The black grouse (Tetrao tetrix) has experienced a serious decline over the last century. Restoring a healthy mosaic of habitats is crucial for the recovery of this attractive bird.
The black grouse is found throughout northern Eurasia, with a continuous distribution from Great Britain to south-eastern Siberia. The most southerly populations are found in Kyrgyzstan and North Korea, with the northern extent of its range being northern Norway. In western and central Europe its population is highly fragmented: populations are very small and isolated in a number of countries and it no longer breeds in Denmark. Its overall population has declined, particularly in Europe, although its population is more stable in its Russian stronghold. Black grouse usually require a mosaic of habitats, ideally including heath and bog along with open woodland and scrub for cover. There are thought to be seven or eight subspecies of black grouse, the only geographically isolated one being the most westerly of all, Britain’s Tetrao tetrix britannicus.
Distribution in Scotland
This grouse was once distributed through most of Great Britain. However, its numbers have declined drastically over the last century, and its range has retreated rapidly northwards. A 2005 survey coordinated by the Royal Society for the Protection of Birds reported an alarming 22% decline in the preceding ten years. Its core population is now in Scotland, where there are an estimated 3,344 of the UK’s 5,078 displaying males. There are smaller populations in northern England and Wales, although the decline has actually been reversed in the latter.
â€‹The reasons for this decline are varied and complex. Changes in agricultural practices, and in particular the increase in sheep numbers, have led to herb-rich and wet pasture areas becoming overgrazed, with a resulting decline in the insects essential for the survival of young grouse. In addition, overgrazing by sheep and deer has damaged areas of heather moorland; heather (Calluna vulgaris) being an important winter food source for black grouse. Excessive grazing has also suppressed native woodland regeneration, depriving the birds of some valuable food sources as well as refuge from predators. Drainage of bogs (which are important foraging grounds for chicks) has also contributed to the decline, while commercial afforestation has shaded out important berry plants such as blaeberry (Vaccinium myrtillus). High tensile deer fences pose a serious hazard to black grouse: when alarmed, these birds tend to fly fairly low, and seek refuge in nearby trees. They often do not see fences in time and are killed as they hit them. Furthermore, illegal shooting during the breeding season can affect both population and breeding success. Climate further complicates the picture, as cold, wet weather in June and July has increased mortality among newly-hatched chicks, which are unable to regulate their own body temperature and are therefore vulnerable to poor weather.
A number of measures are being used to increase the black grouse population, including restoration of preferred habitats, as well as predator control. Redundant fences are being removed, while those essential for woodland regeneration are marked in various ways to make them more visible, and are strategically positioned so as to pose less of a hazard. Otherwise, alternative methods such as deer culling are preferred ways of encouraging regeneration. Mature, open pine and birch woodland, bogs and heath were once much more widespread in Scotland, and restoration of these habitats is playing a key role in black grouse recovery.
Locally extinct in many regions, the black grouse is the fastest declining bird in the UK and is on the Red List of Birds of Conservation concern. It is protected under the Game Acts (closed season 11 December-19 August); while it may be legally hunted in the open season, many estates choose not to do so. It is classed as Vulnerable in Europe, and is in Annex II/2 of the EC Birds Directive and Appendix III of the Bern Convention. In Britain, the black grouse is a Priority Species, and therefore the subject of a Biodiversity Action Plan (BAP), under the UK government’s response to the Convention on Biological Diversity signed at the Earth Summit in 1992. However, its global population is not thought to be endangered, and it is classified as being of Least Concern.
The black grouse (also known as ‘blackgame’) is a member of the grouse family Tetraonidae. Roughly the size of a domestic hen, the male, or ‘blackcock’, is 49-58 cm. in length with a tail measuring around 15 cm.; he weighs approximately 1.25 kg. The female or ‘greyhen’ is slightly smaller at 40-45 cm., and weighs 950 g. The male has black plumage with a bluish sheen. He has white wing-bars, which are only visible in flight, white under-tail coverts, and a distinctive lyre-shaped tail. The female has grey-brown plumage, (providing excellent camouflage when nesting on the ground) with pale wing bars, and her tail has a slight notch at the end. Both sexes have a red patch called a ‘wattle’ above each eye. Among its calls are a rapid cackling and a harsh hissing sound. When displaying, the males produce a pigeon-like, bubbling call, interspersed with a ‘sneezing’ noise.
The diet varies considerably through the year, and also in different parts of the bird’s range. Birch buds (Betula spp.) along with heather and blaeberry shoots are important winter food sources. Cotton grass (Eriophorum spp.) and larch buds (Larix spp.) are eaten in spring, pine pollen (Pinus sylvestris) in early summer, blaeberries in late summer, and rowan berries (Sorbus aucuparia) in autumn and winter. For the first three weeks of their lives, chicks feed on protein-rich invertebrates, particularly moth caterpillars and sawfly larvae (suborder: Symphyta).
Blackcocks participate in a fascinating territorial and breeding display known as a lek (from the Swedish leka – play). They gather on an open area of ground where they strut, fanning out their tails, spreading their wings slightly and inflating the wattles above their eyes. The dominant males gain the favoured position at the centre of the lek, increasing their chances of mating. The females, who only attend in late March to mid-May, are positioned around the edge of the lek, watching and selecting the most impressive males to mate with. Lekking takes place almost year-round, except for July and August when the males moult. Outside of the breeding season they lek to establish hierarchy and defend territories.
From late April to early June, greyhens typically lay a brood of 6-10 eggs, which are buff with brown spots. They are normally laid in a simple hollow in the ground, with little lining, although they are usually concealed by surrounding tall vegetation such as heather or rushes (Juncus spp.). The eggs are incubated for about 24 days; the chicks hatch in mid to late June and fledge after about four weeks. Black grouse do not form pair bonds, and the male plays no part in rearing the chicks. The average lifespan of a black grouse is around five years.
As with other herbivorous animals, the black grouse plays a role in keeping the vegetation structure in an area more varied than if it were completely ungrazed. During their insectivorous phase as fledglings they also help to regulate numbers of the caterpillars and other invertebrates they eat.
The black grouse is prey for numerous predators, including raptors such as golden eagles (Aquila chrysaetos) and hen harriers (Circus cyaneus). Pine martens (Martes martes), foxes (Vulpes vulpes), crows (Corvus corone), and stoats (Mustela erminea) eat the birds as well as their eggs.
Black grouse are host to a variety of parasites. These include feather mites, for example Tetraolichus gaudi, tapeworms such as Hymenolepis spp., and blood parasites such as the protozoan Leucocytozoon lovati. On an evolutionary timescale, these parasites improve the health and vigour of the species overall, by selecting out weaker individuals.
The black grouse depends on other animals to provide some of the habitat it requires. In some areas conservationists use cattle to maintain the open habitats the grouse need for their leks. It is likely that in former times, herbivores such as the extinct wild cattle, or auroch (Bos primigenius) would have played a role in keeping patches of the forest relatively open.
Human management for the black grouse also has a knock-on effect for other wildlife. As this bird requires a variety of habitats, management for the recovery of black grouse benefits a wide range of other species. Conservationists are working hard to aid the recovery of this attractive bird, and there is still hope that the overall downward trend can be reversed.
Mullarney, K., Svensson, L., Zetterstrom, D., Grant, P.J. (1999). Collins Bird Guide. Collins: London.