From Academic Kids

This article is about the bird. Capercaillie is also the name of a Scottish folk band.
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Scientific classification
Binomial name
Tetrao urogallus
Linnaeus, 1758

The Capercaillie or Wood Grouse (Tetrao urogallus) is the largest member of the grouse family. The huge male is 74-90 cm in length, and the female 54-63 cm.

It is a sedentary species, breeding across northern parts of Europe and western and central Asia in mature conifer forests with diverse species composition and a relatively open canopy structure.

At one time it could be found in all the taiga forests of northern and northeastern Eurasia within the cold temperate latitudes and the coniferous forest belt in the mountain ranges of warm temperate Europe. The Scottish population became extinct, but has been reintroduced; in Germany it is on the "Red list" as a species threatened by extinction, and is no longer found in the lower mountainous areas of Bavaria. In the Bavarian Forest, the Black Forest and the Harcynian mountains numbers of surviving Capercaillies decline even under massive efforts to breed them in captivity and release them into the wild.

The most serious threats to the species are habitat degradation, particularly conversion of diverse native forest into often single-species timber plantations, and to birds colliding with fences erected to keep deer out of young plantations. Increased numbers of small predators (e.g. Red Fox) due to the loss of large predators (e.g. Wolf, Brown Bear) also cause problems in some areas. In some areas, declines are due to excessive hunting, though game laws in many areas have stopped this. It has not been hunted in Scotland or Germany for over 30 years.

Its name in English is derived from the Gaelic capull coille, meaning "horse of the woods".



Male and female Capercaillie - the cocks and the hens - can be discriminated easily by their size and colouration. The cock is much bigger, weighing 4-5 kg on average. He is approximately 90 cm long and has a wingspan of 1 m. The body feathers are coloured dark grey to dark brown, breast feathers are dark green metallic shining. The belly and undertail coverts vary from black to white depending on race (see below).

The hen is much smaller, weighing about half as much as the cock. Her body from beak to tail is approximately 60 cm long and the wingspan is 70 cm. Feathers on her upper parts are brown with black and silver barring, on the underside they are more light and buffish-yellow.

Both sexes have a white spot on the wing bow. They have feathered legs, especially in the cold season for protection against cold. Their toe rows of small, elongated horn tacks provide a snowshoe effect that led to the German family name "Rauhfusshhner", literally translated as "raw feet chickens".

These so called "courting tacks" make a clear track in the snow in winter. Both sexes can be distinguished very easily by the size of their footprints.

There is a bright red spot of naked skin above each eye. In German hunters' language, these are the so-called "roses".

There are several races, listed from west to east:

  • T. urogallus cantabricus - NW Spain
  • T. urogallus aquitanicus - Pyrenees
  • T. urogallus major - Central Europe (Alps to Baltic States)
  • T. urogallus rudolfi - Southeast Europe (Bulgaria to southwest Ukraine)
  • T. urogallus urogallus - Scandinavia; introduced in Scotland (1837)
  • T. urogallus karelicus - Finland, Karelia
  • T. urogallus lonnbergi - Kola Peninsula
  • T. urogallus pleskei - Belarus, central European Russia
  • T. urogallus obsoletus - Northern European Russia
  • T. urogallus volgensis - Southeast European Russia
  • T. urogallus uralensis - Ural Mts., western Siberia
  • T. urogallus taczanowskii - Central Siberia to northwest Mongolia

The races show increasing amounts of white on the underparts of males from west to east, almost wholly black with only a few white spots underneath in western and central Europe to nearly pure white in Siberia. Variation in females is much less. The native Scottish population, which became extinct between 1770-1785, was probably also a distinct race, though it was never formally described as such; the same is also likely of the extinct Irish population.

The small chicks resemble the hen in their cryptic colouration, which is a passive protection against predators. Additionally, they wear black crown feathers. At an age of about 3 months, in late summer, they moult gradually towards the adult plumage of cocks and hens. The eggs are about the same size and form as chicken eggs, but are more speckled with brown spots.

The Capercaillie lives on a variety of food types, including buds, leaves, berries, insects, grasses and in the winter mostly conifer needles; you can see the food remains in their droppings, which are about 1 cm in diameter and 5-6 cm in length. Most of the year the droppings are of solid consistency, but with the ripening of blueberries, these dominate the diet and the faeces become formless and bluish-black.

Capercaillies are not elegant fliers due to their body weight and short, rounded wings. While taking off they produce a sudden thundering noise that deters predators. Because of their body size and wing span they avoid young and dense forests when flying. While flying they rest in short gliding phases. Their feathers produce a whistling sound.

Behaviour and ecology

The Capercaillie is adapted to its original habitats - old coniferous forests with a rich interior structure and dense ground vegetation of Vaccinium species under a light canopy. They mainly feed on Vaccinium species, especially blueberry, find cover in young tree growth, and use the open spaces when flying. As habitat specialists, they hardly use any other forest types.

Capercaillie, especially the hens with young chicks, require a set of particular resources which should occur as parts of a small-scaled patchy mosaic: these are food plants, small insects for the chicks, cover in dense young trees or high ground vegetation, old trees with horizontal branches for sleeping. These criteria are met best in old forest stands with spruce and pine, dense ground vegetation and local tree regrowth on dry slopes in southern to western expositions. These open stands allow flights downslope and the tree regrowth offers cover.

In the lowlands such forest structures developed over centuries by heavy exploitation, especially by the use of litter and grazing livestock. In the highlands and along the ridges of mountain areas in temperate Europe as well as in the taiga region from Fennoscandia to Siberia the boreal forests show this open structure due to the harsh climate, hence offering optimal habitats for Capercaillie without human influence. Dense and young forests are avoided as there is neither cover nor food and flight of these large birds is greatly impaired.

The Capercaillie is a highly specialized herbivore, which feeds almost exclusively on blueberry leaves and berries along with some grass seeds and fresh shoots of sedges in summertime. The young chicks are dependent on protein-rich food in their first weeks and thus mainly prey on insects. Available insect supply is strongly influenced by weather - dry and warm conditions allow a fast growth of the chicks, cold and rainy weather leads to a high mortality among them.

During winter, when a high snow cover prevents access to ground vegetation, the Capercaillie spends almost day and night on trees, feeding now on coniferous needles of spruce, pine and fir as well as on buds from beech and rowan.

In order to digest this coarse winter food the birds need grit, small stones which they actively search for and devour (gizzard stones). Together with their very muscular stomach, these grit stones function like a mill and break needles and buds into small particles. Additionally Capercaillie have two appendixes which grow very long in winter. With the aid of symbiotic bacteria, the plant material is digested there. During the short winter days the Capercaillie feeds almost constantly and produces a pellet nearly every 10 minutes.

The abundance of Capercaillie depends - like in most other species - on habitat quality, it is highest in sun-flooded open, old mixed forests with spruce, pine, fir and some beech with a rich ground cover of Vaccinium species.

Spring territories are about 250,000 square metres per bird. Comparable abundances are found in taiga forests. Thus, Capercaillie never had particularly high densities, despite the legends that hunters like to speculate about. Adult cocks are strongly territorial and occupy a range of 500,000 to 600,000 square metres optimal habitat. Hen territories are about 400,000 square metres. The annual range can be several square kilometers when storms and heavy snowfall force the birds to winter at lower altitudes. Territories of cocks and hens may overlap.

Capercaillie are diurnal game, i.e. their activity is limited to the daylight hours. They spend the night time in old trees with horizontal branches. These sleeping trees are used for several nights, they can be mapped easily as the ground under them is covered by pellets.

The hens are ground breeders and spend the night on the nest. As long as the young chicks cannot fly the hen spends the night with them in dense cover on the ground. During winter the hens rarely go down to the ground and most tracks in the snow are from cocks.

Courting and reproduction

The courting season of the Capercaillie starts according to spring weather progress, vegetation development and altitude between March and April and lasts until May or June. Three-quarters of this long courting season is mere territorial competition between neighbouring cocks or cocks on the same courting ground.

At the very beginning of dawn, the tree courting begins on a thick branch of a lookout tree. The cock postures himself with raised and fanned tail feathers, recked neck, beak pointed skywards, wings held out and drooped and starts his typical aria. This consists of four parts, tapping, drum roll, cork pop and gurgling or wheezing.

It is only towards the end of the courting season that the hens arrive on the courting grounds, also called leks, meaning dance in Norwegian. Now the cocks continue courting on the ground, this is the main courting season.

The cock flies from his courting tree to an open space nearby and continues his display. The hens, ready to get mounted, crouch and utter a begging sound. If there are more than one cock on the lek, it is mainly the alpha-cock who copulates with the hens present. In this phase Capercaillies are most sensitive against disturbances and even single human observers may cause the hens to fly off and prevent copulation in this very short time span where they are ready for conception.

There is a smaller courting peak in autumn, which serves to delineate the territories for the winter months and the next season.

About three days after copulation the hen starts laying eggs. Within 10 days the clutch is full, the average clutch size is 8 eggs but may amount up to 12, rarely only 4 or 5 eggs. The subsequent breeding lasts about 26-28 days according to weather and altitude.

At the beginning of the breeding season the hens are very sensitive towards disturbances and leave the nest quickly. Towards the end they tolerate disturbances to a certain degree, crouch on their nest which is usually hidden under low branches of a young tree or a broken tree crown.

After fledging the chicks are dependent on getting warmed by the hen. Like all precocial birds the young are fully covered by down feathers at fledging but are not yet able to maintain their body temperature which is 41C in birds. In cold and rainy weather the chicks need to get warmed by the hen every few minutes and all the night.

They seek food independently and prey mainly on insects, like butterfly caterpillars and pupae (there is a specialised butterfly species whose caterpillars develop only on Vaccinium myrtillus), ants, myriapodae, ground beetles and the like.

They grow rapidly and most of the energy intake is transformed into the protein of the flight musculature (the white flesh around the breast in chickens). At an age of 3-4 weeks they are able to perform their first short flights, from this time on they start to sleep in trees in warm nights. At an age of about 6 weeks they are fully able to maintain their body temperature. The down feathers have been moulted into the immature plumage and at an age of 3 months another moult brings them in their subadult plumage and now the two sexes can be easily distinguished.

From the beginning of September the families start to dissolve. First the young cocks disperse, then the young hens, both sexes may form loose foraging groups over the winter.

The Capercaillie in our man-made landscape

The main causes for the recent decline of Capercaillie all over their range are climate change and nitrogen oxide emissions with their massive effects on vegetation development, intensified forestry and increasing disturbance by tourism and recreational use.

Conservation measures usually are confined to forestry and hunting practices. By setting aside special game sanctuaries together with regulations of banning to leave paths and forest roads the human impact can be canalised especially in the most sensitive periods. Additionally predators are to be rigorously controlled.

It is imperative to conserve and create stable and mixed forests over large areas which fulfill all habitat requirements of Capercaillies. Especially the amount of old, open forests with rich ground vegetation dominated by Vaccicnium must be kept as high as possible, additionally habitat corridors and habitat stepping stones must be created between those old forest tracts which are used by Capercaillies.

Serious dangers come from deer fences which are responsible for 30% of all casualties in young Capercaillie. Metal fences in higher altitudes should be replaced by wooden substitutes or conspiciuously marked.

Tourists can contribute to Capercaillie conservation by: staying on paths, especially during the breeding and fledging seasons from April through the end of July, also in winter, staying on paths in the game sanctuaries; not letting dogs stroll freely around; leaving no waste; no excursions between dusk and dawn; no further development or intensifying of touristic infrastructures in highest altitudes and along the ridges of the mountains.

The late Alfred Brehm wrote in 1876 in his famous "Thierleben" (Animals' Life): "The largest and most distinguished of all grouse species is the Capercaillie, the grace of our forests, the joy of the gentle hunter".

It is only by joint and coordinated conservation efforts over large areas that we will be able to maintain this key species of mountain forests as part of our natural heritage.

The male bird is known as "Auerhahn" in German.


Capercaillie are known to hybridise occasionally with Black Grouse (these hybrids being known by the German name Rackelhahn) and CommonГлушэц de:Auerhuhn ja:ヨーロッパオオライチョウ lt:Kurtinys nl:Auerhoen pl:Głuszec sv:Tjder wa:Cok di brouhire


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