The Uplands team are pleased to deliver some new research from the Langholm Moor Demonstration Project. Please see below the abstracts from three of our published papers, the full list of all LMDP publications can be found here.
Ludwig, S., Roos, S., Rollie, C. & Baines, D. (2020). Long-term changes in the abundance and breeding success of raptors and raven in periods of varying management of a Scottish grouse moor. Avian Conservation and Ecology 15(1): 21.
Management of heather moorland for driven Red Grouse Lagopus lagopus scotica shooting in the British uplands may benefit some raptors by reducing predation risk, especially when breeding, and by increasing food availability. We describe changes in abundance and breeding success of four raptor species and Raven Corvus corax during a 27-year study on a grouse moor in SW Scotland in relation to whether or not the moor was managed by gamekeepers. Ground-nesting raptors, Hen Harrier Circus cyaneus and Merlin Falco columbarius, increased during periods of grouse moor management and had a higher proportion of successful nesting attempts. Predation was the main apparent cause of breeding failure. In contrast, grouse moor management did not influence either abundance or breeding success of tree- and crag-nesting species, i.e. Peregrine Falco peregrinus, Common Buzzard Buteo buteo and Raven. Buzzard sightings increased during the study, in line with their national recovery, whereas Peregrine and Raven showed little change in abundance. The results of our study highlight that management for Red Grouse can benefit both Hen Harrier and Merlin, but on a UK scale these benefits to Hen Harriers, but not Merlin, are outweighed by their illegal killing, caused by fears that their consumption of Red Grouse can undermine the economics of grouse moor management.
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Ludwig, S., Roos, S. & Baines, D. (2020). Fluctuations in field vole abundance indirectly influence red grouse productivity via a shared predator guild. Wildlife Biology 2020: wlb.00642.
Changes in the abundance of one prey species may indirectly affect other prey species by triggering responses in generalist predators. Here we examine relationships between two prey species that do not compete directly, the field vole Microtus agrestis, a common rodent with fluctuating populations, and the red grouse Lagopus lagopus scotica, a gamebird inhabiting open moorland, during a 27-year study on a moor in south-west Scotland. First, we test whether vole abundance was related to grouse density and demographic rates. Second, we test whether vole abundance was related to abundance indices of four common predators of both voles and grouse (red fox Vulpes vulpes, weasel Mustela nivalis, hen harrier Circus cyaneus and common buzzard Buteo buteo). Third, we test whether these vole-grouse and vole-predator relationships differ in relation to grouse management, which includes the culling of foxes and weasels. We found no association between vole abundance and grouse densities, adult summer survival or nesting success. However, the ratio of young grouse per adult and the proportion of female grouse with broods in July were negatively associated with field vole abundance, suggesting increased predation of grouse chicks in years with high vole abundance. Fox indices showed a weak positive association with vole abundance when their numbers were not controlled, whilst weasel indices showed no relationship with voles. The numbers of breeding hen harriers and buzzards were also not associated with vole abundance, but the number of buzzard sightings was higher when voles were more plentiful. Our results are consistent with a negative interaction between field voles and red grouse chick survival in a pattern expected for apparent competition. Although the underlying mechanisms could not be disentangled, this interaction may be at least partly mediated by rodent-hunting raptors such as buzzards and, in periods without grouse management, foxes.
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Ludwig, S.C., Aebischer, N.J., Richardson, M., Roos, S., Thompson, D.B.A., Wilson, J.D. & Baines, D. (2020). Differential responses of heather and red grouse to long-term spatio-temporal variation in sheep grazing. Biodiversity and Conservation 29: 2689-2710.
During the last century, afforestation and intensification of sheep grazing in the British uplands have led to widespread declines in globally rare heather moorland. We quantified changes in heather cover over 70 years in relation to changes in sheep grazing on Langholm Moor, and examined the impact on red grouse, a gamebird inhabiting heather moorland. Between 1948 and 2009, when grazed heavily by sheep, heather-dominated vegetation declined from 53% to 14% cover. Large-scale sheep reductions from 2011 then allowed increase of heather-dominated vegetation cover to 18% by 2015. However, changes in heather cover were associated with changes in grouse abundance only where heather-dominated cover was reduced below thresholds of 27% (95% CL 18-36%; pre-breeding) and 17% (95% CL 13-20%; post-breeding). The number of grouse shot between 1951 and 1992 remained high where 37-65% of dominant heather cover was retained, but then declined between 1992 and 1996 following increased predation by raptors, leading to the cessation of shooting. Subsequently, grouse densities fluctuated in relation to periodic management by gamekeepers (1992-1999 and 2008-2016), but heather loss continued possibly until 2011, and predation in this context prevented sustained increases sufficient for ‘driven’ shooting. Grouse shooting provides an economic incentive to maintain and restore heather moorland. On Langholm Moor, however, afforestation in the surrounding landscape and isolation from other heather moors may have led to a grouse population less well buffered against growing predation pressure, especially outside keepered periods. As grouse shooting could not be restored, the future management of the moor remains uncertain.
Read the paper here