Red grouse and hen harriers on Langholm Moor
A hen harrier brood at Langholm. © Sonja Ludwig/GWCT
KEY FINDINGS
Grouse moor management had a positive effect on abundance and breeding success of red grouse and hen harriers. Fox abundance was negatively associated with grouse density and harrier breeding success. Crow abundance was negatively associated with grouse breeding success.
Sonja Ludwig Dave Baines
Since 1992, Langholm Moor has hosted studies that focused on the conflict between grouse moor management and raptor conservation. During this time, the moor was subject to the cessation and subsequent restoration of grouse moor management. Up to 1999 and from 2008-2015 the moor was managed by gamekeepers for grouse shooting, which involved heather burning and legal control of generalist predators. In the intermediate years (2000-2007), no full-time gamekeepers were employed to routinely control predators. We considered how these changes influenced the abundance and breeding success of grouse and harriers, as well as the abundance of their likely predators, red fox and carrion crow. Grouse moor management in both periods was associated with 50-70% lower
ACKNOWLEDGEMENTS
This study was part of the Langholm Moor Demonstration Project, a partnership between the Game & Wildlife Conservation Trust, Scottish Natural Heritage, Buccleuch Estates, RSPB and Natural England. For more details see Ludwig et al. (2016) Wildlife Biology, DOI 10.2981/wlb.00246.
Figure 1
Annual variation in abundance of carrion crows and fox scat index
Carrion crow abundance Fox scat index
Keepered periods
crow indices and with 65% lower fox indices in the second period only as foxes were not measured in the first (see Figure 1). Furthermore, grouse densities (see Figure 2) and breeding success (see Figure 3) were two- to three-fold higher than when the moor was not managed for grouse. When looking at annual values, there were more grouse when there were fewer signs of foxes and grouse reared more chicks when there were fewer crows. However, as we cannot disentangle the relative contribu- tion of predator control from simultaneous changes in heather management or the introduction of diversionary feeding in the second managed period, other factors may further explain changes in grouse breeding success and densities. Grouse moor management also had a positive effect on harrier breeding success, which was two- to three-fold higher than during the unmanaged period (see Figure 3), and tended to be lower in years with higher fox indices. Since grouse moor manage- ment was re-established in 2008, no harrier nests have failed through fox predation. Hen harrier abundance decreased after the cessation of grouse moor management in 1999 (see Figure 2), however, despite the high breeding success numbers started to recover only six years after management was resumed in 2008. This study confirms that both grouse, in the presence of low numbers of harriers, and harriers, if not controlled illegally, can benefit from grouse moor management.
1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 54 | GAME & WILDLIFE REVIEW 2016
www.gwct.org.uk
0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0
Crows per kilometre
Fox scats per kilometre per 10 days
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