The effect of management for red grouse shooting on the population density of breeding birds on heather‐dominated moorland

Abstract

Summary1. Breeding birds, vegetation and moorland management were surveyed in 320 1-km squares on 122 estates in upland areas of eastern Scotland and northern England where red grouse shooting is a widespread land use. We assessed whether population densities of 11 species of breeding birds differed between heather-dominated moorland managed for red grouse shooting and other moorland with similar vegetation. 2. We classified estates that had a full-time equivalent moorland gamekeeper as grouse moors. The mean density of red grouse shot per year was four times higher and the mean density of gamekeepers was three times higher on grouse moors than on other moors. Rotational burning of ground vegetation covered a 34% larger area on grouse moors than on other moors. 3. Selection of heather-dominated squares resulted in similar composition of vegetation on grouse moors and other moors (about 76% heath, 12% grass, 8% bog, 2% flush and < 1% bracken on both types). However, grouse moors tended to have less tall vegetation than other moors and differed significantly in some other characteristics of the vegetation, topography and soil type. 4. Densities of breeding golden plover and lapwing were five times higher and those of red grouse and curlew twice as high on grouse moors as on other moors, while meadow pipit, skylark, whinchat and carrion/hooded crow were 1·5, 2·3, 3·9 and 3·1 times less abundant, respectively, on grouse moors. The differences in density between moorland types remained significant ( P < 0·001) for golden plover and crow and approached significance ( P < 0·10) for lapwing and meadow pipit after allowing for variation among regions. 5. We used Poisson regression models to relate bird density to vegetation cover, topography, climate and soil type. After adjusting for significant effects of these habitat variables, significant differences in bird density between the two moorland types remained for six species, although their magnitude was reduced. 6. Correlations of adjusted bird density with measures of different aspects of grouse moor management provided evidence of a possible positive influence of predator control (assessed using crow density) on red grouse, golden plover and lapwing. The control of crows by gamekeepers is the most probable cause of the low densities of crows on grouse moors. There was evidence of a positive effect of heather burning on the density of red grouse and golden plover and a negative effect on meadow pipit. Multiple Poisson regression indicated that predator control and heather burning had significant separate effects on red grouse density. Significant relationships between adjusted breeding bird densities and the abundance of raptors and ravens were few and predominantly positive.

Predation in bird populations

“…Some studies have concluded that predators are important in determining the size of bird populations, where increasing predator numbers result in lower prey populations (e.g. Tharme et al 2001;Smith et al 2010;Fletcher et al 2010). But others have shown that predator numbers or predator presence do not change prey numbers (e.g.…”

Ecological effects of game management: does supplemental feeding affect herbivory pressure on native vegetation?

“…Similarly, the hatching success of 5 out of 6 wader species in Scotland increased significantly after crow and gulls were controlled (Parr 1993), although breeding numbers over the three years of the study did not increase. Tharme et al (2001) found that density of golden plover, lapwing and curlew were higher on grouse moors where predators where culled than on moors where no predator control was implemented, while meadow pipit, skylark, whinchat and crows were less abundant (although the latter was probably due to habitat rather than predator management). Stoate and Szczur (1994) found that hatching success of some songbirds (particularly those having low values of hatching success in control conditions) increased as a result of corvid removal.…”

“…However, they found no difference in strike rates between the habitats, suggesting that prey were not more abundant on grouse moors, only more available maybe due to changes in vegetation structure, prey behaviour or predator behaviour. Tharme et al (2001) compared densities of different bird species in moorland areas managed and not managed for grouse. According to their analyses, densities of breeding golden plover and lapwing were 5 times higher and those of curlew twice as high on grouse moors as on other moors, while meadow pipit, skylark, whinchat, and carrion/hooded crow were less abundant on grouse moors.…”

The importance of altitude and aspect for breeding WhinchatsSaxicola rubetrain the uplands: limitations of the uplands as a refuge for a declining, formerly widespread species?

“…Other published studies have found Whinchats on British moorland to be associated with dense vegetation, particularly bracken, and variation in dwarf shrub cover, to show a quadratic relationship with ground cover by fine grass (peaking at about 20% cover) and a negative relationship indicating avoidance of short graminoids (Pearce-Higgins & Grant 2006) and to be positively associated with bracken and wet flushes (Stillman & Brown 1994). They were also found to be less abundant on heather moors that were managed for the driven shooting of Red Grouse (Willow Ptarmigan) Lagopus lagopus scotica than 'other' moorland (Tharme et al 2001). Many of these features are probably indicators of what might be considered as marginal uplands rather than 'true' upland heather moorland or blanket bog and perhaps be indicators of similarity to the kind of terrain of the principal Ochil Hills study site and also of those in Wales.…”