Do birds hibernate in winter? Nightjar is a bird that hibernates Birds that hibernate

Many animals spend the winter in a state called hibernation. However, out of several thousand species of birds known today, only one goes into hibernation - the California nightjar.

This bird is active mainly at night, and during the cold winter months it hides in cracks between stones and other shelters. Its normal body temperature is 35-45.5°C, but during hibernation it drops to 20°C and lower if it gets cold. This is how the bird saves energy obtained from fat reserves.

Scientists previously had no idea that the nightjar hibernates. It was only in 1946 that a sleeping bird was discovered in one of the Californian canyons. However, the Indians probably knew about this, since they called this bird “dormouse.”

In deep sleep

The nightjar hibernates in secluded places such as cracks between stones. Every year he spends about 90 days without moving, with his eyes closed.

When threatened with attack, the nightjar inflates its body and spreads its wings. The nightjar is a nocturnal bird that feeds on insects. She spends the day in bushes or in trees.

Hibernation Hibernation (winter - hibernation, summer - estivation) is a period of slowdown in life processes and metabolism in homeothermic animals during periods of low food availability, when it is impossible to maintain activity and a high level of metabolism. It is characterized by a decrease in body temperature, slowing of breathing and heartbeat, inhibition of nervous activity (the so-called “deep sleep”) and other physiological processes. Usually, before hibernation, animals feed heavily and accumulate large reserves of nutrients in the form of fat (in the case of seasonal hibernation, up to 30-40% of body weight) and take refuge in shelters with a suitable microclimate (nests, burrows, hollows, etc.). Depending on the regularity, the following types of hibernation are distinguished: daily hibernation in hummingbirds and bats; seasonal hibernation - winter (hibernation) in insectivores and rodents or summer (estivation) in desert animals; irregular - with the sudden onset of unfavorable conditions (raccoon dogs, squirrels). Some large mammals (bears, badgers, raccoons) enter hibernation, a type of hibernation with a smaller decrease in the levels of physiological processes and metabolism. In a brown bear, during winter sleep, the body temperature decreases slightly (from 37° to approximately 31°C), and rises easily and quickly upon awakening. Some species spend part of their pregnancy in hibernation, in which case birth occurs immediately after emerging from hibernation. During hibernation, in addition to periods of actual hibernation, there are also periods of increased body temperature to normal levels. Among mammals, rodents, one species of lemur, the European hedgehog and other insectivores and marsupials hibernate. Pliny the Elder believed that swallows are also capable of hibernation, but this is erroneous - birds, with the exception of nappers, usually do not hibernate. Hummingbird and swift chicks fall into a state similar to hibernation (sharply lowered body temperature and torpor) in the absence of their parents. It has long been believed that primates do not hibernate. But in 2004, evidence was published that the little dwarf lemur from Madagascar hibernates in tree cavities for seven months of the year. This is especially interesting in light of the fact that winter temperatures in Madagascar can exceed 30°C. Apparently, the hibernation of this lemur is not caused by the need to wait out low temperatures. Hibernation can last from several days to several months depending on the species, external temperature and other environmental conditions. During hibernation, there are periods when body temperature is restored to normal values. During hibernation, the animal’s body is nourished by the reserves of nutrients accumulated the day before (fat, etc.). The animal traditionally considered capable of hibernation is the bear. But the degree to which a bear's metabolic processes slow down in winter is much less than that of rodents, insectivores and other animals - so biologists usually believe that this cannot be called hibernation in the real biological sense. Also, during hibernation, a bear’s body temperature does not decrease very much (from 37° to about 31°C), and is easily and quickly restored; while in ground squirrels (genus Xerus) the body temperature during hibernation can drop to −2°C. A process similar to hibernation is known in several species of reptiles, but it is not yet known whether it is true hibernation. Typically, before hibernation, animals feed heavily and accumulate relatively large reserves of nutrients in the form of fat. Several species spend part of their pregnancy in hibernation, in which case birth occurs immediately after emerging from hibernation. For several decades, it was believed that the giant shark hibernates during the winter, descending to the bottom horizons of the northern regions of the ocean. But research conducted in 2003 by David Sims refuted this, showing that sharks actively move at this time in search of places with the largest amount of plankton. According to the depth of hibernation, they are distinguished: Seasonal or facultative hibernation. It is characterized by the fact that the animal’s body temperature, respiratory rate and overall metabolic rate decrease slightly. If you are anxious, sleep can easily be interrupted. Characteristic of bears, raccoons, raccoon dogs, badgers. True continuous seasonal hibernation. It is characterized by loss of the ability to thermoregulate (heterothermia), a sharp decrease in the frequency of respiratory movements and heart contractions, and a decrease in metabolic activity. Summer hibernation or aestivation, also called summer diapause, is characteristic of organisms at low latitudes and ensures their survival during the dry season. It can often be observed in rodents deprived of complete and water-rich food during the summer. For example, the sand squirrel in Central Asia enters summer hibernation in June - July. In gophers, summer hibernation usually passes into winter hibernation without interruption. Summer hibernation is also observed in some inhabitants of the tropical zone. In the African hedgehog Atelerix albiventris it lasts up to three months, and in the Madagascan insectivores tenrecs it lasts up to four months. List of animals that hibernate[edit | edit wiki text] Rodents Lesser dwarf lemur Bear Hedgehog American white-throated nightjar Australian echidna Australian pygmy possum Chilean possum Bat Hamster Dormouse Marmot Chipmunk Gopher Badger Frogs

Hibernation is more than just an adaptation for animals to survive the cold season. For hedgehogs, dormouse and horseshoe bats, this is the only way to avoid starvation. At the beginning of winter, when the temperature drops below 15 ° C, the marmot curls up in a ball in its hole and hibernates. Sometimes they wake up Some animals sometimes wake up during winter sleep. Bats sleep longer without interruption, but their sleep lasts no more than a month. From time to time they wake up and, having moved to another place, fall asleep again. Some species even catch insects in their wintering grounds. The hedgehog sleeps for no more than 2-3 weeks, and then wakes up for a short time. Frequent awakenings during warm winters do not benefit the hedgehog, since in this case fat reserves are used up faster. Other insectivores, for example, the little shrew, which weighs 2 g, are an example of the other extreme: in cold weather they fall into a state of torpor for several hours. However, this is not true hibernation.

Hibernation (hibernation) is a slowdown in vital processes and metabolism for a certain period of time. At the same time, body temperature decreases, breathing and pulse slow down, nervous activity and other body processes are inhibited. During the winter, many animals find it difficult to find food for themselves and they choose this method of survival in order to survive until warmer days. Before hibernation, they feed with a vengeance, thus accumulating the energy they need during the hibernation period. Animal hibernation is a perfect way, invented by nature, to save its offspring from conditions unusual for their normal life. There are a huge variety of animals that hibernate in winter. Most of them live in a temperate climate, characterized by warm summers and cold winters, during which it is difficult for them to find food. Some of them will be discussed below. Bear The most famous representative of the animal kingdom that hibernates in winter is the bear. It should be noted that its hibernation is considered shallow. It's more like a nap. Its body temperature does not become as low as that of other animals in true hibernation. The same goes for his heartbeat. This means that if you try to touch him in this state, he can wake up very quickly and immediately begin a fight. Bears are animals that hibernate in winter without losing their orientation in space and time. However, bears can remain in this state without touching food or water for seven months. This becomes possible thanks to the fat accumulated over the summer, the layer of which can reach 15 cm. In the summer, a bear not only eats food, it brutally overeats. This process is somewhat reminiscent of fattening a pig, and is also equal to 30 full meals eaten per day by a person. What animals hibernate in winter? Common hedgehog Hedgehogs are engaged in active life from 4 to 7 months, dividing this period into three stages: awakening, reproduction, preparation for long hibernation. With the onset of cold weather, they hibernate. The main reason for this phenomenon for hedgehogs is lack of food, the secondary reason is cold. They do not store food for the winter because they feed on insects. Therefore, they have to store up fat in the summer season and hibernate in the winter. In addition, their thermoregulation is imperfect, which leads to the need for prolonged winter torpor. Gophers Gophers, in terms of hibernation, are among the animals that are in a state of torpor for the longest time, to be more precise, up to nine months a year. Moreover, the cyclical nature of their stay in this state is noted. A short active period of life alternates with long-term torpor, after which active life begins again. It is replaced by prolonged hibernation, etc. This feature of their body is hereditary. Frogs Frogs, in comparison with animals that hibernate or are in a torpor, can be in a state of deeper suppression of vital activity - in suspended animation. At the same time, their metabolism slows down as much as possible, and survival is carried out at the expense of internal energy reserves. Depending on the species, frogs can hibernate in burrows they have dug, in crevices that they themselves fill with leaves, and also at the bottom of reservoirs. Bats In winter, bats, having found a suitable shelter, fall into torpor for 7-8 months. Their sleep is interrupted every 2-3 weeks by awakenings to search for warmer shelter and matchmaking, since winter for these animals is the period of reproduction. Animals that hibernate also include rodents, Australian echidnas, Chilean opossums, hamsters, dormice, chipmunks and badgers. All animals, without exception, prefer rest, either at night or during the day, to active wakefulness. They especially like to fall into a state of stupor or catalepsy. In countries with cold and temperate climates, the usual pastime of animals is six-month hibernation. Hibernation is a hereditary reaction of living organisms to temperature changes, formed millions of years ago. It was possible to survive these changes only by learning to regulate your own temperature during the onset of cold or heat. The life of the animal depended on the ability to sleep through difficult times. Why do animals hibernate? This is how nature took care of its creatures - this skill will be useful to them if the climate on Earth changes again. Hibernation is characterized by a slowdown in life processes and metabolism in animals during periods when food is inaccessible, which means it is impossible to maintain activity and a high level of metabolism. Preparing for hibernation. In preparation for a long sleep, animals accumulate reserves of nutrients, their weight due to fat can increase by 40%, and also store food. Nutrition during the preparatory period is rich in fatty acids, which increase immunity and resistance to prolonged torpor. Rodents spend the winter in families or alone. The burrows they dig can stretch three meters or more inward. They store grains, nuts and seeds to maintain vitality. The shelter (hollow, nest, cave, burrow) is selected taking into account safety, protection from predators, and microclimate: the temperature of the shelter should be slightly above zero, even in severe frosts outside. Based on the method of maintaining body temperature, animals are divided into: Endothermic, which maintain thermoregulation using internal resources. These include all warm-blooded organisms: mammals, birds. Fish sleep, wrapped in silt at the bottom of dry reservoirs. Turtles and rodents, deprived of food, fall asleep until winter, when the swamps and plants dry out from the heat. Some inhabitants of the tropics also tend to fall asleep for long periods: African hedgehogs sleep for about three months, and the insectivores of Madagascar for about four. The hibernation record is broken by rodents. The sand squirrel sleeps for nine months in a row. Falling into summer hibernation at the end of July, the animal enters winter hibernation without waking up. Periodic awakenings. Some animals wake up from sleep from time to time. Scientists do not know exactly the purpose and reason for this behavior. Awakening can last from several minutes in small organisms to several hours in large ones. So many living organisms go into hibernation that it is very difficult to list them all. Soviet zoologist N.I. Kalabukhov argued that there are much more animals in a state of torpor in winter than those who are awake. Physiology of hibernation. Body temperature. Sleeping animals are only a fraction of a degree warmer than the surrounding air. The body temperature of the dormouse drops from 38 degrees to 3.7 (ten times!). In some species it can drop to zero or even minus five degrees Celsius. The dalliya fish, a rare warm-blooded fish, falls asleep when the water bodies of Chukotka freeze through. If a dallia frozen in a piece of ice is placed in warm water, then as soon as the ice melts, the fish will come to life. Thanks to the unique glycerin-like impregnation, ice crystals that can rupture cell membranes do not form in dahlia tissues. The hypothermic state in everyone else is manageable. Brain regulators, led by the tireless hypothalamus (the part of the brain responsible for the constancy of the internal environment of the body), turn on fat heating in a timely manner so that the body temperature does not fall below a critical level. Metabolism during hibernation decreases in animals to 10-15% of normal. Breathing in sleeping mammals decreases 40 times. In many species, it alternates: rapid superficial breathing is replaced by apnea (lack of breathing), lasting more than an hour, which causes oxygen starvation. Gas exchange decreases by 10 times. The hedgehog, curled up into a ball, takes a subtle breath just once a minute. Brain activity is preserved only in the hippocampus, a section adjacent to the hypothalamus. The heart slows down the rate of contractions per minute to 5-10 beats; in a hedgehog, it beats even at zero body temperature. This is surprising, because in animals that do not hibernate, the heart stops at 15 degrees body temperature. Blood pressure decreases slightly, from 20% to 40, as blood viscosity increases due to a decrease in temperature. Thanks to increased blood viscosity, the heart is better supplied with “brown fat,” a source of energy. Before hibernation, the hormonal system adjusts to a new rhythm: the animal accumulates fat, enzymes, vitamins, especially vitamin E, which inhibits metabolism. In the summer, animals get fat, increasing their weight three times by the fall, and in the spring they wake up thin and weakened. An interesting fact: the hibernation of the brown bear, squirrel and prairie dog is not real - they fall into a state of superficial torpor. Their metabolism slows down slightly, and their body temperature, pulse and breathing are at levels typical for normal sleep. Most of them hide in their shelters and support their existence from the food and fat reserves they have collected for this occasion. A bear's consciousness does not turn off during hibernation; it is easy to wake him up. Pros and cons of hibernation. An undoubted advantage is the reduction in the animal’s energy consumption: it spends only 15% of the energy that it would need to maintain normal body temperature in winter when awake. For 4-7 months they can exist due to accumulated reserves of fat and other nutrients. Disadvantages: the possibility of dying from desiccation or exhaustion, the development of atrophy of the skeletal muscles, decreased immunity, freezing at extremely low temperatures is possible, defenselessness against predators. Scientists' research into the mechanisms of animal hibernation has a practical purpose: the formula of chemical substances that immerse animals in long-term suspended animation will make it possible to carry out surgical operations, cooling the human body to the required temperature.

So, we found out 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, for example, 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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So, we found out 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 autumn, when the 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 birds 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 - 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, the 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 for food, will linger 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 (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 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.

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 its 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.”