About bird eggs and parents. The structure of a bird egg: diagram, features Other elements of the oocyte structure
The round or elongated shape of the egg depends on whether the bird likes to fly.
Bird eggs are difficult to confuse with something else, but their appearance is still very diverse. And if everything is more or less clear with coloring - the color of the shell makes the eggs invisible, and, moreover, without parents - then with the form there is no such clarity.
And the shape of eggs in different species can differ quite greatly, for example, in waders, the eggs at one end narrow quite strongly, so that they look like a pear, in owls, the eggs are spherical and resemble tennis balls, and in hummingbirds they are bean-shaped. All eggs have the same function - to protect and nourish the chick during its embryonic development; This means that the variety of forms arose for some extraneous reason.
Mary Stoddart ( Mary Stoddard) from Princeton University and Lakshminarayanan Mahadevan ( Lakshminarayanan Mahadevan) from Harvard, together with colleagues from other research centers, analyzed the geometric shape of almost 50,000 eggs belonging to 1,400 species of birds. The researchers even developed a special program that could be used to accurately determine how different an egg is from a perfect ball.
Eggs, as we said, are very different, very elongated, not very elongated, with a pointed end, etc., and various geometric features are combined with each other in different ways. However, as it turned out, there are no eggs in the world that are short and pointed - that is, not a single bird lays eggs that look like a balloon.
The shape of the egg actually depends not on the shell itself, but on the soft membrane - the subshell membrane, which initially contains the entire contents of the egg; the shell appears later, when the egg has already formed. The membrane has thicker and less thick sections, somewhere it stretches more, somewhere weaker - all in order to be strong enough to withstand the pressure from inside the egg as it grows and swells in the bird's genital tract. As calculations have shown, a variety of geometric shapes are suitable for this. However, in theory, it turned out that one of such solutions could well be the shape of a balloon, meanwhile, as we said, there are no such eggs in nature.
Then the researchers tried to compare the eggs with the behavior of birds. Among the thousands of species that were chosen for analysis, it was possible to identify several groups with eggs of similar shape. However, there was no relationship between the shape and type of nest, or the choice of nesting site, or the number of eggs in a clutch (although both have often been put forward in the past as explanations for the variety of egg geometry). The coincidence was found in another way: it turned out that the shape of the eggs often corresponds to the parameters of the wing, the ratio of its length and width.
The length and width of the wing determine the flight pattern - in other words, the geometry of the eggs depended on how the bird flies. Those who fly well and spend a lot of time in the air (like albatrosses and hummingbirds) have elongated and asymmetrical eggs; if birds take to the air reluctantly, spend a lot of time on the ground or fly short distances from bush to bush and from tree to tree (such as African pittas and trogons), then their eggs will be more rounded. To calmly lay a rounded egg, we need a wide oviduct and a wide pelvis, but if we want to fly quickly and maneuver in flight, the body must be light and elongated, and a wide pelvis is not at all appropriate here. (Presumably, the same applies to birds that swim and dive a lot - they also need a narrow, streamlined body shape.)
That is, various combinations of elongation and pointedness are all the results of attempts to combine the need for a narrow oviduct with the need to supply the egg with a sufficient amount of nutrients. The combination of a spherical shape with a sharp end (like the notorious balloon) turns out to be meaningless - the pointedness gives an advantage only if the egg is also elongated; if the bird flies little and therefore can afford spherical eggs, then the sharp end will simply be unprofitable because it will reduce the volume of the egg.
Original taken from pystelgga in Bird's eggs
As they say, a precious egg for Christ’s Day. With Easter approaching, it's time to talk a little about what distinguishes the reproductive processes in birds from similar processes in mammals, namely eggs.
All birds lay eggs. There are no exceptions. The size of the egg depends on the size of the bird, and the shape depends on its living conditions. If it lays eggs in a hole, they are round; in the nest - oval; if it nests on rock ledges, it is oblong. Coloration also varies greatly because the eggs must be invisible to surrounding predators. If a bird builds a nest in which the eggs are not visible, then they may be white; if it nests on the ground, then the eggs can be grayish, variegated, green, etc., to match the color of grass or stones. The thickness of the eggshell also depends on the nesting conditions. Interestingly, eggs breathe through many microscopic pores in the shell.
The largest eggs, as is known, are laid by the female African ostrich: weight up to 2 kg, length - 15-20 cm; the smallest are dwarf hummingbirds: weight less than 0.4 g, length up to 1 cm. There are exceptions to the rules: the relatively small kiwi bird (5 kg) lays eggs the size of 1/4 of its body. (In the small gray kiwi, the yolk content in the egg is 65% (while in other birds it is no more than 35-40%). Thanks to this amount of yolk, a newly hatched chick can go without food for up to 10 days). The weight of a standard chicken egg is 47-50 grams; goose - 160-200 g; turkey - 75-90; quail - 12-15 g.
This is what the eggs of the inhabitants of our forests look like: 
And these are plover eggs:
Blackbird eggs: 
Tinamou bird eggs from the South American tropics: 
(By the way, the weight of a tinamu’s heart is only 0.002 of its body weight, which is why these birds are extremely reluctant to fly).
Lapwing eggs: 
Oocytes (eggs) are usually the embryonic form of an animal or egg cell. They are studied by oology, a special branch of zoology.
general information
Their sizes may vary. For example, in a mouse the size of an egg is approximately 0.06 millimeters, but the diameter of the embryonic form of an African ostrich can reach 15-18 centimeters. The shape can also be different. But usually eggs are spherical or oval in shape. In some living creatures they can be oblong, elongated, as, for example, in mule fish, hagfish or insects. Depending on the degree of distribution and amount of nutrients inside the egg, the size and other characteristics are determined. The accumulation of yolk (this substance) occurs either in the form of a solid mass or in the form of granules. Depending on this, experts divide oocytes into different types. The fertilization process takes place in the upper section of the oviduct. As the oocyte passes through the canal, fragmentation occurs. This process proceeds according to the discoidal incomplete type. Due to the fact that the beginning of crushing occurs already in the oviduct, in birds a laid egg can remain at one of the stages of crushing (as, for example, in a pigeon) or gastrulation (as in a chicken).
bird egg
Females of all species of feathered fauna lay oocytes. Different species lay differently shaped eggs. This is due to the location where the masonry will be located. For example, if the nest is made in holes or holes, then the eggs will be round. In birds whose clutches are located on rocky ledges, the oocytes will be elongated. Typically, the larger the bird, the larger the egg size. But there are exceptions to this rule. For example, brood species, the offspring of which are immediately adapted to self-feeding, lay eggs whose size is larger (compared to the female’s body) than those whose chicks are born helpless. Moreover, the ratio of oocyte mass to body weight in small species is often greater than in larger species. It is believed that the largest eggs are laid. Relative to the body weight of this feathered representative, its oocyte makes up 1% of the body weight. But the weight of a hummingbird egg is 6% of the bird’s weight.
Some structural features of a bird egg
In birds living in mountainous areas, oocytes have “ribs”, like stiffeners. They are necessary to maintain the integrity of the eggs so that they do not break when the birds land in a nest that has a small area. It should be noted, by the way, that this rib can withstand pressure of about 40 kg/sq. cm, and the side where it is missing is no more than 2 kg/sq. cm. The surface of eggs can be rough or smooth, shiny or matte. The color can be absolutely anything: from pure white to green and dark purple. The surface of the eggs of some species is covered with specks, in some cases forming a corolla around a blunt edge. The color will depend on the type and location of nesting. Thus, many secretly laying eggs and domestic birds have a white shell. For those who leave the nest on the ground, the color becomes identical to the surrounding conditions: it blends in with the pebbles or plant debris that lines the nest. The egg receives its color in the female's birth canal. For example, biliverdin (pigment) in combination with zinc gives a blue or green color to the surface of the egg. Protoporphyrin produces a red or brown color, or spots of such shades. Next, let's take a closer look at the internal structure of a bird's egg.
Oocyte device
Birds fit for purpose. It contains everything necessary for the formation and development of a young body. The embryo in the egg is nourished by compounds contained in the yolk. This mass is presented in two types - white and yellow. They are arranged in concentric alternating layers. The yolk is enclosed in a vitelline membrane. It is surrounded by protein. In the early stages of egg shell development, birds' eggs perform a nutritional function. The protein, in addition, provides protection for the new organism from contact with the shell. The contents of the oocyte itself are surrounded by two subshell layers: outer and inner. Considering the structure of a bird's egg, it is necessary to say a few words about the shell itself. It consists mainly of calcium carbonate. After laying, an air chamber gradually forms on the blunt edge of the oocyte.
Yolk
Considering the structure of a bird's egg, the diagram of which is given below, it should be said that deutoplasm (yolk) is an integral component of the internal contents of the oocyte. The yolk mass contains all the necessary substances that provide nutrition and normal development of the body. Deutoplasm is found in the egg cell of not only birds, but also other animals (and humans) and is an accumulation of plates or grains, merging in some cases into a solid mass. The amount of yolk, as well as its distribution, may vary. With a small volume of deutoplasm, grains or plates are distributed evenly throughout the cytoplasm. In this case, they speak of “isolecithal” eggs. With a large amount of yolk, the components accumulate either in the central region of the cytoplasm - near the nucleus or in the vegetative part of the oocyte. In the first case, they speak of centrolecithal eggs, and in the second, telolecithal eggs. In accordance with the volume and degree of distribution of the yolk mass, the type of oocyte fragmentation is determined. The chemical structure of a bird's egg includes three types of deutoplasm. The yolk can be carbohydrate, fat or protein. But, as a rule, in most individuals the yolk components include, in addition to the indicated compounds, minerals, pigments, and ribonucleic acid, thus having a complex chemical structure. So, for example, in a chicken oocyte that has completed its growth, the yolk contains 23% neutral fat, 16% protein, 1.5% cholesterol, 11% phospholipids and 3% mineral compounds. Various organelles participate in the accumulation and synthesis of the yolk component: mitochondria, Golgi complex. The synthesis of the protein component of the yolk structure in many animals occurs outside the ovary. By pinocytosis, the protein component penetrates into the developing egg.
Other elements of the oocyte structure
All shells prevent spreading, drying out and damage to the egg. But they do not provide the necessary moisture to a growing organism. It is formed. In particular, they include the aqueous layer (or due to it, the amnion cavity is limited, which is filled with fluid, where, in fact, the organism develops. Together with the aqueous layer, two more layers are formed: vascular and serous (or allantois). In birds and reptiles this layer is an organ of excretion and respiration. Chalazae - protein twisted dense cords - extend from the egg to the blunt and sharp edges of the egg. They ensure a stable position of the nucleus, preventing displacement from the average position.
Shell
When studying the structure of a bird's egg, one should dwell in more detail on the layers surrounding the core. The hardest outer layer is the shell. It is quite dense and serves as protection against mechanical damage and the negative influence of the external environment. Under the shell there are subshell membranes. At the blunt end they diverge and form an air chamber. It contains oxygen, which is necessary for the respiration of the new organism.
Trophic oocytes
There is a type of eggs that, when laid, serve as food for the offspring. As a rule, they are unfertilized, and their appearance is practically no different from ordinary ones. They are laid by the females of some ants and the queens of termites until the colony begins to produce enough food. In some cases, unfertilized oocytes of meat-egg and egg chicken breeds are also mistakenly called trophic, since they are used as food not by the birds themselves, but by humans and sometimes domestic animals.
The central part of the egg is occupied by the yolk. It consists of 5-6 alternating concentric layers of yellow and light colors, 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 - latebra, which has the shape of a flask and is connected through a neck to the embryonic part of the egg (in an unfertilized egg - with a blastodisc, in a fertilized egg - with a germinal disc). The yolk is always oriented with the embryonic part upward, which has important adaptive significance during egg incubation. 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 vitelline 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 essential nutrients.
Egg white consists of four fractions. Directly around the yolk there is a thin layer of internal dense, or hailstone, protein, from which hailstones (chalaza) 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 white and thus, as if by stretch marks, hold the yolk in the center of the egg. The hailstone protein is surrounded by a thicker layer of internal liquid protein, consisting of a semi-viscous homogeneous substance, similar 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 the outer dense protein.
The protein sac at the sharp and blunt poles of the egg is attached to the inner shell membrane. It contains many mucin fibers, which help maintain its shape and serve to protect the yolk.
Between the albumen sac and the subshell films (except for the poles) there is a 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 sac - 57; external liquid - 23.
The protein is a later formation in the evolution of birds and has less structural stability than the yolk. It mainly has a protective function, being at the same time a reservoir of water.
The protein is surrounded by shell membranes. The inner (protein) shell covers the entire protein and is tightly fused to the outer shell. In the region of the obtuse pole, the commissure between them is weakened. After the egg is laid and cooled, the yolk and white slightly decrease in volume, at the blunt pole the shell membranes separate, and an air chamber forms between them. On average, the mass of the shell shells 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 of the egg has a diameter of less than 1 cm, then it increases depending on the storage period, temperature and humidity of the surrounding air. The size of the air chamber, other things being equal, is an indicator of the freshness of the eggs.
The egg is covered with a hard calcareous shell - a shell, which protects its contents from mechanical damage and is a difficult barrier to microbial infection and water evaporation. The thickness of the shell varies greatly, mainly due to the outer spongy layer. Chicken eggs have an average shell thickness of close to 0.35 mm. In thick-shelled eggs it is thicker at the sharp pole, and in eggs with a very thin shell it is thicker at the blunt pole. In the “equator” zone, the thickness of the shell is more constant and mainly characterizes the average for a given egg.
The shell is riddled with pores, the number of which in a chicken egg is usually more than 7 thousand, and per 1 cm 2 - more than 100. 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 quite easily washed off with hot water and is damaged by friction. The shell takes on a shiny appearance. By this sign you can judge the quality of the egg. However, some chickens lay eggs whose shells are practically devoid of cuticle.
Thus, the yolk is surrounded by four protein layers, two subshell films, a shell and a cuticle, i.e. eight shells, each of which performs its own specific function.
The excretory system includes two kidneys, which remove waste products from the blood and form urine. Birds do not have a bladder, and the water passes through the ureters directly into the cloaca, where most of the water is absorbed back into the body.
The reproductive system consists of the gonads, or sex glands, and the tubes extending from them. Male gonads are a pair of testes in which male reproductive cells (gametes) - sperm are formed.
The female gonads, the 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. Sperm enter the female's cloaca during copulation and swim 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 shell.
Brood- these are birds whose chicks are able to see, hear, run and feed independently 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 fly.
U chicks In birds, the clutch is usually smaller than in brood birds; 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 hen can fit under her. The nest of representatives of the nestling group is usually more complex and massive than that of the brood group, well camouflaged and insulated with soft material. Such a structure camouflages the chicks from prying eyes and protects them from bad weather.
U nesting the opposite is true - their chicks hatch naked, blind and helpless. In the first days they need constant heating, and their parents bring them food until they leave the nest and even longer. Such chicks leave their home without really knowing how to fly. At this time they are called fledglings. Chick 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 They differ from other groups in that they have rather small legs, as well as medium-sized heads. Their neck is 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 to get food in the swamps.
- Birds of open spaces They are adapted to migration and therefore have very strong wings. Their bones weigh less than those 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 feed on fish.
There are five groups of birds in total. nesting sites. The main difference is only in the type of nest in which these birds live:
- Crown-nesting birds they build their nests, as the name suggests, in the crown of trees (orioles, zabliki).
- Bush birds they place their nests near or in the bushes themselves (wren, robin).
- Ground-nesting decide to place their nest directly on the ground (larks, pipits, buntings, waders).
- Hollow-nesting birds live directly in hollows (woodpeckers, tits, pikas, flycatchers).
- And the last group of birds, burrowers(shore swallows, bee-eaters, kingfishers), live in burrows, underground.
bird egg the egg itself, or egg cell, with all the membranes that cover it: yolk, albumen, double shell and shell. Strands of thick protein (chalaza) hold the yolk in a certain position so that its side, on which the germinal disk is located, always faces upward. At one end of the egg, the subshell membrane exfoliates, forming an air chamber - puga (see. rice.
). Dimensions of P. i. range from 8×13 mm(for hummingbirds) up to 135×170 mm(in the ostrich), and the number in the clutch is from 1 (tube-nosed birds, many guillemots, lyrebirds, etc.) to 20 or more (chickens). The shape of the eggs varies from spherical to elongated oval. Their color also varies greatly: spotted or plain - from white or blue to almost black. A laid egg (except for food) usually already contains an embryo. Bird eggs, especially domestic ones, are used by humans for food (see Edible egg). In a number of countries, mass collection of eggs is practiced in colonial nesting areas of birds, for example, in bird markets (See Bird markets) .
A. I. Ivanov.
Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .
See what a "Bird's egg" is in other dictionaries:
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