What materials are used in building nests. Birds. The emergence of modern birds

Birds build nests to lay their eggs there. Nests keep the eggs from the cold and from egg-loving animals. The method of building a nest depends on the habitat of the bird.

Some forest birds make nests from twigs and leaves high in trees or in plant thickets close to the ground. Others weave nests hanging from branches. Woodpeckers nest in hollows, which they make in tree trunks with their powerful beaks. Many seabirds lay their eggs simply on ledges or cliff faces. This provides the eggs with good protection, as it is difficult for enemies to reach them. Some birds dig holes in the ground, and there are those that use bird houses built by man or.

woven nest

A small remez builds an elegant nest, resembling a bag hanging from a branch. The nest is woven from fragments of plants and animal hair, for example, sheep's wool. Hole on one side only. Eggs, and then chicks, are securely hidden inside the nest.

Nest in the ground

The rabbit owl, native to America, lays its eggs in a hole in the ground. Sometimes she uses the holes left by the American groundhog or other animals, but with the help of her beak and strong paws she can dig a hole herself.

glued nest

Swifts build their nests on sheer cliffs, cave walls or even houses. The nest is built from leaves, stems and feathers glued together with sticky saliva.

Nest on the water

The coot builds a floating nest attached to reeds or other aquatic plants. The male brings dry leaves and stems, and the female builds a nest from them.

slender-billed murre

This bird lays a single egg on a bare rock ledge on the sea coast. It would seem that the egg can easily roll down, but this is not so: one end of it is sharp, and when pushed, the egg rotates in a circle, and does not roll. All six families of the woodpecker order spend most of their lives in and near trees and build their nests in hollows. Most of these birds have strong claws with which they grab onto branches and trunks. Short, rounded wings make it easier for them to fly between trees. They have large, powerful beaks. Jacamars and honeybees feed mainly on insects, but most of the birds of this order eat both insects and fruits.

When the first Europeans found themselves in the mountain forests of New Guinea, many amazing discoveries awaited them. But one of the wonders of this tropical island has long gone unnoticed by people from the Old World. Encountering under the canopy of the forest rounded, more than half a meter high huts, built of twigs, neatly attached to a tree trunk, with a floor lined with green moss and bright flowers, and even a courtyard in front of the entrance, surrounded by a fence and also decorated with colorful berries, flowers, shiny shells and pebbles, the Europeans did not pay much attention to them, as they were sure that these gazebos were toy houses of native children.

It could not even occur to them that small, starling-sized birds, alarmingly screaming in neighboring bushes, had something to do with these buildings, and besides, bird eggs were never found in the gazebos. Nevertheless, it turned out that such gazebos are built and decorated during the breeding season by the males of the striped gardener - a bird belonging to the bower family.
Bower arbors are designed to attract females, courtship and mating rituals take place around them, and the testicles of the female of these birds are laid in a traditional cup-shaped nest twisted in the neighborhood. The mating behavior of male bowerbirds, who spend a lot of time and effort on the construction of "arbors of love", is a unique phenomenon in the world of birds. The building abilities of other birds are manifested only when creating nests intended exclusively for breeding, and only a few species also use them for overnight stays outside the breeding season.
Well-known to us kingfishers, bee-eaters, rollers, shore swallows arrange nests in deep burrows dug in steep cliffs.

Many birds nest in the hollows of trees, and some of them (such as woodpeckers) hollow them out on their own, while others use the results of someone else's labor or natural hollows.

In the event that the nest is not hidden securely in the depths of a hole or hollow, but is located openly, and even raised high above the ground for safety reasons, a sufficiently strong structure is needed. An example of solidity is platform nests made of branches and twigs, which are built by diurnal birds of prey, herons, storks.

Quite often, such nests have been used for many years and even pass by inheritance (the nest of white storks is known to have existed for about 400 years). Since the birds repair and build on the nest every year, its size and weight increase from year to year. For example, the weight of one nest of bald eagles, measured after the branches supporting it broke off and it fell to the ground, was 2 tons.
If the platform nests of large birds are able to amaze with their durability and size, then smaller bird houses amaze with the functionality of the design and the variety of materials used. The nest of the smallest birds of our northern forests - kinglets - only in appearance seems to be an unpretentious soft cup of mosses and lichens, lined inside with fluff and wool.

But this house, weighing only about 20 g, keeps heat so securely that the bird can leave it for almost half an hour without fear that the tiny eggs will cool down. And during rain, it absorbs more than 60 g of water, remaining completely dry inside, the strongest wind cannot rip it off the branch, but when the chicks grow up and their total weight reaches almost 100 g, it stretches by a third, without losing strength. Such exceptional properties of the nest are achieved due to a rather complex three-layer structure, carefully selected heat-insulating materials, as well as the fact that its frame is made of cobwebs - a fantastically strong and elastic material.
The most complex design problems have to be solved by birds whose nests do not rest in the fork of branches, but are suspended from them. However, this location of the nest is the safest, so many birds spare no time and effort to build such dwellings. So, Remeza tits hang mitten nests on thin branches of trees leaning over the water. The basis of the nest is skillfully intertwined straws, roots, nettle fibers, the gaps between which are so carefully caulked with plant fluff that the resulting fabric is not inferior to wool felt in its properties.

One of the most numerous birds in the tropical regions of Africa, weavers have mastered the macrame technique to perfection, having learned not only to weave, but also to tie plant fibers and blades of grass with various knots. In order to stock up on building materials, birds tear off flexible straws of green cereals or, grabbing the edge of a palm leaf with their beak, soar up, dissolving it into narrow strips. In some species of weavers, the nests look like neat balls, in others they look like long bags or mittens, weavers living in colonies arrange "apartment buildings" in which hundreds of separate nests are located under a common roof.

In the craftsmanship of construction with weavers, a dressmaker bird from Southeast Asia, a close relative of our warblers, can compete. She arranges her nest in a bag folded from one large or several small leaves. So that the edges of the bag do not diverge, the bird makes holes in them, through which it stretches plant fibers or cobwebs, tying the free ends with knots.

Clay is a fertile material for building a nest. Magpies, field thrushes coat the nest tray with it, many species of swallows mold jug nests of the most diverse forms from it. But the most solid clay buildings are erected by South American birds - red stove-makers. On thick horizontal branches, fence posts or roofs of houses, they arrange a massive foundation for the future building from lumps of clay mixed with manure, then they lay out walls and a domed ceiling. It turns out a structure similar to a round furnace with an oval entrance-let leading to the "front", through a low partition from which there is a nesting chamber lined with soft material. After drying under the rays of the hot sun, the walls of the building become as strong as stone, and they can only be broken with a sledgehammer.

Recognized originals in the construction of nests - swifts widely use their own saliva as a cementing material, which quickly hardens in the air. Ordinary inhabitants of our cities, black swifts, pick up vegetable fluff, scraps of paper and other garbage in the air and, sticking it all together with saliva, build bowl-shaped nests in secluded niches in attics. The nests of Cayenne swifts living in the tropical regions of America are long (up to half a meter) tubes hanging from rocky cliffs, the walls of which consist of plant materials glued together with saliva. But all were surpassed by small swifts gray salangans nesting in the caves of some regions of Southeast Asia. Their nests, which look like translucent cups, consist entirely of frozen saliva. If such a nest is boiled by adding spices, then a dish is obtained that is similar in taste and nutritional value to a gelatin solution - the famous "swallow's nest soup". The Chinese love him very much, so large colonies of gray salangans have become a rarity these days.

Among the most phenomenal achievements of building art, there are real unique ones, which are the nests of the crested swift. These swifts attach a tiny, slightly concave plate of saliva and pieces of bark to a horizontally located branch, where they lay a single egg, also gluing it with saliva for reliability. The nest is so small and fragile that the incubating bird does not sit in it, but on a branch; very soon a chick that has grown out of its nest is also forced to move here. And absolutely in Spartan conditions the palm swift breeds chicks. This bird sticks a plate of saliva and plant fibers to the underside of a coconut palm leaf, and 2 eggs to it. The palm leaf hangs down, and the bird, clinging to the nest with its claws, incubates the clutch not sitting, but hanging on it. In the same position, the chicks spend 2-3 weeks until they fledge and can finally leave their uncomfortable cradle.

Features of the construction of the nest and its location are the same characteristic features of the species as the color of plumage or behavior. Therefore, even without seeing the bird itself, a specialist, having looked at the nest, can quite clearly determine which bird it was built by. True, birds can change long-established traditions and experiment, for example, with new nesting materials. Of course, there is nothing surprising in the fact that they use cotton wool, paper picked up from human habitation for lining the nest, or arrange nests in tin cans, but there are also quite curious cases. So, at one of the ornithological congresses, a crow's nest was presented, built entirely of artificial materials.

Nest-building skills are hereditary, and most captive-bred birds who have never seen what their nest should look like are able to build one more or less accurately if they are provided with the right materials. But at least some species of birds can learn this craft. Male weavers start trying nest-building long before they reach sexual maturity, destroying the first unsuccessful results of their work and going back to work until they finally have a nest that can please picky females. After all, the construction of a house for chicks must meet numerous and varied requirements. Both the shape and the location of the nest are important here, and even its color, because in such a serious matter as breeding offspring, there are no trifles.

The content of the article

BIRDS(Aves), a class of vertebrates that unites animals that differ from all other animals in the presence of a feather cover. Birds are distributed throughout the world, are very diverse, numerous and easily accessible for observation. These highly organized creatures are sensitive, receptive, multicolored, elegant and have the most interesting habits. Since birds are highly visible, they can serve as a convenient indicator of the state of the environment. If they prosper, then the environment is prosperous. If their numbers are declining and they cannot reproduce normally, the state of the environment is likely to leave much to be desired.

Like other vertebrates - fish, amphibians, reptiles and mammals - the basis of the skeleton of birds is a chain of small bones - vertebrae on the dorsal side of the body. Like mammals, birds are warm-blooded; their body temperature remains relatively constant despite fluctuations in ambient temperature. They differ from most mammals in that they lay eggs. The features specific to the class of birds are primarily associated with the ability of these animals to fly, although some of their species, such as ostriches and penguins, lost it in the course of their later evolution. As a result, all birds are relatively similar in shape and cannot be confused with other taxa. They stand out even more thanks to their feathers, which are not found in any other animal. So, birds are feathered, warm-blooded, egg-laying vertebrates, originally adapted for flight.

ORIGIN AND EVOLUTION

Modern birds, according to most scientists, descend from small primitive reptiles, pseudosuchians, who lived in Triassic period approximately 200 million years ago. Competing with their brethren for food and escaping from predators, some of these creatures in the course of evolution have become more and more adapted to climbing trees and jumping from branch to branch. Gradually, as the scales lengthened and turned into feathers, they acquired the ability to plan, and then to active, i.e. waving, flying.

However, the accumulation of fossil evidence has led to the emergence of alternative theory. More and more paleontologists believe that modern birds evolved from small predatory dinosaurs who lived at the end of the Triassic and in the Jurassic, most likely from the group of the so-called. coelurosaurs. They were bipedal forms with long tails and small prehensile forelimbs. Thus, the ancestors of birds did not necessarily climb trees, and there was no need for a gliding stage to form active flight. It could arise from the flapping movements of the forelimbs, probably used to knock down flying insects, for which, by the way, the predators had to jump high. In parallel, there were transformations of scales into feathers, reduction of the tail, and other profound anatomical changes.

In light of this theory, birds represent a specialized evolutionary lineage of dinosaurs that survived their mass extinction at the end of the Mesozoic era.

Archeopteryx.

The discovery in Europe of the remains of an extinct creature, Archeopteryx ( Archeopteryx lithographica), who lived in the second half of the Jurassic, i.e. 140 million years ago. It was about the size of a dove, had sharp, well-pitched teeth, a long, lizard-like tail, and forelimbs with three toes bearing hooked claws. In most ways, Archeopteryx looked more like a reptile than a bird, except for the real feathers on the forelimbs and tail. Its features show that it was capable of flapping flight, but only for very short distances.

Other ancient birds.

Archeopteryx for a long time remained the only link known to science between birds and reptiles, however, in 1986, the remains of another fossil creature were found that lived 75 million years earlier and combined signs of dinosaurs and birds. Although this animal was named Protoavis(the first bird), its evolutionary significance is controversial among scientists. After Archeopteryx, there is a gap in the fossil record of birds lasting approx. 20 million years. The following finds are Cretaceous period, when adaptive radiation has already led to the emergence of many species of birds adapted to different habitats. Among the approximately two dozen Cretaceous taxa known from fossils, two are of particular interest - Ichthyornis And Hesperornis. Both were discovered in North America, in rocks formed on the site of a vast inland sea.

Ichthyornis was the same size as Archeopteryx, but outwardly resembled a seagull with well-developed wings, indicating the ability to powerful flight. Like modern birds, it lacked teeth, but its vertebrae looked like those of a fish, hence the generic name meaning "fish bird". Hesperornis ("western bird") was 1.5–1.8 m long and nearly wingless. With the help of huge flipper-like legs, moving sideways at a right angle at the very end of the body, he apparently swam and dived no worse than loons. It had teeth of a "reptilian" type, but the structure of the vertebrae corresponded to that typical of modern birds.

The appearance of flapping flight.

In the Jurassic period, birds acquired the ability to actively fly. This means that thanks to the swing of the forelimbs, they were able to overcome the effect of gravity and received a lot of advantages over their ground, climbing and gliding competitors. The flight allowed them to catch insects in the air, effectively avoid predators and choose the most favorable environmental conditions for life. Its development was accompanied by the shortening of the long burdensome tail, replacing it with a fan of long feathers, well adapted for steering and braking. Most of the anatomical transformations necessary for active flight were completed by the end of the Early Cretaceous (about 100 million years ago), i.e. long before the extinction of the dinosaurs.

The emergence of modern birds.

With the onset of the Tertiary period (65 million years ago), the number of bird species began to increase rapidly. The most ancient fossil penguins, loons, cormorants, ducks, hawks, cranes, owls and some song taxa date back to this period. In addition to these ancestors of modern species, several huge flightless birds appeared, apparently occupying the ecological niche of large dinosaurs. One of them was Diatryma, found in Wyoming, 1.8–2.1 m tall, with massive legs, a powerful beak and very small, underdeveloped wings.

At the end of the Tertiary period (1 million years ago) and during the early Pleistocene, or epoch of glaciation, the number and diversity of birds reached a maximum. Even then, there were many current species that lived side by side with those that later became extinct. An excellent example of the latter Teratornis incredibilis from Nevada (USA), a huge condor-like bird with a wingspan of 4.8–5.1 m; it is probably the largest known bird capable of flight.

Recently extinct and endangered species.

Man in historical times, no doubt, contributed to the extinction of a number of birds. The first documented case of this kind was the destruction of a flightless dodo ( Raphus cucullatus) from the island of Mauritius to Indian Ocean. For 174 years after the discovery of the island by Europeans in 1507, the entire population of these birds was exterminated by sailors and animals that they brought on their ships.

The first species of North America to become extinct at the hands of man was the wingless auk ( Alca impennis) in 1844. She also did not fly and nested in colonies on the Atlantic islands near the continent. Sailors and fishermen easily killed these birds for meat, fat and making cod bait.

Shortly after the disappearance of the great auk, 2 species became human victims in the east of the North American continent. One of them was the Carolina parakeet ( Conuropsis carolinensis). Farmers massacred these flocking birds as thousands of them regularly raided the gardens. Another extinct species is the passenger pigeon ( Ectopistes migratorius), ruthlessly exterminated for meat.

From 1600 all over the world disappeared, probably ca. 100 kinds of birds. Most of them were represented by small populations on sea islands. Often incapable of flight, like a dodo, and almost not afraid of man and the small predators he brought, they became easy prey for them.

Currently, many species of birds are also on the verge of extinction or, at best, threatened by it. In North America, the California condor, yellow-footed plover, American crane, Eskimo curlew and white-billed king woodpecker (possibly now extinct) are in the most deplorable position. In other regions, a great danger threatens the Bermuda typhoon, Philippine harpy, kakapo ( owl parrot) from New Zealand - a flightless nocturnal species, as well as an Australian ground parrot.

The unenviable position of the birds listed above was mainly due to the fault of man, who brought their populations to the brink of extinction through uncontrolled hunting, the ill-considered use of pesticides, or the radical transformation of natural habitats.

SPREADING

The distribution of any bird species is limited to a specific geographical area, the so-called. an area that varies greatly in size. Some species, such as barn owl ( Tyto alba), almost cosmopolitans, i.e. found on several continents. Others, say the Puerto Rican owl ( Otus nudipes), the range does not extend beyond the boundaries of one island. In migratory species, nesting areas are distinguished in which they breed, and sometimes wintering areas that are very remote from them.

Due to the ability to fly, birds tend to be widespread and expand their ranges whenever possible. As a result, they are constantly changing, which, of course, does not apply to the inhabitants of small isolated islands. Natural factors may contribute to the expansion of the range. It is likely that prevailing winds or typhoons carried the Egyptian heron around 1930 ( Bubulcus ibis) from Africa to the eastern shores South America. From there, it began to rapidly move north, in 1941 or 1942 it reached Florida, and now it is found even in the southeast of Canada, i.e. its range covered almost the entire east of North America.

Man contributed to the expansion of ranges, introducing species into regions new to them. Two classic examples are the house sparrow and the common starling, which traveled from Europe to North America in the last century and spread throughout that continent. By changing natural habitats, man has also unintentionally stimulated the spread of some species.

Continental areas.

Land birds are distributed over six zoogeographic regions. These areas are as follows: 1) Palearctic, i.e. non-tropical Eurasia and northern Africa, including the Sahara; 2) Nearctic, i.e. Greenland and North America, except for the lowlands of Mexico; 3) Neotropics - the plains of Mexico, Central, South America and the West Indies; 4) Ethiopian region, i.e. Sub-Saharan Africa, southwestern corner of the Arabian Peninsula and Madagascar; 5) Indo-Malay region, covering the tropical part of Asia and the adjacent islands - Sri Lanka (Ceylon), Sumatra, Java, Borneo, Sulawesi (Celebes), Taiwan and the Philippines; 6) Australian region - Australia, New Guinea, New Zealand and the islands of the southwestern part of the Pacific Ocean, including Hawaii.

The Palearctic and Nearctic are inhabited by 750 and 650 bird species, respectively; this is less than in any of the other 4 areas. However, the number of individuals of many species is much higher there, since they have more extensive habitats and fewer competitors.

The opposite extreme is the Neotropics, where approx. 2900 species of birds, i.e. more than in any other area. However, many of them are represented by relatively small populations confined to individual mountain ranges or river valleys of South America, which is called the "Bird Continent" because of the abundance and diversity of birds. Colombia alone has 1,600 species, more than any other country in the world.

There are approximately 1900 species of birds in the Ethiopian region. Notable among them is the African ostrich, the largest modern representative this class. Of the 13 families endemic to the Ethiopian region (that is, not beyond its borders), five are found exclusively in Madagascar.

In the Indo-Malay region, there are also approx. 1900 species. Almost all pheasants live here, including the Indian peacock ( pavocristatus) and banking jungle chicken ( Gallus gallus), from which domestic chicken originated.

The Australian area is inhabited by approximately 1200 species of birds. Of the 83 families represented here, 14 are endemic, more than in any other area. This is an indicator of the originality of many local birds. Endemic groups include large flightless kiwis (in New Zealand), emus and cassowaries, lyrebirds, birds of paradise(mainly in New Guinea), arbor birds, etc.

Island areas.

As a rule, the farther from the continents the oceanic islands, the less bird species there are. The birds that managed to reach these places and survive there are not necessarily the best flyers, but their ability to adapt to the environment clearly turned out to be on top. Long isolation on islands lost in the ocean has led to the accumulation of evolutionary changes sufficient to turn the settlers into independent species. An example is Hawaii: despite the small area of ​​the archipelago, its avifauna includes 38 endemic species.

Marine areas.

Birds that forage in the sea, and visit the land primarily for nesting, are naturally called sea birds. Representatives of the Procellariiformes order, such as albatrosses, petrels, fulmars and storm petrels, can fly over the ocean for months and feed on aquatic animals and plants without even approaching land. Penguins, gannets, frigatebirds, razorbills, guillemots, puffins, most cormorants, as well as some gulls and terns feed mainly on fish in the coastal zone and are rarely seen far from it.

Seasonal areas.

In each specific area, especially in the Northern Hemisphere, this bird species can only be found in a certain season, and then migrate to another place. On this basis, 4 categories of birds are distinguished: summer residents nesting in this area in summer, transit species stopping there on migration, winter lodgers arriving there for wintering, and permanent residents (sedentary species) that never leave this area.

ecological niches.

No bird species occupies all parts of its range, but is found only in certain places or habitats, for example, in a forest, in a swamp or in a field. In addition, species in nature do not exist in isolation - each depends on the vital activity of other organisms occupying the same habitats. Thus, each species is a member of a biological community, a natural system of interdependent plants and animals.

Within each community there are so-called. food chains that include birds: they consume some kind of food and, in turn, serve someone else as food. Only a few species are found in all parts of the habitat. Usually, some organisms inhabit the soil surface, others - low shrubs, others - the upper tier of tree crowns, etc.

In other words, each bird species, like representatives of other groups of living things, has its own ecological niche, i.e. a special position in the community, like a "profession". The ecological niche is not identical to the habitat, or "address" of the taxon. It depends on its anatomical, physiological and behavioral adaptations, i.e., say, on the ability to nest in the upper or lower tier of the forest, endure summer or winter there, feed during the day or at night, etc.

Territories with certain type vegetation are characterized by a specific set of nesting birds. For example, such species are confined to the northern tundra as white partridge and bunting. Coniferous forests are characterized by capercaillie and crossbills. Most of the species we know well live in areas where natural communities have been destroyed, directly or indirectly, by civilization and replaced by anthropogenic (man-made) forms of the environment, such as fields, pastures, and green suburbs. Such habitats are more widespread than natural ones, and are inhabited by numerous and diverse birds.

BEHAVIOR

The behavior of a bird covers all its actions, from ingestion of food to the reaction to environmental factors, including other animals, including individuals of its own species. Most of the behavioral acts in birds are innate, or instinctive, i.e. their implementation does not require previous experience (learning). For example, some species always scratch their heads by bringing their leg over the lowered wing, while others simply stretch it forward. Such instinctive actions are as characteristic of the species as body shape and coloration.

Many forms of behavior in birds are acquired, i.e. based on learning and life experience. Sometimes what seems to be pure instinct requires a certain amount of practice in order to normalize and adapt to the circumstances. Thus, behavior is often a combination of instinctual components and learning.

Key incentives (releasers).

Behavioral acts, as a rule, are induced by environmental factors, which are called key stimuli, or releasers. They can be shape, pattern, movement, sound, etc. Almost all birds respond to social releasers - visual or auditory, with which individuals of the same species transmit information to each other or cause direct responses. Such releasers are called signal stimuli, or demonstrations. An example is the red spot on the mandible of adult herring gulls, which elicits a begging reaction in their chick.

Conflict situations.

A special kind of behavior occurs in a conflict situation. Sometimes it is a so-called. shift activity. For example, a herring gull, driven from its nest by a stranger, does not rush into a counterattack, but instead cleans feathers, which are already in excellent condition. In other cases, it may be redirected, say, in a territorial dispute, to vent its hostility by pulling out blades of grass instead of fighting.

Another type of behavior in a conflict situation is the so-called. initial movements, or movements of intention. The bird crouches or throws up its wings, as if trying to take off, or opens its beak and clicks it, as if wanting to pinch an opponent, but remains in place.

Marriage demonstrations.

All of the listed forms of behavior are of particular interest, since in the course of evolution they can be ritualized within the framework of the so-called. marriage demonstrations. Often the movements associated with them become, as it were, emphasized and, therefore, more noticeable, which is facilitated by bright coloring corresponding parts of the plumage. For example, offset feathering is common in duck mating displays. Many species of birds use wing tossing during courtship, which initially played the role of the initial movement in a conflict situation.

Addictive.

This word refers to the fading of the response to a repeated stimulus, followed by neither "reward" nor "punishment". For example, if you knock on the nest, the chicks raise their heads and open their mouths, since for them this sound means the appearance of a parent with food; if food does not appear several times after the impact, such a reaction in the chicks quickly fades. Taming is also the result of habituation: the bird stops responding to human actions, which at first caused her fear.

Trial and error.

Trial and error learning is selective (uses the principle of selection) and is based on reinforcement. The fledgling that left the nest for the first time in search of food pecks at pebbles, leaves and other small objects that stand out against the surrounding background. Eventually, by trial and error, he learns to distinguish between stimuli that are rewarding (food) and those that do not.

Imprinting (imprinting).

During a short early period of life, birds are capable of a special form of learning called imprinting or imprinting. For example, a newly hatched gosling that sees a person before its own mother will follow on its heels, not paying attention to the goose.

Insight.

Ability to decide simple tasks, without resorting to trial and error, is called "capturing relationships", or insight. For example, woodpecker tree finch ( Catospiza pallida) from the Galapagos Islands “by eye” picks up a needle from a cactus in order to extract an insect from a cavity in the wood with it. Some birds in particular great tit (Parus major), immediately begin to pull the food suspended on it by the thread.

individual behavior.

social behavior.

A lot of the actions of birds are related to social behavior, i.e. relationship between two or more individuals. Even with a solitary lifestyle, they are in contact with their sexual partners during the breeding season or with other individuals of their species occupying neighboring territories.

Communication.

Birds use complex communication systems, including primarily visual and sound signals or demonstrations. Some of them are used to intimidate another individual during a conflict with it. A bird that has adopted a threatening posture often turns towards the enemy, stretches its neck, opens its beak and presses its plumage. Other demonstrations are used to appease the opponent. At the same time, the bird often retracts its head and fluffs its feathers, as if emphasizing its passivity and safety for others. The demonstrations are clearly visible in the reproductive behavior of the birds.

defensive behavior.

All birds react with special defensive behavior to danger-related sound and visual stimuli. The sight of a flying hawk encourages small birds to rush to the nearest shelter. Once there, they usually "freeze", pressing down their plumage, bending their legs and following the predator with one eye. Birds with cryptic (camouflage, or patronizing) coloration simply crouch in place, instinctively trying to blend into the background.

Warning shouts and shouts.

Almost all birds have a behavioral repertoire that includes alarm and warning calls. While these signals do not appear to have been originally intended to startle other members of their own species, they nevertheless encourage pack members, mates, or chicks to freeze, crouch, or take flight. When faced with a predator or other dangerous animal, birds sometimes use threatening actions that are very similar to intraspecific threat displays, but more striking in their manifestation. On a predator sitting in the field of view, such as a hawk or an owl, a group small birds reacts so-called. barking, similar to barking in dogs. It allows you to warn of the potential danger of all birds in the immediate area, and during the breeding season - to divert the attention of the enemy from hidden chicks.

Flock behavior.

Even outside the breeding season, most species of birds tend to unite in flocks, usually single-species. Apart from crowding in places of lodging for the night, members of the pack maintain a certain distance between themselves. For example, barn swallows perch on wires with intervals of about 10 cm between individuals. An individual attempting to close this distance is immediately confronted by a threatening display of a neighbor. Numerous sound signals emitted by all members of the pack help keep it from scattering.

Inside the pack there is a so-called. social relief: if one individual begins cleaning, eating, bathing, etc., those nearby soon begin to do the same. In addition, a pack often has a social hierarchy: each individual has its own rank, or “social position”, determined by sex, size, strength, color, health and other factors.

BREEDING

Reproduction in birds involves the establishment of a nesting territory, courtship, copulation, pair formation, nest building, egg laying, incubation and care of growing chicks.

Territory.

At the beginning of the breeding season, individuals of most species establish the boundaries of their territory, which they protect from relatives. Usually only the male does this. There are four types of such territories.

Territory for mating, nesting and feeding.

This type is the most common and characteristic, for example, of song zonotrichia. The male arrives at the selected site in the spring and establishes its boundaries. Then the female arrives, mating takes place, a nest is built, and so on. The couple searches for food for themselves and their chicks without leaving the territory.

Territory for mating and nesting, but not for feeding.

Many songbirds, including the red-winged troupial, guard a fairly large area around the nest, but go to other places in search of food.

Territory for mating only.

Males of some species use restricted territories for mating displays and to attract females. Those nest in another place without the participation of a sexual partner. So, several males of the sagebrush grouse attract females (“lek”), having gathered on a small area, which is called a current.

Limited territory for mating and nesting.

Birds such as gannets, gulls, terns, herons and some species of swallows nest in colonies, within which each individual occupies the territory immediately surrounding the nest. They start building it in the same place where the mating took place.

The area that includes the feeding area must be large enough to provide food for both the breeding pair and its chicks. In a large bird, such as a bald eagle, it occupies an area of ​​​​about 2.6 km 2, and in song zonotrichia it is no more than 0.4 ha. In species nesting in dense colonies, the size of the territory should be sufficient so that adjacent pairs cannot reach each other with their beaks.

Singing.

The main sound demonstration of birds is a song, i.e. a stable sequence of sounds that allows identification of the species. They are issued mainly by the male, and usually only during the breeding season. Any sounds can be used - from the repetition of the same tone to a complex and long melody, sometimes very musical.

Birds sing especially often when establishing a nesting territory, less often after hatching, and usually stop singing when the young become independent and territorial behavior fades away. At the peak of the breeding season, one zonotrichia sang 2305 times a day. Some resident birds sing throughout the year.

Many birds try to catch the eye while singing, getting out to open places (perches). Larks, plantains and other inhabitants of treeless landscapes sing songs in flight.

Singing is most developed in the so-called. passerine songbirds, but almost all birds use some form of vocal display to announce their presence. They can be reduced to a kind of croaking from a pheasant or a roar from penguins. Some birds make sounds not with the larynx, but with other parts of the body, making specific movements for this. For example, a woodcock flowing over a forest clearing, flying up in a spiral into the sky, “shorts” due to sharp flapping of its wings, and then “bleeps” with its voice during a steep zigzag descent. Some woodpeckers use a drum roll instead of a song, beaten out with a beak on a hollow stump or other object with a good resonance.

During the peak breeding season, some birds sing almost continuously throughout the day. However, it is more common for most species to sing at dawn and in the evening. Mockingbird and nightingale can sing on moonlit nights.

Pairing.

After the female arrives at the nesting site, the male activates his auditory and visual displays. He sings louder and periodically pursues the female. At first, it is non-receptive, i.e. not capable of fertilization, but after a few days its physiological state changes and copulation occurs. At the same time, a more or less strong connection between partners is often established - a couple appears.

Songbirds are mostly monogamous. During the entire breeding season, they have only one partner, forming a stable pair with him. In some species, each nesting during one season is accompanied by a change of partner. Geese, swans and large birds of prey pair for life.

For a number of species, including some songbirds, polygamy is characteristic. If a male mates with two or more females, they speak of polygyny; if a female with two or more males - about polyandry. Polygyny is more common (for example, in the rice troupial); polyandry is known in, say, the spotted American carrier. Indiscriminate copulation without the formation of persistent pairs between partners is called promiscuity. It is typical, for example, for black grouse.

Following the formation of a pair, males take care of its preservation. They bring material for the nest, sometimes help build it, and usually feed the incubating female.

Nest types.

Being warm-blooded, birds not only protect the eggs from the influence of adverse weather conditions, but also warm them, facilitating the development of the embryo. To do this, they must have a nest, i.e. any place where eggs can be laid and where they will incubate.

There are open ground nests, located in shelters, platform nests and bowls. The first two categories do not have a specific structure, but may be lined with small pebbles, plant rags, or the bird's own down, although this is not necessary. The sheltered nest is in a kind of cave, made by the bird itself or otherwise. Tree ducks use ready-made hollows, woodpeckers themselves hollow them out in tree trunks, kingfishers dig holes in river banks.

The platform nest is a bunch of boughs with a hole in the center for eggs. Such nests are built by herons and many birds of prey. The eagles use the same platform year after year, adding new material to it every season, so that the mass of the building can eventually reach more than a ton.

The cup-shaped nests that most songbirds build have a well-defined structure: they have a dense bottom and walls, and are lined with soft material inside. Such a nest can lie on a support, like in thrushes, hold on to it with its edges, like in a vireo, or hang in the form of a long wicker bag, like in an ivory. In some species, it is attached to the wall, such as the phoebus and the swift, is in a hollow, like a tree swallow, in a hole, like a shore swallow, or on the ground, like a field lark. Among the most unusual and large are the nests of the pheasant-like Australian eyed chicken. These birds dig deep holes, fill them with plant material, bury their eggs in it and leave; incubation is provided by the heat released during decay. The hatched chicks get out on their own and then live on their own, not knowing their parents.

Nest building.

Tree-nesting songbirds first collect coarse material for the bowl itself, and then finer material for its lining. As it is added, they form a nest, rotating in it with their whole body. In some species, such as the rice troupial, only the female builds the nest; in others, the male supplies her with material for work. In the Western American jay, both partners do all construction together.

In some species, the male prepares several "preliminary" nests in his area. For example, the house wren often carries sticks to various secluded places, from which the partner chooses one for laying eggs. Virginian eagle owls use the abandoned nests of other birds, and sometimes they drive the owners out of the newly built ones.

Eggs.

As a rule, the larger the bird, the larger the eggs it lays, but there are exceptions to this rule. The eggs of brood species, from which downy young hatch, immediately able to run and feed on their own, are larger in relation to the mother's body than in nestling species, whose offspring are born naked and helpless. Thus, the eggs of shorebirds are relatively larger than those of songbirds of the same size. In addition, the ratio of egg weight to body weight in small species is often greater than in large ones.

The shape of the eggs of most birds resemble chickens, but there are many options here. In kingfishers they are almost spherical, in hummingbirds they are elongated and blunt at both ends, and in waders they are strongly pointed at one of them.

The surface of the egg can be rough or smooth, matte or shiny, and almost any color from dark purple and green to pure white. In some species, it is covered with speckles, sometimes forming a corolla around the blunt end. The eggs of many secretly nesting birds are white, and those that lay them on the ground often blend in with the background of pebbles or plant rags that line the nest.

Masonry size.

After the nest is ready, the female usually lays one egg per day until the clutch is completed. Clutch is the number of eggs laid in one nest. Its size varies from one egg in the black-browed albatross to 14 or 15 in some ducks and quails. It also fluctuates within the species. The wandering thrush may lay five eggs in the first clutch of the season and only 3 or 4 in the second and third. The clutch size is sometimes reduced due to bad weather or lack of food. Most species lay a strictly limited number of eggs; some do not have such certainty: they replace accidentally lost eggs with new ones, bringing the clutch to a standard volume.

Incubation.

Both partners or only one of them can participate in incubation (incubation) of eggs. Such a bird usually develops one or two brood spots - featherless areas on the lower chest. Their heavily perfused skin is in direct contact with the eggs and transfers heat to them. The incubation period, culminating in the hatching of chicks, lasts from 11–12 days for the sparrow to about 82 days for 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.

Hatching.

The embryo develops a special outgrowth at the end of the beak - an egg tooth, with the help of which, when hatching approaches, it scrapes the shell from the inside, reducing its strength. Then, resting on his legs and wings, he pushes cracks in it, i.e. hatches. After hatching, hatching can take from several hours for small birds to several days for the largest. All this time, the embryo squeaks abruptly, to which the parents respond with increased attention, sometimes pecking at cracks in the shell and tearing off small pieces of it.

Chick.

Songbirds and many other birds are chicks: their chicks hatch naked, blind, and helpless. Waders, ducks, chickens and some other birds are called brood birds: their chicks are immediately covered with down, they are able to walk and provide themselves with food. Between the typical chick and brood species, there are many intermediate options.

Immediately after hatching, typical chicks are unable to control their body temperature and need to be kept warm by their parents. They can only raise their heads, open their mouths wide and move in the nest when its concussion indicates the arrival of an adult bird. The bright mouths of the chicks serve as signal stimuli for her - "targets for food", stimulating its delivery to the right place. The parent either passes food from beak to beak or regurgitates it directly into the throats of offspring. Pelicans bring fish in a throat bag to the nest, open their huge beak wide and allow each chick to stick its head in there to feed on its own. Eagles and hawks deliver prey in their claws and tear it into pieces that are fed to their descendants.

Adult birds, having fed the chicks, as a rule, expect the appearance of their droppings, which are secreted in the mucous sac, carry it away and throw it away. Some species maintain perfect cleanliness in the nest, while others, such as kingfishers, do nothing for this.

Nestlings of nesting birds sit in the nest from 10 to 17 days, and after leaving it, for at least another 10 days they depend on their parents who protect and feed them. In species with a long incubation period, the chick stays in the nest longer: in the bald eagle, 10–12 weeks, and in the wandering albatross, the largest flying seabird, approx. 9 months The duration of nesting life is affected by the degree of its safety. The chicks emerge relatively early from open ground nests.

Contrary to popular belief, parents do not encourage offspring to live independently. The chick leaves the nest voluntarily, having acquired the necessary coordination of movements. For the first time, the "fledglings" that fluttered out of it still do not know how to fly properly.

Nestlings of brood birds spend much more time in the egg than chicks, and at hatching are usually developed in the same way as those at the time they left the nest. As soon as the fluff has dried, the brood chicks begin to accompany their parents in search of food. During the first few days, they may still need to be heated. These chicks clearly respond to the voice of their parents, “freezing” at the alarm signal and rushing to them in response to an invitation to eat.

However, they quickly learn to get food on their own. An adult bird brings them to the feeding place and can show edible objects, peck them and release them from the beak. However, more often than not, parents only look after the kids, while they, through trial and error, comprehend what is suitable for food. Almost immediately after hatching, plover chicks begin to peck seeds and small insects from the ground, and ducklings follow their mother in shallow water and begin to dive in search of food.

POPULATIONS

According to ornithologists, there are approx. 100 billion birds of approximately 8600 species. The number of individuals of one species varies from a few dozen, for example, in the critically endangered American crane, to many millions, as in Wilson's storm-petrel, an ocean bird, perhaps the champion in numbers among wild birds.

Birth and death rates.

Population size, i.e. the totality of individuals of a species in a given territory depends on the levels of fertility and mortality. When these parameters are approximately equal (as they usually are), the population remains stable. If the birth rate exceeds the death rate, the population grows, otherwise it declines.

Birth rate is determined by the number of eggs laid during the year and hatching success. In birds that lay one egg every two years, like the Californian condor, each pair adds only “half an individual” to the population per year, and, on the contrary, species with 2–3 large clutches can increase it annually by 20 individuals over the same period .

Lifespan.

Under ideal conditions, many species, especially large ones, live for a very long time. For example, some eagles, vultures and parrots in captivity have reached the age of 50–70 years. However, in nature, the bird age is much shorter. According to data obtained by ringing, large birds potentially live longer than small ones. The maximum recorded age for some birds in nature is as follows: gulls and waders - 36 years, terns - 27 years, hawks - 26 years, loons - 24 years, ducks, geese and swans - 23 years, swifts - 21 years and woodpeckers - 12 years . It is likely that predators like condors and eagles, as well as large albatrosses, live longer.

population density.

Populations tend to maintain their characteristic density for a long time, i.e. the number of individuals per unit area. A catastrophe that wipes out a significant part of the population is often followed by a significant decrease in mortality, and its size is quickly restored. For example, a harsh winter, which many birds did not survive, is usually followed by a spring and summer with unusually high chick survival rates. This is largely due to the fact that the few surviving individuals get plenty of food and convenient nesting sites.

Another important factor that regulates the size of a population is the area available to it. Each pair needs a specific area of ​​suitable habitat for nesting. After the pairs have occupied all the space suitable for the species, none of their relatives can no longer settle there. "Superfluous" birds have to either nest in unfavorable conditions, or not breed at all.

With scarcity of food resources and high population density, its size is usually limited by competition for food. It seems to be strongest at the end of winter and between individuals of the same species, since they all need the same diet.

In overpopulated areas, competition for food can lead to emigration (migration), which reduces the population density in a given place. Individuals of some species, such as snowy owls, in years with their high numbers, lack of food resources, or both at the same time, appear in masses outside their usual range.

Although predation is the most visible cause of bird death, it has a much weaker effect on population size than adverse environmental conditions. The victims of predators are usually individuals weakened by old age or disease.

MIGRATION

The flight allowed birds to adapt better than many animals to changing environmental factors, in particular, periodic fluctuations in meteorological conditions, food availability and other parameters. It is possible that the birds began seasonal migrations in the Northern Hemisphere during the glacial period, when the southward advance of the glacier pushed them southward during the cold months, but the melting of the ice allowed them to return to their parental nesting sites in the summer. It could also be that some species, under the influence of fierce interspecific competition in tropical areas, during the retreat of the glacier, began to temporarily migrate north to nest in a less densely populated environment. In any case, for many current birds, flights closer to the equator in autumn and back in spring are an integral species feature.

Synchronization.

Migration is synchronized with the season and breeding cycle; it will not occur until the bird is physiologically ready for it and receives an appropriate external stimulus. Before migration, the bird eats a lot, accumulating weight and storing energy in the form of subcutaneous fat. Gradually, she comes into a state of "migratory anxiety." In spring it is stimulated by elongation daylight hours, which activates the gonads (sex glands), changing the work of the pituitary gland. In autumn, the bird reaches the same state as the length of the day shortens, which causes inhibition of the function of the gonads. In order for an individual ready to migrate to set off, it needs a special external stimulus, such as a change in the weather. This stimulus is provided by the movement of a warm atmospheric front in spring and a cold one in autumn.

During migration, most birds fly at night, when they are less threatened by winged predators, and spend the day feeding. Both single-species and mixed flocks, family groups and single individuals travel. On the road, birds are usually in no hurry, spending several days, or even a week, in a favorable place.

Flight paths.

Many birds have short journeys. Mountain species descend lower until they find enough food, spruce crossbills fly to the nearest area with a good harvest of cones. However, some birds migrate great distances. The Arctic tern has the longest flight path: every year it flies from the Arctic to the Antarctic and back, covering at least 40,000 km both ways.

Speed

migration depends on the species. A flock of waders can accelerate up to 176 km/h. Stonestone flies 3,700 km south, making an average of 920 km per day. Radar measurements of airspeed have shown that for most small birds on calm days it ranges from 21 to 46 km/h; larger birds, such as ducks, hawks, falcons, waders, and swifts, fly faster. The flight is characterized by a constant, but not the maximum speed for the species. Since it takes more energy to overcome a headwind, birds tend to wait it out.

In spring, species migrate north as if according to a schedule, reaching certain points at the same time from year to year. Extending non-stop flight segments as they approach the target, they cover the last few hundred kilometers at a much higher speed.

Heights.

As radar measurements show, the altitude at which the flight is made varies so much that it is impossible to speak of any normal or average values ​​here. However, nocturnal migrants are known to fly higher than daytime migrants. Among migratory birds recorded over the Cape Cod Peninsula (USA, Massachusetts) and the nearest ocean area, 90% stayed at an altitude of less than 1500 m.

Night migrants tend to fly higher in overcast conditions as they tend to fly above the clouds rather than below and through them. However, if the cloud cover extends to high altitudes at night, birds may fly under it as well. In doing so, they are attracted to tall, illuminated buildings and lighthouses, sometimes leading to deadly encounters.

According to radar measurements, birds rarely rise above 3000 m. However, some migrants reach amazing heights. In September, over the south-eastern part of England, birds were noted flying at around approx. 6300 m. Radar tracking and observation of silhouettes crossing the disk of the moon showed that nocturnal migrants, as a rule, do not "attach" to the landscape in any way. Birds flying during the day tend to follow long north-south landmarks—mountain ranges, river valleys, and long peninsulas.

Navigation.

As experiments have shown, to determine the direction of migration, birds have several instinctive methods in their basis. Some species, such as the starling, use the sun as a guide. With the help of "internal clocks" they maintain a given direction, making allowance for the constant displacement of the luminary above the horizon. Night migrants are guided by the position of bright stars, in particular Ursa Major and the North Star. Keeping them in sight, birds instinctively fly to the north in spring, and away from it in autumn. Even when dense clouds reach high altitudes, many migrants are able to keep the right direction. They may be using the direction of the wind, or familiar terrain cues if they are visible. It is unlikely that any species is guided in navigation by a single factor of the external environment.

MORPHOLOGY

Morphology is usually understood as the external structure of the animal, in contrast to the internal, which is usually called anatomical.

Beak

the bird consists of the upper and lower jaws (mandible and upper beak), covered with horny sheaths. Its shape depends on the method of obtaining food characteristic of the species, therefore it allows us to judge the feeding habits of the bird. The beak is long or short, curved up or down, spoon-shaped, serrated or with crossed jaws. In almost all birds, it wears off at the tip from use, and its horny cover must be continuously renewed.

Most species have a black beak. However, there are a variety of variants of its coloration, and in some birds, such as puffins and toucans, this is the brightest part of the body.

Eyes

in birds they are very large, because these animals are guided mainly by sight. The eyeball is mostly hidden under the skin, and only the dark pupil is visible, surrounded by a colored iris.

In birds, in addition to the upper and lower eyelids, there is also a “third” eyelid - the nictitating membrane. This is a thin, transparent fold of skin, approaching the eye from the side of the beak. The nictitating membrane moisturizes, cleanses and protects the eye, instantly closing it in case of danger of contact with an external object.

ear holes,

located behind and slightly below the eyes, in most birds they are covered with feathers of a special structure, the so-called. ear coverings. They protect the ear canal from the ingress of foreign objects, while at the same time not interfering with the propagation of sound waves.

Wings

birds are long or short, rounded or sharp. In some species they are very narrow, while in others they are wide. They can also be concave or flat. As a rule, long narrow wings serve as an adaptation for long-range flights over the sea. Long, wide and rounded wings are well adapted for soaring in ascending currents of air heated near the ground. Short, rounded and concave wings are most convenient for slow flight over fields and among forests, as well as for rapid rise into the air, for example, in a moment of danger. Pointed flat wings contribute to rapid flapping and rapid flight.

Tail

as a morphological section, it consists of tail feathers that form its posterior margin, and coverts overlapping their bases. The tail feathers are paired, they are located symmetrically on both sides of the tail. The tail is longer than the rest of the body, but sometimes it is practically absent. Its shape, characteristic of different birds, is determined by the relative length of the various tail feathers and the features of their tips. As a result, the tail is rectangular, rounded, pointed, forked, etc.

Legs.

In most birds, the feather-free part of the leg (foot) includes the tarsus, toes, and claws. In some species, such as owls, the tarsus and fingers are feathered, in a few others, in particular swifts and hummingbirds, they are covered with soft skin, but usually there is a hard horny cover, which, like all skin, is constantly updated. This cover may be smooth, but more often it consists of scales or small irregularly shaped plates. In pheasants and turkeys, there is a horn spur on the back of the tarsus, and in collared hazel grouse, on the sides of the fingers, there is a fringe of horn spikes, which falls off in spring and grows back in autumn to serve as skis in winter. Most birds have 4 toes on their feet.

Fingers are arranged differently depending on the habits of the species and their environment. For grasping branches, climbing, catching prey, carrying and manipulating food, they are equipped with sharply curved sharp claws. In running and burrowing species, the fingers are thick, and the claws on them are strong, but rather blunt. Waterfowl have webbed fingers, like ducks, or leathery lobes on the sides, like grebes. In larks and some other song species of open spaces, the back toe is armed with a very long claw.

Other signs.

In some birds, the head and neck are bare or covered with very sparse feathers. The skin here is usually brightly colored and forms outgrowths, for example, a crest on the crown and earrings on the throat. Often, well-marked bumps are located at the base of the upper jaw. Typically, these features are used for demos or simpler communication signals. In carrion-eating vultures, the bare head and neck are probably an adaptation that allows them to feed on rotting corpses without soiling feathers on areas of the body that are very difficult to clean.

ANATOMY AND PHYSIOLOGY

When birds acquired the ability to fly, they internal structure has changed a lot compared to the ancestral, characteristic of reptiles. To reduce the weight of the animal, some organs became more compact, others were lost, and the scales were replaced by feathers. Heavier, vital structures have been moved closer to the center of the body in order to improve its balance. In addition, the efficiency, speed and control of all physiological processes have increased, which provided the power required for flight.

Skeleton

birds are characterized by remarkable lightness and rigidity. Its relief was achieved due to the reduction of a number of elements, especially in the limbs, and the appearance of air cavities inside certain bones. Rigidity is provided by the fusion of many structures.

For convenience of description, the axial skeleton and the skeleton of the limbs are distinguished. The first includes the skull, spine, ribs, and sternum. The second is formed by arcuate shoulder and pelvic girdle and the bones of the free limbs attached to them - the anterior and posterior.

Scull.

The skull of birds is characterized by huge eye sockets corresponding to the very large eyes of these animals. The brain box is adjacent to the eye sockets from behind and is, as it were, squeezed by them. Strongly protruding bones form toothless upper and lower jaws, corresponding to the upper and lower beaks. The ear opening is located under the lower edge of the orbit, almost close to it. Unlike the human upper jaw, in birds it is mobile due to a special articulation to the brain box.

Spine,

or the vertebral column consists of many small bones called vertebrae, which are arranged in a row from the base of the skull to the tip of the tail. In the cervical region, they are isolated, mobile, and at least twice as numerous as in humans and most mammals. As a result, the bird can bend its neck and turn its head in almost any direction. In the thoracic region, the vertebrae are articulated with the ribs and, as a rule, are firmly fused with each other, and in the pelvic region they are fused into a single long bone - a complex sacrum. Thus, birds are characterized by an unusually rigid back. The rest of the vertebrae - the caudal - are mobile, with the exception of the last few, which are fused into a single bone, the pygostyle. It resembles a plowshare in shape and serves as a skeletal support for long tail feathers.

Rib cage.

The ribs, together with the thoracic vertebrae and the sternum, surround and protect the outside of the heart and lungs. In all flying birds, the sternum is very wide, growing into a keel for attaching the main flying muscles. As a rule, the larger it is, the stronger the flight. Completely flightless birds have no keel.

Shoulder girdle,

connecting the forelimb (wing) with the axial skeleton, is formed on each side by three bones arranged like a tripod. One of its legs, the coracoid (crow bone), rests against the sternum, the second, the shoulder blade, lies on the ribs, and the third, the clavicle, is fused with the opposite clavicle in the so-called. fork. The coracoid and the scapula at the meeting point form an articular cavity in which the head of the humerus rotates.

Wings.

The bones of a bird's wing are basically the same as those in a human hand. The humerus, the only one in the upper limb, is articulated in the elbow joint with two bones of the forearm - the radius and the ulna. Below, i.e. in the hand, many elements present in humans are fused or lost in birds, so that only two carpal bones remain, one large metacarpal bone, or buckle, and 4 phalangeal bones corresponding to three fingers.

The wing of a bird is substantially lighter than the forelimb of any terrestrial vertebrate of similar size. And the point is not only that the hand includes fewer elements - the long bones of the shoulder and forearm are hollow, and in the shoulder there is a special air bag related to the respiratory system. The wing is further facilitated by the absence of large muscles in it. Instead, his main movements are controlled by the tendons of the strongly developed musculature of the sternum.

Flying feathers extending from the hand are called large (primary) fly feathers, and those attached in the zone of the ulna of the forearm are called small (secondary) fly feathers. In addition, three more wing feathers are distinguished, attached to the first finger, and covering feathers, smoothly, like a tile, overlapping the bases of the flight feathers.

Pelvic girdle

on each side of the body it consists of three bones fused together - ischium, pubic and ilium, the latter fused with a complex sacrum. All this together protects the outside of the kidney and provides a strong connection of the legs with the axial skeleton. Where the three bones of the pelvic girdle meet each other is the deep acetabulum, in which the head of the femur rotates.

Legs.

In birds, as in humans, the femur forms the core of the upper part of the lower limb, the thigh. The lower leg is attached to this bone in the knee joint. If in humans it includes two long bones, the tibia and tibia, in birds they fuse with each other and with one or more upper tarsal bones into an element called tibiotarsus. Only a thin short rudiment adjacent to the tibiotarsus remains visible from the fibula.

Foot.

In the ankle (more precisely, intratarsal) joint, a foot is attached to the tibiotarsus, consisting of one long bone, a tarsus, and bones of the fingers. The tarsus is formed by elements of the metatarsus, fused with each other and with several lower tarsal bones.

Most birds have 4 fingers, each of which ends in a claw and is attached to the tarsus. The first finger is turned back. In most cases, the rest are directed forward. In some species, the second or fourth toe points back along with the first. In swifts, the first finger is directed forward, like the rest, and in the osprey, it is able to turn in both directions. In birds, the tarsus does not rest on the ground, and they walk on their toes with their heel torn off the ground.

Muscles.

Wings, legs and the rest of the body are driven by about 175 different skeletal striated muscles. They are also called arbitrary, i.e. their contractions can be controlled "consciously" - by the brain. In most cases, they are paired, symmetrically located on both sides of the body.

Flight is provided mainly by two large muscles, the pectoral and supracoracoid. Both of them start at the sternum. The pectoral muscle, the largest, pulls the wing down and thus in the air causes the bird to move forward and upward. The supracoracoid muscle pulls the wing up, preparing it for the next stroke. In domestic chicken and turkey, these two muscles represent the "white meat", while the rest correspond to the "dark meat".

In addition to skeletal muscles, birds have smooth, layered in the walls of the organs of the respiratory, vascular, digestive and urogenital systems. Smooth muscles are also found in the skin, where they determine the movement of feathers, and in the eyes, where they provide accommodation, i.e. focusing the image on the retina. They are called involuntary, as they work without "volitional control" from the brain.

Nervous system.

Central nervous system It consists of the brain and spinal cord, which, in turn, are formed by many nerve cells (neurons).

The most noticeable part of the brain of birds is the cerebral hemispheres, which are the center of higher nervous activity. Their surface is smooth, without furrows and convolutions, characteristic of many mammals, its area is relatively small, which correlates well with the relatively low level of “intelligence” of birds. Inside the cerebral hemispheres there are centers for the coordination of instinctive forms of activity, including feeding and singing.

The cerebellum, which is of particular interest in birds, is located directly behind the cerebral hemispheres and is covered with furrows and convolutions. Its complex structure and large size correspond to the difficult tasks associated with maintaining balance in the air and coordinating the many movements necessary for flight.

The cardiovascular system.

The heart of birds is larger than that of mammals with a similar body size, and the smaller the species, the relatively larger its heart. For example, in a hummingbird, its mass is up to 2.75% of the mass of the whole organism. In all birds that fly frequently, the heart must be large in order to ensure rapid blood circulation. The same can be said about species living in cold regions or at high altitudes. Like mammals, birds have a four-chambered heart.

The frequency of contractions correlates with its size. So, in a resting African ostrich, the heart makes approx. 70 “beats” per minute, and for a hummingbird in flight - up to 615. Extreme fright can raise blood pressure in birds so much that large arteries burst and the individual dies.

Like mammals, birds are warm-blooded, and the range of normal body temperatures is higher than that of humans - from 37.7 to 43.5 ° C.

The blood of birds usually contains more red blood cells than most mammals, and as a result, it can carry more oxygen per unit time, which is necessary for flight.

Respiratory system.

In most birds, the nostrils lead into the nasal cavities at the base of the beak. However, cormorants, gannets, and some other species do not have nostrils and must breathe through their mouths. Air, once in the nostrils or mouth, is directed to the larynx, from which the trachea begins. In birds (unlike mammals), the larynx does not produce sounds, but forms only a valve apparatus that protects the lower respiratory tract from food and water entering them.

Near the lungs, the trachea divides into two bronchi, one for each. At the point of its division is the lower larynx, which serves as a vocal apparatus. It is formed by expanded ossified rings of the trachea and bronchi and internal membranes. Pairs of special singing muscles are attached to them. When air exhaled from the lungs passes through the lower larynx, it causes the membranes to vibrate, producing sounds. In birds with a wide range of emitted tones, there are more singing muscles that strain the vocal membranes than in poorly singing species.

Upon entering the lungs, each bronchus divides into thin tubes. Their walls are permeated with blood capillaries that receive oxygen from the air and release carbon dioxide into it. The tubules lead into thin-walled air sacs that resemble soap bubbles and are not penetrated by capillaries. These bags are located outside the lungs - in the neck, shoulders and pelvis, around the lower larynx and digestive organs, and also penetrate into the large bones of the limbs.

The inhaled air moves through the tubes and enters the air sacs. When you exhale, it goes out of the bags again through the tubes through the lungs, where gas exchange again takes place. This double breathing increases the supply of oxygen to the body, which is necessary for flight.

Air sacs perform other functions as well. They humidify the air and regulate body temperature by allowing surrounding tissues to lose heat through radiation and evaporation. Thus, the birds seem to sweat from the inside, which compensates for their lack of sweat glands. At the same time, air sacs ensure the removal of excess fluid from the body.

Digestive system,

in principle, it is a hollow tube extending from the beak to the opening of the cloaca. It takes in food, secretes juice with enzymes that break down food, absorbs the formed substances and removes undigested residues. Although the structure of the digestive system and its functions are basically the same for all birds, there are differences in details associated with specific feeding habits and the diet of a particular group of birds.

The process of digestion begins when food enters the mouth. Most birds have salivary glands that secrete saliva, which wets the food and begins its digestion. Salivary glands Some swifts secrete a sticky fluid that is used to build nests.

The shape and function of the tongue, like the beak, depend on the lifestyle of the bird. The tongue can be used to hold food, manipulate it in the mouth, feel it, and taste it.

Woodpeckers and hummingbirds can protrude their unusually long tongue far beyond the beak. In some woodpeckers, it has serrations at the end that point backwards, which help to pull insects and their larvae out of holes in the bark. In hummingbirds, the tongue is usually forked at the end and folded into a tube for sucking nectar from flowers.

Food passes from the mouth into the esophagus. In turkeys, grouse, pheasants, pigeons and some other birds, a part of it, called the goiter, is constantly expanded and serves to accumulate food. In many birds, the entire esophagus is sufficiently distensible to temporarily accommodate a significant amount of food before it enters the stomach.

The latter is divided into two parts - glandular and muscular ("navel"). The first secretes gastric juice, which begins to break down food into substances suitable for absorption. The "navel" is distinguished by thick walls with hard internal ridges that grind food obtained from the glandular stomach, which compensates for the lack of teeth in birds. In species that eat seeds and other solid food, the muscular walls of this section are especially thick. In many birds of prey, in the muscular stomach, indigestible parts of the food, in particular bones, feathers, hair and hard parts of insects, form flat, round pellets that periodically burp.

Behind the stomach, the digestive tract continues with the small intestine, where food is finally digested. The large intestine in birds is a short straight tube leading to the cloaca, where the ducts of the genitourinary system also open. Thus, fecal matter, urine, eggs and sperm enter it. All these products leave the body through a single opening.

Urogenital system.

This complex consists of closely related excretory and reproductive systems. The first operates continuously, and the second is activated at certain times of the year.

The excretory system includes two kidneys that remove waste products from the blood and form urine. Birds don't have Bladder, and it passes through the ureters directly into the cloaca, where most of the water is absorbed back into the body. The white, mushy residue is eventually thrown out along with dark-colored feces that have come from the large intestine.

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. The shape of the testicles is oval or elliptical, and the left one is usually larger. They lie in the body cavity near the anterior end of each kidney. Before the onset of the breeding season, the stimulating action of pituitary hormones causes the testes to increase hundreds of times. Through a thin convoluted tube, the vas deferens, spermatozoa enter the seminal vesicle from each testis. There they accumulate until the ejaculation that occurs at the time of copulation, at which they go into the cloaca and through its opening - out.

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. Its main part by weight is the yolk - a nutrient material for the embryo developing after fertilization. From the ovary, the egg enters a tube called the oviduct. The muscles of the oviduct push it past the various glandular areas in its walls. They surround the yolk with albumen, shell membranes, hard, calcium-containing shells, and finally, they add shell-coloring pigments. It takes approx. 24 hours

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 shell.

FEATHERS

Feathers protect the skin of a bird, provide thermal insulation of its body, since they keep a layer of air near it, streamline its shape and increase the area of ​​\u200b\u200bthe bearing surfaces - wings and tail.

Nearly all birds appear to be fully feathered; only the beak and feet look partially or completely naked. However, the study of any flight-capable species reveals that feathers grow from rows of depressions - feather bags grouped in wide stripes, pterylia, which are separated by bare skin, apteria. The latter are imperceptible, since they are covered with feathers from adjacent pterylae overlying them. Only in a few birds do feathers grow evenly throughout the body; usually flightless species such as penguins.

Pen structure.

The primary wing feather is the most complex. It consists of an elastic central rod, to which two wide flat fans are attached. Internal, i.e. facing the center of the bird, the fan is wider than the outer one. The lower part of the rod, the core, is partially immersed in the skin. The core is hollow and free from fans attached to the upper part of the rod - the trunk. It is filled with a cellular core and bears a longitudinal groove on the underside. Each fan is formed by a number of parallel grooves of the first order with branches, the so-called. grooves of the second order. On the latter there are hooks that are hooked on adjacent grooves of the second order, connecting all the elements of the fan into a single whole - according to the mechanism of zippers. If the grooves of the second order have disengaged, it is enough for the bird to smooth the feather with its beak in order to “fasten” it again.

Feather types.

Almost all well-marked feathers are arranged as described above. Since it is they who give the body of the bird the external shape, they are called contour. In some species, such as grouse and pheasant, a small side feather similar in structure departs from the lower part of their shaft. It is very fluffy and improves thermal insulation.

In addition to the contour ones, on the body of birds there are feathers that are different in structure. The most common down, consisting of a short rod and long flexible beards that do not interlock with each other. It protects the body of chickens, and in adult birds is hidden under the contour feathers and improves thermal insulation. Down feathers are also located there, serving the same purpose as down. They have a long shaft, but unlinked barbs, i.e. in structure, they occupy an intermediate position between contour feathers and down.

Scattered among the contour feathers and usually hidden by them are thread-like feathers, clearly visible on a plucked chicken. They consist of a thin rod with a small vestigial fan on top. Filamentous feathers depart at the bases of the contour and perceive vibrations. It is believed that these are sensors of external forces that are involved in the stimulation of the muscles that control large feathers.

The bristles are very similar to filamentous feathers, but stiffer. They stick out in many birds near the corners of the mouth and probably serve for touch, like the vibrissae of mammals.

The most unusual feathers are the so-called. powder down, located in special zones - powders - under the main plumage of herons and bitterns or scattered over the body of pigeons, parrots and many other species. These feathers grow continuously and crumble at the top into a fine powder. It is water-repellent and probably, together with the secretion of the oil gland, protects the contour feathers from wetting.

The shape of contour feathers is very diverse. For example, the flight feathers of owls have fluffed edges, which makes the flight almost silent and allows you to quietly approach the prey. The bright and unusually long feathers of birds of paradise in New Guinea serve as "decoration" during demonstrations.

Molt.

Feathers are dead formations that are not capable of self-healing, so they need to be replaced periodically. The loss of old feathers and the growth of new ones in their place is called molting.

Most birds molt with the replacement of all feathers at least once a year, usually in late summer before the autumn migration. Another molt, observed in many species in the spring, is usually partial and affects only the feathers of the body, leaving the flight and tail feathers in place. As a result of molting, males acquire a bright courtship outfit.

Shedding occurs gradually. No pterylia loses all its feathers at once. In most flying birds, flight and tail feathers are replaced in a certain sequence. Thus, some of them are already growing while others fall out, so the ability to fly is maintained throughout the molt. Only in a few groups of flying birds, and exclusively aquatic ones, all primaries are shed at the same time.

The totality of a bird's feathers at a given time is called its plumage, or attire. During life, an individual replaces several types of plumage as a result of molts. The first of these is natal fluff, which is already present at the time of hatching. The next type of plumage is juvenile, i.e. corresponding to immature individuals.

In most birds, juvenile plumage is replaced directly by adults, but some species have two or three more intermediate appearances. For example, a bald eagle only at the age of seven acquires a typical adult appearance with a pure white head and tail.

Plumage care.

All birds clean their plumage (this is called “pring”), and most also bathe. Swallows, swifts and terns dive into the water several times in a row on the fly. Other birds, standing or crouching in shallow water, shake their fluffy feathers, trying to moisten them evenly. Some forest species bathe in rainwater or dew accumulated on leaves. The birds dry, fluffing and shaking the feathers, cleaning them with their beaks and flapping their wings.

Birds lubricate themselves with fat, which is secreted by the oil gland at the base of the tail. They apply it to their feathers with their beak, thereby making them water-repellent and more elastic. To lubricate the plumage of the head, birds rub their legs with fat with their beaks, and then scratch their heads with them.

Feathers are determined by both chemicals (pigments) and structural features. Carotenoid pigments are responsible for the red, orange and yellow colors. Another group, melanins, gives a black, gray, brown or brown-yellow color, depending on the concentration. "Structural colors" are due to the characteristics of the absorption and reflection of light waves that do not depend on pigments.

Structural coloring is iridescent (rainbow) and monophonic. In the latter case, it is usually white and blue. A pen is perceived as white if it is almost or completely devoid of pigment, transparent, but due to its complex internal structure, it reflects all light waves of the visible spectrum. It appears blue if it contains densely packed cells with brown pigment under a transparent membrane. They absorb all the light passing through the transparent layer, with the exception of blue rays, which are reflected to them. As such, there is no blue pigment in the pen.

Iridescent coloration, which changes depending on the angle of view, is mainly due to the mutual superposition of peculiarly expanded, twisted and containing black melanin beards of the second order. So, American grackle birds look either multi-colored or black. The throat spot of the common ruby-throated hummingbird either flashes bright red or appears brownish black.

Pattern.

For no other group of living beings is the color of the body of such great importance as for birds. It can be cryptic, or patronizing if it imitates the surrounding background, making the individual invisible. This is especially common in females; as a result, sitting motionless on the eggs, they do not attract the attention of predators. However, sometimes both sexes are cryptically colored.

Many birds living among the grass have a pattern of longitudinal stripes. In addition, they often have relatively dark tops and lighter bottoms. Since the light falls from above, the lower parts of the body turn out to be shaded and approach the upper ones in color, and as a result, the whole bird looks flat and does not stand out from the surrounding background.

In other cases, the coloring is dissecting, i.e. consisting of an irregular shape of clearly defined contrasting spots, which “breaks” the contours of the body into seemingly unrelated parts that do not look like a living creature. Sandpipers painted in this way, such as the Turnstone and the Noisy Plover, are almost invisible against the background of the pebbly beach.

Conversely, some birds have bright markings on their tail, body, and wings that “flash” during flight. Examples are the white tail feathers of the junco, the white body of the avocet woodpecker, and the white stripes on the wings of the dusky nightjar. Bright markings play a protective role. By suddenly "flashing" in front of an attacking predator, they frighten him for a moment, giving the bird extra time to escape; and can also divert the attention of the enemy from the most important parts of the body. In addition, highly visible color adult important when a bird pretends to be injured, leading a predator away from the nest or chick. It is likely that bright spots also contribute to intraspecific recognition, acting as signal stimuli that strengthen the bond between pack members.

The color pattern helps to find a sexual partner during the breeding season. Usually brighter and more contrasting colors are characteristic of males, who use them during courtship displays.

FEEDING HABITS

For the most part, birds are either predators that feed on other animals, or phytophages that eat plant material. Only relatively few species are omnivorous, i.e. consume almost any food.

Most birds of prey are strictly carnivorous; they prey on a wide variety of animals, including amphibians, reptiles, birds and beasts. The same category includes vultures that feed exclusively on carrion. The osprey and many aquatic birds are also fish-eating predators, and many small birds eat insects, spiders, earthworms, slugs, and other invertebrates. Strictly herbivorous species include grass-grazing African ostriches and geese.

Only a few birds have a specialized diet. For example, a public slug-eating kite eats exclusively snails of the genus Pomacea. The strongly curved beak of this bird is well suited for extracting the body of a mollusk from the shell, but is of little use for any other operations.

Many species change their diet depending on the season, climate, location, and also with age. During the winter in the southern United States, up to 90% of the feed of savannah bunting is of plant origin, and in the summer, after migrating north, it contains up to 75% of insects. Immediately after hatching, chicks of almost all species consume animal food. In most songbirds, they feed mainly on insects, although, having matured, they can almost completely switch to seeds or other plant food.

Some species store food, usually in the fall, to be used in the winter when food is scarce. For example, nuthatch and ant woodpecker hide nuts in bark cracks, and European nutcracker ( Nucifraga caryocatactes) bury them in the ground. Studies of the latter species have shown that the bird finds up to 86% of its underground reserves even under a layer of snow 25 cm thick.

African honeyguides “lead” a person or honey badger from the mustelid family to the nest of bees, flying from branch to branch, calling invitingly and waving their tail. When the mammal opens the nest, getting to the honey, the bird feasts on the wax combs.

The herring gull is an omnivorous species, sometimes including bivalve mollusks in its diet. To break their tough shell, the bird lifts the prey high into the air and drops it onto a hard surface such as a rock ledge or a highway.

At least two bird species use tools to forage. One of them is a woodpecker tree finch ( Cactospiza pallida), already mentioned above, and the second is the common vulture ( Neophron percnopterus) from Africa, which takes a large stone in its beak and drops it on an African ostrich egg.

Some species take food from other birds. Notorious pirates are frigatebirds and skuas that attack other seabirds, forcing them to abandon their prey.

The most characteristic way of locomotion of birds is flight. However, birds are adapted to varying degrees for movement on the ground, and some of them are excellent swimmers and divers.

In the air.

The structure of the bird's wing, in principle, ensures the movement of the body in the air. The extended wing thins out from a thick and rounded leading edge with skeletal support inside towards the rear edge formed by the flight feathers. Its upper side is slightly convex, and the lower one is concave.

During normal flapping flight, the lower surface of the inner half of the wing, which is tilted with the trailing edge down, is affected by the pressure of the oncoming air flow. By deflecting it downward, the wing provides lift.

The outer half of the wing in flight describes a semicircle, moving forward and down, and then up and back. The first movement pulls the bird forward, and the second serves as a swing. When swung, the wing is semi-folded, and the flight feathers are spread apart to reduce air pressure on its upper side. Owners of short and wide wings in flight must wave them often, since their area is small compared to body weight. The long, narrow wing does not require a high beat rate.

There are three types of flight: gliding, soaring and flapping. Gliding is just a smooth downward movement on extended wings. Soaring is essentially gliding as well, only without losing altitude. Soaring flight can be dynamic or static. In the first case, this is planning in ascending air currents, in which the effect of gravity is compensated by the pressure of the rising air. As a result, the bird flies without literally moving its wings. Buzzards, eagles and other large broad-winged species even migrate along the meridian-running mountain ranges using the vertical component of the wind that rises obliquely up the windward slope.

Dynamic soaring is sliding in horizontal air currents that differ in speed and height, with an alternate transition between them up and down. Such a flight is characteristic, for example, of albatrosses, which spend most of their lives above the stormy sea.

The flapping flight already described is the main mode of locomotion for all birds when taking off, landing and moving in a straight line. Individuals starting from a high perch simply rush down to gain enough speed to fly in the fall. When taking off from land or water, the bird, quickly moving its legs, accelerates against the wind until it picks up speed sufficient to lift off the surface. However, if there is no wind or it is impossible to accelerate, it gives its body the necessary momentum due to the forced flapping of its wings.

Before landing, the bird must slow down. To do this, it orients the body vertically and slows down, widely spreading its wings and tail to increase the oncoming air resistance. At the same time, she stretches her legs forward to absorb the impact on the perch or the ground. When landing on water, the bird does not have to slow down much, since the risk of injury is much less.

The tail complements the bearing surface of the wings and is used as a brake, but its main function is to serve as a rudder during flight.

Birds can perform special aerial maneuvers according to their specific adaptations. Some, rapidly flapping their wings, hover motionless in one place. Others intersperse spurts of flapping flight with gliding periods, making the flight undulating.

On the land.

Birds presumably evolved from arboreal reptiles. They probably inherited from them the habit of jumping from branch to branch, characteristic of most birds. At the same time, some birds, such as woodpeckers and pikas, acquired the ability to climb vertical tree trunks using their tail as a support.

Descending in the course of evolution from trees to the ground, many species gradually learned to walk and run. However, progress in this direction has been different types unequally. For example, the wandering thrush can both jump and walk, while the starling normally only walks. The African ostrich runs at speeds up to 64 km/h. On the other hand, swifts are unable to jump or run, and use their weak legs only to cling to vertical surfaces.

Birds walking in shallow water, such as herons and stilt, are characterized by long legs. Birds that walk on carpets of floating leaves and bogs are characterized by long fingers and claws so as not to fall through. Penguins have short and thick legs located far behind the center of gravity. For this reason, they can only walk with their bodies upright, in short steps. If it is necessary to move faster, they lie on their belly and glide like on a sleigh, pushing off the snow with flipper wings and legs.

In water.

Birds are originally land creatures and always nest on land or in rare cases on rafts. However, many of them have adapted to an aquatic lifestyle. They swim by alternating strokes with their feet, usually equipped with membranes or paddles on the fingers, acting like oars. The wide body provides waterfowl with stability, and their dense feather cover contains air that increases buoyancy. The ability to swim, as a rule, is necessary for birds that forage under water. Swans, geese and some ducks in shallow water practice partial diving: turning their tail up and stretching their neck down, they get food from the bottom.

Gannets, pelicans, terns and other fish-eating species dive into the water from summer, and the height of the fall depends on the size of the bird and the depth that they seek to reach. Thus, heavy gannets, falling like a stone from a height of 30 m, plunge into the water by 3–3.6 m. Light-bodied terns dive from a lower height and plunge only a few centimeters.

Penguins, loons, grebes, diving ducks and many other birds dive from the surface of the water. Lacking the momentum of dive divers, they use the movements of their legs and/or wings to dive. In such species, the legs are usually located at the rear end of the body, like a propeller under the stern of a ship. When diving, they can reduce buoyancy by pressing the feathers tightly and squeezing the air sacs. Probably, for most birds, the maximum diving depth from the surface of the water is close to 6 m. However, the dark-billed polar loon can dive to 18 m, and the diving duck long-tailed duck to about 60 m.

SENSORS

In order to see well enough during a fast flight, birds have better eyesight than all other animals. They also have a well-developed hearing, but the sense of smell and taste in most species are weak.

Vision.

The eyes of birds have a number of structural and functional features that correlate with their lifestyle. They are especially noticeable big sizes which provide a wide field of view. In some birds of prey they are much larger than in humans, and in the African ostrich they are larger than in an elephant.

Eye accommodation, i.e. their adaptation to a clear vision of objects when the distance to them changes, in birds occurs with amazing speed. The hawk, chasing the prey, continuously keeps it in focus until the very moment of capture. A bird flying through the forest must clearly see the branches of the surrounding trees so as not to collide with them.

There are two unique structures present in the bird's eye. One of them is the scallop, a fold of tissue that protrudes into the inner chamber of the eye from the side of the optic nerve. It is possible that this structure helps to detect movement by casting a shadow on the retina when the bird moves its head. Another feature is the bony scleral ring, i.e. a layer of small lamellar bones in the wall of the eye. In some species, especially diurnal raptors and owls, the scleral ring is so strongly developed that it gives the eye the shape of a tube. This moves the lens away from the retina, and as a result, the bird is able to distinguish prey at a great distance.

In most birds, the eyes are tightly fixed in the sockets and cannot move in them. However, this disadvantage is compensated by the extreme mobility of the neck, which allows you to turn your head in almost any direction. In addition, the bird has a very wide overall field of vision as the eyes are located on the sides of the head. This type of vision, in which any object at a time is visible only with one eye, is called monocular. The total field of monocular vision is up to 340°. Binocular vision, in which both eyes are turned forward, is peculiar only to owls. Their total field is limited to about 70°. There are transitions between monocularity and binocularity. The woodcock's eyes are so far back that they perceive the rear half of the field of vision no worse than the front. This allows him to keep an eye on what is happening above his head, probing the ground with his beak in search of earthworms.

Hearing.

Like mammals, the organ of hearing in birds includes three parts: the outer, middle, and inner ear. However, there is no auricle. The "ears" or "horns" of some owls are simply tufts of elongated feathers that have nothing to do with hearing.

In most birds, the outer ear is a short passage. In some species, such as vultures, the head is naked, and its opening is clearly visible. However, as a rule, it is covered with special feathers - covering the ear. In owls, which, when hunting at night, are guided mainly by hearing, the ear openings are very large, and the feathers covering them form a wide facial disk.

The external auditory meatus leads to the tympanic membrane. Its vibrations, caused by sound waves, are transmitted through the middle ear (an air-filled bone chamber) to the inner ear. There, mechanical vibrations are converted into nerve impulses that are sent along the auditory nerve to the brain. The inner ear also includes three semicircular canals, the receptors of which ensure the balance of the body.

Although birds hear sounds in a fairly wide frequency range, they are especially sensitive to the acoustic signals of their own species. As experiments have shown, various species perceive frequencies from 40 Hz (budgie) to 29,000 Hz (finch), but usually the upper limit of hearing does not exceed 20,000 Hz in birds.

Several species of birds nesting in dark caves avoid hitting obstacles there thanks to echolocation. This ability, also known in bats, is observed, for example, in guajaros from Trinidad and northern South America. Flying in absolute darkness, he emits "bursts" of high-pitched sounds and, perceiving their reflection from the walls of the cave, easily orients himself in it.

Smell and taste.

In general, the sense of smell in birds is very poorly developed. This correlates with the small size of their olfactory lobes and the short nasal cavities located between the nostrils and the oral cavity. The exception is the New Zealand kiwi bird, in which the nostrils are at the end of a long beak and the nasal cavities are elongated as a result. These features allow her to stick her beak into the soil, sniff out earthworms and other underground food. It is also believed that vultures find carrion with the help of not only sight, but also smell.

The taste is poorly developed, because the lining of the oral cavity and the integument of the tongue are mostly horny and there is little space for taste buds on them. However, hummingbirds clearly prefer nectar and other sweet liquids, and most species reject highly acidic or bitter foods. However, these animals swallow food without chewing, i.e. seldom hold it in the mouth long enough to subtly distinguish the taste.

BIRD PROTECTION

Many countries have laws and participate in international agreements for the protection of migratory birds. For example, US federal law, as well as US treaties with Canada and Mexico, provide for the protection of all such species in North America, with the exception of diurnal predators and introduced species, regulate the hunting of migratory game (for example, waterfowl and woodcock), as well as certain resident birds, in particular black grouse, pheasants and partridges.

However, a more serious threat to birds does not come from hunters, but from completely “peaceful” types of human activity. Skyscrapers, TV towers and other tall buildings are deadly obstacles for migratory birds. Birds are knocked down and crushed by cars. Oil spills in the sea kill many aquatic birds.

Your way of life and impact on the environment modern man created advantages for species that prefer anthropogenic habitats - gardens, fields, front gardens, parks, etc. That is why North American birds such as the wandering thrush, blue jay, house wren, cardinals, song zonotrichia, troupials, and most swallows are now more numerous in the United States than before the arrival of European settlers in these places. However, many species that depend on swamps or mature forests are threatened by the destruction of a large number of such habitats. Swamps, which many consider suitable only for drainage, are in fact vital for shepherds, bitterns, marsh wren and many other birds. If the swamps disappear, the same fate befalls their inhabitants. Similarly, deforestation means the complete destruction of certain species of grouse, hawks, woodpeckers, thrushes and warblers, which require large trees and natural forest floor.

An equally serious threat is posed by environmental pollution. Natural pollutants are substances that are constantly present in nature, such as phosphates and waste products, but normally maintain a constant (equilibrium) level to which birds and other organisms are adapted. If a person greatly increases the concentration of substances, violating the ecological balance, pollution of the environment occurs. For example, if sewage is drained into a lake, its rapid decomposition will deplete the oxygen dissolved in the water. The crustaceans, mollusks and fish that need it will disappear, and with them the loons, grebes, herons and other birds that will be left without food will disappear.

Artificial pollutants are chemical substances, which are practically absent in virgin nature, such as industrial fumes, exhaust gases and most pesticides. Almost no species, including birds, is adapted to them. If a pesticide is sprayed over a swamp to kill mosquitoes, or over crops to control crop pests, it will kill not only the target species, but many other organisms as well. Worse than that, some pesticides remain in water or soil for years, are included in the food chain, and then accumulate in the body of large birds of prey, which are the top of many of these chains. Although small doses of pesticides do not directly kill birds, their eggs can become infertile or develop abnormally thin shells that break easily during incubation. As a result, the population will soon begin to decline. For example, the bald eagle and the brown pelican were at such risk because of the insecticide DDT consumed along with fish, their main food. Now, thanks to conservation measures, the number of these birds is recovering.

It is hardly possible to stop the advance of man on the world of birds; the only hope is to slow it down. One measure could be stricter liability for the destruction of natural habitats and environmental pollution. Another measure is to increase the area of ​​protected areas in order to preserve natural communities which include endangered species.

CLASSIFICATION OF BIRDS

Birds make up the class Aves of the Chordata type, which includes all vertebrates. The class is subdivided into orders, and those, in turn, into families. The names of the orders have the ending "-iformes", the names of the families - "-idae". This list includes all modern orders and families of birds, as well as fossil and relatively recently extinct groups. The number of species is indicated in parentheses.

Archaeopterygiformes: Archeopteryx-like (fossil)
Hesperornithiformes: hesperornithes (fossils)
Ichthyornithiformes: ichthyornithids (fossil)
Sphenisciformes: penguins
Spheniscidae: penguins (17)
Struthioniformes: ostriches
Struthionidae: ostriches (1)
Rheiformes: nandu-shaped
Rheidae: rhea (2)
Casuariiformes: cassowaries
Casuariidae: cassowaries (3)
Dromiceidae: emu (1)
Aepyornithiformes: epiornithiformes (extinct)
Dinornithiformes: moa-like (extinct)
Apterygiformes: kiwi-shaped (wingless)
Apterygidae: kiwi, wingless (3)
Tinamiformes: tinamou
Tinamidae: Tinamou (45)
gaviiformes: loons
Gaviidae: loons (4)
Podicipediformes: grebes
Podicipedidae: grebes (20)
Procellariiformes: petrel (tube-nosed)
Diomedeidae: albatrosses (14)
Procellariidae: petrels (56)
Hydrobatidae: storm-petrels (18)
Pelecanoididae: diving (whale) petrels (5)
Pelecaniformes: pelecaniformes (copepods)
Phaethontidae: Phaetonidae (3)
Pelecanidae: pelicans (6)
Sulidae: boobies (9)
Phalacrocoracidae: cormorants (29)
Anhingidae: darters (2)
Fregatidae: frigatebirds (5)
Ciconiiformes: stork-like (ankle-legged)
Ardeidae: herons (58)
Cochleariidae: shuttlebills (1)
Balaenicipitidae: whaleheads (1)
Scopidae: hammerheads (1)
Ciconiidae: storks (17)
Threskiornithidae: ibis (28)
Phoenicopteriformes: flamingos
Phoenicopteridae: flamingos (6)
Anseriformes: anseriformes (lamellar-beaked)
Anhimidae: palamedeans (3)
Anatidae: duck (145)
falconiformes: falconiformes (diurnal predators)
Cathartidae: American vultures, or condors (6)
Sagittariidae: secretary birds (1)
Accipitridae: accipitridae (205)
Pandionidae: hobos (1)
Falconidae: Falconidae (58)
Galliformes: chicken
Megapodiidae: bigfoot or weed chickens (10)
Cracidae: tree hens, or gokko (38)
Tetraonidae: grouse (18)
Phasianidae: pheasants, or peacocks (165)
Numididae: guinea fowl (7)
Meleagrididae: turkeys (2)
Opisthocomidae: hoatzins (1)
gruiformes: crane-like
Mesitornithidae: Madagascar shepherds or partridges (3)
Turnicidae: three-fingered (16)
Gruidae: cranes, or true cranes (14)
Aramidae: Aramidae (1)
Psophiidae: Trumpeters (3)
Rallidae: shepherds (132)
Heliornithidae: Pawfoot (3)
Rhynochetidae: kagu (1)
Eurypygidae: sun herons (1)
Cariamidae: cariams, or seriemes (2)
Otididae: Bustards (23)
Diatrymiformes: diatrymic (fossil)
Charadriiformes: charadriiformes
Jacanidae: Jacanidae (70)
Rostratulidae: colored snipe (2)
Haematopodidae: oystercatchers (6)
Charadriidae: Charadriidae (63)
Scolopacidae: snipes (82)
Recurvirostridae: avocets (7)
Phalaropodidae: Phalaropodidae (3)
Dromadidae: crayfish (1)
Burhinidae: Avdotki (9)
Glareolidae: chamois (17)
Stercorariidae: skuas (4)
Laridae: gulls or terns (82)
Rynchopidae: water cutters (3)
Alcidae: auks (22)
Columbiformes: pigeon-like
Pteroclidae: grouse (16)
Columbidae: pigeons (289)
Psittaciformes: parrots
Psittacidae: parrots (315)
Cuculiformes: cuckoo
Musophagidae: banana-eaters (22)
Cuculidae: cuckoo (127)
Strigiformes: owls
Tytonidae: barn owls (10)
Strigidae: true (normal) owls (123)
Caprimulgiformes: nightjars
Steatornithidae: guajaro, or fatty (1)
Podargidae: frogmouths or owl nightjars or whitelegs (12)
Nyctibiidae: giant (forest) nightjars (5)
Aegothelidae: owl nightjars or owl frogmouths (8)
Caprimulgidae: true nightjars (67)
Apodiformes: swift-shaped
Apodidae: swifts (76)
Hemiprocnidae: crested swifts (3)
Trochilidae: hummingbird (319)
Coliiformes: bird-mouse
Coliidae: mouse birds (6)
Trogoniformes: trogon-like
Trogonidae: trogons (34)
coraciiformes: crustaceans
Alcedinidae: kingfishers (87)
Todidae: todi (5)
Momotidae: momots (8)
Meropidae: bee-eaters (24)
Coraciidae: true (arboreal) raksha or funnelflies (17)
Upupidae: hoodoids (7)
Bucerotidae: hornbills (45)
piciformes: woodpeckers
Galbulidae: jacamar or warbler (15)
Capitonidae: bearded (72)
Bucconidae: puffs, or sloths (30)
Indicatoridae: honeyguides (11)
Ramphastidae: toucans (37)
Picidae: woodpeckers (210)
Passeriformes: passeriformes
Eurylamidae: hornbeaks, or broadbeaks (14)
Dendrocolaptidae: dart frogs (48)
Furnariidae: stove makers or potter birds (215)
Formicariidae: anteaters (222)
Conopophagidae: caterpillars (10)
Rhinocryptidae: topacolidae (26)
Cotingidae: Cotingidae (90)
Pipridae: manakins (59)
Tyrannidae: tyrant flycatchers (365)
Oxyruncidae: sharp-beaked (1)
Phytotomidae: grass cutters (3)
Pittidae: pittas (23)
Acanthisittidae: New Zealand wrens (4)
Philepittidae: Madagascar Pittas, or Philepittidae (4)
Menuridae: lyre birds, or lyrebirds (2)
Arichornithidae: bushbirds (2)
Alaudidae: larks (75)
Hirundinidae: swallowtails (79)
Campephagidae: larvae (70)
Dicruridae: Drongidae (20)
Oriolidae: Orioles (28)
Corvidae: corvids or crows (102)
Callaeidae: New Zealand starlings or huyas (2)
Grallinidae: magpie-larks (4)
Cracticidae: flute birds (10)
Ptilonorhynchidae: arbor birds, or bowerbirds (18)
Paradisaeidae: birds of paradise (43)
Paridae: tits (65)
Aegithalidae: long-tailed tits
Sittidae: nuthatch (23)
Certhiidae: pikas (17)
Timaliidae: thymeliidae (280)
Chamaeidae: wrens, or American thymelia (1)
Pycnonotidae: Bulbul Thrushes (109)
Chloropseidae: leaflets (14)
Cinclidae: dipper (5)
Troglodytidae: wrens (63)
Mimidae: mockingbirds (30)
Turdidae: thrush (305)
Prunellidae: convoluted (12)
Motacillidae: wagtails (48)
Bombycillidae: waxwings (3)
Ptilogonatidae: silken waxwings (4)
Dulidae: Palm Seed Eaters or Dulidae (1)
Artamidae: swallow shrikes (10)
Vangidae: vangidae (12)
Laniidae: shrikes (72)
Prionopidae: spectacled shrikes (13)
Sturnidae: Starlings
Cyrlaridae: parrot vireos (2)
Vireolaniidae: shrike vireos (3)
Sturnidae: starlings (104)
Meliphagidae: honeyeaters (106)
Nectariniidae: nectarine (104)
Dicaeidae: flower-eating or flower-sucking (54)
Zosteropidae: white-eyed (80)
Vireonidae: vireonidae (37)
Coerebidae: flower-bearers (36)
Drepanididae: Hawaiian flower girls (14)
Parulidae: American warblers or wood warblers or woodcreepers (109)
Ploceidae: weavers (263)
Icteridae: trupialidae (88)
Tersinidae: swallow tanager (1)
Thraupidae: tanagers (196)
Catamblyrhynchidae: plush-headed finches (1)
Fringillidae: finches (425)

Nests play an important role in the reproduction of birds. Feathers are the most skillful architects in the animal world. Their buildings are often used as dwellings by other creatures.

As soon as it got warmer, a pair of long-tailed tits set to work. These birds are one of the most skilled nest builders in Europe. Although they work from morning to night, to complete architectural masterpiece they will take about 18 days. In shape, the nest, woven from twigs, pieces of lichen, a certain amount of feathers, hair, cobwebs, scraps of rope, shreds of fabric, and even petals, resembles a ball or an egg. It is built at the very trunk or in the fork of a branch and is equipped with a hole in the side wall - a let-hole, and inside it is lined with feathers, soft down and hairs.

Comfort Lovers

Remez tits, relatives of the long-tailed tits, are no less skilled builders. They hang their nests on tree branches, often over water. Using dry grass and plant fluff as building materials, such as willow catkins or cattail, remez weave a structure resembling a mitten with a cut off finger.

Only the male is engaged in building a nest near Remez. First, from dry grass, firmly fastened to a branch, he weaves a kind of rope, and then at its end he makes a loop, around which he builds a bag closed on all sides with a narrow entrance. Remez chicks are born and spend their first days of life in this cozy house.

Minimalist Builders

Some birds, on the contrary, are content with unpretentious nests. Many plovers - lapwings, plovers and plovers - nest right on the ground and lay their eggs in shallow holes, sometimes barely covered with grass. Guillemots lay their eggs on bare ledges of rocks, often even slightly inclined, from which the egg, it would seem, should immediately roll down. But this does not happen due to its conical shape: the egg only rolls in a circle, but does not fall. However, the most amazing example of nesting minimalism is the white tern living in the tropics: it lays a single egg right on a tree branch - in some of its forks.

Everything will work

Most geese and ducks build nests on the ground near water. To make the nest cozier, the female usually lines it with feathers and down plucked from her chest. Eiders are especially famous for their soft and warm fluff - ducks nesting in the polar regions. People collect it from nests for sewing quilts and warm down jackets.

Many birds of prey, as well as storks, use the same nest year after year. The nest often serves eagles for several decades and reaches enormous sizes. So, the height of the bald eagle's nest can reach three meters. The plexus of large branches in the nests of storks often attract sparrows and other small birds, which easily attach their simple dwellings to them.

nesting colonies

Many birds nest in colonies. Their nests are incredibly diverse. For example, for emperor penguins, a pocket formed by a fatty fold of the abdomen serves as a nest - it covers the egg, which the male holds on webbed feet, standing in the snow and warming it with the warmth of his body.

The incubation period lasts approximately 64 days. All this time, the selfless dad does not eat anything. In order to lose less heat, males huddle in dense groups, alternately occupying more warm places in the middle.

Many species of weavers living in sub-Saharan Africa also nest in noisy colonies. Birds build their nests on flexible branches that are hard to reach for predators. The nest must be both strong enough to support the weight of the chicks and light enough so that the branch does not break under its weight. Weavers are brilliant at this complex engineering challenge. Building skills have to be learned: young males train on training models of nests. The technology used by weavers is a cross between weaving and weaving. Their nests look like baskets, usually skillfully woven from dry blades of grass. Weavers got their name for a reason: they really know how to “spin” thick threads from plant fibers, and in addition, knit knots, fastening these threads. As a result, the birds manage to build very strong nests - often close to each other, as, for example, in social weavers. Such a "communal" nest looks like a multi-storey building with a huge number of entrances, each of which leads to a separate nest. Sometimes such a structure weighs a whole ton!

Freemasons

Some birds build nests from damp earth or clay, such as swallows, whose nests are often seen under eaves and balconies. Using its beak like a trowel, the swallow lays down lumps of clay layer by layer, building a cup-shaped nest. The entrance located in the upper part of this cup may differ in size in different species. After drying, the nest becomes very durable. pink flamingos mounds are erected from silt with a recess at the top, where the female lays her egg. Nests in flamingo colonies are so close that incubating birds can hardly move. Similar nests are built by gannets nesting on the islands. Salangan swifts living in tropical Asia, nest in huge colonies in coastal caves. Their nests are molded from dried saliva. People eat them. Swallow's nest soup is a popular Asian dish highly valued by gourmets.

A large rocky nuthatch coats large crevices in the rocks with clay or builds a bulky nest from clay against the rock wall.

Even more impressive is the nest of the red stove bug, a small bird from the order of passeriformes living in the pampas of South America. On a thick branch of a tree, a stove-maker builds a massive nest from clay mixed with plant material, similar to an old stove. The nesting chamber is separated from the "hallway" by a partition. The nest weighs up to 5 kg, and the weight of the bird itself does not exceed 75 g.

Individual style

Nests are built by many other animals. A baby mouse weaves a round cradle of grass on the stems of cereals. For construction, she uses living leaves of neighboring plants, so her nest remains greenish and merges with the surrounding grass: it is not easy for predators to notice it.

Small rodents and rabbits make nests of grass and wool in their burrows so that newborn cubs are warmer and more comfortable.

Gorillas and chimpanzees also build nests, but not for breeding, but for recreation. When evening comes, they begin to weave massive platforms from branches and leaves on the ground or lower branches of trees. These monkeys never reuse the same nest.

Skillful architects are also found among the inhabitants underwater world. Some wrasses secrete a large number of mucus, from which they build themselves a "sleeping bag". In it, fish and rest at night. A wrasse hiding in such a cocoon is less visible to predators.