The Impact of Released Gamebirds on the Nature Conservation Value of Chalk Grassland in Central Southern England.
The recent dramatic increases in the number of pheasants and red-legged partridges being released for the shooting industry have raised concerns that negative ecological effects may be occurring as a result.
Chalk grasslands often form a proximal habitat to release pens making the habitat liable to exploitation by game birds. An artificially high density of a species in ecological systems is a concern in nature conservation, especially if the system is subject to other external pressures. Chalk grassland, as an example of such a system, has shown a sharp decline in extent as a result of agricultural intensification.
Analysis of soil samples found no significant differences in pH, available nitrogen or phosphorus as a result of accumulations of game bird dung. Vegetation surveys, to test for consequent effects on vegetation and physical damage by gamebirds, identified no significant differences in the percent cover of bare ground or litter, sward height or number of positive and negative indicator plant species.
An impact of released gamebird predation on the number of species, abundance or diversity of invertebrates could not be found. Community based analysis revealed no significant effects of released gamebirds on the invertebrate communities recorded during the study.
Significantly more buzzards were counted using the grassland following the release of gamebirds (autumn/winter), suggesting that the release of birds was encouraging predators. Results of spring surveys confirmed that the influx of buzzards to release sites was transitory, related to the release of gamebirds. No differences in the number of other bird species or abundances of birds were recorded as a result of increased predator pressure attracted to the release of gamebirds.
The impact of released game birds on the nature conservation value of chalk grassland appears minimal. Invertebrate availability, gamebird behaviour, diet and density and the provision of good shoot management may have combined to minimize the risk of impact.