A device for terrain orientation in birds. Birds and sky

For a bird to navigate well in space is, first of all, to have reliable information about the surrounding environment. After all, its changes in some cases can turn out to be fatal for the bird, in others, on the contrary, favorable, but it needs to know about both of them in a timely manner. The behavior of the animal will depend on how its senses perceive these changes and how the higher “organ” of orientation—the brain—evaluates them.

It is clear that success in the struggle for existence will accompany the individual whose senses and brain quickly assess the situation and whose response is not long in coming. That is why, when talking about the orientation of animals in space, we must keep in mind all three of its components (landmark stimulus, perceptive apparatus, response).

Despite the fact that in the process of evolution all these components form a certain balanced system, not all landmarks are perceived, since the “throughput” of the senses is very limited.

Thus, birds perceive sounds with a frequency of up to 29,000 Hz, while bats up to 150,000 Hz, and insects even higher - up to 250,000 Hz. Although from a physical point of view the bird’s hearing apparatus in the air is very perfect, in water it fails, and the sound wave travels to the auditory cell along a long and “inconvenient” path - through the entire body, while the eardrum and auditory canal are completely blocked. How would underwater hearing help fish-eating birds!

It is known that dolphins, using their hearing, can accurately determine the type of fish, its size, and its location. For them, hearing completely replaces vision, especially since the capabilities of the latter are even more limited: the visible space, for example, for a kestrel and a barn owl is 160°, for pigeons and passerines - about 300°, for woodpeckers. up to 200°, etc.

And the angle of binocular vision, that is, vision with two eyes, which makes it possible to particularly accurately examine an object, is 30-40° in most birds, and only in owls with their characteristic “face” - up to 60°. Birds have even fewer opportunities for smell - the direction of the wind, dense thickets, and other obstacles make it very difficult to navigate by smells. Even Urubu vultures, descending to carrion from a great height, guided by a thin stream of scent rising to the top, cannot always use this type of orientation.

Thus, the orientation abilities of each individual individual are very limited. Meanwhile, for birds, with their open lifestyle, surrounded by a mass of enemies and other “everyday” troubles, reliable orientation is a matter of life and death. And insufficient individual capabilities are corrected through communication with other individuals, in a flock, in a nesting colony. Every hunter knows that it is much easier to get close to a single bird than to a flock that has many ears and eyes and the warning cry or takeoff of one individual will alarm everyone else.

Various calls, poses, and bright spots in color ensure the joint behavior of birds in a flock and the connection between them. A kind of group, secondary orientation is created, where the ability to navigate and the individual experience of one bird increases significantly at the expense of others. Here it is no longer necessary to see the predator itself; it is enough to hear the warning cry of a neighbor. Of course, the neighbor does not scream because he “wants” to warn others: it is a natural reaction to the enemy, but other birds perceive this scream precisely as a signal of danger.

The matter becomes even more complicated and the capabilities of one individual increase even more when a connection is established between birds of different species within a community. For example, the cry of a small bird “at an owl” gathers a very diverse society in the forest: tits, warblers, nuthatches, finches, crows, jays, even small predators. Exactly the same “understanding” is established between waders, gulls and crows on the sea shallows, between various blackbirds, etc. In the forest, the role of signaller is played by the magpie, whose cry, for example, when a large predator or person approaches, is perceived not only by a variety of birds, but and mammals. Here group orientation goes even further.

Vision, hearing and smell are the main “building blocks” that make up the overall building of spatial orientation. Birds have no equal in visual acuity. The amazing abilities of various predators in this regard are well known. The peregrine falcon sees small birds at a distance of over a kilometer. Most small passerines have visual acuity several times greater than human visual acuity. Even pigeons distinguish two lines running at an angle of 29°, whereas for humans this angle should be at least 50°.

Birds have color vision. You can, for example, teach chickens to peck red grains and not peck blue ones, or to run in the direction of a red screen and not run up to a blue one, etc. This is indirectly proven by the amazing variety of colors of birds, represented not only by all the colors of the spectrum, but also by the most diverse of them. combinations. Coloration plays a large role in the cooperative behavior of birds and is used as a signal in communication.

Finally, we can add that recent experiments by Polish researchers seem to have confirmed the ability of birds to perceive the infrared part of the spectrum and, therefore, see in the dark. If this is so, then the still mysterious ability of birds to live in the dark or in twilight lighting will become clear. In addition to owls, other birds are apparently capable of this: during the long polar night, ptarmigan and tundra partridge, raven, gyrfalcon, redpoll, snow bunting, and various guillemots remain for the winter in the Arctic.

These visual features of birds are provided by the remarkable anatomical structure of their eyes. First of all, birds have relatively huge eyeballs, which in owls and falcons amount to, for example, about Vso body weight, in a woodpecker g/bb” in a magpie 1/?2. The bird's eye has a large number of sensory cone cells, necessary for sharp vision, equipped with red, orange, green or blue oil globules.

It is believed that the oil balls enable the bird to distinguish colors. Another feature of a bird's eye is its fast and precise adjustment - accommodation. This is accomplished by changing the curvature of the lens and cornea. Fast accommodation allows, for example, a falcon striking a flock of ducks from a great height to clearly see the bird and correctly estimate the distance at any moment of its throw. Steppe birds have a special strip of sensory cells in the retina of their eyes, which allows them to view the horizon and distant objects especially clearly and at a great distance. The eyes of cormorants, auks, ducks, and loons that hunt fish underwater have special devices that provide underwater vision.

The sense of smell in birds still remains little studied and very mysterious. For a long time it was believed that birds have a poor sense of smell. however, new experiments say otherwise. Songbirds, ducks, and some chickens distinguish odors, for example, clove and rose oils, amyl acetate, and benzaldehyde. The ducks found a box of food based on a special smell and, from a distance of 1.5 meters, headed straight towards it. Urubu vultures, some nightjars, petrels, and gulls have a good sense of smell.

Albatrosses gather for lard thrown into the water from a distance of tens of kilometers. Hunters know of cases where crows found pieces of meat buried in the snow. Nutcrackers and jaybirds quite accurately search for odorous pieces of food hidden in the litter in the enclosure, apparently also guided solely by their sense of smell.

Birds, in general, have a mediocrely developed taste and only in certain groups, such as granivorous birds, raptors and noble ducks, does it achieve some development.

A large number of nerve endings in the form of tactile bodies are located in the skin of birds, at the base of feathers, and in the bones of the limbs. With their help, a bird can determine, for example, the pressure of air jets, wind strength, temperature, etc. These nerve endings are very diverse in structure and function, and there is an opinion that it is among them that one should look for the still unknown organs of perception of electric and magnetic fields etc.

A large number of tactile bodies are located at the tip of the beak of snipe, woodcock and other waders that obtain food by probing wet earth, mud and mud. In lamellar beaks, such as the mallard, the tip of the beak is also covered with sensitive bodies, which is why the maxillary bone, like that of the woodcock, looks completely cellular.

Perceiving an inherently unified environment in the form of individual stimuli and landmarks, the organs of spatial orientation isolate only some qualities of objects. At the same time, the space in which these landmarks are located is also not unlimitedly analyzed. Some landmarks are perceived at long distances and have a maximum “range”, such as sound, while others act in close proximity, upon contact, such as the tactile corpuscles of the beak.

The effect of the smell of carrion for vultures soaring in the air is limited to a narrow stream of rising air. All sense organs, therefore, have their own spatially limited spheres of action, within which the analysis of objects and landmarks is carried out.

The spheres of action of the sense organs have their own biologically justified orientation. In cases where we are talking about particularly critical situations in the life of a species, for example, about catching prey or avoiding danger, one sense organ, say vision, hearing or smell, is not enough, so several sense organs act together. The spheres overlap.

Steppe birds have a special strip of sensory cells in the retina of their eyes, which allows them to see especially clearly at a great distance.

Thus, in owls and harriers, the existence of which depends on how accurately they determine the location of the mouse, and the action often takes place in dense thickets or with limited visibility, the fields of vision and hearing have a general, forward orientation. The “face” formed as a result of the anterior contraction of the eyes and ears is a very characteristic feature of both owls and harriers.

The work of the brain is primarily associated with higher forms of orientation, the so-called “homing” (return to the nesting site of artificially removed birds), orientation during seasonal flights, weather forecasting, counting, etc.
An open, active lifestyle, a constant alternation of various landmarks, and the need for communication developed in birds “the rudiments of rational activity and the ability for elementary abstractions.

If you sneak up on crows feeding in the field and at the same time lower yourself into a ravine for camouflage, then the birds will wait for you at the other end of the ravine, where you should find yourself, maintaining the original direction of movement. A flock of geese or cranes watching a fox creeping up on them will do the same thing.

However, assessing the direction of movement of a landmark, partly extrapolating it, is no less important in complex forms of orientation than the ability to quantify landmarks.

In experiments, it was possible to teach chickens to peck any grain of their choice - the second, third, etc., and pigeons to distinguish between different combinations of grains. Magpies and crows distinguish well between different sets of objects, for example, the number of people and animals. Birds, for example, can distinguish 5 objects from 6 without counting - a task that is not always accessible even to humans. Special experiments have also shown that birds can clearly distinguish the contours and shapes of objects, geometric figures, etc.

These abilities play a particularly important role in celestial navigation of birds - using celestial bodies as landmarks.

The warblers were placed in a planetarium and the direction of their flight was monitored at different positions of the starry sky. Thus, it was possible to prove that the general picture of the starry sky can be used as a guide during seasonal flights. It is not difficult to imagine the difficulties that a bird faces: the need to extrapolate the movements of stars, precisely, up to 15-20 minutes. Seagulls have a good sense of smell; broody.

From this point of view, orientation is somewhat simpler during daylight hours, according to the sun. But here, the bird faces the need to estimate the angular displacement of the sun and have a very accurate “internal clock”. This is still simpler than using a reference point such as stars, and perhaps that is why this point of view has more adherents and is less controversial. There are attempts to explain the nocturnal flights of birds using solar orientation: at night, birds fly in the direction they chose during the day in the light of the sun.

In addition to these general “universal” guidelines, other, local ones can be of great importance. Where there are constant winds, birds can use the direction of the wind. The direction of mountain ranges, river beds, sea coasts - even wave crests can also play the role of such landmarks.

Despite the two-century history of studying bird migration, the question is far from clear even today. Attempts to explain orientation during flights using only one reference point: Coriolis forces have failed. arising from the rotation of the earth, magnetic or electric fields, etc. Experimental testing of them showed conflicting results, apparently due to the fact that during flights a set of landmarks is used, and not just one landmark. In essence, the search for an “organ of orientation” turned out to be useless.

The brain plays a decisive role in the final assessment of the situation, and the solution to the “mechanism” of orientation during flights lies in the study of the brain activity of birds.

A completely special, no less interesting category of phenomena is “homing” - the return to “home” of artificially removed birds. Forty years ago, experiments with terns showed that, 1200 kilometers away from their nesting sites, they return back after a few days. Swallows, starlings, shrikes, whirligigs and other birds have also discovered this ability. The petrel returned in 14 days from Venice, where it was introduced, to its nest in Scotland, covering 6,000 kilometers. The white-bellied swift returned from Lisbon to Switzerland within three days.

The mechanisms of homing are also unclear at present. So far we can say that in this case, apparently, local landmarks are used to a greater extent, and probably a whole complex of them. Of particular importance are extrapolation and the ability to quantify phenomena, the internal clock and such an important property of brain activity as memory.

“The spatial orientation of birds is an extremely interesting question at all levels of orientation, from the simplest to the most complex. It is gaining great importance now in connection with bionics and the problem of controlling animal behavior.

Bionics is interested in the means and ways of visual, auditory and other types of orientation, the work of auxiliary structures that de-energize the best reception and processing of signals, and the assessment of final information in brain centers. Birds are especially attractive to bionics because of their miniature size, high reliability and performance, wide range of action, cost-effectiveness and other qualities of their sense organs, which are far superior to anything that modern technology has.

By creating artificial landmarks, a person evokes the necessary motor reactions in animals in natural conditions. In some cases, in this way it is possible to attract many animals to a limited area, in others, on the contrary, to disperse them and scare them away from places where they are undesirable.

Currently, there is an energetic search for such means of controlling the behavior of animals and, in particular, birds. Acoustic, optical and olfactory landmarks have already been found, some of which are used in practice. Hunting and fishing, fighting harmful insects, protecting people from bloodsuckers - this is not a complete list of industries where they can be used. Finally, this opens up the possibility of intelligent, rational regulation of natural populations.

Have you ever wondered how birds find the right path, crossing vast oceans and vast deserts during their flights and migrations (read more about)? What guidelines do they use, what senses are they guided by? Hunters often ask these questions, and our publication today is ready to answer this question...

The importance of the ability to navigate in space for birds

For a bird to navigate well in space means, first of all, to have reliable information about their surroundings. After all, its changes in some cases can turn out to be fatal for the bird, in others - on the contrary, favorable, but it needs to know about both of them in a timely manner. The behavior of the animal will depend on how its senses perceive these changes and how their higher organ of orientation, the brain, evaluates them. It is clear that success in the struggle for existence will accompany the individual whose senses and brain quickly assess the situation and whose response is not long in coming. That is why, when talking about the orientation of animals in space, we must keep in mind all 3 of its components - reference stimulus, perceiving apparatus, and response.

Despite the fact that in the process of evolution all these components formed into a certain balanced system, not all landmarks are perceived by birds, since the capacity of their sense organs is very limited.

Thus, birds perceive sounds with a frequency of up to 29,000 Hz, while bats - up to 150,000 Hz, and insects - even higher - up to 250,000 Hz. Although, from a physical point of view, the bird's hearing aid is very perfect in air, it fails in water, and the sound wave travels to the auditory cell in an inconvenient way - through the entire body, while the eardrum and ear canal are completely blocked. Oh, how underwater hearing would help fish-eating birds! It is known that dolphins, using their hearing, can accurately determine the type of fish, its size, and its location. For them, hearing completely replaces vision, especially since the capabilities of the latter are even more limited - the visible space, for example, for a kestrel and a barn owl, is 160 degrees, for pigeons and passerines - about 300 degrees, for woodpeckers - up to 200 degrees. And, the angle of binocular vision, that is, vision with two eyes, which allows you to especially accurately examine an object, is 30-40 degrees in most birds, and only in owls, with their characteristic face, up to 60 degrees.

Birds have even less ability to smell - the direction of the wind, dense thickets and other obstacles make it very difficult to navigate by smells. Even Urubu vultures, descending to carrion from a great height, are guided by a thin stream of scent that has risen upward, and they are not always able to use this type of orientation.

The lack of necessary sense organs leads to the fact that many of the natural phenomena, such as landmarks, are not used by birds or are not used enough. Experimental data and individual field observations give a very contradictory picture. In certain situations, for example, the orientation of birds is influenced by powerful radio stations, however, this does not always happen and not in all cases. Birds certainly perceive changes in pressure, but how subtly the pressure gradient can be used as a guide is completely unclear. Thus, the orientation abilities of each individual individual are very limited. Meanwhile, for birds, with their open lifestyle, surrounded by a mass of enemies and other everyday troubles, reliable orientation is a matter of life and death. And, often, their insufficient individual capabilities are corrected through communication with other individuals, in a flock, in a nesting colony.

Every hunter knows that it is much easier to get close to a single bird than to a flock that has many ears and eyes, and where the warning cry or takeoff of one individual can alarm the rest. Various calls, poses, and bright spots in color provide birds with joint behavior in a flock and communication between them. A sort of group, secondary orientation is created, where the ability to navigate and the individual experience of one bird is significantly increased at the expense of other birds. Here it is no longer necessary to see the predator itself; it is enough to hear the warning cry of a neighbor. Of course, the neighbor does not scream because he wants to warn other birds - this is his natural reaction to the enemy, however, other birds perceive this scream precisely as a signal of danger.

Group or secondary orientation in birds

The matter becomes even more complicated and the capabilities of one individual increase even more when a connection is established between birds of different species within a community. For example, the cry of a small bird at an owl gathers a very diverse society in the forest - tits, warblers, nuthatches, finches, crows, jays and even small predators. Exactly the same understanding is established between waders, gulls and crows on the sea shallows, between various thrushes, etc. In the forest, the role of signaller is played by the magpie - whose cry, for example, when a large predator or person approaches, is perceived not only by a wide variety of birds, but also by mammals. Here group orientation goes even further.

Basic factors of birds for orientation in space

Vision as a way of orientation in space

Birds have no equal in visual acuity. The amazing abilities of various predators in this regard are well known. The peregrine falcon sees small birds at a distance of over a kilometer. Most small passerines have visual acuity several times greater than human visual acuity. Even pigeons distinguish 2 lines at an angle of 29 degrees, while for humans this angle should be at least 50 degrees.

In addition, birds have color vision. You can, for example, teach chickens to peck red grains and not peck blue or white ones, run towards the blue screen in the direction of the red screen, etc. This is indirectly proven by the amazing variety of colors of birds, represented not only by all the colors of the spectrum, but also by the most diverse combinations of them. Coloring plays a big role in the joint behavior of birds and is used by them as a signal when communicating. Finally, we can add that recent experiments by Polish researchers have confirmed the ability of birds to perceive the infrared part of the spectrum, and therefore to see in the dark. If this is indeed the case, then the mysterious ability of birds to live in the dark or in twilight light becomes clear. In addition to owls, other birds are apparently capable of this - in the conditions of the long Polar night, ptarmigan and tundra partridge, raven, gyrfalcon, redpoll, snow bunting, and various guillemots remain for the winter in the Arctic.

These visual features of birds are provided by the remarkable anatomical structure of their eyes. First of all, birds have relatively huge eyeballs, which in owls and falcons are, for example, about 1/30 of their body weight, in a woodpecker - 1/66, in a magpie - 1/72. The bird's eye has a large number of sensory cone cells, necessary for sharp vision, equipped with red, orange, green, or blue oil globules. Experts believe that the oil balls enable the bird to distinguish colors.

Another feature of the bird's eye is its fast and precise adjustment - accommodation. This is accomplished by changing the curvature of the lens and cornea. Fast accommodation allows, for example, a falcon striking a flock of ducks from a great height to clearly see the birds and correctly assess the distance at any moment of its throw. Steppe birds also have a special plane of sensitive cells in the retina of their eyes, which allows them to view the horizon and distant objects especially clearly and at a great distance. The eyes of cormorants, auks, ducks (o), loons hunting for fish under water have special devices that provide underwater vision to birds.

The good vision of birds of prey is used in.

Olfaction as a way of orientation in space

The sense of smell in birds still remains little studied and very mysterious. For a long time it was believed that birds have a poor sense of smell, but new experiments suggest otherwise. Songbirds, ducks, and some chickens can distinguish odors well, for example, clove oil, rose oil, benzaldehyde...

Ducks are able to find a box of food by a special smell from a distance of 1.5 meters and go straight to it. Urubu vultures, some nightjars, petrels, and gulls have a good sense of smell. Albatrosses gather for lard thrown into the water from a distance of 10 kilometers. Hunters also know of cases where crows found pieces of meat buried in the snow. Nutcrackers and jaybirds quite accurately find pieces of food hidden in the litter in the enclosure, guided solely by their sense of smell.

Taste as a way of orientation in space

Birds, in general, have a mediocrely developed taste, and only in certain groups, such as granivorous birds, raptors and noble ducks, does it achieve some development.

Touch as a way of orientation in space

A large number of nerve endings in the form of tactile bodies are located in the skin of birds, at the base of feathers, and in the bones of the limbs. With their help, the bird can determine, for example, air pressure, wind strength and air temperature. These nerve endings are very diverse in structure and function, and there is an opinion that it is among them that one should look for the still unknown organs of perception of electric and magnetic fields.
A large number of tactile bodies are located at the tip of the beak of snipe, woodcock and other shorebirds that obtain food by probing wet soil, mud and mud. In lamellar beaks, for example, the mallard, the tip of the beak is also covered with sensitive bodies, which is why the maxillary bone, like that of the woodcock, looks completely cellular.

Perceiving an inherently unified environment in the form of individual stimuli and landmarks, the bird’s spatial orientation organs isolate only some of the qualities of the object. At the same time, the space in which these landmarks are located is also not unlimitedly analyzed by them. Individual landmarks are perceived at long distances and have maximum range, such as sound. Others act in close proximity, upon contact, as tactile corpuscles of the beak. The effect of the smell of carrion for vultures soaring in the air is limited to a narrow stream of rising air. All sense organs, therefore, have their own spatially limited spheres of action, within which the analysis of objects and landmarks is carried out.

The spheres of action of the sense organs have their own biologically justified orientation. In cases where we are talking about particularly critical situations in the life of a species, for example, about catching prey or avoiding danger, one sense organ, for example, vision, hearing or smell, is not enough, therefore, several sense organs act together. The spheres of their action are layered, and the object found within them is analyzed and will be perceived more comprehensively and accurately.

Thus, owls and harriers, whose existence depends on how accurately they determine the location of the mouse, and the action often takes place in dense thickets or with limited visibility of the field of vision and hearing, have a common forward orientation, resulting from the anterior displacement of the eyes and ears - such a face is a very characteristic feature of owls and harriers.

This duplication of sense organs with each other ensures a complete perception of the environment and natural landmarks. Of course, this integrity is ensured not only by the senses, but also mainly by the brain, which combines information coming through individual channels and evaluates the situation as a whole. The work of the brain is primarily associated with higher forms of orientation, the so-called homing, returning to the nesting site of artificially removed birds, orientation during seasonal flights, weather forecasting, counting, etc.

Bird brain abilities for rational activity

An open, active lifestyle, constant alternation of various landmarks, and the need to communicate have developed in birds the rudiments of rational activity and the ability for elementary abstractions. If you sneak up on crows feeding in a field and at the same time go down into a ravine for camouflage, then the birds will wait for you at the other end of the ravine, where you should find yourself, maintaining the original direction of movement. A flock of geese or cranes watching a fox sneaking up on them will do the same thing.

However, an assessment aimed at the movement of a landmark, partly its extrapolation, is no less important in complex forms of orientation than the ability to quantify orientation. In experiments, it was possible to teach chickens to peck any grain of their choice - the second, third, etc., but they managed to teach pigeons to distinguish between different combinations of grains. Magpies and crows are also good at distinguishing different sets of objects, and even the number of people and animals. Birds, for example, can distinguish 5 objects from 6 without counting - a task not always accessible even to humans. Special experiments have also shown that birds are good at distinguishing the contours and shapes of objects, geometric figures, etc.

These abilities play a particularly important role in celestial navigation of birds - using celestial bodies as landmarks.

Thus, warblers were placed in a planetarium and the direction of their flight was monitored at different positions of the starry sky. It was possible to prove that the general picture of the starry sky can be used by them as a guide during seasonal flights. It is not difficult to imagine the difficulties that arise for the bird - the need to extrapolate the movement of the stars, accurately sense time up to 15-20 minutes, perceive various combinations of constellations, the number of stars, etc.

One of the most interesting mysteries facing science has not yet been solved - the mystery of the seasonal migrations of birds, their extraordinary ability to accurately determine the desired course.

What do birds use as a navigation device?

What sets this device to a given route - the Sun, the stars, the magnetic forces of the Earth, or something else?

One after another, hypotheses appear on this score and are tested in many laboratories around the world.

The material published below is about testing one of these hypotheses.

One of the most fascinating but also difficult mysteries of wildlife is the navigational abilities of birds. How do migratory birds or, for example, carrier pigeons, which have long served humans, navigate in space? How do they find their flight target?

More than twenty years ago, it was suggested that the pigeon has a special memory that records two characteristics of the place where it was born or lived for a long time: the magnitude of the Coriolis acceleration and the strength of the Earth's magnetic field.

Let us recall that Coriolis acceleration occurs, for example, when one body moves translationally over another, which has a rotational motion. In particular, this acceleration causes river flows to erode the right banks of channels in the northern hemisphere and the left banks in the southern hemisphere.

The hypothesis said that when a bird is taken some distance from the house and then released, it flies in the direction where changes in the magnitude of the fields - Coriolis acceleration and magnetic - occur in the direction of those values to which it is accustomed. That is, she flies to the place from where she was taken and where she must return.

This assumption seemed to receive convincing confirmation. If you draw the lines of the Coriolis and magnetic fields on a map, a grid of lines intersecting at an angle is formed. It turns out that each point in the northern hemisphere has a “double” in the southern hemisphere - a point where the magnetic field and Coriolis acceleration have the same value.

The following experiment was carried out: a pigeon that grew up in the northern hemisphere was brought to the southern hemisphere and released not very far from a point “symmetrical” to the point of its deposit. And the pigeon flew to this point without any hesitation, as if it was flying home along a known route.

However, no matter how hard the researchers tried to discover a mechanism in the bird’s body that could determine the magnitude of the Coriolis acceleration, it was not possible to find it.

Experiments reveal new abilities of birds

New experiments have recently been summed up, which seem to bring closer the solution to the abilities of feathered navigators.

After the two-field hypothesis collapsed, scientists turned to the most subtle and ingenious research methods to make nature speak.

The pigeons were sent to the starting point, for example, in rotating drums or along intricate ring roads.

The normal functioning of the balance organ was disrupted by surgery.

The birds were hung with permanent magnets or coils of wire, in which the Earth's magnetic field excited an electromotive force during flight - this is how the interaction of the bird and the planet's magnetic field was studied. The birds were blindfolded. However, no tricks helped scientists confuse the birds. They invariably flew to the right place, and in the shortest possible way.

The high reliability of orientation (the experiments we just talked about certainly prove this) led scientists to the conclusion that the pigeon is armed with several, at least two, spatial orientation systems based on different natural phenomena.

Researchers from Cornell University managed to move forward with a new series of experiments.

In the first group of experiments, pigeons were placed in a hermetically sealed metal chamber, while the heart rate of the birds connected to the instruments could be recorded. From time to time, the air pressure in the chamber changed slightly and at the same time the pigeons received a slight electric shock. This is how the birds developed a conditioned reflex.

In the second half of the experiment, only the air pressure changed. And yet, the birds' heart rates increased, even though they did not receive the shocking shock. Thus, it was possible to establish that pigeons are sensitive to very slight changes in atmospheric pressure.

Experiments with a similar methodology, which also began with the development of a conditioned reflex, were supposed to reveal whether these birds were sensitive to the Earth’s magnetic field. And experiments have proven that pigeons pick up even very weak electromagnetic waves. Researchers estimate that birds are able to respond to changes of one five-hundredth or even a thousandth of the Earth's normal magnetic field.

During explosions on the Sun, which respond to us with magnetic storms, pigeons, when flying home, slightly deviate from the usual, most profitable path.

Similarly, using heart rate as an external indicator of the bird's body reactions, scientists have proven that pigeons, like bees, can distinguish polarized light from ordinary light. This means that it is enough for a dove to see only a single speck of a clear, unclouded sky in the sky so that it can determine the position of the Sun.

Some researchers have long assumed that these abilities are sufficient for birds to solve all their navigation problems. However, subtle experiments have proven that a pigeon, knowing the position of the Sun and using its “internal clock,” can only determine north and south, and not the direction to its native dovecote.

This is also confirmed by experiments with pigeons whose biological clocks were “rearranged”: thanks to artificial lighting and darkening, their idea of day and night was reversed. Such birds, disoriented in time, when they took flight, made an error in choosing a direction, precisely proportional to the temporal error embedded in their consciousness.

Bird orientation systems

However, recently in a laboratory at Cornell University they discovered that when the sky is completely overcast and the pigeon cannot see a direct ray of sunlight anywhere, and its internal clock is “rearranged,” the bird nevertheless correctly finds its way home, as if it had never happened. these two interferences that exclude navigation on the Sun.

It remained to agree that the bird also has a second orientation system, completely independent of the Sun. To search for the second system, it was decided to completely exclude the Sun from the experiments.

At the Cornell University dovecote, two flocks were trained to fly during drizzles and thick, low clouds. Suspicion again fell on the magnetic field.

One flock of pigeons had small permanent magnets attached to their wings. Birds from another flock received weights of the same weight, however, from non-magnetic material. The second flock always returned home amicably, which cannot be said about the pigeons, for which hanging magnets prevented them from correctly perceiving the Earth’s magnetic field.

Scientists have concluded that when there is at least a piece of clear sky, pigeons prefer to use the solar orientation. If there is no star in the sky, they look for direction using a magnetic navigation system.

Many researchers, however, are at a dead end: where are the organs in the pigeon’s body that perceive the natural magnetic field?

A very interesting suggestion has recently appeared on this matter. Shouldn't the bird's circulatory system be considered such an organ?

In fact: blood is an electrolyte (a solution of sodium chloride and other salts), in which ferromagnetic particles (red blood cells containing iron) are also suspended.

In general, the entire system of arteries and veins of a bird is a current-conducting circuit in which, when the bird moves in a magnetic field, an electromotive force must certainly arise. The magnitude of this EMF, in particular, will depend on the angle at which the contour intersects the field lines, that is, in which direction the bird is flying.

Earth's magnetic field and man

Here we still need precise experiments and measurements. But it is a fact that even coarse human organisms, not so sensitive to natural phenomena, react to changes in the Earth’s magnetic field, especially during explosions on the Sun.

They have the greatest impact on people with a diseased circulatory system. It is no coincidence that medical institutions where there are such patients receive warnings from astronomers conducting solar services about the approaching magnetic storm.

Recently, scientists have discovered that humans - and not only the sick - are also influenced by softer factors associated with the Earth's magnetic field - and not just storms.

So, the pigeon has at least two orientation systems. However, as we see, there are still quite a lot of unsolved riddles that winged navigators pose to researchers.

A relatively small number of species and individuals of Anseriformes, grebes, great-creepers, raptors, waders, gulls, and passerines winter in the southern regions of the former USSR along the shores of the Black Sea, in Transcaucasia, in the south of the Caspian Sea, and in some areas of Central Asia. The vast majority of our bird species and individuals winter outside the country in the British Isles and Southern Europe, the Mediterranean, and many areas of Africa and Asia. For example, many small birds from the European part of the former USSR winter in South Africa (warblers, warblers, swallows, etc.), flying up to 9-10 thousand km from their wintering grounds. The flight paths of some species are even longer. Arctic terns, Sterna paradisea, nesting along the coasts of the Barents Sea spend the winter off the coast of Australia, flying up to 16-18 thousand km in one direction only. The flight path is almost the same for brown-winged plovers, Charadrius dominica, nesting in the tundra of Siberia, wintering in New Zealand, and for spiny-tailed swifts, Hirundapus caudacutus, flying from Eastern Siberia to Australia and Tasmania (12-14 thousand km); part of the way they fly over the sea.

During migration, birds fly at normal speeds, alternating flights with stops for rest and feeding. Autumn migrations usually occur at a slower rate than spring migrations. During migration, small passerine birds move an average of 50-100 km per day, ducks - 100-500 km, etc. Thus, on average per day, birds spend a relatively short time on migration, sometimes only 1-2 hours However, some even small land birds, for example, American tree warblers - Dendroica, migrating over the ocean, are able to fly 3-4 thousand km without stopping. for 60-70 hours of continuous flight. But such intense migrations have been identified only in a small number of species.

Flight altitude depends on many factors: the type of bird and pellet capabilities, weather, speed of air flows at different altitudes, etc. Observations from airplanes and using radars have established that migrations of most species take place at an altitude of 450-750 m; individual flocks can fly very low above the ground. Migrating cranes, geese, waders, and pigeons were observed much less frequently at altitudes of 1.5 km and higher. In the mountains, flocks of flying waders, geese, and cranes were observed even at an altitude of 6-9 km above sea level (at the 9th kilometer the oxygen content is 70% less than at sea level). Water birds (loons, grebes, auks) swim part of the flyway, and the corncrake walks. Many species of birds, usually active only during the day, migrate at night and feed during the day (many passerines, waders, etc.), while others maintain the usual daily rhythm of activity during the migration period.

In migratory birds, during the period of preparation for migration, the nature of metabolism changes, leading to the accumulation of significant fat reserves with increased nutrition. When oxidized, fats release almost twice as much energy as carbohydrates and proteins. Reserve fat enters the bloodstream as needed and is delivered to working muscles. The oxidation of fats produces water, which compensates for the loss of moisture during respiration. Fat reserves are especially large in species that are forced to fly non-stop for long periods of time during migration. In the already mentioned American tree warblers, before flying over the sea, fat reserves can amount to up to 30-35% of their mass. After such a throw, the birds feed intensively, restoring energy reserves, and again continue their flight.

A change in the nature of the metabolism that prepares the body for flight or wintering conditions is ensured by a combination of the internal annual rhythm of physiological processes and seasonal changes in living conditions, primarily by changes in the length of daylight hours (lengthening in spring and shortening in late summer); Seasonal changes in feed probably also have a certain significance. In birds that have accumulated energy resources, under the influence of external stimuli (changes in day length, weather, lack of food), so-called migratory restlessness occurs, when the bird’s behavior changes sharply and a desire to migrate arises.

The overwhelming majority of nomadic and migratory birds have clearly expressed nest conservatism. It manifests itself in the fact that the breeding birds return from wintering to the previous nesting site the next year and either occupy the old nest or build a new one nearby. Young birds that have reached sexual maturity return to their homeland, but more often they settle at some distance (hundreds of meters - tens of kilometers) from the place where they hatched (Fig. 63). Less clearly expressed nesting conservatism in young birds allows the species to populate new territories suitable for it and, by ensuring mixing of the population, prevents inbreeding (inbreeding). The nesting conservatism of adult birds allows them to nest in a well-known area, which makes it easier both to search for food and to escape from enemies. There is also constancy of wintering places.

How do birds navigate during migration, how do they choose the direction of flight, arriving in a certain area for the winter and returning thousands of kilometers to their nesting site? Despite various studies, there is no answer to this question yet. Obviously, migratory birds have an innate migratory instinct that allows them to choose the desired general direction of migration. However, this innate instinct can apparently change quickly under the influence of environmental conditions.

The eggs of resident English mallards were incubated in Finland. The grown young mallards, like local ducks, flew away for the winter in the fall, and the following spring a significant part of them (36 out of 66) returned to Finland to the release area and nested there. None of these birds have been found in England. Black geese are migratory. Their eggs were incubated in England, and the young birds behaved like sedentary birds in the new place in the fall. Thus, it is not yet possible to explain both the desire to migrate and orientation during the flight only by innate reflexes. Experimental studies and field observations indicate that migrating birds are capable of celestial navigation: choosing the desired flight direction based on the position of the sun, moon and stars. In cloudy weather or when the picture of the starry sky changed during experiments in the planetarium, the ability to navigate noticeably deteriorated.

To correctly plot the course to the intended goal, the navigator of a ship or aircraft resorts to the help of complex navigation instruments, uses maps, tables, and now GPS navigation, GPS monitoring. In this regard, the ability of birds and animals to orient themselves with amazing precision relative to the surface of the earth seems all the more surprising in this regard. Birds behave especially unerringly in space. The distances that birds cover during seasonal migrations are sometimes very long. For example, Arctic terns make a two-month flight from the Arctic to the Antarctic, covering about 17 thousand kilometers. And shorebirds migrate from the Aleutian Islands and Alaska to the Hawaiian Islands, flying about 3,300 kilometers over the ocean. These facts are of interest not only from a physiological point of view. Particularly surprising is the unmistakable orientation of birds over the ocean. If, when flying over land, one can assume the presence of some familiar visual landmarks, then what landmarks can be encountered on a monotonous water surface?

It is also known that birds always return to their places after long journeys. Thus, American terns, transported 800-1200 kilometers from their nesting grounds, returned to their old places, to the shores of the Gulf of Mexico, after a few days. Similar experiments have been carried out with other birds. The results were the same.

Not only “migratory” birds, but also “sedentary” birds have a certain ability to navigate (a trained one can return to the dovecote from a distance of 300-400 kilometers). The ability of birds to navigate in space has been known since ancient times. At that time they already used pigeon mail. However, observations of bird migrations and their behavior alone yielded practically nothing to clarify the reasons for orientation. Until now, there are only numerous guesses and theories on this issue.

The English scientist Metoz experimentally established that carrier pigeons orient themselves worse on cloudy days. Launched from a distance of more than 100 kilometers, they deviated by a known angle from the correct direction of flight. On a sunny day this error was much smaller. On this basis, the opinion was put forward that birds navigate by the sun.

It is known that orientation by the sun actually exists in nature. For example, some aquatic insects, sea spiders, have the ability to navigate by the sun. Released into the open sea, they will unmistakably rush back to the shore - their usual habitat. When the position of the sun changes in the sky, spiders change the angle and direction of movement accordingly.

All these facts to some extent speak in favor of the theory of Metosis. However, a significant objection to it is the night migration of many birds. True, some scientists believe that in this case the birds navigate by the stars. The so-called magnetic theory has become widespread. The idea that birds have a special, “magnetic sense” that allows them to navigate the Earth’s magnetic field was expressed back in the mid-19th century by Academician Miedendorff. Subsequently, this theory found many adherents. However, numerous laboratory experiments during which magnetic fields were created that were many times greater in intensity than the Earth’s magnetic field did not have any visible effect on the birds.

Recently, the “magnetic theory” has been criticized by physiologists and physicists. However, it should be noted that migratory birds show a certain sensitivity to some special types of electromagnetic vibrations. For example, amateur pigeon keepers have long noted that pigeons are less able to navigate near powerful radio stations. Their statements were usually not taken seriously. But during the Second World War, numerous information was obtained about the influence of ultrashort waves emitted by radar installations on migratory birds. It is curious that the radar radiation had no visible effect on sitting birds, even from a very close distance, but the radiation directed at flying birds broke up their formation.

From the point of view of science, which studies the living conditions of various animals. It is quite natural for birds to have the ability to navigate in space. The extraordinary speed of movement and the ability to cover significant distances in a short period of time sets birds apart from other representatives of the living world of our planet. The search for food far from the nest undoubtedly contributed to the development of extraordinary abilities to navigate in space compared to other animals. However, as we see, the mechanism of this interesting phenomenon has not yet been revealed. For now, we can only assume that the complex instinct of birds is not based on any one factor. Perhaps it includes elements of astronomical orientation to the sun, especially since a number of animals have this ability.

Obviously, visual orientation on the surface of the Earth can also play an important role, given that the vision of birds differs in a number of features. There are certainly some other important factors that are still unknown to science. It is not yet possible to say with certainty whether the so-called magnetic sense of birds is included in their number. Only further research with the participation of scientists from various specialties will apparently help resolve this mystery of nature.