The hazel grouse (Latin Bonasa bonasia) is a bird of the genus of grouse, a subfamily of grouse, a detachment of chickens. A widespread species, living almost everywhere in the forest and taiga zone of Eurasia, from Western Europe to Korea. Ryabchik – the smallest representative of grouse.
The weight of even the largest individuals rarely exceeds 500 grams. In the forest, it is difficult to confuse it with other grouse birds, from which it differs not only in small size, but also in sufficiently recognizable color. Despite the motley, “pockmarked” plumage (from which the bird got its Russian name), from a short distance the hazel grouse appears monophonic, gray-reddish. Sexual dimorphism in the hazel grouse is much weaker than in other black grouses – it is very difficult to distinguish a male from a female in nature. In addition, unlike other grouse, hazel grouse is a monogamous bird.
The life of the hazel grouse has been studied quite fully. It is a sedentary bird that does not commit long-range migrations. The hazel grouse, like all black grouses, is mostly herbivorous, although in summer in its diet animal feeds occupy a significant place; chicks also feed mainly insects. In winter, the hazel grouse must be satisfied with rough and malnourished plant food. In the presence of snow cover hazel grouse in winter burrows into the snow, spending the night in it and the coldest hours of the day. It also gives some protection from predators, from which the hazel grouse suffer greatly both in winter and in summer.
Despite the reduction in the world population and the periodic decline in the number of individual populations, hazel grouse is still numerous and is beyond threat of extinction. Most of the world’s number of grouse, numbering up to 40 million birds, is in Russia. There are usually 11 subspecies of hazel grouse, which differ slightly from the nominative.
Ryabchik is one of the most famous forest birds in Europe. First of all, it matters as an important hunting bird with delicacy meat. In the past, in many countries, hazel grouses were practiced on an industrial scale, and hundreds of thousands of hazel grouse were exported annually from the Russian Empire and the USSR until the 1970s. Now hazel grouse remains important as a popular object of sport hunting.
Dimensions
Ryabchik is the smallest member of the grouse family, much smaller than the black grouse. The length of an adult bird with a tail is 35-37 cm, the wingspan is 48-54 cm [13]. The weight of males varies within the limits of 327-580, females – 305.5-560 g [14]. Weight significantly fluctuates in the seasons, reaching a maximum in late autumn and early winter. Nevertheless, fattened large males with a mass of 500 g or more are rare enough [15]. For a cold season hazel grouses strongly lose weight and in April – May are much easier than in autumn [14] [15].
Appearance
Small, the size of a daw, a plump bird with a disproportionately small head and a short beak. Most of the time he spends on the ground, where he leads a secretive way of life. When approaching a person runs away or hides. Caught unawares, flies to 40-80 m and sits on a branch of a coniferous tree closer to the trunk at a height of not less than 5-7 m, trying to merge with it.
The overall color of the fir grouse is variegated – the bird is covered with black, red, brown and white spots and stripes, which, however, do not create the impression of a sharp contrast of colors; on the contrary, hazel grouse from a certain distance seems to be a uniform smoky-gray tone (sometimes with a red tinge). Around the eye is a well-marked bright red ring; eyes are black. The beak is also black, legs are dark gray. A flying bird has a noticeable dark strip at the base of the tail. Due to the characteristic color, as well as the small size of the hazel grouse, it is well distinguishable from other forest game. Only in the Far East it can be confused with the same little dikusha, which nevertheless is distinguished by lighter feathers and the absence of a dark strip on the chest.
The male is characterized by a black stain on the throat and a well-defined tuft. Differences in the coloring of plumage in the male and female are insignificant, however, in the male the throat and the lower part of the head are black, and the female has gray or dirty white. The female also has less developed tuft on the head, and the red ring around the eye is somewhat paler. In addition, the female is slightly smaller than the male. But in general, these signs are noticeable only when looking at a killed or caught bird, in the nature of a male from a female it is almost impossible to distinguish even near. In autumn and winter, hazel grouse seems lighter and grayer than at other times, because of the wider tops of the feathers of the winter dress.
The beak, like all the grouse, is relatively short, but strong, slightly curved. The length of the hazel beak is 10.4 mm on average. The edge of the beak is very sharp, which helps the birds to break rough shoots and twigs. The traces of the hazel grouse are similar to the traces of the capercaillie and black grouse, but much less. They are four-fingered – three fingers fan-shaped forward, one strictly back. The size of the print without the rear finger is 4.6 × 5 cm. The length of the grouse step, depending on the speed of movement of the bird, varies on average from 9 to 13 cm.
A well-known Russian writer, a passionate hunter and connoisseur of birds ST Aksakov noted:
The hazel grouse in many places is called a puffer; He deserves these names: he is all pock-marked, all variegated. The size of the hazel grouse, the oldest, is slightly larger than the Russian pigeon, but it will be somewhat round and dented. Its warehouse is absolutely grouse.
The hazel grouse is similar to the black grouse, only much smaller in size. It has the appearance of “sausages” about 4.5 to 0.6 cm, yellowish in color; the end of the sausages is always white. In winter it is colored yellow if the bird feeds on birch, or in rusty, if it feeds on alder earrings and branches. It is interesting that hazel grouse almost never have a layer of subcutaneous fat, characteristic of most birds in the cold season. Fat accumulates only hazel grouses in a number of regions of Siberia with a very cold climate, but in the Middle Russia, the layer of fat in the hazel grouse has never been noted by researchers.
Vote
It’s quite a silent bird. The main voice signal is a long and very thin whistle, comparable only with the singing of a fox-auburn, a yellow-headed queen and an ordinary remez. This whistle, consisting of two long and several short sounds, can be heard in a quiet weather at a distance of up to 100 m. The nature of the sound pattern is somewhat different in the sexes, in the male it is transmitted as “fiyit, fuiiiit, fyu-ti-ti-te-tju “. Performing the song, the male throws back his head and opens his beak wide. The female singing is shorter and simple.
Both sexes show vocal activity during the mating season, as well as in the fall. The latter is associated with the redistribution of old pairs and the formation of new ones, but only males respond to decoys. Sometimes the whistling of hazel grouse can be heard in winter during the thaw. When communicating birds also echo through the whistle, during the alarm they make a gurgling crackle. Such a trill, only a longer one – “piririririri”, the female publishes, warning the brood about the danger. In addition to the voice signal, the current male on takeoff can make cotton with wings that are louder than usual. In some cases, a fast series of such cotton, outwardly resembling a woodpecker drumrel, follows.
Usually the whistling of males has individual characteristics (mainly in rhythmics), while the bird can whistle slightly differently from time to time. Studying the whistle records of males from different areas of the range showed significant differences in the manner of performance, which, for example, among hazel grouses from France, is more common in the entire local population. The whistling of the hazel grouse is accompanied by a sharp but quiet rustling sound, audible only at the closest distance. The whistling hazel grouse sits on a branch or stands motionless on the ground, drawing its neck deeply and opening its beak. The whistling of the female in timbre is similar to the male’s whistle, but the female’s trill is much shorter and simpler. A frightened bird makes a short trill resembling a gurgling.
Areal
Ryabchik is an inhabitant of the boreal forest zone of Eurasia. The historical area of distribution extends from Western Europe to the east to the Kolyma Range, northern Japan and the Korean peninsula. However, in the West and Central Europe, hazel grouse already disappeared from most habitats in the 19th century, remaining in separate populations in some mountainous areas, although it has been absent for many decades in the Pyrenees.
At a later time, it disappeared in many places in China and Mongolia due to the forest data. In the 1970s, severe hazel-grouse depopulation occurred in Japan – its numbers there decreased several times for reasons that were not fully understood.
Currently, the westernmost nesting areas are found in eastern France and Belgium (the Ardennes Mountains). The southeastern periphery of the range is in the regions of Altai, Khangay, Khantei, Greater Khingan and the middle part of the Korean Peninsula. Outside the mainland, the bird is found on the islands of Sakhalin and Hokkaido. The northern boundary of the range of hazel grouse in places passes the Arctic Circle. At least in Scandinavia and the Kola Peninsula, it occurs up to 69 ° N, in the Urals to 67 °, on the Kolyma to 68 ° 30 ‘. In fact, the northern boundary of its range is everywhere the boundary of forest spread. In the south, hazel grouse is also prevalent mainly up to the border of the forest zone, although it sometimes penetrates into the forest-steppe, which is inhabited there in large forest areas, but is absent in isolated forests of the Caucasus, Tien Shan and Kamchatka.
The total number of hazel grouses has a tendency to decrease due to the general increase in anthropogenic pressure on wildlife, therefore in most densely populated areas the area is severely torn. Nevertheless, at the present time, despite the overall decline in numbers, the border of the range as a whole has remained unchanged and the hazel grouse continues to inhabit most of its historical range.
Habitat
The hazel grouse is a solely forested bird. It never occurs in a field, on a swamp and mountain tundra. Avoids dilapidated forests dominated by a single crop, such as pine or larch forests, as well as forest parks. In predominantly pine plantations, it settles only in the southern part of the range, where a dense fern undergrowth is well developed. The hazel grouse does not hold even at the edge of the forest, avoiding approaching the edge more than 200-300 m.
A typical hazelboot habitat is a mixed forest with a crossed relief, a network of streams, ravines, the presence of glades. The forest plots with an abundance of fallen trees, a dense closed fir grove and interspersed with birches and aspens serve as ideal protective and feeding conditions for the existence of hazel grouses. Most often such areas are found in interfluves and slightly swamped, low-lying areas. In such areas, there is always an increased concentration of grouse. Pure birch and alder stands hazel grouses are avoided, despite the fact that these tree species provide them with the main food in the winter.
At the same time, the hazel grouse prefers to stay where there are spruce forests, which gave some scientists even reason to believe that the presence of spruce is an indispensable condition for the dwelling of this bird. However, spruce has a value for hazel grouse only as a good shelter, and in places where it does not grow, hazel grouse still occurs. In a pure pine forest hazel grouse does not live, except in cases when there are abundant thickets of ferns in which the bird finds shelter. The hazel grove avoids glades with high and dense grass. He willingly keeps himself at the forest roads, which are covered with edible plants along the roadside, with the constant presence of water in the ruts and the scattering of pebbles.
In the past, when the hazel grouse was more numerous, the density of its livestock in the forest zone was very high. So, according to the data cited in the literature of the early 1950s, in the European North of the USSR in the forests of the Prippechorsky forests in an area of 1 km? totaled from 17 to 37 birds, in the Gorky region in some places – up to 75-100 grouses in 1 square. km .
general characteristics
In general, the way of life of hazel grouse is similar to that of other northern grouse, especially black grouse. It is a sedentary bird that does not commit long-distance movements and migrations. The hazel grouse rarely rises to the tops of trees, preferring to sit a few meters above the ground, usually no higher than half the height of trees, choosing thick horizontal branches. He almost never sits on top. Most of the time in the warm season the hazel grouse conducts on the ground.
The hazel grouse, like a black grouse and a wood grouse, flies up with a loud noise and flapping its wings, but flies silently, holding on to the middle of the trees. Scared bird usually makes a quick turn and disappears in branches, hiding. For hiding, he prefers usually coniferous trees, usually spruce or fir, but where the hazel grouse is not frightened, he can hide even on a bare birch, where it is clearly visible. If the hazel grouse is familiar with a person, he is usually very cautious – scared, flies away, to 100 m, then firmly lurking in the thick spruce branches. The hazel grouse is running fast and fast on the ground, moving quickly among the windbreaks and thickets. On the run, he slightly hunches, stretching his head and neck forward.
Like other grouse, hazel grouse often bathe in dust and sand, thus relieving from ectoparasites and peeling feathers. The place where the hazel grouse took a dust bath (“flounder”) looks like a shallow oval fossa about 18-20? 6 cm in size. In addition to dust baths, hazel grouses in the spring also carry out an interesting procedure related to care of the plumage and cleansing it of ectoparasites – bathing in anthills (so-called “ant”). Birds climb on the newly thawed anthills on which ants begin to appear, and, pricking feathers, provoke an attack of ants spraying feathers of birds with formic acid.
General characteristics of food
Like other grouse, hazel grouse is mainly a herbivorous bird, although feed animals occupy an important place in its diet. A characteristic feature of hazel grouse is the pronounced seasonal nature of its ration. No other hunting bird in the fauna of the former USSR has such a strong seasonal variation in feed. It is interesting that blind outgrowths of the intestines in which fermentation of the phytogenically swallowed plant food takes place, in the summer (when animal and soft plant food predominates in the diet) do not function. But they start to act in the winter, helping the bird to acquire roughage. Young birds in the first days of life feed mainly on animal feed – mainly insects, as well as ant eggs (“eggs”), but very soon they begin to eat more and more vegetable food – green herbs and berries.
Like almost all chicken, for normal digestion hazel need to swallow small pebbles, which perform in the stomach the role of millstones, grinding food (so-called touring). Chicks of hazel grouse already starting from the age of 10 start to grit sand and various pebbles from quartz, limestone and other minerals. Sometimes, instead of pebbles in the stomach of hazel grouse, there are solid bones of cherry, hips and bones. The grouse is most active in collecting pebbles in September and October. At this time, they are often found on forest roads, in outcrops of soil and in general of any places where there are deposits of pebbles. The total weight of gastrolits in the bird’s stomach in the summer is 1.5-2.5 g, in winter, when it is required to digest the hard food – 3.5 g. According to other data, the number of gastrolites reaches a peak at the time of transition to winter food, then decreases somewhat.
Diet in the warm season
Berries cranberries, eagerly eaten by hazel grouse in warm weather
In the spring, after the disappearance of the snow cover and in summer, the hazel grouse feed more on the ground, eating mostly berries: strawberries, blueberries, cranberries, bones, etc., as well as grass seeds. In addition, insects and spiders are eaten, but even at the height of summer, their share in the total balance does not usually exceed 5%. The more the hazel grouse lives in the south, the more diverse is the animal feed that it consumes, which can also include ants, slugs, beetles and orthopterans.
At the end of summer and autumn, hazel grouse often feed on the fruits of mountain ash. According to the research, 25 species of plants are included in the spring diet of hazel grouses that inhabit the Altai, 45 in the summer, and 60 in the Ussuri taiga. In this case, the predominance of a particular plant species is usually observed, depending on the bird’s habitat and the season. So, in the northeastern Altai, flowers and leaves of the Altai windmill (52%), then earrings, buds and birch branches (23.8%) are in the first place, but in the same places during the mass fly of the forest bug in autumn the hazel grouses eat only these insects.
In the south-eastern Altai at the end of August only fruits of redcurrants were found in the stomachs of hazel grouses, birds from the vicinity of the Karelik River at the end of June – exclusively borage seeds. The grouse willingly eats pine nuts and, in case of a good harvest, they gain weight very much. Conversely, in the case of poor harvest of pine nuts, the number of hazel grouse is usually reduced. In places where hazel grouses accumulate subcutaneous fat (studies were conducted in Central Siberia), the fat content of birds depends directly on the yield of fir cones, the seeds of which the hazel grouse feed mainly during the pre-winter period.
Diet in late autumn and winter
The transition to the autumn-winter diet occurs simultaneously with the breakdown into pairs. It is caused by lowering the air temperature below 0 ° and extending the night. In most of the range this transition begins long before the establishment of the snow cover, in the middle latitudes – already in September. The colder the autumn, the faster this transition takes place, which can also be accelerated by crop failures.
Autumn and winter hazelnut fodder – mainly earrings and buds of deciduous trees (in the central zone of Russia – birch and hazelnut). Often the hazel grouse tears off the soft tips of the branches. In winter, in frost, the kidneys and earrings are eaten frozen and ice-cold. Due to the inadequate winter feed, the hazel grouse is forced to eat it in much larger quantities than the summer forage. The content of goiter in the winter grouse is on average 30-40 g, sometimes up to 50, while in the summer – 12-15 g. After winter fodder, the seeds that fall out of fir cones unfolding under the rays of the March sun are a good aid to hazel grouses.
Conjuration
The grouse begins at the end of March or the beginning of April, when the first thawed patches appear in the snow in the forest. The marriage period lasts quite a long time – in central Russia, in the Southern Urals and Altai, until the middle of May, in the Pechora taiga – until the middle of June, in the Ussuri taiga – even before the beginning of July. The terms of the mating season, as well as reproduction in general, vary from year to year among hazel grouses, depending on the weather. It is indicated, however, that the development of male gonads is not related to weather conditions and depends solely on the reaction of the bird’s organism to the duration of the day.
The current male takes characteristic postures – plumage plumage, quickly runs along the ground and thick branches, dragging open wings and unfolding the tail with a fan. At the same time he makes a characteristic whistle. Unlike the black grouse, hazel grouses do not gather in groups on the tarmac; each male of the hazel grouse picks separately on its own site, expelling from its territory other males appearing there. The female, as a rule, keeps nearby and runs to the male’s invocatory whistle, from time to time issuing a more coarse and abrupt whistling.
With further warming, the number of birds is increasing, couples often are near one another. In such cases, there are fights of males. The male, in any case, after hearing the current whistle of another male, goes to him to engage in a fight. At the same time, he takes a characteristic pose of aggression, lifting feathers, raising his half-opened tail and stretching his neck and head forward, and the feathers on his chin stand erect, as on the “beard” of the mewing male wood-grouse.
In the n hunting literature of the XIX century there were colorful and accurate descriptions of the marital behavior of grouse:
With the first glimpse of the morning dawn, a furious little boy awakens, fluttering to the Elinka with a noise and starting his sonorous treble trill. In the depths of the fir grove, the peasant answered and, with a revulsion, led the wife into raging enthusiasm: he swiftly descends from the tree to the ground and, spreading his tail with his fan, spreading his wings, raising his hawl and fluttering as if running towards the voice of the female … Here the furious man makes a short trill, breaks and flies without stopping in the direction of the voice, meets the ryabushka and melds with passion; then both run together to eat a few berries of cranberries, somehow separate, and the male starts to poke again, comes to the same excitement, and the same conjugal tenderness is renewed. For the variety of the picture is often a randomly encountered opponent, and peaceful scenes are violated by a fierce fight.
During the current, males almost do not eat and lose weight heavily; Testes on the other hand, greatly increase. On the contrary, females, on the other hand, feed intensively and reach a maximum of spring weight at the time of laying eggs.
Laying eggs
The female builds a nest on the ground (like all pheasant ones), usually under a bush or a heap of fallen trees, where it is visually very difficult to detect it. LP Sabaneev reported that in the Urals, with a purposeful search, he only found a hazel grouse twice, while the nests of the grouse were 15 times. The mottled coloring of a female sitting on eggs perfectly masks it among last year’s grass. The nest is a small hole, lined with dry grass or leaves, a diameter of 20-22 cm and a depth of about 5 cm. Egg laying takes place in the middle or end of May. In rare cases, hazel grouse can be found in abandoned nests of other birds. The hazel grouse was found in the old nest of a jay, a crow, a buzzard.
Eggs of hazel grouse
Eggs of hazel grouse smooth, shiny, their color is brownish-yellow, with rare red-brown specks, which sometimes can not be. The basic color also varies from light yellow to almost brown. The color of the eggs will fade a little during the incubation period. On average, the masonry consists of 3-14 eggs, usually 7-9. In exceptional cases, the nest can hold up to 20 eggs, which, most likely, is the result of the deposition by two females. The size of the eggs: (36-43)? (25-30) mm. Nasizhivanie begins after the laying of the last egg and is made only by the female. The male at this time keeps close to the nest. Nasizhivanie lasts 21 days, according to other sources, it can last for 25-27 days. The female sits on the nest so tightly that sometimes allows a person to touch herself. Being frightened, she tries to take the enemy away from the nest, mostly by a dash across the land.
Development of the brood
The chicks of hazel grouse, as is typical for the entire detachment of chickens, brood type, that is, they come out of eggs already covered with down and can run now after they have dried under the wings of the mother. They are more thermophilic than chicks, for example, wood grouse, and in the first days, after 5-6 minutes after feeding, they need heating from the mother’s side. On the second day the female takes them to light grassy lawns and fringes, where the chicks find small insects and caterpillars, which constitute their main food in the first days. It is known that the female helps chicks to feed on ant eggs, digging them out of anthills.
The chicks feed in the morning and in the evening, spending the rest of the day secretly, hiding in a thick bed or a fallen tree.
Insects with downy chicks in most areas of the range are observed in the first half of June, in the north and in the upper belts of the mountains in the second half of June and even in early July. Some sources reported that the role of the male in rearing the offspring was not clarified, although in general the authors agree that the male does not participate in the brood rearing, but is always nearby, as during the incubation period. On the other hand, the well-known naturalist MA Mensbir reported that in case of death of the female, the male can take care of the offspring, guarding the brood and collecting fledglings by voice signals, which are usually given by the female.
In the early days the chicks of hazel grouse grow slowly, but quickly fledge. On the 4th-5th day, they are already trying to flutter, and by the tenth and eleventh day they are able to fly to trees. Some authors indicate that the chicks can sit on the branches already in 7 days. At this age the young grow to the size of a sparrow. After this, the chicks begin to gain weight quickly. If at 10 days of age they weigh on average about 10 g, by the end of the second decade the weight increases to about 40 grams, the fourth – 200 grams, the fifth – 250 grams, the sixth – 325 grams. In the last two decades, the youth feather outfit is replaced with a dress adults.
At the age of two months, young adults reach the level of adults (this happens in temperate regions usually by the end of August) and differ from them only with the feathers of the youthful attire on the head. Soon molting ends completely, after which the broods disintegrate, and the young begin to lead an independent way of life. In areas with a cold climate, all the dates indicated are shifted to a later time; The same applies to hazel grouses in the highlands.
Winter way of life
Features of winter behavior
In winter, hazel grouses are strictly sedentary, and although they continue to occupy former individual plots, very few move. Often they spend a lot of days in one area, bounded by a small meadow or a group of trees. They are kept mainly in pairs, which are broken in the fall, less often in places where the feeding is abundant – in groups of 5-10 heads.
The hazel grouse is well adapted to severe winters. Its winter feather is much denser than summer and protects well from frost. This is caused, first of all, by a special “double” structure of the winter dress – each feather, in contrast to the summer, has, in addition to the main rod, an additional, with a developed fan. In winter, at the hazel grouse, the plyna is fully covered with feathers, almost hiding the back finger. On the lateral sides of the fingers, special elongated outgrowths of horny scales appear to the winter, which increases the area of support when the bird moves through the snow (all these signs are also characteristic of other northern grouses). However, despite the good adaptability to the frosty and snowy climate, hazel grouse in severe winters suffer greatly from the cold and lack of feed.
In the cold, hazel grouses lead an extremely inactive way of life, trying to fly as little as possible. They feed exclusively on trees, going down to the ground usually just to burrow into the snow. If the birds do not bury themselves in severe cold, they spend the night on the branches of spruce, choosing the most dense and dense branches.
Burying in the snow
If there is a thick enough snow cover, grouse, like the black grouse, sleep in the snow. This is of the utmost importance both as a way to escape from the cold, and as a shelter from predators. In addition, a hazelber who has eaten frozen birch buds or earrings, it is necessary to begin to thaw them into the goiter as soon as possible with the warmth of one’s body, which requires considerable energy expenditure that the bird can not afford while sitting outdoors.
Therefore, in winter, hazel grouses usually dive into the snow directly from those trees, which were fed, immediately after the end of fat. The hazel grouse hide in the snow when its depth reaches 15 cm. In loose fluffy snow, birds dive straight from the trees, in a denser dig a hole consisting of a hole at a depth of 15-20 cm and a snow course leading to it. The length of the stroke is often more than 1 m, it was reported even about 4-meter courses. Usually hazel grouses winter in pairs, less often flocks; their holes are usually located at a distance of 2 to 5-8 m from one another.
Having ducked, the bird sweeps the snow with the weight of the body, and then starts digging. When digging the course, the hazel grouse pierces the snow ceiling every 15-25 cm and looks around. Sometimes a bird makes up to 5-7 such watch holes before settling down for the night. Ryabchik digs the snow first with his feet, then with lateral movements of the wings, which causes the feathers on his sides and neck to be noticeably erased by the end of winter due to constant friction against the snow. The shape of the snow stroke can be very diverse: horseshoe, rectilinear, zigzag. In the case of severe cold, especially in January – February, hazel grouses are buried in the snow even in the daytime.
Sometimes they spend 18-19 hours a day in the snow. It was noted that birds can be in the snow even 23 hours a day, limited to only one flight for feeding. Ryabchik prefers to dive in the snow almost in the same place. In winter, this place can be easily detected by leaving the bird around the litter piles, which the hazel grouse can make up to 180 around its sleeping hole during the winter.
Having finished digging holes, hazel grouse with head movements clog the entrance with snow. The temperature in the sleeping hole of hazel grouse in the snow is kept at a level of 4-5 ° and depends little on external factors. If it starts to rise, the bird’s head pierces the hole in the ceiling and the temperature goes down. Interestingly, the walls of the burrow are never icy and do not melt. At a temperature of about 0 °, the hazel grouse does not burrow into the snow, and the buried bird, when warming above 0 °, leaves the burrow, since being in the snow in this case threatens with wet plumage
