Grand Tétras

Identification

Male and female western capercaillie can easily be differentiated by their size and colouration. The cock is much bigger than the hen. It is one of the most sexually dimorphic in size of living bird species, only exceeded by the larger types of bustards and a select few members of the pheasant family.<p>Cocks (males) typically range from 74 to 85 centimetres (29 to 33 inches) in length with wingspan of 90 to 125 cm (35 to 49 in) and an average weight of 4.1 kg (9 lb 1 oz). The largest wild cocks can attain a length of 100 cm (40 in) and weight of 6.7 kg (14 lb 12 oz). The largest specimen recorded in captivity had a weight of 7.2 kg (15 lb 14 oz). The weight of 75 wild cocks was found to range from 3.6 to 5.05 kg (7 lb 15 oz to 11 lb 2 oz). The body feathers are dark grey to dark brown, while the breast feathers are dark metallic green. The belly and undertail coverts vary from black to white depending on race (see below).<p>The hen (female) is much smaller, weighing about half as much as the cock. The capercaillie hen's body from beak to tail is approximately 54–64 cm (21–25 in) long, the wingspan is 70 cm (28 in) and weighs 1.5–2.5 kg (3 lb 5 oz – 5 lb 8 oz), with an average of 1.8 kg (3 lb 15 oz). Feathers on the upper parts are brown with black and silver barring; on the underside they are more light and buffish yellow.<p>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 "Rauhfußhühner", literally translated as "rough feet chickens".<p>These so-called "courting tacks" make a clear track in the snow. The sexes can be distinguished very easily by the size of their footprints.<p>There is a bright red spot of naked skin above each eye. In German hunters' language, these are the so-called "roses".<p>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 three 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.

Taxonomie

The species was first described by Carl Linnaeus in his 1758 10th edition of Systema Naturae under its current binomial name.<p>Its closest relative is the black-billed capercaillie, Tetrao parvirostris, which breeds in the larch taiga forests of eastern Russia and parts of northern Mongolia and China.<p>The western capercaillie has 8 recognized subspecies:<p>Subspecies of the western capercaillie show increasing amounts of white on the underparts of males distributed west to east, almost wholly black with only a few white spots underneath in western and central Europe to nearly pure white in Siberia, where the black-billed capercaillie is located. There is less variation in the females of this species. <p>A native Scottish population of western capercaillie which became extinct between 1770 and 1785 was probably a distinct subspecies, although it was never formally described as such. The western capercaillie found in Scotland is an introduced population of the nominate subspecies urogallus.<p>Western capercaillies are known to hybridise occasionally with black grouse (these hybrids being known by the German name Rackelhahn) and the closely related black-billed capercaillie.

Nom scientifique

Tetrao urogallus

Autorité

Linnaeus, 1758

Ordre

Galliformes

Famille

Phasianidae

Genre

Tetrao

Répartition et habitat

The capercaillie is a non-migratory sedentary species, breeding across northern parts of Europe and the Palearctic in mature conifer forests with diverse species composition and a relatively open canopy structure.<p>At one time it was present in all the taiga forests of the Palearctic in 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 from the Swedish population; 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 Harz mountains numbers of surviving western capercaillie decline even under massive efforts to breed them in captivity and release them into the wild. In Switzerland, they are found in the Swiss Alps and in the Jura; they are also present in the Austrian and Italian Alps. In Ireland it was common until the 17th century, but was extirpated in the 18th century. In Norway, Sweden, Finland, Russia and Romania populations are large, and it is a common bird to see in forested regions; especially in Central Finland, that it occurs in the coat of arms of the region and is also a regional bird.<p>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 that prey on capercaillies (e.g., red fox) due to the loss of large predators who control smaller carnivores (e.g., gray wolf, brown bear) cause problems in some areas.<p>This species has an estimated range of 1,000,000–10,000,000 km2 (390,000–3,860,000 sq mi) and a population of between 1.5 and 2 million individuals in Europe alone. There is some evidence of a population decline, but the overall species is not believed to approach the IUCN Red List threshold of a population decline of more than 30% in ten years or three generations. It is therefore evaluated as least concern.<p>As reported by the Spanish researcher Félix Rodríguez de la Fuente in his "Fauna" series, the northwestern Spanish subspecies T. u. cantabricus—an Ice Age remnant—was threatened in the 1960s by commercial gathering of holly fruit-bearing branches for sale as Christmas ornaments—a practice imported from Anglo-Saxon or Germanic countries.<p>In Scotland, the population has declined greatly since the 1960s because of deer fencing, predation and lack of suitable habitat (Caledonian Forest). The population plummeted from a high of 10,000 pairs in the 1960s to fewer than 1000 birds in 1999. It was even named as the bird most likely to become extinct in the UK by 2015, a survey then identified 1114 birds, occupying a reduced range of terrain. In mountainous skiing areas, poorly marked cables for ski-lifts have contributed to mortality. Their effects can be mitigated by proper coloring, sighting and height alterations.<p>A study published in 2022 by NatureScot scientific advisory committee recommended 'renewed intensive measures' to maintain the population, especially steps to assist in the survival of eggs and chicks. Predators like crows, foxes and pine martens are blamed for the decline, as well as the deer fences, and increased human recreation in the territory which can injure adult birds.It was declared as 'extremely vulnerable' and requiring urgent action. Biodiversity Minister for Scotland, Lorna Slater, MSP described capercaillie as 'magnificent birds' and ' iconic' for Scotland and called for 'partnership working' to reverse the decline.

Migration

Resident species

Comportement

The western 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 bilberry, find cover in young tree growth, and use the open spaces when flying. As habitat specialists, they hardly use any other forest types.<p>Western 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 wingspan they avoid young and dense forests when flying. While flying they rest in short gliding phases. Their feathers produce a whistling sound.<p>Western capercaillie, especially the hens with young chicks, require resources that 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.<p>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, 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.<p>The abundance of western capercaillie depends—as with most 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.<p>Spring territories are about 25 hectares (62 acres) per bird. Comparable abundances are found in taiga forests. Thus, the western capercaillie never had particularly high densities, despite the legends that hunters may speculate about. Adult cocks are strongly territorial and occupy a range of 50 to 60 hectares (120 to 150 acres) optimal habitat. Hen territories are about 40 hectares (100 acres). The annual range can be several square kilometres (hundreds of hectares) when storms and heavy snowfall force the birds to winter at lower altitudes. Territories of cocks and hens may overlap.<p>Western capercaillie are diurnal game, i.e., their activity is limited to the daylight hours. They spend the night 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.<p>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.

Conservation

Tendance de la population

declining