The relative effects of raptor predation and shooting on overwinter mortality of grey partridges in the United Kingdom

Abstract

Summary 1.Factual information is key to resolving conflicts between raptor conservation and gamebird management, especially when the conservation status of one of the species involved is threatened. The grey partridge Perdix perdix is a UK Biodiversity Action Plan species because of a marked decline in abundance caused by agricultural intensification. Recently, the number of raptors present on farmland and the commercial shooting of red-legged partridges Alectoris rufa have both increased. To inform conservation action, the relative impacts of these two factors on grey partridge populations urgently require quantification. 2. On our study site areas of low density of grey partridges coincided with areas of high raptor density. However, these areas were managed intensively for shooting and for two areas that suffered local partridge extinction, the 3-year average percentage of partridges shot exceeded 50%. 3. Grey partridge mortality to raptors between autumn and spring lay between 9·5% of autumn density (assumes losses to raptors occurred before shooting) and 15% of post-shooting density (if all losses to raptors were post-shooting). A deterministic model suggested that this rate of loss would reduce the equilibrium density of spring pairs by 11-26% relative to a situation without raptors. In comparison, shooting losses across the study area amounted to 35-39% of autumn density, more than double the losses to raptor predation, with a predicted reduction of 68-85% in equilibrium density of spring pairs. 4. Synthesis and applications. Shooting based on large-scale releases of red-legged partridges acts in a density-independent manner and can lead to local grey partridge extinction. Removing the grey partridge from the UK quarry list would be counterproductive, as most action to boost wild grey partridge densities is carried out by enthusiasts with shooting as the incentive. However, it is imperative that managers of intensive shoots based on gamebird release adopt measures to reduce shooting pressure on wild grey partridges at low density. These include training shooters to distinguish between grey and red-legged partridges and implementing a warning system (whistle) to alert the gun line when birds of the non-target species are approaching. Such voluntary measures are effective in addressing overshooting, which has greater implications for grey partridge conservation than raptor predation.

Decline and potential recovery of the European grey partridge (Perdix perdix) population—a review

“…Apparent competition between ring-necked pheasants and grey partridges, mediated via the caecal nematode, may be one cause of the recent decline in UK grey partridge numbers and may be hampering current efforts to re-establish and increase wild populations (Tompkins et al 2001(Tompkins et al , 2000a. Releasing pheasants and red-legged partridges also leads to unsustainable heavy losses of grey partridges by shooting as they inadvertently become caught up in the drives of released gamebirds (Watson et al 2007). As a result, grey partridge numbers decreased more on estates with game bird releasing compared to estates with no releasing (Aebischer and Ewald 2004).…”

“…Important to note in these studies is that hunting mortality (albeit sometimes strongly reduced) remained next to predation an important mortality factor. The mortality caused by hunting (35-39%) in some areas in the UK was more than double the losses caused by raptor predation (9.5-15%; Watson et al 2007).…”

An ethological perspective on defecation as an integral part of anti-predatory behaviour in the grey partridge (Perdix perdix L.) at night

“…In the study reported here, the defecation behaviour of the grey partridge (Perdix perdix) was examined at night time and discussed in the context of predator avoidance behaviour against the background of a night-time environment dominated by the risk of predation by the red fox (Vulpes vulpes). Watson et al (2007) estimate that fox predation accounts for 44% of the natural mortality of the grey partridge during winter. This high mortality is despite measures undertaken to reduce the number of foxes and the well-known anti-predation measures adopted by partridges to avoid predation by foxes, which hunt at night using scent.…”

How effective and selective is traditional Red Fox snaring?

“…Reynolds & Tapper 1995b), is regarded by game managers or hunting groups throughout the country as the main cause of decline of populations of small game (Vargas & Muñoz 1996). Intensive fox culling programmes in Spain are largely undertaken within those estates dedicated to hunting of rabbits and partridges, with frequent game restocking, and hence intensively managed (Watson et al 2007, Beja et al 2009). Removal of foxes affects productivity (Heydon & Reynolds 2000, López-Martín et al 2007, as well as the spatial dynamics of populations (Von Schantz 1981, Reynolds 2000.…”