Features of the flight of birds of different species. Flight of bird. Internal structure of birds

It is very curious to watch the flight of a bird. It is especially interesting when you are standing at the stern of a moving vessel, and at this time seagulls are flying after it. Some of them flap their wings quickly, and some calmly and gracefully maneuver in the air currents. What allows them to do such incredible tricks for a person? Let's try to figure it out.

Bird flight principle

How does a bird fly? First of all, you need to understand that there are two ways of a bird's eye flight - flapping and gliding. About each in order:

Planning flight method

To understand the principles of the bird's wing, you will have to recall the school course in aerodynamics. The main postulates of this science are: for the formation of lift under the wing of an aircraft, a significant difference between the air pressure above the wing and under the wing is required. The denser the air under the wing, the faster and higher the plane rises into the sky.

Why are we talking about an airplane? The fact is that a person often constructs his inventions, starting from the world around him. The airplane example perfectly captures the way a bird's wings work. Such a flight is called gliding: the bird simply hovers in the air, using the force of the wind to move in the desired direction. To climb up, the rear surface of the wing is lowered to the ground, and to descend, on the contrary, it is raised. You may have noticed that seagulls fold their wings at the moment of a high-speed fall.

Flapping way of flying

Science is trying to unravel this way of bird flight to this day. It is known that energy efficiency the flight of a bird is ten times the efficiency of any aircraft. How is this possible?

At first glance, it is obvious that the flapping movements of the wings, given their proper position, should move the bird forward. However, scientists have noticed an important detail. From the point of view of physics, the angle of rotation of the bird's wing must constantly change in order to achieve straight flight horizontally - in other words, only forward. Otherwise, we will observe either the movement of the bird towards the ground along an arc (parabolic trajectory), or the same movement upward. However, this in no way describes the actual flight of an ordinary bird! And the angle of rotation of its wing does not change.

For a long time this problem could not find a solution until one curious theory appeared.

According to the creators of the theory, which may become a clue to the balanced flight of a bird, the matter is in the physiological characteristics of the wing. The wing and feathers of the bird are very flexible at the edges. With an active flapping movement, the ends of the feather move in the opposite direction from the main movement. For example, when a wing moves downward, the ends of its feathers move upward. The aerodynamic properties of the wing naturally change, which leads to uniform forward movement along the horizontal. The flexible structure of the wings and feathers allows the bird to fly forward unhindered without falling down or climbing up.

Why doesn't the plane fly like a bird?

Today, science, having realized the peculiarities of the structure of birds, is not yet able to reproduce such a thing. Such engines and materials have not yet been created that would provide a uniform flight by the flapping method. Frankly, this is not necessary. Today's aircraft are very successful in jet-powered flights.

However, research by scientists in this direction does not stop. As we have already noted above, the efficiency of a bird's flight exceeds the same indicator of a technical device many times. This means that by studying the principles of a bird's flight, one can try to reduce the energy consumption of the aircraft and increase its carrying capacity, flight range and other indicators.

For those who are interested in learning more about the peculiarities of bird flight, we recommend that you familiarize yourself.

Bird flight can be divided into two main categories: hover or passive flight and waving or active flight. When soaring, the bird moves in the air long time without flapping the wings and using the ascending air currents, which are formed due to the uneven heating of the earth's surface by the sun. The speed of these air currents determines the flight altitude of the bird.

If the air stream moving upward rises at a speed equal to the speed of the bird falling, then the bird can hover at the same level; if the air rises at a speed exceeding the speed of falling of the bird, then the latter rises up. Using the differences in the speed of the two air streams, the uneven effect of the wind - its strengthening and weakening, changes in the direction of the wind, air pulsations, - a soaring bird can not only stay in the air for hours without spending special efforts but also rise and fall. Terrestrial soaring species, for example, vultures feeding on carrion, etc., usually use only ascending air currents. Soaring marine forms - albatrosses, petrels that feed on small invertebrates and are often forced to descend and rise to the water - usually use the effect of wind action, differences in the speed of air currents, air pulsations and eddies.

For soaring birds characterized by large sizes, long wings, long shoulder and forearm (a large development of the bearing surface of secondary flight feathers, the number of which in vultures reaches 19-20, and in albatrosses even 37), a rather short brush, relatively small heart sizes (since passive flight does not require increased work of the muscles). The wing is sometimes wide (terrestrial species), then narrow (marine species). Flapping flight is more difficult and more varied than hovering. It is worth comparing the flight of a swift, the flight of a raven slowly moving its wings, a kestrel fluttering in the air and a peregrine falcon rushing swiftly at its prey, a fast-flying duck and a pheasant flapping heavily in order to be convinced of the validity of this remark. There are various and rather contradictory attempts to classify different types of flapping flight, which we will not dwell on here.

The bird usually uses more than one type of flight, but combines them depending on the circumstances. It should also be borne in mind that flying movements consist of phases successively replacing one another. The flapping of the wings is followed by phases when the wing does not make rowing movements: this is a gliding flight, or soaring. Such a flight is used mainly by birds of medium and large sizes, with sufficient weight. Small birds usually work vigorously with their wings all the time, or at times can fold their wings, pressing them to the body. The latter is especially characteristic of finch birds. Acceleration in flight is achieved by a bird by increasing the weight load of the bearing surface, for which it is necessary to fold the wings somewhat. A slow-flying bird has a fully extended tail and spread wings. As the movement accelerates, it folds down the flight feathers somewhat, and in all well-flying birds they form a continuous surface (in a falcon, gull, swift, swallow, etc.).

Wind is of great importance for the speed of movement of birds.... Generally speaking, a tailwind or somewhat crosswind is favorable for flight, but a headwind is favorable for take-off and landing. A tailwind during flight increases the bird's flight speed. This increase is quite significant: for example, according to observations of pelicans in California, it was found that an increase in air speed from actual calm to 90 km / h contributed to a change in the flight speed of pelicans from 25 to 40 km / h. However, a strong tailwind requires a lot of effort on the part of the bird to maintain the ability to actively control the flight.

The duration and speed of flight of birds is very great, although exaggerated ideas are usually widespread in this respect. The very phenomenon of migration shows that birds can make long movements. European swallows, for example, overwinter in tropical Africa, and some waders nesting in Northeast Siberia fly to New Zealand and Australia for the winter. The speed and altitude of birds are significant, although they have long been surpassed by modern flying machines. However, the bird's flapping wing gives it many advantages, primarily in maneuverability, over modern aircraft.

Modern technical means(observations from aircraft, high-speed shooting, radars, etc.) made it possible to more accurately determine the flight speed of birds. It turned out that, on average, birds use higher speeds when migrating than when moving outside the migration season. Rooks travel at a speed of 65 km / h on flights. The average speed of their flight outside the time of migration - during the nesting period and during wintering - is approximately 48 km / h. On migrations, starlings fly at a speed of 70-80 km / h, at other times 45-48 km / h. According to observations from airplanes, it was found that the average speed of movement of birds during flights fluctuates between 50 and 90 km / h. So, gray cranes, herring gulls, large sea gulls fly at a speed of 50 km / h, finches, siskins - 55 km / h, killer whales - 55-60 km / h, wild geese (various species) - 70-90 km / hour, sviyazi - 75-85 km / h, waders (various species) - on average about 90 km / h. The highest speed was noted for the black swift - 110-150 km / h. These figures refer to the most intense spring migrations and are likely to reflect the highest bird speeds. Autumn migrations proceed much more slowly, for example, the flight speeds of storks on autumn migrations are hardly half the speed of their spring movement.

The question of the flight altitude of birds remained unclear for a long time. The old idea that the movement of birds takes place, as a rule, at high altitudes (500-1600 m above sea level), raised doubts. However, astronomical observations have shown that, in all likelihood, the maximum flight altitude of birds reaches 2000 and even 3000 m. To some extent, this was confirmed by the use of radars. It turned out that flights in spring occur at higher altitudes than in autumn, that birds fly at higher altitudes at night than during the day. Sparrow birds, for example, finches, fly at altitudes somewhat less than 1500 m; larger passerines, such as thrushes, are at an altitude of 2000-2500 m. Sandpipers fly at an altitude of about 1500 m. Although flight is the main and most characteristic mode of movement of birds, other very diverse modes of movement are characteristic of them.

The well-known divisions of birds into aquatic, terrestrial, and arboreal indicate the well-known differences between these groups in relation to movement.

Consider a horizontal air flow relative to the inclined surface of the wing in the case when its leading edge is raised above the trailing edge. In this sense, the wing acts as a load-bearing plane. The air flow over the wing meets less resistance and develops a higher speed than under the wing (Fig. 17.52). As a result, the air pressure above the wing decreases and under the wing increases. This is how lift... Its value depends on the size and shape of the wing, its angle of inclination in relation to the long axis of the body (angle of attack) and flight speed. In the air, another force acts on the bird's body, which seeks to pull the wing back in the direction of the air flow; it is called frontal, or aerodynamic drag... The mechanical efficiency of a wing depends on its ability to develop high lift with a small relative increase in drag.

There are three main types of flight: flapping, hovering (gliding) and hovering.

Flapping flight

In birds such as the pigeon, whose wings do about two beats per second, the main power is developed when the wings are lowered. This is due to the reduction of highly developed large pectoral muscles, which are attached at one end to the humerus, and the other to the keel of the sternum. When taking off from the ground, the wing at the beginning of the swing descends almost vertically and its leading edge is located below the trailing edge. Flight feathers of the 1st order are deflected upwards under air pressure. They are tightly coupled to provide maximum air resistance and therefore maximum lift. Then, as it descends, the wing moves forward and rotates so that its leading edge deflects upward. In this position, the wing creates a force that lifts the body. The air passing between the flight feathers tends to separate them and bend upward (Fig. 17.53).

Wing lift begins when the wing is not fully lowered yet. The inner part of the forearm rises sharply up and back, with the leading edge of the wing tilted over the rear. This is done by the pectoralis minor muscles attached to the dorsal surface of the humerus and to the sternum. When the wing moves upward, it bends at the wrist and the hand turns in such a way that the first-order flight feathers are abruptly retracted back and upward until the entire wing is to some extent straightened over the bird's body. During this movement, the 1st order flywheels are disconnected, so that air passes between them and its resistance decreases. Backward movement of these feathers mainly creates a powerful push, which the bird uses to move forward. Even before the first order flywheels rise to the highest point, the pectoralis major muscles, lowering the wings, begin to contract again, and the whole process is repeated.

With prolonged flapping flight, the work of the wings is noticeably modified and requires much less energy than when taking off from the ground. At the same time, the sweeps are not so strong, the wings do not touch behind the back, and there is no forward movement on final stage lowering the wings. The wings are usually extended, and the up and down swing occurs at the wrist (the junction of the bones of the forearm and wrist). There is no active abduction of the hand up and back - the wing rises passively as a result of air pressure on its lower surface.

At the end of the flight, the bird lands, lowering and spreading its tail, which simultaneously serves as a brake and a source of lift. After this force is created, the legs are lowered and the bird stops moving. The tail in flight also serves as a rudder, and the stability of the bird is provided by nervous control with the participation of the semicircular canals. They generate impulses that stimulate the accessory muscles that change the shape and position of the wings and the relationship between their flaps.

Different birds fly at different speeds. These differences are due to the shape of the wings and its changes in flight, as well as the frequency of flaps. Rice. 17.54 allows you to compare the wings of fast flyers (such as swifts) and slow ones (like sparrows).

17.9. List characteristics swift, allowing him to fly quickly.

Planning and soaring flight

When gliding, the wings are motionlessly spread at an angle of 90 ° relative to the body, and the bird gradually loses height. When the bird, gliding, descends, gravity acts on it, which can be decomposed into two components, one of which (thrust) is directed forward along the flight line, and the other downward at right angles to the first (Fig. 17.55). As the gliding speed increases, this second force is balanced by the increasing lift, and the thrust is balanced by the drag, and from that moment the bird glides at a constant speed. The speed and angle of glide depend on the size, shape and angle of attack of the wings and on the weight of the bird.

Birds that live on land use thermal ascending air currents when planning, which occur when a horizontal stream, encountering an obstacle (for example, a mountain), deviates upward or when warm air is displaced by cold air and rises up; this happens, for example, over cities. Birds with light bodies and wide wings, such as buzzards and eagles, are adept at using thermal streams and can gradually gain altitude in small circles. Gliding without losing altitude and even climbing is called hovering.

Have seabirds, for example, albatrosses, the shape of the body and wings is different, and they soar in a different way (Fig. 17.56). The albatross has a large body and very long narrow wings, and uses the gusts of wind above the waves. While sliding upwind, it rises to a height of about 7-10 meters. Then it turns in the wind and descends downward with great speed on the wings bent back. At the end of the downward slide, the albatross makes an arc, returning to the oncoming air flow with its wings extended somewhat forward. This position of the wings and the rapid forward movement in relation to the air provide the lift necessary to climb before the next descent. The albatross is also capable of soaring, covering long distances parallel to the crests of waves; he uses small upstreams air from the waves, just as land birds use currents over mountain slopes.

Hovering flight

When hovering, the bird flaps its wings, but at the same time remains in one place. The wings perform about 50 strokes per second, and the upward thrust they develop balances the body's weight. Birds capable of hovering have highly developed flying muscles (1/3 of body weight). Their wings can tilt at almost any angle. Most of the flight feathers are 1st order (there are only six 2nd order flight feathers), and they are used to create thrust.

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Conquerors of the air

Flight of bird

The flight of a bird is usually compared to the flight of an airplane. This comparison can only be made up to certain limits, since there are many differences in the flight of vehicles with flapping and fixed wings. Why does a bird, which is much heavier than air, still get off the ground? As in the case of an airplane, this is due to the generation of aerodynamic forces during forward motion. There are two of these forces: frontal resistance, which seeks to delay the forward movement, and lift, which lifts the wing, and with it the body of the bird. To trace the emergence of these forces, let us consider the phenomenon in more detail.

Take a flat plate and move it in the air (Fig. 7). Then the traction force and the force of air resistance will act on it. The latter will increase in proportion to the area of ​​the plate and the square of the speed of movement. When the plate is tilted (Fig. 8), it seems to throw the air that meets it on the way down, and itself tends to rise up. The reaction of the air is called the impedance force. On the one hand, it prevents the plate from moving forward (drag), and on the other hand, lifts it up (lift). The angle between the horizontal direction and the tilt of the plate is called the angle of attack.

We now have an almost finished wing model. It remains only to change its shape. Let it be a convex-concave plate, the front end of which is rounded and thickened, and the back end disappears. It resembles the profile of a bird's wing (Fig. 9).


Its advantage is that even at a zero angle of attack, that is, when moving forward parallel to its chord ab, lift still arises, which is impossible in the case of a plate. When it meets the wing, the air changes its speed, it increases above the convex surface of the wing, and a smaller number of air particles get under the wing, and their movement is slowed down here. Air pressure is inversely proportional to its speed of movement. Therefore, it is increased under the wing, and decreased above the wing. The thickening of the jets and their greatest speed are at the front, thickened part of the wing. The wing has maximum lift at angles of attack of 16-24 °. These are the critical angles of attack.

Lift arises mainly between the torso and the wrist fold, and the wing hand itself, carrying long flight feathers, twists slightly during flight, as if screwed into the air and creates thrust. Thus, the main difference between a bird and an airplane is that the bird's wing combines the functions of both the propeller of the airplane and its bearing planes, which create lift. Together they form a highly complex aerodynamic complex with many variable characteristics that are extremely difficult to study and model. Without going into details, let us point out that the idea that a bird gets a push upward, dropping its wings down, and raising the wing causes the bird to descend, is completely wrong. Therefore, birds do not have devices that reduce air resistance when raising the wing. Both when the wing is raised and when it is lowered, there is a force that opposes the force of gravity. But the thrust arises only when the wing is lowered, and even then only in its end part: it balances the drag acting during the flapping.



Those who wish to understand in more detail the mechanism of flight, we refer to the book by N. A. Gladkov "Biological Foundations of the Flight of Birds" (Moscow, 1949). The source of energy for flight lies in the musculature of the bird, and the job is to overcome the force of gravity. With fixed wings, the energy source lies outside the bird - in the movement of air masses.

Birds... The wing should be considered the most important morphological adaptation to the air environment.

Wing- This is the bearing plane, which is formed by the flight feathers. On the fingers and wrists there are 11 first-order flight feathers, and on the forearm there are 12 second-order flight feathers. The base of the flight feathers is a rigid rod, to which the barbs that make up the fan are attached symmetrically on both sides.

In order for the wing to generate lift, the bird must pick up the starting speed. Then the air flow is distributed relative to the plane of the wing in such a way that an increased air pressure is created under the wing. Above the upper surface of the wing, air moves faster, resulting in a relative vacuum. There is a lifting force, which the bird manipulates by changing the angle of attack, wing area, braking by tail feathers.

The speed of movement in the air is maintained in various ways. Different birds develop different speeds in the air. It depends on the size and shape of the wing, the ability of the bird to change the shape of the wing during flight, on the frequency of wing flaps, as well as on the ability of the bird to use the energy of the air currents. It is customary to distinguish several types of flight: flapping, gliding (soaring), hovering.

Flapping flight suggests that the bird has short and moderately wide wings and well-developed pectoral muscles, as, for example, in a pigeon. The mass of the pectoral muscles can reach 30-40% of the body weight. The frequency of wing beats in a pigeon is approximately 2 beats in 1 second, in more large birds it is less common. Birds use the tail and partly the wings as a brake.

In the organization of the flight important role the plumage of a bird is playing. It gives the body a streamline, absorbs the influence of air currents. When pushing, the flight feathers close due to the adhesion of the hooks and grooves and form a relatively rigid bearing plane of the wing. When the wing is raised, the feathers open, as a result of which the air resistance is sharply reduced. When landing, the bird stops flapping its wings, keeping them at the required angle.

In the final part, tail tail feathers and wing flight feathers are used as a brake, which unfold with a ventral surface almost perpendicular to the direction of travel.

Planning flight... During a gliding flight, birds use the energy of the movement of air currents. Birds have a large wing area, either due to their length (frigate), or due to their length and width (eagles). When gliding the bird, the wing takes on its maximum length and is set within the plane of motion at an angle of 90 ° with respect to the longitudinal axis of the body. When gliding, the birds move without losing height or even gain height when minimum costs energy. Vaping reduction is also possible without additional energy consumption due to the descending air currents.

Birds such as eagles, kites and, to a lesser extent, crows, use the energy of ascending and descending air currents when planning. The surface of the earth warms up and cools unevenly. Warmer air is displaced by cold air, as a result of which there is a vertical movement of air masses. In addition, air movement also occurs in the horizontal plane. In mountainous areas, horizontally moving air currents hit an obstacle (mountainside) and rise up.

In seabirds (albatrosses, frigates), the flight is somewhat different from the gliding flight of birds living on land.

They have long and narrow wings (in a frigate and albatross up to 4 m) with a rather large body. Birds take advantage of the gusts of wind that arise over the waves. Using oncoming air currents, birds gain height. They then turn 180 ° and glide downwind at high speed on the backward wings, losing altitude. This is followed by a turn in a wide arc with the wings extended forward towards the air flow. Similar maneuvers are available to land birds. But the albatross periodically hovers above the waves due to the air currents rising from the surface of the water, just as land birds do.

Hovering flight... This type of movement in the air seems to be the most energy intensive. To stay in place and not lose height, the birds must simultaneously create a lot of lift and brake linear advancement with braking. In hovering flight, birds perform wing flaps with a high frequency (about 50 flaps per second). In such birds (kestrel, hummingbird), the muscles that move the wing have a very large mass. Only the pectoral muscles can have a mass that is 1/3 of the total body weight. The thrust is created lung work and a very mobile wing, which is dominated by long and relatively rigid primary flight feathers of the 1st order. Flight feathers of the 2nd order in birds using hovering flight are not 12, but only 6.

Mammals... Locomotion in the air in mammals is a rare phenomenon. Most adapted to flight the bats... These animals move uncertainly on the ground (more precisely, along the vertical surfaces of trees, caves), but masterfully move in airspace. Separate types(for example, a long-winged) develop a speed of up to 35-40 km / h in flight over short distances.

Bats, or bats (Chiroptera), have a large flying membrane. It is a fold of skin between the forelimbs, trunk and hind limbs, and between the toes of the forelimbs, trunk and tail. The hypertrophied pectoral muscles and forelimbs set in motion the flying membrane. Among bats, depending on the structure of the flying membranes, sharp-winged, long-winged, broad-winged and blunt-winged bats are distinguished. The biomechanics of movements of bats in the air does not fundamentally differ from that of birds.

In bats, the same three types of flight can be observed as in birds: flapping, hovering (fluttering) and gliding.

In addition to bats, locomotion in the air is available to flying squirrels, monkeys, and some other small arboreal animals. Among the squirrels that use air for linear movement, the most famous are the northern flying squirrel and the giant flying squirrel. The latter, despite its considerable size (body length 40-50 cm, tail length - up to 60 cm), although it is not really capable of flying, nevertheless, due to planning, covers distances of up to 500 m.In this case, the squirrel moves from one high wood to another. Due to such locomotion, the rodent avoids dangerous neighbors on the ground and changes forage lands without going down to the ground. From the heels to the wrists of flying squirrels, wide membranes stretch along the body, which, when jumping, create a load-bearing plane with a rather large surface.

The northern flying squirrel is smaller. The length of its body does not exceed 25 cm, the tail is 18 cm. However, this squirrel can easily fly from tree to tree at a low speed of about 100 m / min. Despite the fact that such a flight is passive, nevertheless, it allows proteins to solve vital problems: to escape from predators, find sexual partners and develop new food resources.

Fishes... The flight of fish is even rarer than the flight of mammals. However, its effectiveness can be comparable to the flight of birds.

Fish use their pectoral fins for gliding in the air. Thus, flying fish, when frightened, due to the throwing movement of the trunk muscles, muscles of the caudal peduncle and intensive work with the lower blade of the caudal fin, jump out of the water and fly distances in the air, allowing them to get rid of their pursuers.

On the surface of the water, a flying fish works with its tail for a rather long time, developing a large thrust, which allows it to overcome the force of gravity. The flight speed of these small fish exceeds the speed of the pursuers (tuna, swordfish), and the distances they fly reach several hundred meters.

Other types of fish, such as fingerwings, can not only hover, but also perform complex maneuvers in the air. The finger wing rises to the surface of the water and glides along it at a speed of 18 m / s. Such high speed the fish acquires due to the zigzag movements of the caudal fin with a hypertrophied lower lobe.

The flight speed of the finger wing is comparable to the speed of movement of modern sea ​​vessels and often is 60-70 km / h. A strong blow of the tail lifts the fish into the air to a height of 5-7 m. The finger wing flies in the air up to 200 m, using the air currents. The fish is able, if necessary, to change the direction of flight due to the movements of the caudal fin. She also showed oscillatory movements of the pectoral fins.

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