PUBLICATIONS


2017

Ludwig, S. C., Roos, S., Bubb, D. & Baines, D. (2017) Long-term trends in abundance and breeding success of red grouse and hen harriers in relation to changing management of a Scottish grouse moor. Wildlife Biology 2017: wlb.00246.

http://www.bioone.org/doi/pdf/10.2981/wlb.00246

Abstract

Large areas of heather moorland in the British uplands are managed for shooting red grouse Lagopus lagopus scotica. However, there has been a long-standing conflict between grouse moor management and the conservation of raptors, particularly the hen harrier Circus cyaneus. Langholm Moor, a grouse moor in south-west Scotland, has hosted studies aiming to resolve this conflict for 24 years. Between 1992 and 1997, whilst managed as a grouse moor, hen harrier numbers increased from two to 20 breeding females, and raptor predation removed large proportions of both adult grouse and chicks. As driven shooting was no longer viable, grouse moor management ceased in 1999, and was not restored until 2008. This paper considers how cessation and subsequent restoration of grouse moor management, which involved heather management and legal control of generalist predators, affected the abundance and breeding success of red grouse and hen harrier, as well as the abundance of their perceived key predators; red fox Vulpes vulpes and carrion crow Corvus corone. Grouse moor management had a positive effect on abundance and breeding success of grouse and harriers, which were two- to three-fold higher when fox indices and crow abundance were reduced by 50-70%. Fox indices were negatively correlated with red grouse density and harrier breeding success, whereas crows were negatively correlated with grouse breeding success.

This study confirms that both grouse and harriers can benefit from grouse moor management, if harriers are not persecuted. However, restoration of grouse moor management, in combination with diversionary feeding of harriers, has not yet resulted in a sufficiently increased grouse density to allow driven shooting on Langholm Moor, and thus the management to be considered as economically viable.


Francksen, R.F., Whittingham, M.J., Ludwig, S.C., Roos, S., Baines, D. (2017) Numerical and functional responses of common buzzard Buteo buteo on a Scottish grouse moor. Ibis 159: 541-553.

http://onlinelibrary.wiley.com/doi/10.1111/ibi.12471/full

Abstract

Predators will often respond to reductions in preferred prey by switching to alternative prey resources. However, this may not apply to all alternative prey groups in patchy landscapes. We investigated the demographic and aggregative numerical and functional responses of Common Buzzards Buteo buteo in relation to variations in prey abundance on a moor managed for Red Grouse Lagopus lagopus scotica in south-west Scotland over three consecutive breeding and non-breeding seasons. We predicted that predation of Red Grouse by Buzzards would increase when abundance of their preferred Field Vole Microtus agrestis prey declined. As vole abundance fluctuated, Buzzards responded functionally by eating voles in relation to their abundance, but they did not respond demographically in terms of either breeding success or density. During a vole crash year, Buzzards selected a wider range of prey typical of enclosed farmland habitats found on the moorland edge but fewer Grouse from the heather moorland. During a vole peak year, prey remains suggested a linear relationship between Grouse density and the number of Grouse eaten (a Type 1 functional response), which was not evident in either intermediate or vole crash years. Buzzard foraging intensity varied between years as vole abundance fluctuated, and foraging intensity declined with increasing heather cover. Our findings did not support the prediction that predation of Red Grouse would increase when vole abundance was low. Instead, they suggest that Buzzards predated Grouse incidentally while hunting for voles, which may increase when vole abundances are high through promoting foraging in heather moorland habitats where Grouse are more numerous. Our results suggest that declines in their main prey may not result in increased predation of all alternative prey groups when predators inhabit patchy landscapes. We suggest that when investigating predator diet and impacts on prey, knowledge of all resources and habitats that are available to predators is important.


2016

Francksen, R. F., Whittingham, M. J. & Baines, D. (2016) Assessing prey provisioned to common buzzard Buteo buteo chicks: a comparison of methods. Bird Study 63 (3): 303-310.

http://www.tandfonline.com/doi/full/10.1080/00063657.2016.1183111

Abstract
Capsule: Methods of assessing raptor diet carry significant inherent biases which can vary over time.

Aims: To compare methods of assessing Common Buzzard Buteo buteo diet composition and assess how any differences vary between years.

Methods: Diet was assessed at 32 Common Buzzard nests on an area of upland heather moorland in Britain, managed for Red Grouse Lagopus lagopus scotica, over three years. Data obtained from nest cameras were compared with data from prey remains and regurgitated pellets.

Results: Diet composition differed between methods in all years. Methodological differences varied between years in relation to an almost twelve-fold change in Field Vole abundance, a key prey of Common Buzzards, while abundances of alternative prey changed little. Small mammals were underestimated by prey remains in all three years, while herpetofauna were underestimated by prey remains and pellets in two years. Large birds were overestimated by prey remains, significantly so in one year. Pellets overestimated invertebrates in all years. By combining prey remains and pellets, significant yearly variations in biases were eliminated, although the combined measure overestimated large birds and invertebrates.

Conclusion: Our results suggest that future studies should consider not only how chosen methods may affect results, but also how effects can differ between years.


Francksen, R. M., Whittingham, M. J., Ludwig, S. C. & Baines, D. (2016) Winter diet of Common Buzzards Buteo buteo on a Scottish grouse moor. Bird Study 63 (4): 525-532.

http://www.tandfonline.com/doi/full/10.1080/00063657.2016.1238868

Abstract
Capsule: The winter diet of Common Buzzards Buteo buteo on a Red Grouse Lagopus lagopus scotica moor was dominated by small mammals, whilst grouse were a minor prey item.

Aims: To assess winter diet of Common Buzzards from pellets collected at roost sites on and around a managed Red Grouse moor, and to explore temporal, spatial and age-related variation in diet composition.

Methods: Forty-four winter roost sites were located during two winters using a combination of observations from vantage points and individual Common Buzzards equipped with either radio or satellite transmitters. Pellets were collected between October and March each winter and analysed to assess dietary composition.

Results: Small mammals were the main prey in both years, comprising 60–67% of items and occurring in 88–92% of pellets. Diet varied between years, with more lagomorphs and birds (passerines, corvids and pigeons) but fewer Red Grouse eaten when grouse abundance declined. Grouse formed 1.1% and 0.6% of prey items, and occurred in 3% and 2% of pellets from each winter, respectively.

Conclusion: Common Buzzards rely on small mammal prey during winter. When available, Red Grouse are a minor dietary component, the amount of which reflects their abundance in the environment. The opportunism of Common Buzzards can result in temporal variation in winter diet.


Thompson, D.B.A., Roos, S., Bubb, D., Ludwig, S.C. (2016) Hen Harrier. Version 1.0. In: Gaywood, M.J., Boon, P.J., Thompson, D.B.A. & Strachan, I.M. (Eds.) The Species Action Framework Handbook. Scottish Natural Heritage, Battleby, Perth.

http://www.snh.gov.uk/docs/A2169322.pdf


2015

Fingland, K. & Ludwig, S. C. (2015) Clutch abandonment as a result of brood adoption in the red grouse. British Birds 108: 294-295.

https://britishbirds.co.uk/article/british-birds-may-2015/

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Langholm Moor - Laurie Campbell