Black grouse

The following will give you information on what work has been taking place through the Species Action Framework:

• Updates on recent action 
• Action up to start of SAF, April 2007 

What action is going on for this species?

Species background

The male black grouse (black cock) (Tetrao tetrix) has blue-black plumage, with white wing-bars, white under the tail, and curled outer tail feathers; the female (greyhen) has a barred, dark brown plumage and a whitish wing-bar. Both sexes have red wattles above the eye.

Why is this on the Species Action List?

It satisfies criterion 1a of the Species Action Framework as a species for conservation action.

This species has undergone a rapid decline over the last 25 years, and is in urgent need of further targeted management action.

Black grouse are a UKBAP Priority Species and the species is also on the Scottish Biodiversity List.

Ecological research on the species has been carried out, primarily by the Game and Wildlife Conservation Trust and the RSPB.

Habitat, distribution and abundance

A national survey in 2005 found about 3,344 displaying males in Scotland, down 29% from a prior survey in 1995-96.  There was some recovery in Perthshire, but numbers fell by 69% in Lothian and Borders and by 49% in south-west Scotland (Dumfries & Galloway and southern Argyll).  In the mid 1990s, there was a 10% year-on-year decline in Argyll, and the remaining birds here are increasingly isolated from other Scottish populations.  There have been no recent significant changes elsewhere in Scotland.  The UK population is estimated at 5,078 calling males.

Black grouse are largely dependent upon a mosaic of woodland and scrub and an understory of heather and bilberry.  This can often be provided by the suitable management of moorland / woodland / farmland edges.  Black grouse also utilize young conifer plantations and clear-felled areas with well developed field and shrub layers that include rushes, cotton-grass, heather and bilberry.  Mature plantations with widely-spaced trees also support suitable ground vegetation and can be important for the species.

General ecology

In Spring, black grouse gather at traditional 'lek' sites where males display competitively and the females select their mates.  Males then take no further part in caring for the eggs or young.  Females nest on the ground in dense vegetation (higher than 40cm) and lay 6 -11 eggs in late April-early June. 

The adult diet includes bilberry and heather but the young depend largely on invertebrates for their first three weeks, after which they gradually shift to a herbivorous diet.

History of decline, contributory factors and current threats

The UK population of black grouse has been declining in range and numbers since the 1900s.  Its range declined by 28% between 1968-72 and 1988-9, while the UK population declined dramatically from an estimated 25,000 lekking males in 1990 to just 6,510 in 1996. The 2005 survey revealed a continuing UK decline of 22% since 1995-96. 

The declines are due to a number of factors, including:

• the loss of important plant food sources, such as bilberry, heather and birch scrub, due to over-grazing and agricultural intensification; 
• these species also support invertebrate prey items important for chicks, and provide nest sites;
• maturing conifer plantations shade out the shrub understory vegetation utilized by black grouse; 
• collisions with fences put up to exclude deer in order to prevent over-grazing in woodlands;
• drainage and over-grazing of bogs destroy two important black grouse food sources -the flowers of cotton grass, and invertebrates; 
• rushes, which provide nesting cover and sources of insect food, are also affected adversely;
• loss of wet flushes and riparian vegetation in afforested areas may lead to the decline of food plants and invertebrates; 
• re-seeding traditional hay fields or enclosed rough grazing reduces the abundance of food plants, and excessive moorland burning can lead to the formation of impoverished acidic grasslands;
• fragmentation of black grouse habitat can lead to small populations which are unlikely to persist; 
• predation, mainly by foxes and crows, may be a limiting factor in some regions; and, 
• human disturbance of lekking birds has been identified as a severe problem at some isolated sites.

The 'Species Lead' at Scottish Natural Heritage

Susan.Haysom@snh.gov.uk  Tel. 01463 725000