (pheasants, grouse, wood grouse, black grouse), many passerines (the so-called birds of paradise, orioles, finches, redstarts, etc.). In related groups, differences in the color of the sexes, in general, are of a similar nature even among 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, the males have red colors, which are absent in females, for example in bee-eaters, crossbills, bullfinches, especially in lentils, etc.). Sometimes females develop a color similar to the color of males (the so-called rooster feather color in grouse, in some passerines - redstarts, shrikes, etc. ). In addition, with age, females with functioning gonads sometimes develop features similar to the coloration of the male; this happens, for example, in birds of prey (merlins, etc.). Sexual differences in color are expressed not only in the color of the 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 the males is the same (gray), while the females are dimorphic (in addition to the gray color, there is also a red color). Sexual differences are also expressed in the presence of outgrowths and appendages of skin on the head (for example, in chickens), in the development of individual feathers (crests, long tail coverts in peacocks, feathers on the wing and tail in birds of paradise, long tail feathers in pheasants and etc.), in the proportions, sizes and shape of individual parts of the body, in the structure of the internal organs (the vocal apparatus of many species, the throat sac of a male bustard, etc.), in the overall size. Male gallinaceous birds develop spurs on their legs, and males and females of many species have different beak sizes (hornbills, ducks, scoters, some passerines, etc.). As a rule, males are larger than females. This is especially pronounced in chickens and bustards. In other groups, females are larger than males. This is observed in those species in which males take care of the offspring (phalaropes, colored waders, snipe, tinamous, some cuckoos, kiwi and cassowaries). Larger females, however, are also found in those species in which the main part of caring for the offspring lies with the females (in most diurnal raptors, owls, and many waders).

With the onset of spring, when life begins to revive everywhere in nature, the behavior of birds also changes. Migratory species leave their wintering grounds and go to their distant homeland. Nomadic birds that do not migrate also begin to approach their nesting areas. Sedentary species appear at the nests. This spring revival does not occur simultaneously in all places and not in all bird species. The further south the territory, the earlier, of course, the spring revival of nature begins there. For each species of bird, spring revival is associated with the onset of special circumstances favorable for this species. Sometimes it’s even difficult to understand why one bird flies to the nesting site early and another late. The bearded vulture, or vulture, which lives high in the mountains, begins nesting in the Caucasus and Central Asia in February, when everything around is covered with snow; This early start of nesting is explained by the slow development of the 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, feeding conditions, etc. If bearded vultures began nesting later, then raising their 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 time to hatch the young before the onset of harsh autumn weather. The desert saxaul jay begins 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 allows the desert jay to hatch its young in relative safety. Its nest is easily accessible to the main enemies of birds of the Central Asian deserts - various snakes and monitor lizards, but early nesting allows jay chicks to learn to fly before the revival of reptile activity begins with the onset of warmth. The last example is the swift and the swallow. Both birds fly excellently and feed on insects, but the swift arrives late and flies away 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 feeding the chicks occur later for it than for the swallow. The difference in the structure of the eyes allows the swallow to see well both in front of itself and to the sides, while the swift sees well only in front of itself. Therefore, a swift can only catch flying insects, and a swallow, in addition, can peck or grab in flight those insects that sit on buildings, trees, etc. The mass flight of insects falls at the warmest time, while sitting insects in large numbers can be found earlier and later. That is why the swift appears in our country later than the swallow and flies away earlier.

Many birds mate for life; This includes large predators, owls, herons, storks, etc. Others form seasonal pairs (songbirds). There are, however, also species that do not form pairs at all and in which all care for the offspring falls to the share of one sex alone. Most often this gender is female. This is exactly how the summer life goes for most of our chicken birds - capercaillie, black grouse, pheasant, as well as the common sandpiper. However, among the phalaropes living in the north and among the three-fingered sandpipers found in the Far East, the male takes care of the brood. In the mentioned chickens and turukhtans, the males are brighter in color; than females. The opposite phenomenon occurs in phalaropes and threefingers: the female is taller and more elegantly plumed than the male. Birds that form pairs are called monogamous; birds that do not form pairs are called polygamous. The behavior of birds during the mating season, which usually falls in the spring months and early summer, differs in a number of features. For many birds, their appearance changes at this time. By spring, a number of birds change part of their plumage and put on mating plumage, usually different from the autumn bright colors. In some species, males display, that is, they take special poses that are conspicuous from a distance, and emit special calls. Such display is especially well expressed in gallinaceous birds - black grouse, wood grouse, white partridge, and some waders. Other birds do this in the spring peculiar movements in the air - soar high up, fall down, soar again, emitting loud cries. Such a mating flight is performed, for example, by birds of prey; the spring pull of woodcocks and the spring “bleating” of snipe have the same meaning. In small passerines Male birds sing during the mating season, enlivening with their singing inhospitable deserts, harsh tundras, and human settlements.The same phenomena include the spring “dances” of cranes, the cuckooing of cuckoos, the spring drum trill of woodpeckers, and the cooing of pigeons. Each species of bird is characterized by a specific spring behavior that is different from other species - voice, posture, etc. Each songbird - nightingale, starling, finch - sings in its own way. Showing, therefore, refers only to other individuals of the same species and serves as a specific signal for them. These signals are by no means always directed towards individuals of the other sex. For a long time it was thought that the singing of male birds only related to females and attracted them. In reality this is not the case. The meaning of singing, first of all, is to show other males of the same species and possible competitors that the nesting territory is occupied. Birds in the spring, as is known, jealously guard the places they occupy (nesting sites) and expel from them all other individuals of the same species. The nesting site is especially zealously protected during the most “critical” periods, immediately before laying eggs in the nest and during incubation. Interesting observations were made in England. A weasel appeared near the nest of a 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, abandoning the weasel, began to chase the bunting. This scene was repeated three times in a row. The significance of displaying also lies in the fact that it expresses and enhances the excitement of the displaying bird and individuals of the other sex. This is the only meaning that mating has in those species that do not form mating pairs (grouse, black grouse, roach).

The center of the bird's nesting area is the nest - the place where the female lays her eggs. However, not all birds build nests for themselves. In the north, for example, on the islands, in the White Sea, on Novaya Zemlya, as well as on the Chukotka Peninsula, Kamchatka, and the Commander Islands, seabirds (guillemots, guillemots, auks) nest in huge numbers, forming flocks of thousands of people, the so-called “bird colonies” " But they do not actually make nests, and each female lays her egg directly on the rock ledge. The nightjar and the hawkpoor do not make nests: they lay their eggs directly on the ground. Some birds only clear a place for laying and sometimes also make a simple bedding from dry grass, moss, feathers, etc. This is done by pheasants, wood grouse, hazel grouse, white partridges, black grouse, waders, most owls, some predators, as well as those birds that hatch chicks in hollows - woodpeckers, whirligigs. Most birds, however, make nests, and each species has a particular way of making a nest and selecting certain materials for its construction. Young birds, having never seen how a nest is built, build it in the same way as their parents. Most often, nests are made of twigs, grass or moss; These nests are either folded or woven, and special additional materials are often used to fasten them and line them. Blackbirds weave a nest from stems and coat it with clay. The finch makes a nest of moss, camouflaging it with lichen. The titmouse skillfully weaves a nest of wool in the form of a purse with a long side corridor. Small birds (larks, wagtails) nesting on the ground make nests out of grass or line a hole 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 spare ones. In large birds of prey (eagles, eagles), the nest serves for many years in a row and, as a result of amendments and additions, turns over the years into a huge structure up to 2 m in height and in diameter. Such nests, in the end, usually fall to the ground during storms, since the branches that serve as their support cannot withstand their weight. The inside of the nest is usually recessed, and the edges are raised; the recessed part of the nest - the tray, or tray, is used to place eggs and chicks. Some birds make molded nests. Flamingos make nests from mud in shallow water. Rock nuthatches living in the mountains build nests from clay. The barn swallow makes a saucer-shaped nest under roofs made of clay and mud, glued together with saliva. The city swallow, or swallow, makes a nest covered with a roof from the same materials. Some birds nest in burrows. In kingfishers, a zigzag passage breaks through the roots in earthen cliffs on the banks of rivers; this passage leads to a cave, the bottom of which is lined with fish scales. Shore swallows 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. Rosy starlings, shelducks, rollers and bee-eaters nest in the minks. Finally, the common sandpiper, found along the sandy shallows of rivers in Turkmenistan, simply buries its eggs in the hot sand. This method of nesting is somewhat reminiscent of the activities of the weed chickens, or large-footed chickens, living in Australia and on the islands lying southeast of Asia. Weed chickens lay eggs in huge heaps of sand or rotting plants, these heaps sometimes reach 1.5 m in height and 7-8 m in circumference. The eggs here are well protected from cooling, and the embryo’s own heat is enough for its development. A place to build a nest in those birds that actively defend their nesting area, i.e., passerines, nightjars, some waders, etc., is found by the male, who also usually returns from wintering or migrations 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 with favorable temperature conditions, and especially nutritional conditions, the number of eggs in a clutch is greater than in bad years. This has been established for many owls, chicken owls, etc. In particularly unfavorable years, such birds do not nest at all. The age of the bird is also known to matter. Among predators, ravens, old females apparently lay fewer eggs than young ones. In chickens, on the contrary: in the first year, females lay fewer eggs; Young females of some passerines, such as starlings, also lay fewer eggs. Due to different nesting conditions for the same bird species, the number of eggs in a clutch in the north and in the temperate zone is greater than in the south. For example, in the common 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 unfavorable climatic conditions, and also corresponds to large the possibilities of feeding chicks in the north (long days and almost round-the-clock insect activity). There is always one egg in a clutch for some predators (for example, the snake eagle), the common sandpiper, the tubenosed fish, and many guillemots. Nightjars, pigeons, cranes, flamingos, pelicans, gulls, and terns have 2 eggs per clutch. In waders and triplets, 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 duck eggs, the teal has the largest number of eggs - 16, of the chicken eggs, the gray partridge - 25. The usual number of eggs in a clutch of chicken and duck eggs is 8-10. The color and shape of bird eggs are very diverse. Some, for example, owls, have eggs that are almost round, while others have elongated eggs. One end of the egg is usually wide, the other narrower. The narrowing of one end of the egg and the widening of the other are especially pronounced in various guillemots nesting in colonies in the north. For those birds that lay eggs in closed nests, hollows and burrows, or cover their eggs, the color of the shell is white. White eggs are found in owls, kingfishers, rollers, woodpeckers, and many passerines. Birds that nest in open nests, and even more so on the ground, have colorful eggs, and their color is very similar to the color of the landscape surrounding the nest. You can approach two or three steps to a clutch of a sandpiper or partridge lying on the ground and not notice it. The thickness of the shell 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 thickest shells are those belonging to the gallinaceous birds. The size of eggs depends on a number of reasons. Small birds lay fairly large eggs compared to their own weight, while large birds lay small eggs. The more eggs in a clutch, the smaller the relative size of an individual egg. Finally, those birds whose chicks leave the nest well developed and capable of independent movement and obtaining food lay relatively larger eggs compared to those whose chicks are born helpless. The cuckoo lays very small eggs, this is probably explained by the fact that it does not hatch them itself, but throws them into the nests of small birds. Both the cuckoo and the snipe weigh about 100 g, but the snipe egg weighs about 17 g, the 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 clutch. In some birds, the weight of the clutch even exceeds the body weight of an adult bird: in a crake with a clutch of 12 eggs it is 125% of the bird’s weight, in a carrier sandpiper - 117%, in a kinglet with a clutch of 11 eggs - 120%, in a goldeneye duck with clutch of 12 eggs - 110%.

According to the methods of development of chicks, all birds can be divided into two categories: some are called brood birds, others are called chick birds. The chicks of brood birds immediately or very shortly after leaving the egg leave the nest and can move independently. They emerge from the nest with their eyes and ears open, wearing a well-developed downy plumage. This group includes those birds that stay primarily on the ground or near water, but not in trees: ducks, geese, rails, bustards, cranes, loons, grebes, gulls, waders, hazel grouses, flamingos, triplets. Young chicks emerge from the egg with poorly developed muscles of the limbs, bare or slightly pubescent, often blind and deaf. They do not yet have a constant body temperature, and in this respect they resemble lower vertebrates. These chicks are thus completely helpless and spend the first days or weeks of their lives in the nest until they develop plumage and are able to move independently. We can say 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, rakshi, kingfishers, copepods (pelicans and cormorants), as well as raptors, owls and tubenoses. Young chicks have a very characteristic coloring of the mouth and its edges - usually bright (yellow or pink). Caring for the brood is also different in brood and nestling birds. In brood birds, an adult bird, with young ones (in some species a male, in most - a female, less often part of the brood is with a male and part with a female, as is the case with grebes and cranes), leads the brood, protects it, covers it with its body when unfavorable weather occurs (cold, rain), it searches for and points out food to the chicks. However, little ducklings immediately begin to find their own food on their own. In some waterfowl, in the first days of life, when tired, the chicks sit on the mother’s back, and grebes hold the chicks under their wings when swimming and even diving. The relationship between parents and offspring is more complex in nestling birds. In cases where both sexes participate in incubation or when the male feeds the incubating female, both parents jointly feed the chicks, but the nature of their participation in feeding is not the same. At first, in birds of prey, it is mainly the male who catches prey, and the female feeds the chicks, tearing the prey into pieces. When the chicks grow up and begin to tear the prey themselves, both parents bring them food. It has already been noted that feeding chicks requires a lot of effort from old birds. Feeding chicks with food occurs differently in different species. When insectivorous birds arrive at the nest, they give food to only one chick (with rare exceptions), while meat-eating and granivorous birds give food to the entire brood. The sequence and uniformity of feeding chicks in granivores is ensured by the movement of “well-fed” and “hungry” chicks in the nest. Fed chicks usually move to the edge of the nest and defecate, raising their tail high; the hungry move to take their place in 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 the chicks than cold, the parents shade the nest during the hours when direct rays of the sun fall on the brood; an adult bird stands over the nest and slightly opens its wings. Many predators shade their chicks with green tree branches. In nestling birds, the chicks usually leave the nest after they learn to fly. Different species of birds have different periods of time for chicks to stay in the nest. In small passerine birds, the period of stay of the chick in the nest from hatching of the egg to departure is about two weeks or slightly more (in the blue tit it is 18 days, in the kinglet 18-19 days, in the robin 15 days, in the wren 17 days), i.e. e. approximately coincides with the incubation period. In large species, development is slower, 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 the 60-day-old chick. Passerine birds most likely develop chicks of ground-nesting forms (the lark flies out of the nest on the 9th day after hatching, the nightingale - on the 11th), while the chicks of hollow-nesting nuthatches sit in the nest for 25-26 days, the chicks of the great tit - 23 days, starling chicks - 21-22 days. Species nesting in the north are also developing 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 full development of the outfit of feathers, which replace the chick's downy clothing. The 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, i.e. that is, next spring. Even those birds that by this time wear plumage that differs in color from the plumage of adults (for example, a falcon, a hawk) nest. It is interesting that the weight of chicks immediately before leaving the nest is often greater than the weight of young birds in subsequent months. This is explained by the fact that exercise in movement and independent flights sometimes cause the young bird to lose its fat reserves.

How many years do birds live? There is relatively little information about their life expectancy in natural conditions. A well-known idea of ​​the longevity of birds is provided by the results of their tagging and banding, as well as observations of the life of birds kept in captivity. It is necessary to distinguish between the maximum potential life expectancy from a physiological point of view and the real, average one that exists in nature, where various reasons act that limit the life of a bird: unfavorable weather (meteorological) and feeding conditions, the activity of all kinds of predators, and finally, diseases. Generally speaking, large birds have a longer lifespan than small birds. It was not possible to establish a definite connection between life expectancy and reproductive characteristics (fertility, type of development - nestling or brood) in birds. Finally, there are differences in life expectancy among different systematic groups of birds. It may be noted that small passerine birds live relatively longer than small species of mammals. 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 little. According to his calculations, the average life expectancy of raven birds and cockatoos 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 , in gulls 17 years, in ratites 15 years, in pigeons 12 years, in chickens 13 years. For domestic chickens, the life expectancy is, of course, as an exception, 24, 25 and even 30 years. (However, signs of aging - decreased fertility - are observed in Leghorn hens after 3 years of life.) A few figures about the potential life expectancy of birds kept in captivity. From the order of passerines, the age of 60 and even 69 years was recorded 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 order of owls, eagle owls lived to 34, 53 and 68 years. Parrots are also long-lived: the age of the red macaw is 64 years, for the cockatoo - more than 56 years, for the gray parrot - more than 49 years. For daytime raptors, the following data is 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, the griffon vulture more than 38 years. Of the anseriformes, the Canada goose lived more than 33 years, the little swan 24/2 years. Of the cranes, the sandhill crane lived 47 years, the gray crane 43 years, and the antigone crane 42 years. The African shoebill lived 36 years. Herring gulls lived to be over 20 years old, and one even lived to be 49 years old. The pink pelican lived to be 51 years old. Some pigeons lived for about 30 years. Ostriches lived up to 40 years, emus up to 28 years. However, in a natural environment, the natural mortality of birds significantly limits their life expectancy and they can reach the “maximum” age only as an exception. The mortality of young birds is especially significant during the first year of life. 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-years is 60% of their total number, and in the redstart it is even up to 79%. Of the 77 killer whale chicks ringed in one area in Germany, 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 adult and up to 74% of young first-year birds die over the winter. Similar phenomena occur in other birds. For example, among emperor penguins in the harsh Antarctica, the mortality rate of young in unfavorable years reaches 77%. Of the peregrine falcons ringed in Germany, 44 were taken 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 taken in older years. In Wilson's storm petrels on Graham Land in Antarctica, up to 65% of the chicks die in the burrows where these birds nest, mainly due to snow debris. In the common tern, up to 95% of young die in the first year of life, but the average mortality rate of terns surviving the first year of life at all ages is only 17.2%. Moreover, the average age of birds in a breeding colony (not counting young ones) is 3-5 years. Aquatic birds, especially colonial birds, have a higher average age than passerines, and natural adult mortality is relatively lower.

Among other general questions of bird biology, which are in a certain connection with the phenomena of reproduction, it remains for us to dwell on molting and migration. The need for molting, i.e., periodic change of plumage, is explained by the fraying and fading of the feather. Under the influence of the sun, moisture, dryness, the color of the pen changes: black becomes brownish, dark brown becomes pale brown, gray becomes brownish-gray, etc. The erasing of the edges of the pen, accompanied by a violation of its structure, is even more important, since small the adhesive barbs are partially destroyed. Particularly weakly pigmented or non-pigmented parts of the feather become worn out. These changes are also more significant in the most important elements of the plumage during flight - the flight and tail feathers. Wearing feathers has a detrimental effect on 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 find a partial explanation in the fact that both of them require a large amount of energy and therefore can hardly occur simultaneously in the bird’s body. The normal course of molting requires good nutrition of the body; weakening of nutrition causes a slowdown in the process of molting and irregularities in the structure of the feather (on large feathers, transverse depressions appear, running along the fan and making the feather fragile). While the feather has not yet reached half its normal length, its growth proceeds quickly, and then slows down. Small birds' feathers grow more slowly than large ones. In the sparrow, the secondary flight feathers grow at a rate slightly exceeding 4 mm per day; in the saker falcon, the daily growth of the flight feathers in the last period of growth is 6-7 mm per day. In each species of bird, molting occurs at a very specific time and in a certain sequence. Birds belonging to the same family or order usually have the same molting course, and it thus serves as one of the systematic characteristics of groups. There are well-known general patterns regarding the change of flight and tail feathers. Tail feathers change either centripetally, i.e. from the outer pair to the middle one, or centrifugally, i.e. from the middle pair to the outer one, or, finally, as happens in woodpeckers, molting begins from the pair adjacent to the middle ones and goes to the edge of the tail, and ends with the central tails. Secondary flight feathers usually molt concentrically, that is, molting begins with the outermost and innermost feathers and ends with the middle feathers, or centrifugally. The molting of the primary flight feathers ends with the replacement of the front (second and first) feathers; in some species it begins from the middle feathers (from the seventh) and goes to the inner (proximal) edge of the row, i.e., first the eighth, ninth, tenth, and then the sixth, fifth, fourth, third, etc.; in other species, the primary flight feathers are replaced in a row - the tenth, ninth, etc. In some species - loons, ducks, geese, swans, flamingos, cranes, rails, guillemots - the flight 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 feathers coincides, but the change of the anterior primary flight feathers, as the most important feathers in flight, usually occurs at the very end of the molting, after full development other parts of the plumage. The different types of molt in birds can be broadly described as follows. When emerging from the egg, the young bird is dressed in embryonic down, which is replaced by the first outfit of contour (definitive) feathers. This (first) outfit of contour feathers is called nesting. It is often distinguished by its special color (often similar to the color of females), softness and lower density of the feathers, as well as greater width and sometimes length of the tail and flight feathers. Birds wear nesting plumage for varying periods of time - from several weeks to 16-18 months. In many passerines, its change - post-nesting molt occurs at the end of summer. In pigeons, rollers and owls it occurs in the first autumn. Birds of prey begin to molt at about one year of age - sparrowhawks around May, golden eagles in April, peregrine falcons in March and May; Their molting ends in late autumn or early winter, so they nest in their nest plumage with a small admixture of feathers from the next plumage. Many waders, as well as rails, chickens and grebes moult, changing their nesting plumage, in autumn or winter at the age of 5-8 months; herons moult later, in the spring; at the age of 8-10 months, tubenoses change their nesting plumage. In ducks, post-nesting molt begins in September and ends in winter or even in spring. Post-nesting molt sometimes leads to a change in the entire plumage and is then called complete, or during it only part of the plumage (small feathers) is replaced, and then it is called partial. An example of partial post-nesting molting in passerines is the molting of the families of ravens, finches, wagtails, tits, flycatchers, warblers, and thrushes. For example, in a white wagtail, at about 2% of the month, the coverts of the head, body, small and medium wing coverts, part of the greater wing coverts, inner secondaries, and sometimes the middle pair of tail feathers are replaced. However, the extent of such partial molting varies among different genera. In other passerines (larks, starlings, etc.), the post-nesting moult is complete. After a complete post-nesting molt, the bird puts on an outfit that will be worn for a year and replaced either once a year and completely - this is the so-called annual outfit (of a falcon, hawk, starlings, larks), or (which happens rarely) will be replaced twice a year (so called pre-nuptial plumage of the common grouse, city swallow). With partial post-nesting molt, subsequent molts can cover the entire plumage. Then the plumage put on by the bird as a result of post-nesting molting is called a combined annual plumage (since in it the large plumage, in particular the flight feathers and tail feathers, remains from the nesting plumage); This outfit is worn, for example, by ravens, tits, common buntings, and mountain buntings (but not all buntings). If the plumage, put on as a result of partial post-breeding molting, is then replaced twice a year, then it is called a combined prenuptial plumage (flycatchers, wagtails, many warblers). Further molts proceed like this. The annual plumage changes as a result of molting, which usually occurs in late summer - early autumn. This molt is called the annual molt. In the event that the color of the annual plumage, put on as a result of the post-nesting molt, differs from the final coloring of adult birds (this happens, for example, in large gulls, eagles and sea eagles), the corresponding annual plumage is noted as transitional. If three or four years pass before receiving the final plumage, then for the corresponding bird we have the first transitional annual plumage, the second transitional annual plumage, etc. The change of breeding plumage, like the change of annual plumage, occurs at the end of summer - early autumn. Subsequent molts take place regularly according to this pattern. Birds wearing annual plumage change it once a year as a result of annual molting. In forms that molt twice a year, the interbreeding, or postnuptial, plumage as a result of the nuptial molt is replaced by a combined nuptial one, then the postnuptial molt occurs, etc. In many cases, molting brings with it a change in color. Sometimes, by spring, a change in color in birds occurs without molting, as a result of the 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.). d.). But no recoloring of the grown feather - a physiologically dead formation, contrary to the opinion of old authors, does not occur and cannot occur. Marriage attire is usually brighter than intermarital attire, and gender differences in it are more pronounced. The molting process reaches the greatest complexity in the white partridge, in which four plumages can be distinguished in a year: two of them (spring and winter) correspond to mating and interbreeding, and summer and autumn have no analogues among other groups of birds. Different animals react differently to unfavorable environmental changes, such as a decrease or increase in temperature, loss of snow cover, or a decrease in the amount of food. With such changes, many animals reduce their vital activity, become inactive, hide in various types of shelters, and finally fall into a state of numbness, the so-called hibernation. This happens in reptiles and even in many mammals. Birds are a different matter. Their body reacts to the above environmental changes by increasing activity. This specificity of the activity of the avian organism is most clearly expressed in seasonal flights, or migrations. Many hypotheses have been expressed about the origin of flights, often contradictory. 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 in any way be associated only with the events of the so-called Ice Age, when glaciers have made the northern hemisphere unsuitable for 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 existed in Tertiary times, before the onset of the great glaciation. This is indirectly indicated by the existence of regular migrations of many bird species in the tropical and subtropical zones. The Quaternary glaciation, of course, influenced the pattern of bird flights in the northern hemisphere, but it was not the cause of their occurrence. It must be remembered that the unevenness of glaciation, the movement of glaciation centers in the meridional direction (which caused a difference in climate not only along the north-south line, but also along the west-east line) should have had a very difficult influence on changes in the nesting areas and wintering areas of birds and create an environment in many places that is convenient for nesting, but not for a sedentary lifestyle. The long northern day, of course, was always favorable for feeding offspring, and the intensity of lighting in the north for local bird species was a necessary condition for the normal development of the genital organs during the breeding season. The general retreat of glaciers, which created a more favorable climatic situation and thereby stimulated reproduction, caused birds to occupy new nesting territories in the northern hemisphere, which, however, due to the large differences between the seasons, had to be periodically vacated. It can be assumed that the territory and directions of flight in most cases reflect the route of entry of the bird into a given nesting area. The general scheme of the phenomenon of flights in a historical perspective comes down to the adaptation of the avian organism to covering long distances in order to find the most favorable territories for its existence, with stimuli associated with reproduction predominant in the spring, and stimuli associated with nutrition in the fall. 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. Nutritional conditions (associated with worsening conditions for obtaining food, a decrease in the number of prey, a reduction in the daylight hours, etc.), without a doubt, can to a certain extent explain the autumn departure. However, this phenomenon is associated with the onset of certain physiological changes in the body that accompany the end of the reproductive period. The influence of external conditions on the state of the body of birds has been mentioned above repeatedly. It is useful to recall here that birds living all year round in monotonous and fairly favorable conditions lead a sedentary lifestyle. It can be assumed that the stimuli for flights are periodically caused by changes in external conditions, fluctuations in the body's nutrition, which are inextricably linked with certain phases of the annual activity of the gonads. Since the periodicity of nesting cycles for birds is hereditary, the very desire to migrate must be innate in some forms. Of great importance here is the question of the “attachment” of birds to the nesting territory and competition. The specific phenological situation does not determine the beginning of migrations, although, of course, it influences 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. The intermediate stage for many species is the formation of flocks and migrations. As a rule, areas with cold climates are occupied later in the spring and abandoned by birds earlier in the fall than warmer climates. In some species, females fly earlier than males; for others it is the other way around; in most species both sexes fly at the same time. Often in the fall, young birds fly away earlier than older ones. The migratory order of birds is also different; some species fly during the day, others at night, some silently, others emit characteristic calls (the purring of cranes, the cackling of geese, etc.). Usually those species that fly at night are forced to expend a lot of energy during the flight; this requires intensive feeding during the day. During the day, well-flying forms fly, which can largely make do with energy reserves accumulated in the body during flights. It is known that before migrating birds are usually quite 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 migrations using the ringing method has definitively proven that for each bird and for each bird population of a certain area belonging to a given species, 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 one. year. This is closely related to the repeatedly noted conservatism of birds in relation to the choice of habitat. Wintering sites are similarly strictly defined. 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 site, but the wintering site will not always be the ecologically favorable area closest to the nesting site. Probably, competition in the form of occupation of the nearest suitable wintering areas by other populations of this species also plays a role here. For example, perhaps this is why northern forms of one species often winter further south than subspecies of the same species nesting in the middle zone, etc. To explain the occurrence of distant wintering grounds, historical reasons must also be invoked. This can be seen, for example, in the course of migrations of spreading species. The Green Warbler, which has been spreading westward in recent decades, still winters in Southeast Asia; Lentils do the same; the Common Warbler from Scandinavia flies to India for the winter; on the other hand, the horned lark, which 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 to the south, but also to the west. England, with its mild winters and light snowfalls, for example, provides shelter for many Central European and Northern European birds - passerines, woodcocks, lapwings, etc. South-Western Europe and especially the Mediterranean attract even more birds. There is a huge concentration of birds in the Nile Valley. African wintering grounds are generally very abundant, with 76 European bird species reaching the Cape. Some Siberian and Arctic birds also fly here. Many of our game birds winter in Western Europe and North Africa - waterfowl and quail (which, unfortunately, suffer greatly from the disorder of hunting in Mediterranean countries). In India, southern China, and the islands of the Indo-Australian archipelago, there are mass wintering grounds for many northern and arctic birds. On the territory of Russia, masses of waterfowl winter in the Southern Caspian Sea, where the Kyzyl-Agachsky named after was created to protect them. S. M. Kirov and Gasan-Kulisky reserves (the first in Lenkoran, the second in the lower reaches of the Atrek in Turkmenistan). In the form of a diagram, it can be assumed that the majority of northern birds nesting west of the Yenisei fly to the southwest in the fall (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 travel even further, reaching New Zealand, as do the East Siberian godwits and Icelandic sandpipers. In America, unlike in Europe, the influence of the Gulf Stream does not cause a deviation in the migratory movement, and birds fly more or less directly to the south. It should be added that the wintering areas of different subspecies of the same species are usually well demarcated. The direction of flights is determined, of course, by the location of nesting sites and wintering grounds. At the same time, with a certain number of exceptions, the movement proceeds, perhaps, along paths that are favorable in an ecological sense (convenience of orientation, nutrition, 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, and less often south and southeast; in North America, as already said, 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 is usually “more friendly” and faster). The movement of birds along ecologically favorable stations was the reason for the emergence of the widespread theory of flyways, which was widespread until recently. According to the theory developed by Palmen, birds during migration seem to move only along relatively narrow and strictly fixed “paths”, and do not fly outside them. In fact, birds move differently. Landscape factors, as well as conditions of food, rest, etc., determine the movement of flocks of migratory birds. Vast mountain ranges can therefore cause a detour of flight (for example, this explains the insignificance of flight through high Central Asia). Water basins favor aquatic birds, but land birds avoid the ocean whenever 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, the Baltic, the Mediterranean, and the Black Sea. Birds of sea coasts, for example, many waders, also stick to the coasts when migrating. Thus, some waders from North-Eastern Siberia move south along the Pacific coast, and waders from Northern Europe move along the coasts of Scandinavia, the Baltic, and the Atlantic Ocean. Congestions of migratory waterfowl attract passing predators. It should be noted that some birds are more gregarious on migration (for example, storks, cranes), while in others the connection between individuals and groups of individuals is less pronounced.

One should distinguish from migrations the migrations undertaken by many species due to the onset of unfavorable conditions, and irregular and random evictions from the nesting area, examples of which we see in Saji. Mountain forms undertake more or less regular vertical migrations. The complex functioning of the locomotor system of birds, especially during flight, requires a complex orientation mechanism. Let's dwell a little on this issue. 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 take first place among other animals. It is characteristic that among birds there are no forms with underdeveloped eyes, much less blind. 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 the human eye.

Birds have a large field of vision, but vision is predominantly monocular and lateral (lateral). The general field of vision 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 vision of each eye is 150° (i.e. 50° more, than in humans). But the field of binocular vision, i.e. the area of ​​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 facing more or less forward (lateral-frontal), the general field of vision is the same, but the field of binocular vision is wider - about 50° (this includes nightjars, birds of prey and some others). Finally, in owls, whose eyes face forward (frontal position), the lateral field of vision 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 of owls is compensated by the mobility of the neck, in particular the great freedom of its rotation (up to 270°). The maximum 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; Due to the movements of the bird's head, the eyes can diverge, come closer and partially coincide. Visual acuity in birds is very high, and the minimum perception significantly exceeds that of humans (in the buzzard, for example, 4 times): the peregrine falcon sees doves at a distance of more than 1000 m. There is reason to believe that in terms of the perception of space and distance, birds occupy first place among all animals. This, of course, is directly related to the speed of movement of birds in the air. Perhaps a sense of position in space, or geographic location, is associated with the hearing apparatus in birds; it is undoubtedly present, but the mechanism of which remains unclear until recently. This sense is the most interesting aspect of orientation in birds. In a number of cases, the bird's finding the target of movement cannot be explained either by optical stimulation or visual memory. So, for example, among the swiftlets, which nest colonially in deep dark caves (near the city of Padang in Sumatra there is a cave 2 km deep where a colony of swiftlets is located), each bird unmistakably finds its own? nest among others in complete darkness. South American Guajaro nightjars also nest colonially in deep, dark caves. In this case, orientation occurs using echolocation. The impossibility of explaining the location of a target (a nesting or wintering site) by migratory birds by visual stimulation or motor memory alone is indicated by the fact that many species fly at night, that in many migratory birds young birds born in the summer fly away in the fall before older ones (and, therefore, , independently of them and without any experience or example, they make their first journey to the winter). Many species that nest on 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 route (Palma and Tenerife). Finally, numerous experiments have been carried out on the delivery of birds from their nests, and the birds have flawlessly returned back from distances of tens, hundreds and even more than a thousand kilometers. Kluiver (1936) in Holland took starlings from their nests to a distance of 150 km, and the birds were under anesthesia, and 60% of them still returned. This ability to determine geographic location is especially developed in migratory birds. Geographic sense not only guides birds in a certain direction at a certain time, but also stimulates the birds to fly in a certain direction. In the development of this feeling, as we see in the example of carrier pigeons, both heredity and exercise have a certain significance, and its appearance and consolidation in birds is associated with natural selection (those individuals survived that accurately found the goal of movement). Of the existing explanations, the most likely seems to be a connection between the sense of geographical position and certain magnetic phenomena, since it is difficult to imagine any other universal stimulus that changes in connection with changes in geographical position. There is no generally accepted system in the field of bird classification. Different researchers identify either a larger or smaller number of groups. In this book, based on the structural features, lifestyle, as well as probable origin and family ties, we identify the following groups of birds, to which we attach the importance of orders. Many ornithologists distinguish larger groups of birds into orders; in such systems, the orders named below acquire the significance of suborders. The class of birds in its modern form is not divided into subclasses (the extinct Archeopteryx is a separate subclass), but two superorders can be distinguished in it: penguins (Impennes) and typical, or new palate, birds (Neognathae). Perhaps ratites should be placed in a special superorder; the latter should be called running birds (Ratidae).

The bird class is a large class of warm-blooded animals, numbering about 9,000 species. The main difference between representatives of the class from other vertebrates is the ability to fly.

Over the course of many hundreds of years, in the process of evolution, their body formed and developed more and more advanced mechanisms for moving through the air.

general characteristics

The distinctive features of the class of birds are their wings and the ability to use them for flight.

The body and skin are covered with light and smooth feathers that retain heat and provide smooth movement through the air. The forelimbs are transformed into wings.

Appearance, external structure

The bones of birds are thin, strong and hollow inside, so their skeleton in the class of birds is very light.

Bird class brief description

If you compare the weight of the skeleton and the weight of its plumage, it turns out that the feathers weigh more. Low body weight is also ensured by thin and dry skin, the presence of a beak instead of a jaw with teeth, and the absence of a bladder.

Internal structure of the heart, warm-blooded

The heart works in a very intense mode - at rest it contracts at a speed of 400 beats per minute, and during flight - up to 1000 beats. Thanks to this enhanced regime, the body produces enormous work, accompanied by increased energy expenditure and accelerated metabolism.

Bird class general characteristics

Similarly, they are able to maintain a constant temperature at the expense of the body. The normal body temperature of birds is 7–8 degrees higher than that of humans. They cannot sweat, since their cover and skin are not equipped with glands, so they remove excess heat from the body by exhaling.

Habitat

Thanks to their endurance and ability to move long distances, representatives have populated all continents of the globe and all its natural zones. Many species of birds are characterized by migration - during the cold season they fly to warm regions and then return.

Reproduction and development

Birds are warm-blooded, oviparous animals; they inherited the method of reproduction from their ancient ancestors -. They lay eggs covered with a hard shell. In nature, there is not a single species of viviparous birds, because if the female carried a chick within herself, she would become clumsy and clumsy and would not be able to fly.

Birds external structure

They carefully incubate the eggs, and often both parents do this. After the chicks hatch, they are warmed, fed and protected from enemies for a long time.

Taxonomy, meaning

Due to their huge numbers and diversity of activities, birds have a strong influence on the processes occurring in nature. Birds are an important link in the food chain - they significantly reduce the number of insects and small rodents, and also serve as food for large predators.

Nutrition

Birds that feed on plant fruits scatter their seeds along with their droppings. Many birds are domesticated by humans and raised on farms and in private households for their meat, eggs, feathers and fat.

Birds structure and external features

Bird droppings are an excellent soil fertilizer - they contain phosphorus and nitrogen salts needed by plants. Many species of parrots, canaries and pigeons are so adorable that they are kept as pets.

• Starlings;
• blackbirds;
• sparrows and other birds often spoil the harvest by pecking at fruits and berries in garden plots.

• kites;

attack poultry, reducing their numbers and harming agriculture.

1. The benefits that birds bring many times exceed the damage from their activities.
2. In addition to all of the above, representatives of the class delight us with their attractive appearance and wonderful singing.
3. Their return to their homeland from warm lands and the beautiful nightingale trills are symbols of the awakening of nature and the onset of spring.