The western capercaillie (Tetrao urogallus), also known as the Eurasian capercaillie, wood grouse, heather cock, cock-of-the-woods, or simply capercaillie , is a heavy member of the grouse tribe and the largest of all extant grouse species. Found across Europe and the Palearctic, this primarily-ground-dwelling forest grouse is renowned for its courtship display. The bird shows extreme sexual dimorphism, with males nearly twice the size of females. The global population is listed as "least concern" under the IUCN, although the populations of central Europe are declining and fragmented, or possibly extirpated. The western capercaillie is one of two living species under the genus Tetrao, which also includes the lesser-known black-billed capercaillie.
Taxonomy The western capercaillie was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae under its current binomial name Tetrao urogallus. Linnaeus specified the type locality as Europe but this is now restricted to Sweden. The genus name is a Latin word that was used for both the black grouse and the western capercaillie. The specific epithet urogallus is a Neo-Latin partial homophone of German Auerhuhn, a western capercaillie. The word had been used in 1555 by the Swiss naturalist Conrad Gessner in his Historiae animalium. The common name capercaillie is a corruption of the Scottish Gaelic capall coille (Scottish Gaelic pronunciation: [kʰaʰpəɫ̪ˈkʰɤʎə]) "Horse of the woodland". The Scots borrowing is spelled capercailzie (the Scots use of z represents an archaic spelling with yogh and is silent; see Mackenzie (surname)). The current spelling was standardised by William Yarrell in 1843. Its closest relative is the black-billed capercaillie (Tetrao urogalloides), which breeds in the larch taiga forests of eastern Russia and parts of northern Mongolia and China.
Subspecies The western capercaillie has 8 recognized subspecies:
T. u. cantabricus (Castroviejo, 1967) - northwestern Spain T. u. aquitanicus (Ingram, 1915) - Pyrenees of Spain and France T. u. crassirostris (C.L. Brehm, 1831) - Alps to Estonia T. u. rudolfi (Dombrowski, 1912) - Bulgaria to southwestern Ukraine T. u. urogallus (Linnaeus, 1758) - Scandinavia and Scotland T. u. karelicus (Lönnberg, 1924) - Finland and Karelia T. u. lonnbergi (Snigirevski, 1957) - Kola Peninsula T. u. pleskei (Stegmann, 1926) - Belarus (Russia) T. u. obsoletus (Snigerewski, 1937) - northern European Russia T. u. volgensis (Buturlin, 1907) - found in southeastern European Russia T. u. uralensis (Nazarov, 1886) - found in the Urals and western Siberia T. u. taczanowskii (Stejneger, 1885) - central Siberia to Altai Mountains (northwest Mongolia and eastern Kazakhstan) 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. 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.
Hybrids 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.
Description
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. Cocks (males) typically range from 74 to 85 centimetres (29 to 33 in) 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). 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. 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-footed hens". These so-called "courting tracks" make a clear track in the snow. The 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". 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.
Distribution and 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.
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