[order] Galliformes | [family] Phasianidae | [latin] Tetrao tetrix | [UK] Black Grouse | [FR] TÚtras lyre | [DE] Birkhuhn | [ES] Urogallo Lira | [IT] Fagiano di monte | [NL] Korhoen

Korhoen determination

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Male has unique, glossy blue-black plumage, striking white wing-bar and curled outer tail-feathers, giving raised tail lyre-shape. Female much less distinctive, with well-barred grey, ochre, and mostly warm brown plumage, whitish wing-bar and only slightly forked tail. She takes all responsibility for nesting and caring for the chicks, as is typical with gamebirds.

From middle to high latitudes, mainly in boreal, subarctic and arctic-alpine zones. Survives as glacial relict in mid-latitude mountains such as Alps up to c. 2500 m, but mostly in lowlands farther north. Typically in habitats transitional between forest or woodland and open heath, marginal cultivation, bog and fen, or steppe. Presence of trees essential, but they must not be in dense stands or form closed canopy, and should preferably be in scattered groups of no great height, and adjoin open glades, clearings, burnt patches or fringes in course of encroachment by natural regeneration. In different areas, broad-leaved or coniferous stands preferred, and locally orchards of pear or cherry trees or young forestry plantations.

Tetrao tetrix is a widespread resident in northern Europe, occurring more patchily further south, with Europe accounting for less than half of its global range. Its European breeding population is very large (>2,500,000 pairs), but declined substantially between 1970-1990. Although most populations continued to decline during 1990-2000, the species increased in its Russian stronghold, and probably only underwent a slight decline overall. Nevertheless, it total population size clearly remains far below the level that preceded its decline, and consequently it is evaluated as Depleted.
This grouse inhabits boreal, sub-arctic and alpine forests of Eurasia, from the British Isles to Manchuria. In some regions it penetrates the steppe region. In Europe its distribution is strongly fragmented and largely relict. Everywhere a decrease is noticed, mainly because of the destruction and fragmentation of its habitat and because of disturbance by tourism.

Almost exclusively plants; rarely, animal food (mainly insects and spiders). In winter, principally buds and catkins of birches, needles and berries of juniper, fruits of dog rose, and shoots and buds of willow. In spring, green parts of plants and shoots and buds of trees and shrubs become important; in late May, mainly stalks, flowers, unripe seeds, and pods of alpine vegetation. In early August, mainly ripe seeds of alpine plants. In late summer berries become important, and are main food in autumn.

This species has a large range, with an estimated global Extent of Occurrence of 10,000,000 km▓. It has a large global population, including an estimated 5,100,000-6,400,000 individuals in Europe (BirdLife International in prep.). Global population trends have not been quantified; there is evidence of a population decline, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern. [conservation status from birdlife.org]

Egg-laying starts early May in Fenno-Scandia and northern Russia. In Britain, central Europe, and southern Russia up to two weeks earlier. The nest is a depression in the ground in shelter of tall vegetation or low scrub. Rarely in old nest of another species, up to 6 m above ground in tree. It is a shallow scrape c. 15-20 cm diameter and 4-6 cm deep, usually lined grasses and moss. Clutch size is 6-11 (4-15, over 15 probably by multiple females. The eggs are incubated for 25-27 days and the chicks are capable of precocious flight at 10-14 days, they become independent at about 3 months.

Mainly resident, even sedentary in temperate zone, but apparently eruptive at long intervals in north, where major movements over some hundreds of kms reported occasionally. Can begin early autumn, when ultimate factor presumed peak population levels rather than severe weather. Migratory restlessness also noted at times in south Sweden; in Blekinge, male flew 1 km out to sea before returning, and on Íland several times seen attempting to leave from shore though only once did bird disappear from sight over sea.