Increasing forest cover threatens black grouse

Within a forest/moorland landscape it is important to retain sufficient moorland and rough grazing habitats for lekking and breeding. © Nancy Parsons/GWCT

BACKGROUND

Black grouse were once widespread in the UK but following an 80% decline in numbers over the past 25 years they are now red-listed as a species of high conservation concern. In 2005, 5,100 males remained, two-thirds of which were found in Scotland. Increasing forest cover in southern Scotland could threaten the remaining black grouse populations.

Planting of new forests of Sitka spruce in the short-term can provide suitable conditions for black grouse, but birds are quickly displaced following canopy closure after 10-12 years. © Laurie Campbell The black grouse was once a common and widely distributed bird in southern Scotland. However, numbers and range have declined. This has accelerated in recent years, with 49% and 69% declines in the south-west and south-east of Scotland respectively, between national surveys in 1995/96 and 2005. Estimates of remaining males for the two regions in 2005 were 807 and 257. This has resulted in southern Scotland being identified as a priority area for conservation action for the species.

Black grouse frequent a mixture of moorland, moorland fringe, young coniferous forest and broadleaved forest habitats, with birds using a range of these habitats within a one-kilometre (km) radius of the focal display site, known as a lek. In suitable continuous habitats, these leks typically occur at intervals of 2-3km, allowing females to disperse between them. We know from recent studies in north Perthshire that retaining enough heather moorland habitat within a forest-moorland landscape is important, as this provides key habitats for lekking and breeding. In Scotland, Government policy aims to increase forest cover from 18% to 25% by 2050 and remaining moorland habitats may be under increasing threat of afforestation. New woodland planting in the short term may provide favourable conditions prior to canopy closure, but in the longer term it is predicted to further impact on remaining populations by reducing and fragmenting remaining moorland. To help inform black grouse conservation programmes in southern

Scotland we quantified recent trends in numbers, assessed habitat composition within lek ranges and evaluated the size of suitable habitat patches.

We investigated changes in the numbers of males at leks counted between 1989 and 2018 and related these to habitat and gamekeeping levels, categorised according to moorland management: (1) driven grouse shooting, (2) walked-up grouse shooting and (3) no shooting interest. We also used wider surveys of leks counted by a range of partners between 2006 and 2012 in the south-west and south-east to measure habitat within lek ranges and to compare with that in the wider landscape. We also explored whether the number of males attending leks was related to habitat and gamekeeping levels, and whether moorland patch size influenced occupancy.

We found that the number of males at a sample of 121 leks surveyed between 1989 and 2018 fell from 70 males to zero in south-west Scotland and from 340 to 44 in south-east Scotland, with 82% of leks no longer occupied. Leks that were still occupied had more rough grassland (53%) and less conifer cover (6%) within a 1km radius than lek sites which no longer supported any birds (32% and 29%), with declines similar across gamekeeping levels.

Results from wider lek surveys across the south-west and south-east between 2006 and 2012 found that rough grassland and heather moorland were the two preferred habitats within 197 lek ranges. Twice as many males attended leks where driven red grouse shooting was practised, than on walked-up moors or sites with no shooting interest. Remaining birds were found associated with larger contiguous areas of moorland: the extent of occupied moorland habitat patches averaged 157km², 26 times larger than unoccupied patches (6km²).

This study and similar ones in northern England and Perthshire have found moorland to be an important habitat for black grouse. With Government targets to plant more woodland, remaining moorland habitat patches are likely to become more fragmented making them less able to support sustainable connected populations, which may exacerbate declines and enhance the risk of regional extinction. Therefore, to help prevent black grouse extinction in southern Scotland, instigation of immediate conservation measures is required. These include the retention and restoration of rough grassland and moorland surrounding occupied leks, the establishment of small pockets of new native woodlands to provide winter food and cover in areas which do not fragment existing moorland, such as along ghylls and streams, combined with predator control. KEY FINDINGS

Numbers of males at a sample of 121 leks surveyed between 1989 and 2018 fell from 70 males to zero in south-west

Scotland and from 340 to 44 in south-east Scotland, with 82% of leks no longer occupied.

Retained leks had more rough, acid grassland and less conifer cover within a one-kilometre radius than abandoned leks.

Remaining birds were associated with large contiguous moorland areas.

Philip Warren Chris Land Nick Hesford David Baines

Black grouse like some woodland in the landscape, with small patches of native woodland (pictured) providing important winter food resources particularly in periods of prolonged snow. © Phil Warren/GWCT