Reproductive organs. In birds, as in other vertebrates, the reproductive organs are the testes in males and the ovaries in females (see Fig. 165). They are located in the body cavity. The bean-shaped paired testes are located in the sacral region. By the time they reproduce, their size increases a thousand times. Vas deferens extend from the testes and open into the cloaca.
In females, only one - the left - ovary develops. It is located at the upper part of the left kidney. Reduction (disappearance of an organ due to loss of function) of the right ovary is associated with the laying of large eggs covered with a hard shell. Only one egg can move through a narrow pelvis.
Rice. 166. Structure of an egg: 1 - protein; 2 - yolk; 3 - air chamber; 4 - subshell membrane; 5 - chalazas; 6 - shell
Egg development. The eggs of birds are large, rich in yolk. The mature egg enters the oviduct. Fertilization occurs in its upper part. The walls of the oviduct contract, pushing the egg (fertilized egg) towards the cloaca. When moving, it becomes covered with egg membranes, which are formed from the secretions of the glands of the walls of the oviduct. First, the egg is covered with an albumen, then with two fibrous (subshell) and then with a shell membrane.
The egg enters the cloaca and is laid outside. The formation of an egg in the oviduct in birds of different species takes from 12 to 48 hours.
Bird eggs are large and contain a lot of nutrients and water in the white and yolk (Fig. 166). By the time the egg is laid, a germinal disc is visible on top of the yolk - the result of crushing (division) of the fertilized egg. The yolk, suspended on flagella - chalazas, is located in the center of the egg. The lower part of the yolk is heavier, so when turning the egg, the germinal disk is always located on top, in the best conditions for heating during incubation.
The outside of the egg is protected by a calcareous shell, which contains numerous microscopic pores. Through them, gas exchange occurs between the developing embryo and the external environment. The lime from the shell is partially used to form the skeleton of the developing embryo. On top of the calcareous shell, the egg has a thin supershell shell, which protects it from the penetration of microbes. The shells of eggs in open nesting birds have a protective coloring. The shells of eggs of hollow nesters and burrowers are light or pure white.
Development of the embryo. The embryo in the egg develops very quickly at high temperatures (37-38 ° C) and certain humidity. These conditions are provided by the bird incubating the clutch. The hen regularly turns the eggs, changes the density of incubation: when the air temperature is too high, the bird rises in the nest, cools the clutch, periodically wetting the plumage, and protects it from the sun's rays with its own shadow.
Rice. 167. Chicken development: 1 - embryo; 2 - yolk; 3 - protein; 4 - air chamber; 5 - embryonic membranes
The development of the embryo has been well studied in the domestic chicken (Fig. 167). On the second or third day, the circulatory and nervous systems of the chick embryo are formed, and the eye vesicles are clearly visible. At the beginning of development, the forelimbs of the embryo are similar to the hind limbs, there is a long tail, and gill slits are noticeable in the cervical region. This suggests that the ancestors of birds had gills. On the fifth or sixth day, the embryo acquires bird-like features. By the end of development, the chick fills the entire internal cavity of the egg.
When hatching, the chick breaks through the shell (parchment) membrane, sticks its beak into the air chamber and begins to breathe. Using an egg tooth (a tubercle on the beak), the chick breaks the shell and gets out of it.
Rice. 168. Chicks of brood (1) and nestling (2) birds
Birds reproduce through internal fertilization. At the moment of copulation, the male introduces seminal fluid into the female’s cloaca. Spermatozoa, moving through the oviduct, fertilize the egg that has matured inside the ovaries. During its development, it forms into an egg, which, after its full maturation, is hatched out.
Mating of birds begins with a special period called “mating.” This process physiologically prepares birds for copulation, ensures the meeting of individuals ready for sexual contact, and prevents interspecific crossing.
How does fertilization occur?
Birds have a complexly developed reproductive system. Birds reproduce by laying eggs. The eggs are fertilized inside the female. Males outside the period of active reproduction are not capable of fertilization, but by the beginning of mating games, their genitals enlarge and swell. The testes of males are bean-shaped and located above the kidneys. Females have paired ovaries and oviducts connected to the cloaca, along which the egg moves. In the ovaries of the female, oocytes, or eggs, mature (usually 4–6 of them). After ovulation, the mature oocyte descends into the oviduct and awaits fertilization. Since birds do not have genital openings, they are replaced by a cloaca.
Birds copulate in the following way: the male presses his anus against the female's opening. In this way, the sperm that has entered the cloaca is transferred to the female and moves up the oviduct, reaching the egg.
The process of copulation occurs in a few minutes, but the mating season preceding mating sometimes takes weeks. The fertilization process itself is called the “cloacal kiss.”
Sperm can remain in the oviduct for several weeks, waiting for a favorable time for conception. After fertilization, the egg increases in size and begins to form a shell around itself and gradually moves along the oviduct to the exit. The egg contains a supply of nutrients that is necessary for the development of the embryo.
Egg Formation:
- 1. The yolk is formed in the ovary. The egg white and shell are formed in the oviduct. The yolk falls into a long winding tube of the oviduct (its length in chickens is about 70 cm), consisting of five sections.
- 2. A viscous layer of protein is formed in the funnel of the oviduct, a certain amount of which later, as a result of the helical movement of the yolk, forms spiral formations at the ends of the egg.
- 3. In the protein section of the oviduct, the bulk of the protein is formed in about three hours.
- 4. In the isthmus, the duct secretes a sticky substance similar to threads. It forms the shells located under the shell. The egg stays there for a little over an hour.
- 5. The egg enters the uterus, where a hard shell is formed. After 3-4 hours of shaping, the shell is still soft and easily crushed. There it is colored with pigments. The egg remains in the uterus for up to 20 hours.
- 6. The formed egg enters the last section - the vagina and is removed from the cloaca by muscles.
The bird class is a separate progressive branch of animals. They originated from reptiles. Animals of this group, however, were able to adapt to flight.
Before moving on to the question of how birds mate, let's look at their biology.
General characteristics of the class
The progressive features of the organization include the following features.
- High level of development of the nervous system and therefore a wide variety of options
- Constant high body temperature, which is caused by intense metabolism.
- Compared to lower subtypes and classes of animals, birds have a more advanced reproduction mechanism, which is expressed in incubating eggs and feeding offspring.
- The presence of adaptive organs for flight and at the same time the ability to move on the surface of land, and in some species - the ability to swim and move along the water surface.
The above features of the class allowed these animals to spread throughout the globe.
Male genitals
The testes are a pair of bean-shaped bodies that are located above the top of the kidneys. They are suspended on the mesentery. The size of the testes varies throughout the year. During the breeding season, these organs enlarge. So, in a finch, for example, they can increase 1125 times, and in a common starling 1500 times.
Small appendages are attached to the inside of the testes. The vas deferens extend from them, running parallel to the ureters and flowing into the cloaca. There are species of birds in which the vas deferens form small extensions - seminal vesicles, which serve as a kind of reservoir for sperm.
Not available in all species. The functioning penis in birds is a protrusion of the cloaca. It is present in ostriches, tinamou, and geese. In bustards, storks and herons, the copulatory organ is vestigial.
Answering the question of how birds mate, it is worth noting that in most species, fertilization occurs due to the maximum convergence of the cloacal openings of the female and the male, when the male ejects sperm.
Female genitals
A feature of the development of females in birds is that it is sharply asymmetrical in most species, i.e. consists of the left ovary and the left oviduct. The right ovary develops only in a few birds: loons, owls, chickens, rails, parrots, and some diurnal raptors. But even a well-developed gland in this case rarely functions. It happens that a mature egg in the right ovary is excreted through the left oviduct.
The reason for this asymmetry is that female birds lay large eggs with hard shells, which move along the oviduct for quite a long time - about 2 days.
The ovary is a granular body of irregular shape. It is located in front of the kidney. The size of the ovary depends on the maturity of the egg in it.
The oviduct is a long tube through which a mature egg moves. It is connected at one end to the cloaca, and at the other to the body cavity.
The oviduct consists of several sections. The first is rich in special glands that secrete protein. The egg stays in this section for about 6 hours and is covered with the first protective layer. The second section is thinner, where the egg is covered with shell membranes. The next section of the oviduct is the uterus. The egg stays in it for about 20 hours. Here a lime shell and various pigments are formed that color it. The last section is the vagina, from which the egg enters the cloaca, and then out.
The entire passage of an egg through the oviduct in a chicken is about 24 hours, in a pigeon it is 41 hours.
Features of bird breeding
Despite the general breeding pattern, each bird species is individual.
When studying the question of how domestic birds, such as a chicken, for example, mate, it is worth remembering that they can lay eggs without a male. This means that the released egg will be unfertilized.
The testes of males begin to function and increase in size - the males are ready to begin fertilization. Genetic material is transferred to females, who after a certain period begin to lay eggs. Their number varies among different bird species.
Birds breed at different times of the year. The biology of species is very diverse. If one species is ready to reproduce in early spring, then the other is ready only in mid-summer. Some birds lead and nest in the same place, while others fly from distant countries precisely for the nesting and breeding period.
To better understand how birds of a certain species mate, it is necessary to study the individual characteristics of the reproductive system of its representatives.
Birds, like other land inhabitants, are endowed with the function of internal fertilization. Males choose a female, inseminate her through the genital opening, the ejected sperm reach mature eggs in the female’s ovaries and fertilize them. During the extramarriage period, males are sterile, but in the spring their testes enlarge hundreds of times.
In females, only one ovary is developed, the left one. It is located on the mesentery near the anterior end of the left kidney. The Müllerian canal or left oviduct opens as a funnel into the body cavity of the ovary, and its thickened uterine section, which is located behind, flows into the cloaca. Some females are characterized by a blind outgrowth of the cloaca (the remnant of the right reduced oviduct). Some of the follicles increase at the beginning of reproduction, because the oocytes that are in them rapidly accumulate yolk; At the same time, the oviduct lengthens and its walls swell. The wall of the follicle ruptures, the egg falls into the body cavity and enters the oviduct.
Fertilization occurs in the oviduct. The egg moves to the cloaca and is covered with several secretions of the glands of the walls of the oviduct, which form a shell for it. From the moment the egg enters the oviduct, the complete formation of the egg and its preparation for laying occurs from 12 to 48 hours.
Birds begin to mate in a specific season of the year for each species, because... this affects the growth and feeding of chicks (in northern latitudes in May-July; in the tropics in cooler, rainy times, and for piscivorous species, on the contrary, during periods of drought).
Manifestations of mating in birds are unusually diverse, for example, the sonorous song of a sparrow, the dancing of cranes, the cries of owls, etc., these are a kind of mating games. This can also occur during current contact. Current phenomena organize the meeting of a female and a male, facilitating the formation of a pair, so to speak, providing physiological preparation before mating.
Mating of birds occurs at the moment when the male presses against the female's cloaca with the exit of his cloaca, through which sperm is transmitted; the so-called “cloacal kiss” occurs. And only the males of some species of birds (ostriches, geese, ducks) have a copulatory organ, which looks like an eversible part of the cloaca, helping to penetrate the female’s opening intended for fertilization.
For fertilization and further egg laying the following set of factors has been identified:
- favorable temperature;
- required amount of feed;
- availability of nesting space;
- presence of a male.
Preparing birds for breeding
Already with current contact birds begin to build a nest to reproduce. In most cases, the female participates in its formation; she carefully lays out the materials that the male brings. The nature of nests is very diverse; some birds have more similar ecological features. There are also birds that lay their eggs on the ground, covering the hatching site (hole) with branches (waders, guillemots, nightjars, chickens, owls, etc.). Female geese and ducks pluck fluff from their abdomens, which they additionally use to line the nest.
Sparrows are real masters in nest building. A dense bowl made of dry thin twigs, the inside is covered with moss, soft selected wool, feathers and stems.
Nests protect brooding birds and chicks from various predators and adverse weather. In them, females hatch eggs, and males protect their family from possible danger. In brooding females, feathers on the abdomen fall out, thus forming in this place "brood spot". There are about 2 or 3 such spots. As a rule, their presence indicates good heating of the eggs and a laying temperature of approximately 38 degrees. “Roost spots” are not formed only in Anseriformes, because their nest is lined with a lot of fluff.
Birds incubate eggs more intensively after all eggs have been laid, so the chicks hatch almost simultaneously. During the development of the embryo, the salts contained in the shell gradually move to the skeleton, which is why the shell becomes fragile and the formed chick hatches easily.
Incubation time
Hatching duration depends on the following indicators:
- type and size of female;
- type of nest;
- egg size;
- incubation intensity.
Passerines incubate eggs from 11 to 14 days; crow - 17 days, slightly larger crows - up to 22 days, mallards - 26 days, swans - from 35 to 40 days, etc. The longest incubation period for vultures, albatrosses and large penguins is up to 2 months.
How do pigeons reproduce?
Breeding pigeons is a fairly common question that many amateur pigeon breeders are interested in, because the health of the offspring and the production of new breeds depend on the success of the breeding process of this type of bird. To achieve a good result, it is necessary to take into account the characteristics of mating and the conditions necessary for the life of pigeons.
Features of mating pigeons
There are two types of mating:
- Natural (the male chooses the female himself);
- Forced (human actions for the purpose of breeding a certain pigeon breed).
The mating period of pigeons depends on the climate in the region. If we talk about our climatic conditions, then crossing occurs in early spring (March-April).
Pigeons tend to show feelings, so the “marriage ritual” will not be long in coming. As soon as the male chooses a female, he will begin to coo with her, circle around her, in every possible way begging for a response. The doves express their consent by bending towards the ground.
When forced mating, a very important point should be taken into account: before starting this process, it is necessary to separate the residence of males and females for the entire winter period and fully feed the birds with grain containing proteins and carbohydrates (you can add vitamin supplements to strengthen the eggs and bones of the chicks). Pigeons must be at least 1 year old.
There are rare cases where females mate with females. It is difficult to immediately understand what is happening. And only after the doves lay unfertilized eggs, everything becomes clear.
Pigeon nests
Pigeons fight for prepared places; when they build their own nests, there is usually no conflict. If the pigeon breeder himself provides housing for the birds, then places for hatching are needed with reserve. To do this, steam boxes are installed and filled with hay and straw. There must be space between the boxes; this will help pigeon families remember the way to their house (they will choose the box themselves).
The process of hatching and laying eggs
2 weeks after mating, the female lays an egg. This usually happens in the morning. 2 days before oviposition, it becomes inactive and sits in the nest. For young females, the laying process results in great stress, and if the eggs do not come out well, then there is a risk of the dove’s death. The usual clutch is 2 eggs, but young females may have one. The normal weight of an egg is 20 g.
After a week, the shell of the eggs becomes a pale matte color, a little later it acquires a gray tint; when the embryo dies, it is dark blue.
Pigeons take care of their offspring and try to sit in the nest constantly, replacing each other, but they are not so diligent, so it is likely that they can leave the eggs unattended. The female incubates the eggs for about 17 hours, and the male for no more than 12.
Pigeon breeders should keep an eye on the embryos so that they do not become hypothermic, because... this can lead to the death of the embryo or a delay in its development. If it is hot in the pigeons’ home and incubation occurs on hot days, it is necessary to add humidity to the room (spray from a spray bottle).
The incubation period for pigeons is about 19 days. 10 hours before the chick hatches, cracks can be noticed on the shell.
Chicks
Newborn chick weighs 8 - 12 grams, 2 hours after birth he is able to eat. The feeding process occurs when milk is obtained from the parent's crop. Milk contains the required percentage of fat and protein; if the baby pigeon cannot obtain this composition, it will die.
There are cases of lack of parental milk, mainly in young couples. In this case, pigeon breeders resort to the help of nursing birds and feed the chick with grains softened in milk.
Self-feeding chick will be able to in 10 days. During this time, his beak will form; almost the same length as an adult bird.
After 2 months, a healthy chick will weigh the same as its parents.
Steaming pigeons
Many pigeon breeders have noticed that pigeons get used to their partner and their nest, which is why they began to use the term “pairing”.
Fallowing is the artificial selection of birds for the purpose of developing certain characteristics.
These include:
- flight qualities;
- plumage color;
- body shape, etc.
The main task of this process is a successful combination of pairs. If the pairs are chosen correctly, this is, first of all, a step towards the development of healthy offspring, but if the choice turns out to be unsuccessful, the born chicks will be inferior to their parents in development.
By assessing the appearance of newborn chicks, one can draw conclusions about their development and count on mating in the future. In addition to phenotypic qualities, it is also necessary to take into account the pedigree of the birds.
Speaking of inbreeding(closely related mating), then it also has its advantages. It is sometimes very difficult to purchase a pure breed pigeon to inject “fresh blood” into the main core of the farm. You should not give up on inbreeding of pigeons, but, on the contrary, study it in order to use it correctly when mating.
Attention, TODAY only!
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 moults 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 behavior that differs from other species in the spring - 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 away. 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 cover 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 burrows. 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 the greater opportunities for feeding chicks in the north (long days and almost round-the-clock insect activity). There is always one egg in the clutch of 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.