Monday, 29 October 2012

Galliformes 10: The Joy of Leks – The Black Grouse

The third of the British Grouse to cover in this series is one that is threatened in the UK, but is still very widespread abroad – the Black Grouse Tetrao tetrix. With a natural range extending in suitable habitat from Western Europe across to Eastern China, and Korea, the Black Grouse is essentially a bird of early successional forest and forest edge habitats in the Taiga zone, and in the UK is on the extreme edge of its range. In Turkey and the Caucasus mountains it is replaced by the very similar Caucasian Grouse T.mklosiewiczi

In the UK changes in forestry and management of moorland and upland habitats, and maturing of young conifer plantations (at the start these provide good habitat for Black Grouse) has resulted in a contraction of range and fragmentation of the existing populations. This is made worse by the highly sedentary nature of the species – the typical dispersal distances of Black Grouse in the UK are only 800m between the nest they hatched in and where they eventually breed.

Unlike Red Grouse and Ptarmigan, in Black Grouse only the female cares for the chicks. Instead, males gather at special display sites called leks, where they show of in a joint display to visiting females, which pick the bird with the best display to mate with. Given the small Uk population the numbers of male Black Grouse at a UK lek are usually in single figures, but where the birds are commoner the leks can be extremely large – up to 200 displaying males have been recorded in Russia. For a YouTube video of a Black Grouse lek, see here:

After mating, the females return to their home ranges to build their nests, a typical galliforme scrape in the ground. When the chicks hatch they feed on insect larvae of various kinds as with other grouse – chiefly sawfly larvae, but caterpillars, spiders, and other invertebrates are also eaten. As adults they are mostly vegetarian, feeding on the shoots of heather Calluna vulgaris, Bilberry Vaccinium myrtillus, and in the spring on the buds of birch Betula and Larch Larix.

Although Black Grouse, like other grouse, were shot on game estates their decline means this no longer occurs. They are the subject of a Biodiversity Action Plan, which is a joint operation between the RSPB and the Game and Wildlife Conservation Trust to enable recovery of the species by better land management and more direct interventions such as translocations and reintroductions where necessary. As a result of the reluctance of Black Grouse to move far from their birth sites, reintroductions are probably essential in order to restore them as breeding birds at any distance from existing populations, even if they once occurred in the area.

Next week, the largest of the grouse – the Capercaillie.

Images from wikipedia,

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