Many species of ground-nesting moorland bird are declining in number. This has been attributed to changes in land use, which can lead to loss or fragmentation of moorland habitat and increases in numbers of predators. Afforestation and increased intensification of farming in the uplands often make habitat unsuitable for species that breed on moorland. These declines in the uplands follow more severe declines already seen in parts of the lowland UK. Declining numbers on moorland are therefore of concern for the conservation of birds that breed there.
This study looks at trends for moorland birds in south west Scotland, compared to the whole of Scotland, and then focuses on two Special Protection Areas (SPAs) to study changes in land use and moorland bird numbers. Surveys of moorland birds that were carried out in the early 1980s were repeated, and the results found severe declines for several species of ground-nesting birds.
What they did
This study used two parallel approaches to look at the abundance of a group of moorland bird species in south west Scotland:
- One approach analysed data for 13 species that are commonly associated with moorland, to understand the population trends for these species in the region of south west Scotland, and the country as a whole.
- The other produced detailed case studies of two Special Protection Areas (SPAs) that are designated for hen harriers, looking at the trends for birds in these areas, compared to the national and regional trends.
1) Regional and national data
This section of the study used both long and short-term datasets to examine the population trends for red grouse, black grouse, oystercatcher, golden plover, lapwing, dunlin, snipe, curlew, redshank, common sandpiper, hen harrier, merlin and carrion crow.
The data were drawn from six sources:
- The British Trust for Ornithology (BTO)’s Breeding Bird Survey, which is a UK-wide survey carried out by trained volunteers every year. Data were available for all species except black grouse, dunlin, redshank, hen harrier and merlin.
- The Breeding Bird Atlas, for which species are surveyed across the UK approximately every 20 years. Data were available for all species from this source.
- The National Gamebag Census (NGC): a voluntary database from shoots recording the number of different game species shot each year. NGC data for red grouse and black grouse were analysed.
- National surveys of black grouse were carried out in 1995/6 and 2005. These were repeated between 2006-2012 and the data included.
- National surveys for hen harrier and merlin. Data from four national surveys of hen harrier were included (a fifth has since been published), and three for merlin.
- Scottish Raptor Monitoring Scheme (SRMS): a partnership scheme that supports annual monitoring of birds or prey, largely by volunteers. Data were requested from SRMS for hen harrier and merlin within each of the case study sites (see below).
2) Case studies
The two areas studied were the Muirkirk and North Lowther Uplands SPA (referred to as ‘Muirkirk’), and Langholm – Newcastleton Hills SPA (referred to as ‘Langholm’).
The area covered by the Muirkirk SPA includes six privately owned estates. When the study began in 1992, four of these practised some grouse moor management, and two were primarily sheep farms. Grouse moor management gradually declined in the region, with only a single keeper on one moor remaining by 2017.
Red grouse counts were carried out in both spring (March, before breeding) and summer (July, after breeding but before shooting began) between 1992 and 2017. Wader numbers on two of these six moors were surveyed between 1994-99 and again between 2009-17. Lapwing and redshank were surveyed on the enclosed in-bye farmland on the moor edge four times between 1995 and 2017.
Data were extracted from various other surveys, which had been carried out in the area and published in other forms – one scientific paper from 2005 included repeat surveys of Muirkirk SPA undertaken in the 1980s and 1990s, and in 2015 Scottish Natural Heritage (SNH) had commissioned a full survey of breeding waders within the SPA. Results from these surveys were analysed and compared.
Langholm moor has hosted two major studies, which aimed to help resolve conflicts between raptors and management for red grouse. As such, during two periods since 1992, the moor has been managed for grouse with heather management, predator control and protection from illegal raptor killing. An intervening period had limited keepering and no heather management.
Between 1992 and 2016, bird numbers were monitored annually within each of the five management areas on the study site. Abundance and breeding success of red grouse and hen harriers was recorded and analysed with relation to gamekeeping in the different phases of the study. The abundance of curlew, golden plover, snipe and lapwing were also analysed for the three different management phases.
What they found
1) Regional and national data
Although national data suggests that red grouse numbers are stable, and remain widespread through much of Scotland, there have been declines in some south, east and western areas between the 1970s and early 2000s. In south west Scotland, the earlier part of this time interval saw greater declines than the latter. Red grouse bags in Scotland were generally higher before the 1920s than after, with numbers shot in south west Scotland falling most notably since the 1950s. The number of moors reporting shooting in south west Scotland in recent decades was lower than other regions of Scotland, suggesting that grouse shooting has probably ceased on more moors in this region. 42% of 31 moors studied now no longer shoot red grouse.
Black grouse were widespread in Scotland in the 1960/70s, but their range had contracted by half by the early 2000s, and the number shot declined by 93% in the hundred years from 1890 and 1989. In south west Scotland, 28 black grouse were shot in 1980 and zero in 2016. The average number of lekking males was consistently lower than in the rest of Scotland in the period 1989-1993. Further declines have been reported by repeat surveys in 1995/6 and 2005. At two study areas within south west Scotland, the number of males attending leks declined by 80% from the early 1990s to mid-2000s. A wider Scottish survey found twice as many lekking males in areas where gamekeepers were employed to provide driven grouse shooting.
Of those species for which there is enough data from the BBS to calculate a trend, oystercatcher, golden plover, lapwing and curlew all showed significant declines in Scotland between 1995 and 2015. Data from the Breeding Bird Atlas indicated mixed fortunes for wader species, within a general theme of declining distribution.
Carrion crows are widespread in south and east Scotland, with numbers being stable across Scotland between 1995-2015.
Hen harriers and merlin
Hen harrier surveys undertaken five times since 1988/9 show that populations have fluctuated between 436 and 633 pairs in Scotland. The most recent survey in 2016 found 460 pairs, a 9% decline since the previous survey in 2010. Occupied territories are monitored by Raptor Study Group workers, which found gradual declines at a rate of -2.3% per year in the number of territories that were occupied between 2003 and 2015. In south west Scotland there is no downward trend, with increased numbers and breeding success in the Langholm SPA during this period contrasting with declines elsewhere. Data for merlin are less clear, partly because of lower numbers. National surveys suggest a stable population overall, but territory monitoring also suggests fewer occupied territories.
2) Case studies
Red grouse numbers declined over time, which was mainly due to cessation of keepering. Periods when moors were keepered had higher grouse breeding success, and also grouse densities in the earlier time periods of the study, when more moors were keepered.
Wader declines were also observed, with curlew, lapwing and snipe numbers all falling, and golden plover and redshank no longer found at Muirkirk towards the later period of this study. Declines were also found for golden plover, lapwing and curlew in the survey data from other sources that concerned Muirkirk SPA.
When the moor was managed for red grouse and generalist predators were routinely controlled, both red grouse and hen harrier breeding success was two to three times higher than when the moor was not managed.
Curlew, golden plover and lapwing were more numerous in the first keepered period, and numbers fell when keepering stopped. However, although numbers for curlew and golden plover did rise when grouse moor management resumed, this failed to restore numbers to their former levels. Lapwing numbers remained low. One reason for this may be that Langholm is now an isolated moor, with no full-time keepers on any of the surrounding estates.
What does this mean?
This study found clear declines for several species of ground-nesting moorland birds in south west Scotland that closely mirror those seen elsewhere in the UK. They may be attributed to land-use change, including afforestation, agricultural intensification or abandonment, as well as a decline in the extent of grouse moor management. Grouse moor management can help retain heather moorland, and may form stable habitats where prescribed burning, sympathetic grazing and predator control can help conserve numbers of some upland birds.
The effect of losing grouse moor management is clearly shown in both case studies, where significant declines in ground-nesting birds occur in tandem with the loss of keepering. At Langholm this effect was not reversed when predator control and heather management was restored.
This report shows that existing funding schemes for managing moorland birds are not working at an appropriate scale. To prevent further declines, or possible extinctions, of moorland ground-nesting birds, habitat management and predator control are required on an appropriately large scale.
Read the original report
Whitehead, S., Hesford, N. & Baines, D. 2018 Changes in the abundance of some ground-nesting birds on moorland in South West Scotland. Research Report to Scottish Land & Estates and Scottish Gamekeepers Association. Game & Wildlife Conservation Trust, Fordingbridge.