So, we have found that most animals with an unstable body temperature, which depends on the environment, fall into a state of hibernation. But it is surprising that many animals with a constant body temperature, such as birds, can also hibernate during unfavorable seasons. It is known that most birds avoid unfavorable winter conditions by migrating. But even Aristotle (384 - 322 BC) in his multi-volume “History of Animals” drew attention to the fact that “some birds fly away to spend the winter in warm countries, while others take refuge in different shelters, where they fall into hibernation.” This conclusion was also reached by the prominent Swedish naturalist Carl Linnaeus, who in his work “System of Nature” (1735) wrote: “In the fall, when cold weather begins, swallows, not finding enough insects for food, begin to look for shelter for wintering in reed thickets along the banks of lakes and rivers.” For a long time, the statements of Aristotle and Linnaeus were rejected by ornithologists, who referred to the well-known fact that some birds migrate to warm countries, while non-migratory ones are active in winter, and birds hibernating in winter, contrary to the statement many, science does not know. Only after American scientists discovered a nightjar (Phalaenoptilus nuttalii) in a hibernating state in a rock crevice in 1937, it became clear that some bird species can fall into a similar state during unfavorable seasons. Both scientists conducted more in-depth studies and found that before hibernating, this bird species loses a significant part of its weight, and at a certain point, as a result of such exhaustion, the mechanism of transition to a state of torpor is activated. In this state, metabolism decreases sharply, the need for oxygen is reduced by almost 30 times, and body temperature from 40 - 41 ° C drops to 18 - 19 ° C and even lower. The birds fell into a stupor that lasted about 3 months, and it seemed as if they were dead. It was found that during hibernation, a nightjar weighing 40 g consumed 0.15 ml of oxygen per 1 g of weight per hour, whereas in the normal state it was 2.7 ml. The same scientists banded one of these birds, and in subsequent years it turned out that it always wintered in the same place for 4 years. Later it was found that another of its relatives, the small nightjar (Chordeilis minor), also lives in North America and the Antilles, falls into a state of hibernation. In Denmark, a European common nightjar (Caprimutgus europeus) was found in the same condition at an air temperature of 0°C. Experiments carried out with him showed that when the air temperature was artificially lowered to 4°C, the bird fell into stupor, and its body temperature dropped from 37 - 40°C to 16 - 17°C, and its respiratory rate - from 50 - 70 to several minute. There are observations that some species of swallows (barn and cliff) also hibernate in winter. A state of short-term torpor, which scientists call torpidity, has been observed in newly hatched black swift chicks (Apus apus), which enter this state when their parents leave them for several days under unfavorable conditions (for example, during an approaching cyclone). In a state of torpor, the body temperature of these chicks dropped from 39°C to 20°C and even lower, their pulse and breathing slowed down, and they remained in this state for 7 - 12 days. Appearing again, the parents warmed them with their bodies, and the chicks returned to life. In a favorable season, young swifts flew out of the nest after 33 - 35 days, and in unfavorable times, when they fell into a state of torpor, they needed 40 - 50 days. It has long been known that the chicks of some hummingbird species also fall into a similar torpid state if the mother, having flown away to get food, will stay for more than ten minutes (in hummingbirds, only females feed their offspring). After her return, warmed by maternal warmth, they return to life. It has been established that adult hummingbirds of several species (Calypte costae, C. anna, Eugenes lampornis) living on the American continent are also capable of falling into a state of torpor on particularly cold nights, when their body temperature drops to 8.8 ° C. It has been proven that the weight of various species of hummingbirds ranges from 1.7 to 19.1 g, and the oxygen requirement for small specimens at rest is 11 - 16 ml per 1 g of weight per hour, during flight - 70 - 85 ml, and in a state of torpor only 0.17 ml. Hummingbirds have a high energy expenditure, and there is a danger that hummingbirds with a body temperature of 44°C will not be able to survive without food during the period when they sleep, since they will not have enough energy reserves. In this situation, their body, if excessively cooled from exhaustion at night, will lose the opportunity to warm up again at the beginning of its active phase. Meanwhile, as you know, the nights on the South and Central American high plateaus, where hummingbirds live, are cold. That is why hummingbirds have a protective mechanism - they fall into a torpid state at night, and their body temperature is compared with the temperature of the environment; Thus, they do not give up their heat and retain energy, which is not consumed to generate heat in the body. In this case, the law of the Dutch physiologist Van Gough applies, reflecting the relationship between the rate of reactions of chemical processes and temperature (if the body temperature drops by 10°C, metabolic processes will begin to proceed almost 3 times slower). So if a hummingbird’s body temperature drops from 44°C to 34°C, this will lead to a threefold reduction in metabolism and, accordingly, significant energy conservation. Similar regulation of body temperature during torpor was also found in the purple hummingbird (Eulampis jugularis), which, like other hummingbirds, it easily falls into a torpid state. In a state of torpor, the body temperature of this species of hummingbird is usually close to air temperature, but if the latter drops below 18 ° C, the bird’s body temperature no longer decreases and remains at the level of 18 - 20 ° C. The torpor into which some species of birds fall is significantly differs from hibernation, characteristic of many mammals. First of all, the bird’s body not only does not accumulate energy reserves in the form of fat, but, on the contrary, consumes a significant part of it. While mammals hibernate during the winter, gaining noticeable weight, birds lose a lot of weight before going into torpor. That is why the phenomenon of torpor in birds, according to the Soviet biologist R. Potapov, should be called not hibernation, but hypothermia. Until now, the mechanism of hypothermia in birds has not been fully studied. It is interesting that all birds capable of falling into a state of torpor are systematically They are closely related to each other and have common physiological and ecological characteristics. The fall of these birds into a state of torpor under unfavorable living conditions is an adaptive physiological reaction that has been consolidated in the process of evolution.
So, we have found that most animals with an unstable body temperature, which depends on the environment, fall into a state of hibernation. But it is surprising that many animals with a constant body temperature, such as birds, can also hibernate during unfavorable seasons. It is known that most birds avoid unfavorable winter conditions by migrating. It became clear that some species of birds can fall into a similar state during unfavorable seasons. There are observations that some species of swallows (barn and rock swallows) also hibernate in winter. A state of short-term torpor, which scientists call torpidity, has been observed in newly hatched black swift chicks, which enter this state when their parents leave them for several days under unfavorable conditions (for example, during an approaching cyclone). in a state of torpor, the body temperature of these chicks dropped from 39 °C to 20 °C and even lower, their pulse and breathing slowed down, and they survived in this state for 7-12 days. Appearing again, the parents warmed them with their bodies, and the chicks returned to life. in favorable times of the year, young swifts flew out of the nest after 33–35 days, and in unfavorable times, when they fell into a state of torpor, they needed 40–50 days.
It has long been known that the chicks of some species of hummingbirds also fall into a similar torpid state if the mother, having flown away for food, lingers for more than ten minutes (among hummingbirds, only females feed their offspring). After her return, warmed by maternal warmth, they return to life. It has been established that adult hummingbirds of several species living in the Americas are also capable of falling into a state of torpor on particularly cold nights, when their body temperature drops to 8.8 °C. It has been proven that the weight of various species of hummingbirds ranges from 1.7 to 19.1 g, and the oxygen requirement of small specimens at rest is 11–16 ml per 1 g of weight per hour, during flight - 70–85 ml, and in a state of torpor only 0.17 ml. Hummingbirds have a high energy expenditure, and there is a danger that hummingbirds with a body temperature of 44 °C will not be able to survive without food during the period when they sleep, since they will not have enough energy reserves. In this situation, their body, if excessively cooled from exhaustion at night, will lose the opportunity to warm up again at the beginning of its active phase. Meanwhile, as you know, the nights on the South and Central American high plateaus, where hummingbirds live, are cold. That is why hummingbirds have a protective mechanism - they fall into a torpid state at night, and their body temperature is compared with the temperature of the environment; Thus, they do not give up their heat and retain energy, which is not consumed to generate heat in the body. in this case, the law of the Dutch physiologist Van Gough applies, reflecting the relationship between the rate of reactions of chemical processes and temperature (if the body temperature drops by 10 °C, metabolic processes will begin to proceed almost 3 times slower). So if a hummingbird's body temperature drops from 44 °C to 34 °C, this will lead to a threefold reduction in metabolism and, accordingly, significant energy conservation.
A similar regulation of body temperature during torpor has been found in the purple hummingbird, which, like other hummingbirds, easily falls into a torpid state. in a state of torpor, the body temperature of this species of hummingbird is usually close to air temperature, but if the latter drops below 18 °C, the bird’s body temperature no longer decreases and remains at 18–20 °C.
The torpor into which some species of birds fall differs significantly from the hibernation characteristic of many mammals. First of all, the bird’s body not only does not accumulate energy reserves in the form of fat, but, on the contrary, consumes a significant part of it.
While mammals hibernate during the winter, gaining noticeable weight, birds lose a lot of weight before going into torpor. This is why the phenomenon of torpor in birds, according to Soviet biologist R. Potapov, should be called hypothermia rather than hibernation.
Until now, the mechanism of hypothermia in birds has not been fully studied. It is interesting that all birds capable of falling into a state of torpor are systematically closely related to each other and have common physiological and ecological characteristics. The fall of these birds into a state of torpor under unfavorable living conditions is an adaptive physiological reaction that has been consolidated in the process of evolution.
Date added: 2015-08-06 | Views: 366 | Copyright infringement
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Sections: Biology
Goals: increase the areas of student knowledge; learn to analyze the phenomenon of temporary cessation of vital activity in living organisms that use it as a means to adapt and survive in unfavorable conditions.
Equipment: tables of mollusks, crustaceans, insects, fish, amphibians, reptiles, birds, mammals.
The winter season is unfavorable for many representatives of the animal and plant world, both due to low temperatures and a sharp reduction in the ability to obtain food. During evolutionary development, many species of animals and plants acquired unique adaptive mechanisms to survive in unfavorable seasons. In some species of animals, the instinct to create food reserves arose and became established; others have developed another adaptation - migration. Amazingly long flights of many species of birds, migrations of some species of fish and other representatives of the animal world are known. However, in the process of evolution, another perfect physiological adaptation mechanism has been noticed in many animal species - the ability to fall into a seemingly lifeless state, which manifests itself differently in different animal species and has different names (anabiosis, hypothermia, etc.). Meanwhile, all these conditions are characterized by inhibition of the body’s vital functions to the minimum that allows it to survive unfavorable winter conditions without eating. Those species of animals that are unable to provide themselves with food in winter fall into a similar state of imaginary death and are in danger of dying from cold and hunger. And all this, developed in the process of evolution, is subject to strict natural expediency - the need to preserve the species.
Hibernation is a widespread phenomenon in nature, despite the fact that its manifestations vary among representatives of certain groups of animals, be it animals with an unstable body temperature (poikilothermic), also called cold-blooded, in which the body temperature depends on the surrounding temperature, or animals with a constant body temperature (homeothermic), also called warm-blooded.
Among the animals with an unstable body temperature, various species of mollusks, crustaceans, arachnids, insects, fish, amphibians and reptiles enter into a state of hibernation, and among animals with a constant body temperature, several species of birds and many species of mammals.
How do snails winter?
Of the soft-bodied type, many species of snails hibernate (for example, all land snails). Common garden snails enter hibernation in October, which lasts until early April. After a long preparatory period, during which they accumulate the necessary nutrients in their bodies, the snails find or dig holes so that several individuals can overwinter together deep underground, where the temperature will be maintained at 7 - 8 ° C. Having sealed the burrows well, the snails descend to the bottom and lie down with the shell opening facing up. They then close this opening, releasing a slimy substance that soon hardens and becomes elastic (film-like). With significant cooling and a lack of nutrients in the body, the snails burrow even deeper into the ground and form another film, thus creating air chambers that act as an excellent insulator. It has been established that during a long winter, snails lose more than 20% of their weight, with the greatest loss occurring in the first 25-30 days. This is explained by the fact that all metabolic processes gradually die out in order to reach the minimum at which the animal falls almost into a state of suspended animation with barely perceptible vital functions. During hibernation, the snail does not feed and breathing almost stops. In the spring, when the first warm days arrive and the soil temperature reaches 8-10 ° C, when vegetation begins to develop and the first rains fall, snails crawl out of their winter shelters. Then intensive activity begins to restore the depleted food reserves in their body; this is expressed in the absorption of a huge amount of food compared to their body.
Pond water snails also enter a state of hibernation - most of them burrow into the silt at the bottom of the reservoir in which they live.
Where do crayfish spend the winter?
Everyone knows the popular threat: “I’ll show you where the crayfish spend the winter!” It is believed that this saying appeared during the times of serfdom, when landowners, punishing guilty serfs, forced them to catch crayfish in the winter. Meanwhile, it is known that this is almost impossible, since crayfish spend the winter buried deep in holes at the bottom of reservoirs.
From a systematic point of view, the class of crustaceans is divided into two subclasses - higher and lower crustaceans.
Among the higher crustaceans, river, marsh and lake crayfish fall into a state of hibernation. Males overwinter in groups in deep holes at the bottom, and females alone in burrows, and in November they glue fertilized eggs to their short legs, from which crustaceans the size of an ant hatch only in June.
Of the lower crustaceans, water fleas (genus Daphnia) are of interest. They lay, depending on conditions, two types of eggs - summer and winter. Winter eggs have a durable shell and are formed when unfavorable living conditions occur. For some species of lower crustaceans, drying and even freezing of eggs is a necessary condition for the continuation of their development.
Diapause in insects
In terms of the number of species, insects surpass all other classes. Their body temperature depends on the environment, which has a strong influence on the rate of vital influences, with low temperatures greatly reducing this rate. At negative temperatures, the entire development of the insect slows down or practically stops. This anabiotic state, known as “diapause,” is a reversible cessation of developmental processes and is caused by external factors. Diapause occurs when conditions unfavorable for life arise and continues throughout the winter until, with the onset of spring, conditions become more favorable.
The onset of the winter season finds different types of insects at different stages of their development, in which they overwinter - in the form of eggs, larvae, pupae or adult forms, but usually each individual species enters diapause at a certain stage of its development. For example, the seven-spotted ladybug overwinters as an adult.
It is characteristic that the wintering of insects is preceded by a certain physiological preparation of their body, consisting of the accumulation of free glycerol in their tissues, which prevents freezing. This occurs at the stage of insect development in which they will spend the winter.
Even with the onset of the first signs of cooling in the fall, insects find comfortable shelters (under stones, under the bark of trees, under fallen leaves in burrows in the soil, etc.), where after snowfall the temperature is moderately low and uniform.
The duration of diapause in insects is directly dependent on body fat reserves. Bees do not enter a long diapause, but still become numb at temperatures from 0 to 6 ° C and can remain in this state for 7-8 days. At lower temperatures they die.
It is also interesting how insects accurately determine the moment when they should exit the anabiotic state. Scientist N.I. Kalabukhov studied suspended animation in some species of butterflies. He found that the duration of diapause varies among individual species. For example, the peacock butterfly remained in a state of suspended animation for 166 days at a temperature of 5.9 ° C, while the silkworm needed 193 days at a temperature of 8.6 ° C. According to the scientist, even differences in geographic area affect the duration of diapause.
Do fish hibernate during the winter?
Some species of a wide class of fish also adapt to low water temperatures in winter in a unique way. The normal body temperature of fish is not constant and corresponds to the temperature of the water. When the water temperature suddenly drops sharply, the fish go into a state of shock. However, it is enough for the water to warm up, and they quickly “come to life”. Experiments have shown that frozen fish come to life only in cases where their blood vessels do not freeze.
Some fish that live in Arctic waters adapt to low water temperatures in winter in an original way: they change their blood composition. As the water temperature drops in the fall, salts accumulate in their blood in such a concentration as is typical for sea water, and at the same time the blood freezes with great difficulty (a kind of antifreeze).
Of the freshwater fish, carp, ruffe, perch, catfish and others go into hibernation back in November. When the water temperature drops below 8 - 10°C, these fish move to deeper parts of the reservoirs, bury themselves in large groups in the mud and remain there in a state of hibernation throughout the winter.
Some marine fish also tolerate extreme cold in a state of hibernation. For example, herring already in the fall approach the coast of the Arctic Ocean in order to fall into a state of hibernation at the bottom of some small bay. The Black Sea anchovy also winters in the southern regions of the sea - off the coast of Georgia; at this time it is not active and does not consume food. And before the onset of winter, the Azov anchovy migrates to the Black Sea, where it gathers in groups in a relatively sedentary state.
Hibernation in fish is characterized by extremely limited activity, complete cessation of nutrition and a sharp decrease in metabolism. At this time, their body is supported by nutrient reserves accumulated due to abundant nutrition in the autumn.
Hibernation of amphibians
In terms of lifestyle and structure, the class of amphibians is transitional between typically aquatic vertebrates and typically terrestrial animals. It is known that various species of frogs, newts, and salamanders also spend the unfavorable winter season in a state of torpor, since these are animals with an unstable body temperature, which depends on the ambient temperature.
It has been established that winter hibernation of frogs lasts from 130 to 230 days and its duration depends on the duration of winter.
In reservoirs, in order to overwinter, frogs gather in groups of 10-20 individuals, bury themselves in silt, underwater depressions and other voids. During hibernation, frogs breathe only through their skin.
In winter, newts usually roost under warm, rotten stumps and trunks of fallen trees. If they do not find such comfortable “apartments” nearby, they are satisfied with cracks in the soil.
Reptiles also hibernate
From the class of reptiles, almost all species of our fauna fall into a state of hibernation in winter. Low winter temperatures are the main reason for this phenomenon.
Winter quarters are usually underground caves or voids formed around large old stumps with rotten roots, crevices in rocks and other places that are inaccessible to their enemies. A large number of snakes gather in such shelters, forming huge snake balls. It has been established that the temperature of snakes during hibernation is almost no different from the ambient temperature.
Most species of lizards (meadow, striped, green, forest, spindle) also hibernate, burying themselves in the soil, in burrows that are not threatened by flooding. On warm, sunny days in winter, lizards may “awaken” and crawl out of their winter shelters for a few hours to hunt, after which they retreat back into their burrows, falling into a state of torpor.
Swamp turtles spend the winter burrowing into the silt of the reservoirs in which they live, while land turtles climb to a depth of up to 0.5 m into the soil in some natural shelters or holes of moles, foxes, rodents, covering themselves with peat, moss and wet leaves.
Preparations for wintering begin in October, when turtles accumulate fat. In the spring, with temporary warming, they wake up, sometimes for a whole week.
Do birds hibernate during the winter?
Most animals with an unstable body temperature, which depends on the environment, enter a state of hibernation. But it is surprising that many animals with a constant body temperature, such as birds, can also hibernate during unfavorable seasons. It is known that most birds avoid unfavorable winter conditions by migrating. Aristotle, in his multi-volume History of Animals, drew attention to the fact that “some birds fly away to spend the winter in warm countries, while others take refuge in various shelters where they hibernate.”
This conclusion was also reached by the prominent Swedish naturalist Carl Linnaeus, who wrote in his work “The System of Nature”: “In autumn, when the weather begins to get colder, swallows, not finding enough insects for food, begin to seek shelter for wintering in reed thickets along the banks of lakes and rivers. "
The torpor into which some species of birds fall differs significantly from the hibernation characteristic of many mammals. First of all, the bird’s body not only does not accumulate energy reserves in the form of fat, but, on the contrary, consumes a significant part of it. While mammals hibernate during the winter, gaining noticeable weight, birds lose a lot of weight before going into torpor. That is why the phenomenon of torpor in birds, according to the Soviet biologist R. Potapov, should be called hypothermia rather than hibernation.
Until now, the mechanism of hypothermia in birds has not been fully studied. The fall of birds into a state of torpor under unfavorable living conditions is an adaptive physiological reaction that has been consolidated in the process of evolution.
What mammals hibernate?
As in those animals that were discussed earlier, in mammals, hibernation is a biological adaptation for surviving an unfavorable season of the year. Despite the fact that animals with a constant body temperature usually tolerate cold climate conditions, the lack of suitable food in winter has become the reason for the acquisition and gradual consolidation in the process of evolution by some of them of this peculiar instinct - spending the unfavorable winter season in an inactive state of hibernation.
There are three types of hibernation based on the degree of torpor:
1) mild torpor that easily stops (raccoons, badgers, bears, raccoon dogs);
2) complete torpor, accompanied by periodic awakenings only on warmer winter days (hamsters, chipmunks, bats);
3) real continuous hibernation, which is a stable, prolonged torpor (gophers, hedgehogs, marmots, jerboas).
Winter hibernation in mammals is preceded by a certain physiological preparation of the body. It consists primarily of the accumulation of fat reserves, mainly under the skin. In some winter hibernators, subcutaneous fat reaches 25% of their total body weight. For example, ground squirrels gain weight even at the beginning of autumn, increasing their body weight three times compared to the spring-summer weight. Before hibernation, hedgehogs and brown bears, as well as all bats, become significantly fatter.
Other mammals, such as hamsters and chipmunks, do not accumulate large reserves of fat, but store food in their shelter for use during their brief awakening periods in winter.
During hibernation, all species of mammals lie motionless in their burrows, curled up into a ball. This is the best way to preserve heat and limit heat exchange with the environment. The winter quarters of many mammals are the natural cavities of stems and tree hollows.
Among the insectivorous mammals, the hedgehog, in preparation for hibernation, collects moss, leaves, hay in a secluded place and makes a nest for itself. But it “settles” in its new home only when the temperature remains below 10° C for a long time. Before this, the hedgehog eats heavily in order to accumulate energy in the form of fat.
Winter hibernation of brown bears is a slight torpor. In nature, in the summer, a bear accumulates a thick layer of subcutaneous fat and, just before the onset of winter, settles down in its den for hibernation. Usually the den is covered with snow, so it is much warmer inside than outside. During hibernation, the accumulated fat reserves are used by the bear's body as a source of nutrients, and also protect the animal from freezing.
From a physiological point of view, hibernation in mammals is characterized by a weakening of all vital functions of the body to the minimum that would allow them to survive unfavorable winter conditions without food.
Birds are usually divided into sedentary and migratory, depending on their lifestyle. But among them there are very special birds. This is an American White-throated Nightjar. Although these birds do not like the cold season, they are in no hurry to leave their native lands in search of better wintering places. Instead of exhausting and dangerous flights, they chose to hibernate in a cozy place.
The American white-throated nightjar, or sometimes called the California nightjar, is found in the arid regions of western North America. Its habitat extends from the Canadian province of British Columbia in the north to the central regions of Mexico in the south. This is a small bird whose weight reaches only 35-55 grams, and whose body size is 20 centimeters.
Nightjars build their nests on the ground, under the cover of bushes or grass. At the end of spring and throughout the summer, the female usually lays two eggs. But there have been cases where the female makes a second nest and lays a new batch of eggs while the male feeds the hatched offspring. In addition to this feature, nightjars have a very interesting defensive reaction to the appearance of predators: nightjars open their mouths wide and hiss loudly, imitating the behavior of a snake.
Nightjars are active at night, as their main food is nocturnal flying insects. With the onset of the cool season, nightjars fall into a special state, reminiscent of hibernation in mammals. At this time of year, their main food - insects - is practically absent. In order not to complicate their life by searching for food, they hibernate. Nightjars find a quiet place in the crevices of rocks and plunge into torpor, which can last from 10-20 days to 3 months. Studies have shown that the metabolic processes in a bird's body slow down so much that their body temperature can drop to 10 degrees Celsius. Cases have been recorded when the body temperature of birds dropped to 3-4 degrees, and oxygen consumption was reduced by up to 30 times. At the same time, their hibernation places are not completely closed from the outside world. The nightjar settles down for the winter so that the sun's rays fall on it and warm it with its warmth.
Interestingly, not all white-throated nightjars have this ability. The northern population of birds, which lives in Canada and the northern states of the United States, still prefers to fly south to Mexico. But nightjars, which originally live in the south, just hibernate.
Zoologists discovered an interesting feature of nightjars to fall into winter torpor only in 1947, when half-dead birds were discovered in the rocks. But the Native Americans knew about this feature of birds long before the discovery of scientists, because in the language of the Hopi Indians the white-throated nightjar is called “sleeping.”
Nightjar - a bird that hibernates
Even the father of science, Aristotle, in his famous History of Animals, wrote that some birds fly away for the winter to warm countries (more about), but some do not fly anywhere, but hide in secluded shelters and burrows, where they hibernate. This opinion was held in science until the beginning of the 19th century. And even such outstanding naturalists as Carl Linnaeus and Georges Cuvier once wrote that swallows become numb for the winter, spending this unfavorable time at the bottom of swamps. Is this really true? Do birds hibernate? We invite you to find out the answer to this question from our publication...
Do birds hibernate?
When biology sufficiently studied the migrations of birds, the assumption of winter hibernation of birds was completely abandoned and was sometimes cited in textbooks as a curiosity of distant antiquity. However, very recently, reports of strange phenomena in migrating swifts and swallows began to appear again in the scientific literature. Now in one or another secluded place they discovered a large concentration of torpid birds, which, however, came to life and flew away as soon as they were picked up. Such cases were observed, as a rule, during autumn or spring flights in cold, cloudy weather. In connection with such reports, old assumptions about the ability of birds to hibernate have also come to life.
This question has not yet been fully studied, but at least one species of birds is already known that hibernate throughout the winter. This bird is a small North American nightjar, native to the western United States.
An example of nightjar hibernation
In the winter of 1947, one of the naturalists came across a nightjar in one of the gorges, which was in a state of stupor. In subsequent years, zoologists studied in detail the hibernation of this small nightjar and found out many interesting details. So, the bird feeds mainly on nocturnal insects, which become less and less as winter approaches (find out). The birds begin to lose weight, and, apparently, at some certain point of exhaustion in their body, the mechanism of transition to a state of torpor is turned on. This happens in November. Nightjars choose secluded niches or cracks in the rocks - usually on the sunny side - and plunge into torpor, which can last up to 85 days. During this time, the level of metabolism in birds' bodies decreases sharply.
Oxygen consumption, in particular, is reduced by 30 times. And, body temperature can drop to 4.8 degrees.
The bird looks like it's dead. The torpor ends in the month of March, when it becomes warm enough. The bird wakes up quickly, and normal body temperature is restored within a few hours. It should really be borne in mind that in those places where this nightjar winters, the winter is very mild and even in January the air temperature during the day sometimes rises to +23 degrees above zero.
Features of hibernation of nightjars
The torpor that nightjars go into is very different from the hibernation that many mammals go into. First of all, the bird’s body not only does not accumulate energy reserves in the form of fat, but, on the contrary, consumes a significant part of them. If gophers or marmots go into hibernation, literally swimming with fat, then the birds become very skinny before going torpor. Their reserves of energy resources are limited and are only enough to wake up and resume food production. Therefore, the phenomenon of bird torpor is called not hibernation, but hypothermia.
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