| UPLANDS - LANGHOLM MOOR
The impact of buzzards on red grouse We looked at the year-round diet of buzzards at Langholm Moor. © Laurie Campbell
BACKGROUND The Langholm Moor Demonstration Project (2008-2017) aimed to restore economically sustainable driven grouse shooting while maintaining a viable population of hen harriers and to extend and improve the heather habitat.
ACKNOWLEDGEMENTS This study was funded by Buccleuch Estates, Game & Wildlife Conservation Trust, Scottish Natural Heritage and Natural England through contributions to the Langholm Moor Demonstration Project.
72 | GAME & WILDLIFE REVIEW 2019
Human-wildlife conflicts often centre on economic loss caused by wildlife. Despite this being a major issue for some land managers, estimating total prey losses to predation, including that by legally protected predators, can be difficult. Estimating impacts of protected wildlife on economically important prey can also help management decisions to be evidence-led. The recent recovery in numbers and range of common buzzards in Britain has brought them into conflict with some gamebird managers. The magnitude of any impact is poorly understood, having seldom been quantified by empirical field data. A three-year PhD studentship funded by the Langholm Moor Demonstration Project, was conducted with Newcastle University to consider the year-round diet of buzzards at Langholm Moor. Taking into account buzzard abundance and foraging range, the study examined whether buzzards may have impacted the project aim of restoring red grouse numbers sufficiently to re-establish driven grouse shooting. Experimental culling of buzzards to measure their potential impact on grouse was deemed unacceptable for both welfare and logistic reasons. In their absence, bioenergetics models were used that combined measures of buzzard abundance from field surveys with studies of their diet assessed by using cameras and prey remains at nests and pellet analysis over the winter. The resultant measures of seasonal grouse consumption by buzzards were used in conjunction with sample counts of grouse abundance to estimate potential impact on red grouse on Langholm Moor, a 115km² moor in south-west Scotland, managed to restore red grouse shooting. Grouse consumption by an individual pair of breeding buzzards and their chicks varied between pairs and years, averaging 0-5 adult grouse and 0-6 grouse chicks per annum depending on assessment method. This rate was lower than previous estimates for two other raptor species, hen harrier and peregrine, present on the study site. Total consumption by buzzards could, however, have been greater given that an estimated 55-73 buzzards were present on the study site year-round during the study period, making buzzards three-times more abundant than both hen harrier and peregrine combined. Averaging across diet assessment methods, consumption models estimated that during each of the three breeding seasons (April-July 2011-2013), the
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