Description and characteristics of the structure of a bird's egg. The structure of a bird egg: a diagram, features Bird eggs

Once upon a time, vertebrates were able to go to land because they “learned” to lay eggs, the “design” of which allowed the embryo to develop outside the aquatic environment. Such an egg carries within itself everything necessary for its development. Those ancestral species died out long ago, viviparous mammals appeared and spread widely, but even now, after millions of years, species that lay eggs live on Earth: these are reptiles and birds. Bird eggs vary greatly in size and shape, from almost round to elongated or pear-shaped. Scientists have long been interested in the question: why there is such a variety of forms of bird eggs and what it depends on.

An international team of scientists worked with images from the California Museum of Vertebrate Zoology (USA) collection of about 50,000 egg shells from about 1,400 bird species. In order to answer the question of which component of the egg during its development is responsible for its shape, as well as to find the relationship between the shape of the egg and any features inherent in the species, they created the Eggxtractor computer program, with which they characterized the shape of different eggs and developed a mathematical model to explain what defines it.

After fertilization, the egg, moving along the genital tract of the bird, “dresses” in several shells. First comes the protein coat; the substance of the protein is secreted by special glands of the bird. Then the so-called shell membrane is formed, after which the egg absorbs the water necessary for the development of the embryo until the egg reaches its size. At the same time, the shell is stretched, and it is at this stage that the shape of the egg is determined. The shell is formed at the final stage and no longer affects the shape.

Guided by the observation that the thickness of the egg shell is not the same in different parts of it, the scientists calculated how, depending on the thickness of the shell and the pressure of the contents of the egg from the inside, the formation of the entire spectrum of bird egg forms observed in nature is possible. Scholars draw analogies with balloon: if its material is evenly thick, the balloon will become round when inflated, but if it is thinner somewhere, and thicker somewhere, you can get "balls" of different shapes.

Next, the researchers looked for correlations between egg shape and different features species, including nest type and location, number of eggs per clutch, and ability to fly. It turned out that birds that fly well lay more elongated and asymmetrical eggs, and in flightless birds, or in those who fly little and badly, the eggs are more rounded.

For flight, for improvement aerodynamic characteristics the bird needs a "flattened", streamlined body shape; such birds have a narrower pelvis, and, accordingly, narrower genital tracts. In order to maintain the desired volume of the egg without increasing its width, nature has made the eggs of these birds elongated.

And now it's easy to assess how well this or that bird flies: just look at the shape of its eggs.

Prepared by Maria Perepechaeva

From huge emus to small hummingbirds - how birds treat their future offspring

Eggs are an amazing way to produce offspring. Many birds have their own exclusive approach to hatching eggs. Eggs differ in color, shape and size, sometimes quite bizarre specimens come across. "Yod" has chosen a few eggs that are interesting to look at.
blue guillemots

Length - 6.7 cm, width - 3.8 cm.
The shape of the cone is not accidental - it prevents the slope from rolling off the eggs. After all, guillemots live on a rocky coast. If the egg still rolls, then it will simply describe circles around itself.
common cuckoo

Cuckoo (right) and garden warbler
Cuckoo (left) and common redstart
Cuckoo (right) and common bunting
Cuckoo (left) and Shrike Shrike
Length - 2.2 cm, 1.6 cm.
The cunning and impudent cuckoo lays her eggs in other people's nests and flies away. There they resemble the coloring of neighboring eggs, so the new owners do not distinguish them.
Emu

Length - 14 cm, width - 9 cm.
Often several females lay eggs in one nest at once. Over time, the eggs, while the male incubates them, turn purple. In size, they are one of the largest in the world - like a dozen chickens.
hummingbird

Length - 1.4 cm, width - 0.8 cm.
The smallest bird in the world lays the smallest eggs. For understanding, the size of the hummingbird nest itself is only the size of a walnut.
dumb quail

Length - 3 cm, width - 2 cm.
It is curious that females choose a place for laying out depending on the color of the eggs - if the pattern is bright, then on a surface whose color matches the dark spots on the eggs, and if not bright, then in a place with a more neutral color. The dumb quail lives not only on farms, but also in wild nature in China, Korea and Japan.
emperor penguin

Length - 12 cm, width - 9 cm.
The female penguin lays one egg per pregnancy. She covers it with the lower part of the belly, which is called the bag, keeping the temperature around 30 ° C. When a chick is born, a pair of parents screams.
Ocellated chicken

Length - 7 cm, width - 4.5 cm
These eggs are laid in the soil, and when the chicks hatch, they dig their way with their paws. The eyed chicken lives in Australia.
Misery

Length - 3 cm, width - 2.2 cm.
The pale blue color camouflages the eggs by emitting spots from sunlight. In the warm period, the thrush mist lives in central Europe.
Osprey

Length - 6.2 cm, width - 4.5 cm.
Due to the large size and number of eggs of the osprey, which lives on all continents except Antarctica, it is necessary to complete the nest so that they do not fall out.
yellow-fronted jacana

Length - 3 cm, width - 2.3 cm.
The eggs of these birds are notable for their laying place - fragile plants on the water, where the jacana lives. But if the eggs fall out of the nest it is not fatal as they are waterproof. Yacana females are characterized by polyandry. You can see these birds in nature in the Caribbean and southern North America.
house wren

The central part of the egg is occupied by the yolk. It consists of 5-6 alternating concentric layers of yellow and light color, and the yellow color is much wider than the light color (up to 2.8 mm versus 0.25-0.40 mm). It is believed that every two adjacent layers (dark and light) are formed within one day. The center of the yolk consists of a light substance - a latebra, which has the shape of a flask and is connected by means of a neck to the germinal part of the egg (in an unfertilized egg - with a blastodisk, in a fertilized egg - with a germinal disk). The yolk is always oriented with the embryonic part upwards, which is of great adaptive importance during incubation of eggs. The substance of the yolk consists of balls, larger in its yellow layers (up to 0.15 mm in diameter).

The yolk is covered with an elastic yolk membrane about 0.024 mm thick. The shape of the yolk is slightly oblong towards the poles of the egg and slightly flattened at the blastodisc. The color of the yolk ranges from pale yellow to dark orange. It contains the main nutrients.

The egg white consists of four fractions. Directly around the yolk is a thin layer of internal dense, or hailstone, protein, from which hailstones (chalase) stretch towards the poles of the egg. They are firmly attached on one side to the surface of the yolk, and on the other - to the outer dense protein and thus, as if by stretch marks, hold the yolk in the center of the egg. Hailstone protein is surrounded by a thicker layer of internal liquid protein, consisting of a semi-viscous homogeneous substance, close in density to the yolk. The yolk, being suspended in this layer, is well protected from sudden movements inside the egg.

The inner liquid and dense protein, together with the yolk, are placed in the so-called protein sac, which is a thick layer of outer dense protein.

The protein sac at the acute and blunt poles of the egg is attached to the inner shell membrane. It contains a lot of mucin fibers that contribute to the preservation of its shape and serves to protect the yolk.

Between the protein sac and the shell films (except for the poles) is placed the fourth layer - the outer liquid protein, which is very similar in consistency to the inner liquid. The approximate volume of the mentioned layers in a chicken egg is, %: hailstone - 3; internal liquid - 17; protein sack - 57; external liquid - 23.

Protein in the evolution of the bird is a later formation and has less structure stability than the yolk. It mainly has a protective function, being at the same time a reservoir of water.

Protein is surrounded by shell membranes. The inner (protein) shell covers the entire protein and is tightly soldered to the outer shell. In the region of the blunt pole, the spike between them is weakened. After laying and cooling the egg, the yolk and protein slightly decrease in volume, at the blunt pole, the shell membranes diverge, and an air chamber forms between them. On average, the mass of shell membranes of chicken eggs is 0.36 g, which is approximately 0.6% of the mass of the egg, and their thickness is 0.06-0.07 mm.

The air chamber immediately after cooling the egg has a diameter of less than 1 cm, then it increases depending on the storage time, temperature and humidity of the surrounding air. The size of the air chamber, ceteris paribus, is an indicator of the freshness of the eggs.

The egg is covered with a hard calcareous shell - a shell that protects its contents from mechanical damage and is a formidable barrier to microbial contamination and water evaporation. The thickness of the shell varies greatly, mainly due to the outer spongy layer. In chicken eggs, the average shell thickness is close to 0.35 mm. In thick-shelled eggs, it has a greater thickness at the sharp pole, in eggs with a very thin shell - at the blunt one. In the "equator" zone, the shell thickness is more constant and basically characterizes the average for a given egg.

The shell is permeated with pores, the number of which in a chicken egg is usually more than 7 thousand, and more than 100 per 1 cm 2. The pores vary significantly in size, which, taking into account their number, determines the rate of weight loss of the egg during storage and incubation.

The last, outermost shell of the egg - the cuticle, consisting mainly of mucin, covers the surface and pores of the shell with a thin layer (5-10 microns). The cuticle is tightly connected to the shell, but is washed off quite easily with hot water and is disturbed by friction. The shell becomes shiny. On this basis, one can judge the quality of the egg. However, some hens lay eggs, the shell of which is practically devoid of cuticles.

Thus, the yolk is surrounded by four protein layers, two shell films, shell and cuticle, i.e. eight shells, each of which performs its specific function.

The excretory system includes two kidneys that remove waste products from the blood and form urine. Birds do not have a bladder, and it passes through the ureters directly into the cloaca, where most of the water is absorbed back into the body.

The reproductive system consists of gonads, or gonads, and tubes extending from them. Male gonads are a pair of testes in which male sex cells (gametes) are formed - spermatozoa.

Female gonads, ovaries, form female gametes - eggs. Most birds have only one ovary, the left one. Compared to a microscopic sperm, an egg is huge.

Fertilization in birds is internal. Spermatozoa enter the cloaca of the female during copulation and float up the oviduct. Fertilization, i.e. the fusion of male and female gametes occurs at its upper end before the egg is covered with protein, soft membranes and shells.

Brood- These are birds whose chicks are able to see, hear, run and feed on their own almost immediately after hatching from the egg. They need parental care, but do not stay in the nest for a long time, like chicks. One parent or both birds accompany the chicks until they fledge.

At chicks the clutch of birds is usually smaller than that of broods, the number of eggs in it is determined by how many chicks the parents can feed. In broods, the number of clutches depends on how many eggs the brood hen can fit under her. The nest in representatives of the nesting group is usually more complex and massive than in broods, it is well camouflaged and insulated with soft material. Such a building both masks the chicks from prying eyes, and shelters them from bad weather.

At nesting the opposite is true - their chicks hatch naked, blind and helpless. In the early days, they need constant heating, and their parents bring food to them until they leave the nest and even longer. Such chicks leave their homes, not really knowing how to fly. At this time they are called fledglings. Nestling birds include all songbirds, or passerines, as well as swifts, rakshas, ​​woodpeckers, cuckoos and others.

By habitat There are four groups of birds:

• forest birds differ from other groups in that they have rather small legs, as well as a medium-sized head. Their necks are not visible, their eyes are on the sides.
• Birds of the coasts of reservoirs and swamps has a very long neck and long legs. They need them in order to get food in the swamps.
• Birds of open spaces adapted to migration therefore have very strong wings. Their bones weigh less than the bones of other types of birds.
• The last group are waterfowl who live near or in bodies of water. These birds are distinguished by a fairly powerful beak, which helps them eat fish.

There are five groups of birds in total. nesting sites. The main difference is only in the form of a nest in which these birds live:

• crown nesting birds build their nests, as the name implies, in the crown of trees (orioles, glare).
• bush birds have their nests near or in the bushes themselves (wren, robin).
• ground-nesting decide to place their nest right on the ground (larks, skates, buntings, sandpipers).
• Hollow nesting birds live right in the hollows (woodpeckers, tits, pikas, flycatchers).
• And the last group of birds, norniki(shore swallows, bee-eaters, kingfishers), live in burrows, underground.

• Go to the section heading: * Breeding of birds, mating behavior

bird eggs

Birds reproduce by laying eggs. There is a huge variety in size, color, shell structure, etc. etc.

The bird lays an egg in about a day. This process includes the time from the release of the egg from the ovary, the formation of the egg shell and the actual laying of a fully formed egg. Unlike oviparous reptiles, a bird usually lays only one egg at a time. However, a hen from the American city of Mandham set a kind of record - she laid 421 eggs in 223 days.

The composition of the eggshell includes a lot of calcium salts, which the bird tries to include in excess in its diet. Therefore, for example, female penguins in the period of preparation for laying eggs swallow a large number of shells of mussels and other molluscs. In this way penguins get the extra calcium they need to build their shells and make them stronger. Such eggs are more likely not to break when accidentally hitting rocks, ice, and other hard surfaces.

The eggs of many birds, still in the oviduct, just before laying, are covered with special dyes. One or another color of the eggs makes them less noticeable against the background of the nest and the surrounding area. That is why, in birds nesting in hollows and other closed places, eggs are usually monochromatic - white and bluish. But in birds that build open nests, eggs often have a special characteristic pattern and color, which serve as a protective color and play a protective role. Therefore, in some species, the surface of the egg is covered with speckles, sometimes forming a corolla around the blunt end, in others the entire surface is in colored stains or blurry spots.

And the surface of the egg can be either rough or smooth, matte or shiny. And in shape, the eggs of most birds resemble chicken eggs, but there are many exceptions here. So in kingfishers they are almost spherical, in hummingbirds they are elongated and blunt at both ends, and in waders at one end they are very pointed.

And the color of the eggs of various birds includes almost the entire spectrum. Even chickens have green eggs! Japanese breeders brought new breed hens laying pale green eggs. It is believed that such an effect is determined by the specific properties of the spleen of these birds. It turned out that green eggs contain more B vitamins, as well as iron.

Outside eggshell dressed in a thin soluble film that has bactericidal properties and protects the egg from the penetration of microbes into it. Therefore, bird eggs: chicken, quail and others intended for storage, so as not to damage this protective film, should not be washed in water.

Most birds during one breeding cycle lay quite a certain number of eggs: from 1-3 to 10-20, and sometimes more eggs. Therefore, in birds, like the Californian condor, which lay one egg every two years, each pair adds only “half of an individual” to the population per year, and species with 2-3 large clutches of eggs per year can increase it by 20-30 or more individuals.

Incubation is the most important period in the development of eggs. In some species, both partners can participate in incubation of eggs, in others only one of them, male or female. A bird incubating eggs usually develops one or two brood spots, patches of skin located on the underside of the breast and devoid of plumage. The skin of the brood spot, which is strongly supplied with blood, is in direct contact with the eggs and transfers the parental warmth to them. The incubation period, culminating in the hatching of chicks, lasts from 11–12 days in small passerines, to approximately 82 days in the wandering albatross.

Brightly colored males, as a rule, do not sit on eggs if the nest is open. The exception is the red-breasted oak-nosed cardinal, which not only incubates, but also sings. In many alternate incubators, the brooding instinct is so strong that at times one bird will push another off the nest to take its place. If only one partner incubates, he periodically leaves the nest for feeding and bathing.

The ostrich (Struthio) is incubated only by the male. At the same time, several females lay eggs at once, and the male rolls them into the nest, incubates and actively protects. The nest usually contains from 15-20 eggs, up to 50-60.

This is a product consisting of chicken protein and yolk. For their rich composition, they are also called a treasure in the shell: they contain vitamins A, B, E, K, D (they are second only to fish in their content), as well as calcium, phosphorus, iron, manganese, iodine and amino acids. The product is high in calories (in an egg weighing 50 g - about 75 kcal), so nutritionists advise starting the day with it in order to enjoy the feeling of satiety longer. Also, eggs must be in the diet of children and athletes, especially bodybuilders, because it is a source of protein.

Opinions vary on how many eggs should be in the diet, but most nutritionists agree that it is undesirable to eat more than 10 eggs. in Week.

Goose

Goose eggs have appeared in the human diet since the domestication of geese. This refers to the Neolithic era - about 10 thousand years BC. Goose eggs belong to dietary products, the nutritional value of which is several times higher than chicken eggs. The egg is quite large - weighing about 200 g with a white shell. Goose eggs have a fairly dense shell, so to cook hard-boiled eggs, you need to boil them for 15 minutes in salted water under a lid over medium heat. Also, goose eggs are quite dirty and should be washed under running water before use. In terms of fat content, eggs are largely inferior to duck eggs. Depending on the nutrition of the bird, the taste of the eggs also changes. The more fresh grass in their diet, the more tender their taste.

pigeon

Pigeon eggs are quite small in size, 4 cm long. In almost all species of pigeons, the eggs are white without speckles, with a mother-of-pearl, shiny sheen, but in some breeds the eggs are light brown or cream in color. Pigeon eggs are very fragile shell, so they are difficult to transport and need to be handled with care.

Turkey

These are the eggs closest to consumer properties to chickens. The average turkey egg weighs 70-75 g. The shell is quite dense, usually white with a creamy tint and small lighter specks. The size and color of the eggs directly depends on the age of the bird, the younger it is, the smaller the eggs and the lighter the shell.

Chicken

A hen lays an egg every 24-26 hours on average. White eggs are laid by white chickens, and brown eggs are red or dark. In terms of nutritional value, white and brown eggs are no different. The size of eggs depends on the age, weight and breed of chickens. More mature hens lay larger eggs. Egg size is also affected by stress factors: increased temperature, limited space, poor chicken nutrition, etc.

Quail

A quail egg is considered a dietary product that is necessary in the diet for the normal development of the child's body, for recovery in the postoperative period and for various diseases. The egg has a fairly thin light shell with characteristic dark spots. The weight of one quail egg ranges from 10 to 12 g.
Quail eggs and their beneficial features known to mankind since ancient Egypt. The study of the properties of quail eggs in modern society conducted by the Japanese, and the publication of scientific articles on the benefits of this type of eggs made quail eggs world famous.

ostrich

Ostrich eggs have a high commercial value and are not among the main products of ostrich breeding and, in fact, all are sent for incubation. Unfertilized eggs are used in nutrition - table eggs, eggs obtained from young females, early or late eggs. Ostrich eggs are in no way inferior to chicken eggs and are prepared in a similar way. One ostrich egg holds 25-40 chicken and weighs from 450 g to 1800 g, similarity to porcelain allows you to use the shell in art products by painting and engraving. China has registered the world's largest ostrich egg weighing 2.35 kg and 18.67 cm in diameter.

duck

Duck eggs - the most high-calorie eggs waterfowl, in which there is a large amount of fat and at the same time they have a specific smell and taste. The weight of an average duck egg is 90 g, which is 1.5-2 times more than a chicken egg. The shell of the eggs is dense, and its color can vary from white to bluish-green. In some countries, duck eggs are considered a very expensive delicacy. This is how canned duck eggs are prepared in Japan. In China, they are stored for a hundred days, but for this they use an aqueous solution, to which green tea, potash, salt and burnt oak bark are added. In the Philippines, duck eggs are cooked when the chick is already fully formed inside (beak, plumage, skeleton). The dish is called "balut".

pheasants

Pheasant eggs are literally a storehouse of all kinds of useful substances and various vitamins. They are small in size, about half the size of chicken eggs. Pheasant eggs can be painted in sand, dark gray, gray, light gray, greenish gray, light green, green and almost marsh colors, they can be plain or speckled.

Guinea fowl

They belong to dietary products that have low cholesterol levels and hypoallergenic properties. The guinea fowl egg is pear-shaped, yellowish-brown in color and has a very hard shell. That is why they are easy to transport and there is less chance of infection with salmonellosis. Eggs retain their useful properties and freshness for a sufficiently long period (up to six months) at a temperature of 0-10 ° C. The average guinea fowl egg weighs 45-48 g. In most European countries, more guinea fowls are bred than chickens.

Turtles

A very nutritious and rare product that belongs to special delicacies. This type of egg is round in shape, white in color and has a soft leathery shell. The mass of the egg is 30-35 g. The yolk has a color from pale to bright yellow, and in size and taste is very close to chicken. The protein, in turn, has a gelatinous structure and is completely transparent. For European countries, turtle eggs are exotic and are considered a great delicacy. In eastern countries, this product is an everyday everyday food.

emu

Emu eggs are useful, as well as chicken. They don't even differ in cooking methods. The weight of one egg is from 450 gr. up to 1800 gr., which is equal to about 25-40 chicken eggs. The largest egg with a diameter of 18.67 cm and a weight of 2350 gr. was registered in China. The shell of an emu egg is very dense and durable, despite this it is quite easy to break it. It is dark green, almost black in color, and the eggs themselves have a rich yolk and translucent protein.