Feathers distinguish birds from all other creatures living on our planet. Feathers come from the scales that cover reptiles. Plumage is necessary for birds to fly, to keep warm, to attract the opposite sex. Different types of birds differ from each other in color and shape of feathers, and in some cases, thanks to plumage, it is possible to distinguish a male from a female.

The feather is made up of keratin.- the protein that forms our nails and hair. Each feather has a central core, the base of which, a hollow core, is covered by a feather bag in the skin.

The part of the rod on which the filamentous formations or beards are located is called the trunk. On each side of the trunk there are barbs of the first order, forming an angle of about 45º with the trunk. The part of the feather with beards is called the fan. On the barbs of the first order there are microscopic threads called barbs of the second order. They intersect at an angle of 90º. The barbs of the second order, in turn, have hooks that, like a zipper, hook the barbs together, forming a smooth, hard surface of the wing. Without this, the feather would not be able to withstand air resistance in flight. Sometimes the hooks come loose. By caring for feathers, the bird can again give them the desired shape.

Feathers with beards of the 2nd order are called contour, and without them - downy. Some feathers consist of both a contour and down part.

Feathers do not completely cover the bird's body. The feathered areas are called pterylia, and the areas without feathers are called apteria.

Pen Types

Birds have different types of feathers, each with a specific function.
Outline feathers. Contour feathers cover most of the bird's body, giving it a streamlined shape. They protect the bird from the sun, wind, rain and wounds. Often these feathers are brightly colored. Contour feathers are divided into primary and coverts.

flight feathers. These include feathers on the wings and tail.
The flight feathers of the wings can be divided into three groups:
Flight feathers of the first order are attached to the hand and during the flight create traction. There are usually 10 primary flight feathers, which are numbered starting from the inside of the wing.
Flight feathers of the second order are attached to the forearm and are necessary for the bird to rise into the air. They are also used in the courtship process. Usually there are 10-14 secondary flight feathers and they are numbered from the outside of the wing inward.
The flight feathers closest to the bird's body are sometimes called tertiary.
Tail feathers, called tail feathers, help the bird navigate in flight. Most birds have 12 tail feathers.

Flight feathers are covered with smaller contour or cover feathers. There are several layers of integumentary feathers on the wing. Integumentary feathers also cover the ears of the bird.

down feathers. Down feathers are small, soft, fluffy, they are under the contour feathers. They do not have grooves and hooks that interlock the beards on the contour and flight feathers. Therefore, they allow you to maintain thermal insulation, protecting the bird from cold and heat. They are so effective that people use them to warm outerwear.

Some birds (herons, some nightjars, bustards, parrots) have a special type of down feathers - powder feathers, areas with constantly growing down, the tops of which easily break off, forming a fine powder - “powder”. They are usually located on the sides of the chest or on the lower back. With its claws, the bird spreads the “powder” to the entire plumage, which, presumably, increases the water-repellent properties of the plumage. This powder also helps the bird clean its feathers. Its absence in cockatoos or African gray parrots may indicate diseases of the beak and feathers..

thread feathers. These are very thin, thread-like feathers with a long shaft and several beards at the end. They are located throughout the pterylium. It is not entirely clear what their function is, it is believed that they relate to the sense organs, perhaps helping to set the position of the flight feathers in accordance with air pressure.

down feathers. Down feathers provide shape, aerodynamic properties, thermal insulation. They also play a role in the courtship process. They have a thick trunk, but a small fan. They can be caught among the integumentary feathers or in separate areas of the pterylium.

bristles. The setae have a soft stem and several barbules at the base. They are usually located on the head (around the eyelids, mouth, nostrils). They perform both sensitive and protective functions.

Feather growth

Like hair, feathers develop in a special area of ​​the skin called a follicle. When a new feather develops, it has an artery and a vein in the stem that feeds the feather. The pen at this stage is called "bloody". Due to the color of the blood, the stem of the blood feather is dark, while the adult feather has a white stem. The blood feather has more holes than the adult. The blood feather grows from a waxy keratin sheath that protects it during growth. As the feather matures, the blood supply stops and the wax protection is removed by the bird.

Although an adult bird usually changes all its feathers during the molt, the loss of feathers is usually spread over several months, so that enough is left for flight and thermal insulation.

Shedding is usually triggered by a change in day length and may occur after the mating season. Some wild birds, such as goldfinches, molt twice a year, changing their bright "wedding" outfit to a more modest one.

Feather color

The color of bird feathers is determined by the presence of various pigments, such as melanins, carotenoids, porphyrins.

Melanins are brown and black pigments that are also found in mammals. In addition to affecting feather color, they also help feathers be denser and resist wear and tear from sunlight.

Carotenoids are yellow, orange and red pigments. They are synthesized by plants and absorbed by the digestive system of birds, and then enter the cells of the follicle when the feather develops.

Porphyrins are red and green pigments that are produced in avian follicle cells.

The next time you see a bird, you will understand how feathers give it the ability to fly and how they protect it, and you will be able to appreciate the complexity and uniqueness of these representatives of the animal kingdom.

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Feathers

"A bird is recognized by its feathers." This folk wisdom reflects the scientific fact that the feather is a unique entity found in only one class of animals. Indeed, feathers do not exist in any of the living groups of living organisms that exist today, except for birds, and there is no evidence that any extinct group had them.

The role of plumage in the life of birds is difficult to underestimate. It is feathers, creating the bearing surface of the wing and the streamlined shape of the body, that allow birds to fly. The feather is an excellent heat-insulating and waterproof material, and the different colors and features of the shape of the plumage carry information about the species and gender of the bird, thus playing an important role in intraspecific and interspecific communication.

Bird feathers originate from the scales of reptiles and also consist of horny substance. They, like reptile scales, are derived mainly from the superficial, epithelial, layer of the skin (epidermis), and consist of dead and highly modified cells.

Many feathers - good and different

According to the structure, several types of feathers are distinguished: contour, downy, filiform, down and bristles.

I, II - contour feathers; III - downy feather; IV - down; V - threadlike feather; VI, seta; VII - scheme of the structure of the contour pen under high magnification.
1 - chin, 2 - the inner part of the fan, 3 - the outer part of the fan, 4 - the downy part of the fan of the contour feather, 5 - the rod, 6 - the side (additional) rod, 7 - the upper navel of the feather, 8 - the lower navel of the feather, 9 - barbs of the first order, 10 - barbs of the second order, 11 - hooks

contour feathers, apparently, are the most familiar to the reader (Fig. 1, I, II). They cover the entire body of the bird, form wings and tail and create a characteristic "bird" appearance. Externally, the contour pen is subdivided into the one located in the axial part kernel and fan(Fig. 1). The lower, free, part of the rod is called by the way. It has an internal cavity that is filled with spongy tissue. At the lower end of the hole, the cavity opens with a small hole - lower navel pen, and at its upper end on the border with the fan is, respectively, upper navel(Fig. 1, 7, 8 ). The rod in the region of the fan is denser in structure, does not have an internal cavity, and its core is formed by keratinized cells filled with air. The fan itself is formed by small “branches” extending in both directions from the rod - beards of the first order(Fig. 1, VII, 9 ). They are so closely interlocked that they give the impression of a continuous surface. But if you look closely, or even better - put a contour pen under the binocular, you can see that from each barb of the first order, smaller barbs, called beards of the second order, or beards(Fig. 1, 6 ). If, however, we examine this area under even greater magnification, then a certain number of small hooks will be found on each beard of the second order. It is with their help that neighboring barbs are linked to each other, as a result of which a continuous plate is formed (Fig. 1, VII).

Structure down feather similar to the structure of the contour, with the only difference that the beards on down feathers are soft, devoid of hooks, and therefore the beards of the first order are not linked to each other. There is an assumption that feathers with unlinked beards are more primitive than contour ones, and as an indirect confirmation one can cite the fact that ratites (a rather ancient combined group that includes African ostriches, cassowaries, rhea and kiwi) do not have feathers with linked beards at all .

fluff differs from a downy feather in the absence of a rod - its beards, also unlinked, depart immediately from the quill.

Due to this structure of the beards, the feathers of these two types play the role of a "fur coat", holding a fixed layer of air near the skin. In many groups of birds (for example, hens, owls, pigeons) the same purpose is served by additional(side) kernel, which departs from the tip of the contour or down feather. It is always much shorter and thinner than the main one and bears soft beards, as on a downy feather. Loose beards are often present in the lower part of the fan of contour feathers, which also increases body insulation. In general, between contour and down feathers, all intermediate stages are possible.

Interestingly, in species of temperate latitudes, the proportion of down feathers and down in plumage is higher than in tropical species. If a bird has winter and summer plumage (for example, many grouse), then the number of unlinked "downy" beards in winter plumage increases, sometimes occupying almost the entire fan. In this case, “additional feathers” are better developed in winter. In winter, even the number of feathers in sedentary birds of the middle zone increases - mainly due to down, which "sprouts" by winter.

thread feathers and bristles have the simplest structure and consist only of a shaft, thin and soft in filiform feathers and hard and elastic in bristles. The fan is reduced, and only a few beards are preserved at the end of the filiform feathers. Thread-like feathers serve for touch (react to the movement of air currents) and grow throughout the bird's body. Bristles can be found in many species at the base of the beak, where they also perform a tactile function, and in nightjars, swifts, flycatchers and other birds that grab prey on the fly, they “increase” the mouth section with their help. In many birds, bristles grow along the edges of the eyelids, forming eyelashes.

Some groups of birds (herons, some nightjars, bustards, parrots) have powdered- areas with constantly growing fluff, the tops of which easily break off, forming a fine powder - "powder". They are usually located on the sides of the chest or on the lower back. With its claws, the bird spreads the “powder” to the entire plumage, which, presumably, increases the water-repellent properties of the plumage.

Life path of the pen - childhood, adolescence, youth

The skin of vertebrates consists of two layers of different structure and origin: epidermis and dermis(it is also cutis, corium, skin itself). The epidermis is located on the surface and belongs to the epithelial tissues, the dermis - to the connective. Accordingly, in its origin, the epidermis is a derivative of the ectoderm of the embryo, and the dermis is a derivative of the mesoderm. The epidermis of vertebrates is multilayered, the cells of the outer layers are gradually filled with horny substance, die off and exfoliate, while the epidermis is constantly updated due to the constant division of its lowest layers of cells (the so-called germ layer). The main function of the epidermis is protective, it is also the ancestor of a number of skin formations in vertebrates (in addition to feathers, these are claws, mammalian hair, deer horns) and skin glands (sebaceous, sweat, milk). The dermis is rich in blood and lymphatic vessels and provides nourishment to the epithelial tissue, growth and development of its derivatives.

A - stage of the feather papilla; B - tubule stage (barbs develop inside the cap); B - stage of rupture of the cap. 1 - epidermis, 2 - dermis, 3 - feather barbs, 4 - cap, 5 - cavity of the chin, 6 - feather pouch

As a result of cell growth epidermis and dermis a tubercle forms on the skin, similar to the rudiment of reptile scales, which gradually grows in the form of a backward outgrowth, and its base gradually deepens into the skin, subsequently forming a feather bag. From above, the outgrowth is covered with the epidermis, below it there are living tissues of the dermal layer, rich in small blood vessels, which form the feather papilla (Fig. 2, A). As they grow, they stretch the feather outgrowth in length, the epidermal layer gradually becomes keratinized, and the outgrowth itself takes the form of a tube. At the outer end of the feather tube, the epidermis is stratified: its outer thin layer is separated in the form of a conical cap, and the feather barbs are further differentiated from the inner layer of the epidermis. In the case of the development of a contour feather, a series of parallel horny ridges is first formed, one of which, the thickest, subsequently becomes a rod, the rest move onto it as they develop (Fig. 3), turning into barbs of the first order, and barbs of the second order develop on them. With the development of down, the rod is not formed, and all parallel ridges subsequently become downy beards of the first order. All development of the feather takes place inside the case.

a - germ layer; b - case; 1, 2, etc. - serial numbers of epidermal folds - future beards of the first order

As the feather grows, the living feeding cells of the papilla die off, starting from the end of the feather tube, the cap at its end is torn, and the barbs of the feather come out, forming a kind of feather tassel. Usually, after the cap has ruptured, the growth of the feather continues at the base, and the young feather at this stage is much shorter than it should be. It reaches its final length when the fan is completely freed from the cap, the remains of which remain in the form of thin films for several more days at the base of the quill.

The feather is held in the skin by tightly fitting walls of the feather pouch and muscle cords, which ensure its mobility.

Feathers don't grow there...

Speaking of feathers, it is certainly necessary to point out that in most birds, contour feathers do not grow in a continuous layer over the entire surface of the body, but only in separate areas, which are called pterylia(from Greek. pteron- pen and hyle- forest).
Areas that do not bear feathers are called, on the contrary, apteria.

Down feathers grow along with contour feathers on pterylae. Down can either relatively evenly cover the entire body of a bird (in copepods, anseriformes, many diurnal predators, etc.), or be only on apteria (herons, owls, many passerines). Less commonly, it grows only together with contour plumage on pterylae (tinamou). Only a few members of the class have a uniformly feathered body, without apteria: penguins, palamedeas and birds of the ratite group.

The presence of apteria allows the bird not only to “save” on plumage (the body is covered with fewer feathers). Paradoxically, birds with apteria have better thermoregulation. Surely everyone saw a ruffled crow or jackdaw sitting on a branch in winter, or watched a budgerigar fall asleep in a cage - their feathers rise, bristle in all directions, and the bird resembles a fluffy ball. It is the presence of apteria that gives more opportunities for the mobility of the feather, due to which the friability of plumage and the thickness of the air cushion increase, and this, in turn, contributes to the preservation of heat.

Rice. 4. Scheme of the location of the main pterylae on the body of a bird:
1 - head pterylia, 1a - ear region, 2 - flight feathers, 3 - wing pteryla, 4 - humeral pterylia, 5 - dorsal pteryla, 5a - cervical region, 5b - dorsal region, 5c - sacral region, 6 - femoral pteryla, 7 - leg (leg) pterylia, 8 - abdominal pterylia, 8a - thoracic region, 8b - ventral region, 9 - tail pterylia, 10 - tail feathers

Despite the fact that the location and shape of pterylae differ somewhat and may even be a systematic feature, the location of the main pterylae on the body of birds is similar (Fig. 4). They are quite easily distinguished when examining a bird - these are the dorsal, thoracic, humeral, femoral, and cervical pterylia. Of the smaller pterylae, even a novice naturalist can easily find the ear and anal pterylae. In addition to the ear on the head of birds, one can still distinguish a fairly large number of small pterylae, which can only be sorted out by narrow specialists in morphology and molting. And since most readers are still not them, we will limit ourselves to the general name of all the pterylae of this part of the body (by the way, very often used) - head pterylia.

Tail and wings

The plumage of the wings and tail should be discussed separately. Large feathers that form the tail itself are called helmsmen. They differ in that the outer and inner webs are more or less the same width. The feathers that cover the tail feathers above and below are called, respectively, top and undertail coverts.

The number of helmsmen varies in different units. Most often there are 12 of them, but it can be from 8 to 28 (in some waders), in passerines of our fauna - 12 (hereinafter, this order will be discussed separately, since it includes about half of the species of the domestic avifauna). The numbering of the helmsmen is taken from the edge of the tail to the center (in the same direction they are replaced during molting in passerines).

Unlike the tail feathers, the feathers that form the bearing plane of the wing, called flywheels, are clearly asymmetric: the outer edge of the fan is much narrower than the inner one, while in the flight feathers, a notch is often noticeable on the outer fan. Distinguish paramount(they are attached to the back surface of the skeleton of the hand), secondary(attached to the ulna) and tertiary(attached to the humerus and on the wing are usually located one above the other) flight feathers. Also, these feathers can be distinguished from the tail feathers by some concavity, which provides the wing with better aerodynamic qualities in flight. In addition to flywheels on the wing, they distinguish winglet- several feathers attached to the single phalanx of the first finger, which prevent the occurrence of air turbulence during flight (Fig. 5).

Rice. 5. Wing feathers - top view (on the example of a representative of the passerine order).
I - flywheels: 1-10 - primary, 11-16 - secondary, 17-19 - tertiary; II - winglet; III - coverts of primary primaries; IV - greater upper coverts of secondaries; V - middle upper coverts of secondaries; VI - lesser upper coverts of secondaries; VII - shoulder coverts

There are usually 9–11 primary primaries, in passerines of our fauna - 10. The number of secondary primaries varies in different groups from 6 (hummingbirds, passerines) to 40 (large albatrosses). The number of tertiary primaries is also very different, in passerines there are usually 3 of them, with the exception of the Orioles (4), Corvidae (4–6) families. The numbering of the flight feathers is taken from the outer (distal, scientifically) edge of the wing towards the body. It can be either continuous - while separate groups of primary, secondary and tertiary flywheels are not distinguished, or, if the border between primary and secondary is easily distinguishable (for example, among representatives of the passerine order), each group can be considered separately, again starting from the distal end. That is, if you want to indicate the coordinates of the fallen fly feather of your favorite finches (thirteenth in a row from the edge of the wing), you can write it simply as the 13th fly feather or as the 3rd secondary fly feather. The task is somewhat complicated by the fact that in all birds the first primary flight feather is shorter than the others, and in many groups it is greatly reduced, sometimes disappearing almost to nothing (for example, in larks, swallows, wagtails, buntings, etc.), and you can simply not notice it . Therefore, ornithologists agreed to count from the first full-fledged fly feather, considering it the second.

Like the tail, there are upper and lower coverts on the wing. Above the secondary feathers, the upper coverts usually form 3 distinct rows: the first row above the primaries is the large upper coverts of the secondaries, above them are the middle ones, and then the small ones. Behind the lesser coverts are small feathers, collectively called covering propatagium, or, more simply, shoulder coverts.

As for the lower coverts, separate groups are usually not distinguished among them, sometimes classifying according to the primaries that they cover.

Feather: beauty secrets

All the variety of colors, the amazing richness and elegance of the shades of the plumage of birds are created by two groups of pigments and some features of the feather structure. Accumulating in horny cells in the form of lumps and grains melanin give the pen shades of black, brown, reddish-brown and yellow. Lipochromes lie there in the form of fat drops or flakes and provide brightness of color: red (zooerythrin, phasianoerythrin), yellow (zooxanthin), blue (ptelopin) and other colors. The co-occurrence of several pigments in one area of ​​the pen significantly expands the range of shades shown here. In addition to imparting color, pigments, especially melanins, increase the mechanical strength of feathers.

Apparently, this explains the predominantly black or brown coloration of at least part of the flight feathers in most birds, even those with white as the main plumage color (white stork, white goose, many gulls, etc.). An interesting exception here are species with a "reverse" coloration, black with white flight feathers - a black swan, two species of saddle-billed storks, a horned raven from the family of hornbills.

The white color of the plumage is due to the presence in the horn cells of the feather of transparent cavities filled with air, with the complete absence of pigments. If the cell walls are not transparent enough, then the pen acquires a bluish or bluish tint. The metallic luster of plumage, characteristic of many birds, is formed due to the decomposition of light into a spectrum on the surface of the feather, where the outer keratinized cells are a kind of prism.

All these above methods form the color of the feather, it remains only to add that this happens only during its development, and changing the color of the feather during life is impossible (except for the fact that under the influence of natural factors the pigments are destroyed, and over time the feathers fade somewhat ).

Time to scatter feathers...

It should be remembered that in poultry molting can happen at any time of the year. For wild birds, the annual molt is usually confined to a certain season, only in some tropical species it can take place gradually throughout the year. Features of the course of molting differ in different groups of birds; this topic is extensive and deserves a separate discussion. Here, it seems necessary to us to point out that in the process of molting, an age-related and, for many species, a seasonal change of feather plumage occurs. Thus, the same bird can have completely different plumage during its life. Accordingly, several main feather outfits of birds are distinguished.

Embryonic Outfit- is formed during the period of embryogenesis and differs in the degree of development in different orders, usually better developed in chicks with a brood type of development. It may consist of embryonic down and embryonic feather (the latter can be found on the chicks of anseriformes, chickens, tinamou, as well as ostriches and the like). It is completely absent in swifts, woodpeckers, crustaceans, pelicans.

nest outfit(youthful, juvenile) - replaces the embryonic (if present), while part of it replaces the embryonic fluff and feather, and part is formed in new feather papillae. Nesting plumage can be worn by different species for different periods of time - from several weeks to a year, and usually differs from the plumage of an adult bird in color and plumage structure. In a number of species, the differences in color are insignificant, and the young are simply more dull, without a characteristic sheen (crows, some tits, kingfishers, pigeons, many shepherds, etc.).

For other groups, this difference is more noticeable. For example, in most representatives of the thrush family, which are very diverse in color, the young are quite similar - mottled due to bright light spots along the stem and brown edges of feathers. In gulls and light terns, the chicks are motley, brownish-brown. Brownish-gray chicks in white swans, reddish-brown in the Siberian Crane, etc. - There are many examples.

Quite often, the juvenile outfit is colorful due to light buffy spots on the feathers. This type of coloration is considered evolutionarily more ancient for birds. In the presence of sexual dimorphism, it is similar to the coloration of females (chickens, ducks, turukhtans, many passerines). It may simply be more faded - with a pronounced change in seasonal color, it resembles the winter outfit of adult birds (loons, grebes, many waders and auks, etc.). But even in those birds in which the young are almost the same in color as adults (warblers, some warblers and tits, and a number of other species), the feathers of the nesting plumage always differ somewhat in their structure from the feathers of adult birds: beards of the first and second order are located on them. less often and weaker linked to each other, the plumage gives the impression of a looser and softer.

Interestingly, young guillemots and razorbills have two generations of juvenile plumage. The first generation of feathers replaces the embryonic down by the 20th day of life: these feathers are much shorter than the feathers of an adult bird and more loose. In this plumage, young guillemots and auks go to sea and already there, by 2 months, they molt into the final version of the youthful plumage, close to the plumage of adults. All other representatives of auks have only one juvenile outfit and put it on at the age of 1–1.5 months, at the same time they leave the nests.

Often isolated post-nesting attire, which replaces the nesting one during the post-breeding molt. It usually occurs in the first autumn of life before seasonal migrations, rarely stretches and ends already at wintering. Usually this molt does not affect the flight feathers, and sometimes the tail feathers. Often, the post-nesting plumage is practically indistinguishable from an adult in terms of color and structure of plumage, however, in some large birds (swans, gulls, diurnal predators, etc.), the final color is acquired only in the 2nd or even in the 5th year of life. In this case, they talk about the first annual outfit, the second annual, etc.

annual outfit(intermarital) - is formed in adult birds after the post-marital (autumn) molt. Most often, it begins after the completion of nesting and the emergence of the last chicks and ends before the start of autumn migration, but there are also numerous deviations from this pattern. So, in some species, usually quite large in size, it begins simultaneously with the laying of eggs (hawks, wood dove, snowy owl, part of corvids), others molt already on wintering grounds after autumn migration, or part of the plumage changes before migration, and part after and etc.

The example of hornbills is widely known, when the male molts "as expected", and the female does this during the period of incubation of the masonry, while the husband immures her in a hollow, leaving only a narrow hole for feeding.

The annual outfit is worn until the next autumn molt (if the species does not have a mating molt, which will be discussed below). The autumn molt is almost always complete, with the exception of some large birds (herons, storks, eagles, etc.), in which all the primaries do not have time to change during the molt and some of them change every two years. In cranes, the molting of flight feathers always happens every other year.

AT wedding attire birds usually molt before the breeding season at the end of winter-early spring, although there are exceptions (ducks begin to dress in a breeding feather as early as August and finish in winter). The molt can be complete, but more often it is partial, when the entire small contour feather or only part of it changes, while the flight and tail feathers are preserved. Moulting occurs in both sexes, while the coloration of males can change, while females usually remain the same.

In some birds, the change in color for the mating season is not associated with molting, but with the wear and tear of plumage. In the spring, the male house sparrow has a striking black chin, throat and upper chest, although in autumn these areas were almost the same grayish-brown color as the surrounding plumage. In this case, the feather has a black middle part of the fan with light-colored edges to match the rest of the plumage, and since the feathers overlap each other in a tile-like manner, the black color is invisible. During the year, the poorly pigmented (and therefore less durable) edges of the feathers are gradually wiped off, and by spring (i.e., by the beginning of the mating season), male house sparrows acquire a characteristic color. In the same way, the common starling, variegated in autumn, turns solid black with a metallic sheen in spring. By the breeding season, the red color “appears” on male redstarts, tap dances, linnets, etc.

Plumage and horn [edit]

See also: Plumage (biology) and Feather

Feather, 1 - Fan. 2 - Barrel. 3 - Normal surface. 4 - Down part. 5 - Ochin (rod).

Types of feathers in birds: 1 - contour, typical fly feather, 2 - tail feather (tail feather), 3 - integumentary feather, 4 - filiform feather, 5 - brush-like feather, 6 - down feather.

Feathers of a bird's wing: 1 - flight feathers of the 1st order; 2 - large covering feathers; 3 - winglet; 4, 8 - flight feathers of the 2nd order; 5 - plumage of the shoulder; 6 - medium covering feathers; 7 - covering feathers of the wing.

The structure of the blue-yellow macaw feather

The skin of birds is thin and elastic. In the connective tissue layer there are abundant bundles of smooth muscles that attach to the feathers of the contour feathers and change their position. Skin glands are absent, the only skin gland in birds is the coccygeal gland, which is located above the caudal vertebrae (absent in ratites, some bustards, pigeons, parrots, etc.). It secretes an oily secret, which the birds squeeze out with their beak and lubricate their plumage with it, which helps to maintain the elasticity of the feather.

For all species of birds, the presence of a feather cover is characteristic, which is not found in other modern animals. Feathers cover the entire body of the bird, with the exception of the beak and distal parts of the hind limbs. In some birds, such as turkeys and American vultures, plumage on the head and neck is either completely absent or very weakly expressed.

The initial stages of the embryonic development of a feather are similar to the development of scales. Therefore, we can say that feathers arose as a result of evolutionary transformations of scales. The evolutionary origin of feathers can be traced back to the carnivorous dinosaurs Sinosauropteryx and Dilong, covered with fibrous down. True feathers can be observed in Caudipteryx, Sinornithosaurus and Microraptor.

Contour feathers cover the entire body of the bird and have a well-developed dense core, the base of which - a hollow quill - is covered by a feather bag in the skin. The depth of the feather bag is greater in large feathers. Elastic beards extend from the shaft, which bear beards with hooks that interlock with the hooks of neighboring beards, forming a fan of the feather. In the lowest part of the feather, the barbs are usually softer and longer, and their barbules do not have hooks - this area is called the downy part of the fan. Features of the structure of feathers can vary in different groups of birds. So species living in harsh temperature conditions usually have a more strongly developed downy part of the fan. Most birds have down feathers (the stem is soft) and down (the stem is completely reduced), the soft and long beards of which bear soft beards devoid of hooks, which is why a linked fan is not formed. Between the typical feather, down feather and down, there are various intermediate types. Down feathers are usually arranged along the pterylae. Down relatively evenly covers the entire body (copepods, anseriformes, many birds of prey, etc.), or is present only on apteria (herons, chickens, owls, many passerines, etc.), or only on pterilia (tinamou). Usually down feathers and down are covered with contour feathers. Only in a few birds (vultures, marabou, etc.) is the head and part of the neck covered only with down. Filamentous feathers are located under the contour feathers, have a long thin shaft and reduced beards. Apparently, they perform a tactile function.

The winter feather is characterized by the fact that its downy part of the fan and the additional shaft are usually much better developed than in the summer feather. In nightjars, and especially in owls, the velvety (hairiness) of all feathers, including fly and tail feathers, is well drawn out; quenching the turbulence of air currents, hairiness ensures noiseless flight. In waterfowl, the relatively short and strongly curved feathers fit closely together, preventing the plumage from getting wet; at the same time, the water resistance of the plumage is also ensured by the special shape of the barbs and barbules, which contributes to the appearance of a water film on the surface of the feather.

The total number of feathers in large species is greater than in small ones. For example, hummingbirds have about 1000 feathers, small passerines have 1.5 - 2,500, gulls have 5 - 6,000, ducks have 10-12,000, swans have 25,000, etc. The total number of feathers, their size and structural features in also vary among closely related groups depending on their ecological specialization.

The plumage makes the shape of the body streamlined and increases the area of ​​​​the wings and tail, which to a large extent contributes to flight qualities, and also provides thermoregulation. In addition, with the help of feathers, birds transmit signals to each other and camouflage themselves from predators.

Feathers are horny skin growths that grow from rows of skin depressions called pterylia. Only in a few non-flying birds, such as penguins, pterylia are not expressed, and feathers grow evenly throughout the body. The location and shape of the pterylae often serve as a systematic feature. Within the same species, the color and shape of feathers may vary depending on the age, sex, or social status of the bird. During the formation of feathers, pigments are deposited in keratinizing cells, which determine the color characteristic of each species. The most common are two types of pigments: melanins and lipochromes. Melanins cause the color of feathers in different shades of black, brown, reddish-brown and yellow. Lipochromes provide a brighter color: red, green, yellow, blue, etc. The combination of different pigments in one pen complicates the color. The white coloration is created by the total reflection of light from the air-filled transparent hollow horn cells of the feather in the absence of pigments.

The functions of plumage are very diverse. It provides the possibility of flight, forming bearing planes (wings, tail) and creating a streamlined body. Feathers protect the skin from mechanical damage. The waterproof and heat-protective functions of the plumage are very effective: the tops of the contour feathers, which are tile-like adjacent to each other, resist getting wet, and the interweaving of the downy parts of the fans of the contour feathers, down feathers and down keeps a fixed layer of air near the skin, which reduces heat loss.

Periodically, birds molt: old feathers fall out, and new ones grow in their place. Usually molting occurs once a year, less often - two and very rarely, such as in long-tailed ducks ( Clangula hyemalis) - three times a year. Large birds of prey are able to molt once every few years. In the case of repeated molting, nesting and winter outfits are distinguished, as well as a downy outfit for fledglings. As a rule, the change of flight and tail feathers necessary for flight occurs in a certain sequence, so that the birds retain their flying qualities during the molting process. There are exceptions to this rule - for example, in ducks, all flywheels fall off at the same time, as a result of which they lose their ability to fly. Before incubation, in females of most species, a so-called soot spot is formed on the belly - an unfeathered area of ​​\u200b\u200bthe skin with developed blood vessels, with which the bird presses against the eggs and warms them.

Feathers require meticulous care, and birds spend about 9% of their daily time cleaning their plumage, bathing and dust bathing. Fast-flying birds - swifts, swallows and terns plunge into the water on the fly. Others shake themselves in shallow water or soak their feathers in dew or rainwater.

Flight and tail feathers fall out in pairs during molting, so that the correct movements are not disturbed. In most birds, nestling flight feathers do not change during the year, and there is no complete molt for the same amount of time. But in chicks that start flying very early, the chicks wear out quickly and are replaced early with new ones. Duck birds (ducks, geese, swans) immediately lose their primaries and therefore cannot fly for a long time.

Birds are often called feathered. Why? These are the only animals on the planet whose body is covered with feathers. Their color and size can be very diverse. There are several types of feathers, each of which performs its own functions. We will talk about the external structure of birds and the structure of feathers in this article.

general characteristics

Birds are warm-blooded vertebrates that reproduce by laying eggs. Most of them can fly. Flightless birds lost this opportunity for the second time. All representatives of the class have a beak that is completely devoid of teeth. The main distinguishing feature is the feather cover of the body.

For flights, the birds had to change a lot. In the course of evolution, their forelimbs became wings, many vertebrae fused, forming a strong frame. Some of their bones are filled with air, giving them extra lightness. Flying birds have a flat bony outgrowth on the sternum - the keel, to which the muscles that lower the wing are attached.

The ability to fly was reflected in the shape of the body, respiratory and digestive systems. The feathered body is streamlined, which reduces friction with the air. They are able to travel considerable distances and travel hundreds or even thousands of kilometers. This requires a lot of energy, and an accelerated metabolism helps to get it.

Birds are the most numerous group of higher vertebrates. More than 10,600 species are known from the living ones. They settled in almost all corners of the planet, from isolated ocean islands to megacities, from deserts and tropics to the interior of Antarctica.

Plumage

Feathers grow in birds on all parts of the body, they are absent only on the beak and hind limbs. In some species, such as American griffins, ostriches, turkeys, the plumage on the neck and head is thin and rare, and sometimes completely absent.

The structural features of bird feathers, their appearance and quantity depend on the specific species and lifestyle of animals. And the color of the covers is largely related to their habitat. As a rule, the larger the species, the more feathers it has. So, in swans, their number reaches 25 thousand, in gulls - up to 6 thousand, in the smallest representatives of the class, hummingbirds, there are about a thousand of them.

There are no glands on their skin, the only one is located at the base of the tail and is called the oil gland. It releases a special secret that makes feathers more elastic, disinfects and prevents them from sticking together when wet. Animals squeeze it out with their beak and lubricate the plumage several times a day.

Bird feather structure

All birds have the same. In ostriches, kiwis, cassowaries and penguins, feathers cover the body evenly. In other species, they grow in rows, leaving between them empty areas - apteria. The growth lines are called pterylia. They are divided into shoulder, tail, dorsal, thoracic, femoral, head, etc.

In the structure of a bird's feather, a core, a rod and a fan are distinguished. Ochin is the "naked" part of the feather barrel. It is round in section, and there is a hole at its end. The lower part of the chin enters a depression in the skin and contains a branch of the artery.

After it follows a hollow rod, having four faces in diameter. Fans are attached to it on both sides - the hairy parts of the feather. There are two of them, each consists of first and second order beards (beards).

A similar principle is observed in the structure of the tree crown. The first beards grow directly from the rod, and the beards are already moving away from them. Barbs of the second order have hooks that are attached to adjacent barbs. This structure of the bird's feather does not allow air to pass through and allows you to push off from it during flight.

Classification

The fan of birds is very strong and elastic. It is made up of the protein keratin, the same material that makes up our hair, nails, turtle shells, and rhinoceros horns. The general structure of bird feathers is the same, but their elements may differ in appearance and quality. Based on this, contour, flight, down, thread-like feathers are distinguished.

Contour or covering feathers are the main ones. They are superimposed on each other, like tiles or fish scales, covering the entire body and giving it a streamlined shape. Flight feathers are more elongated and longer. They are located on the wing and are essential when flying.

About a dozen flight feathers are located on the bird's hands, several dozen are placed on the forearm. On the tail are steering elements. They are involved in changing direction and balancing. Some species reach quite large sizes.

The structure of the downy feather of birds and their down is different from others, as they are necessary to maintain heat. They have a thin rod, and their beards are devoid of hooks and scatter in different directions. The down core is even weaker, and the fan is not expressed and outwardly resembles cotton wool.

On the beak are thin single feathers, devoid of fans. They look like sparse hairs. These are thread-like feathers or vibrissae that serve for touch.

Color and its meaning

Color is as important as the structure of a bird's feather. For flight, it is of no importance, but plays a decisive role in survival and reproduction. The color of plumage is given by pigments: melanin (brown, yellow, black), carotenoids (yellow, orange, red) and porphyrins (green, red).

In many species, the color matches the environment, masking its owner. For example, in the steppe and rocky inhabitants, the plumage is gray, gray, and brown. Tropical species have brighter and more varied colors.

In addition, color is important in the social life of birds. So, within the same species and population, the color may differ in animals of different sex, age and status. Males, as a rule, look brighter and pretentious, as they are forced to compete for the attention of females during the mating season.

The body of the bird has a feather and down cover. However, in most birds, feathers do not grow over the entire surface, but in certain areas. They usually run along the body (in the direction of flight) in different species of birds in different ways and have names in accordance with the part of the body on which they are located: head, neck, wing, shoulder, lateral, thoracic, dorsal-lumbar, abdominal, femoral , shins, caudal, anal, etc.

Areas of the body free from plumage - apteria. They are also named according to their topography. At the same time, the feathers are arranged in such a way that they cover the apteria, forming a continuous feather cover. In flightless birds (ostrich, penguin), feathers grow over the entire surface of the body.

The purpose of the feather cover is to protect the body from mechanical stress and one of the devices that maintain body temperature. In the regulation of heat transfer, plumage plays an important role (while the chicken is covered with down, the difference between the temperature of the skin and air is 13-15 ° C, with the appearance of feathers it reaches 17-19 ° C). The plumage increases thermal insulation, creates a layer of still air around the body, which prevents heat transfer. By changing the slope of the feathers, the bird can regulate heat transfer.

In addition to the thermoregulatory function, the feather cover creates a streamlined body shape that facilitates flight and creates load-bearing surfaces that make flight possible.

Feathers, depending on the form and function, are divided into:

• ? contour,
• ? downy,
• ? semi-down,
• ? filiform,
• ? brush,
• ? bristles,
• ? powder down (powder).

contour feathers - the most common type of feathers. They define the outlines of the bird's body. Among them are distinguished:

• ? covering,
• ? flywheels,
• ? steering feathers.

Cover feathers located on the head and neck pterylae. From the lateral, thoracic, sternal and abdominal pterylae, the covering feathers of the thoracic part of the body, the chloup (tip of the sacrum) and the abdomen depart. The covering feathers of the dorsal-lumbar and caudal pterylae form the plumage of the loin and covert feathers of the tail; in roosters they form large and small braids. The covering feathers of the lower leg form trousers.

A mature covering feather consists of a stem, a shaft, and a fan (Fig. 4). The lower part of the trunk (up to the fan) is cylindrical in shape and is called the chin (calamus). The lower part of the chin is enclosed in a feather pouch and immersed in the skin. At the end of the hole there is a recess with a hole - the lower navel. In this recess is the rudiment of the next generation of feathers. The walls of the chin are composed of a fairly transparent horny substance. In a young contour feather, the greater part of the quill is filled with a connective papilla with a rich circulatory network, which gives it a red or blue color. As the papilla matures, it shortens, the pit fills with air, and the keratinized cells of the epidermis, remaining in their original places, turn into funnel-shaped films, as if marking the stages of papilla reduction, at the level of the fan, gradually narrowing, the pit passes into a tetrahedral rod. At the transition point there is a recess - the upper navel. From it begins an additional pen.

Rays (beards) of the first order depart from the rod in both directions at a certain angle, forming together a fan - an elastic feather plate. the lowest small part of the fan is called silky, the middle one is downy, the upper one is called contour. The outer half of the covering feather web is narrower and tighter, while the inner half is wider and softer. From the rays of the first order, numerous rays (barbs) of the second order depart symmetrically at an angle in both directions, and on the one hand they are located somewhat higher than on the other. On the underlying barbs of the second order there is a ridge, bent in the form of a cornice, running along the upper edge of the beam.

The overlying rays of the second order bear rays (beards) of the third order, which are outgrowths of keratinized epithelial cells in the form of cilia and hooks. The hooks go beyond the crests of the rays of the second order of the adjacent feather, along which they can slide, maintaining an elastic connection with each other. The structure of the hooks and their number are species-specific. cilia create a roughness that prevents the feathers from sliding over each other, increasing friction, which helps to keep the feathers in the form of a continuous cover.

The silky part of the covering feather fan is characterized by a rudimentary state of rays of the second order. In the downy part, cilia and hooks (rays of the third order) are undeveloped.

The rod and rays of the first order are formed by three layers of cells.

The outermost - the cuticle - consists of one row of squamous keratinizing epithelium.

The middle layer - cortical - is formed by a large number of rows of elongated and flattened keratinized epithelial cells, tightly adjacent to each other, which ensures the strength of the feather. The inner layer - the medulla - consists of multinucleated large keratinized cells filled with air, which makes the pen more light. In the eye and rays of the second and third orders, the medulla is not expressed. The shape of cells and layers is species-specific.

Rice. 6 .

1 - rod, 2 - fan, 3 - chin, 4 - rays of the first order, 5 - rays of the second order, 6 - hooks, A - fly feather, B - section of the fan.

Cover feathers are mobile. This is provided by well-developed smooth muscles that wrap around the feather follicle and end in the dermis. In this case, each covering feather turns out to be naturally associated with four adjacent feathers. This connection allows you to synchronously raise and lower the covering feathers of the body, the muscles of the follicles. The areas of skin adjacent to them are abundantly innervated by both free nerve endings and Herbst's bodies.

Flight and tail feathers arranged similarly to covering ones. Unlike the latter, they have longer quills, the silky and downy parts of the fan are less developed, and the covering part of the fan is longer.

Down feathers or down- small, have a short apex, an underdeveloped shaft and a fan with unconnected rays due to the absence of hooks and cilia. The rod may not be developed, in which case the rays depart directly from the apex. there is down on the pterylia between the contour feathers, but it can also grow on the apteria, especially in the area of ​​​​the chloup and abdomen. The main function is thermal insulation, warming the bird's body. The most developed down in waterfowl.

semi-puffy feathers- have the same structure as down, but their shaft is always developed. feathers of this type are common in the area of ​​​​the flap and the abdomen.

thread feathers- have a long, very thin rod, on top of which there is a small fan, consisting of only a few connected rays. They are located in the amount of 1-8, always near the contour feather, covered by it and apparently develop from the same papilla with it. In a turkey, they grow on the chest in the form of a bundle.

Numerous nerve endings were found in the bags of threadlike feathers. It is believed that they have a receptor function, with their help the bird feels the disorder in the contour feather and eliminates it. Perhaps from them comes the signaling necessary to control the movement of the plumage. In this case, it is obvious that the reflex arc closes on the muscles of the contour pen.

Brush feathers have a thin trunk and weakly linked rays, diverging like brush hairs, are located around the duct of the coccygeal gland.

bristles- short feathers, consisting of a small trunk without a fan. They are at the base of the beak, near the nostrils and eyes.

powder down(crumbling, powdery) is well developed in birds in which the coccygeal gland is absent or poorly developed (pigeons, herons, etc.)