Cereal farming, pesticides and grey partridges.

Abstract

The decline of the grey partridge Perdix perdix parallels that of a suite of bird species currently declining on farmland. Unlike the other species, however, the status, ecology and population dynamics of the grey partridge have been the subject of research, both intensive and extensive, stretching back to the early 1930s. As a result, the science base is strong and the causes of the partridge decline are known: a collapse of biodiversity on farmland particularly in cereal crops, which involved hundreds of species of plants and insects as well as the birds.
Four successive developments are singled out as particularly important, all aspects of intensification in the cereal ecosystem: the use of herbicides; the abandonment of undersowing as the technique for establishing grass/legume leys; the polarization of grassland and cereal ecosystems including the abandonment of arable farming in hill regions; and the summer use of foliar insecticides. The impact on partridges of this intensification has been through the increased mortality of chicks starved of insect food.
The 28-year study of grey partridges on the Sussex Downs is used to quantify the effect of these developments in cereal husbandry and to judge the repercussions of the CAP Reforms of 1992. Contrary to what was intended in those Reforms, intensification has continued with, simultaneously, adverse effects of set-aside, increased use of insecticides and, locally, the arable reversion option as one of the agri-environment measures.
The partridge decline could readily be reversed by more effective policies. A biodiversity initiative grant-aided scheme for conservation headlands and undersowing together with more widespread use of the wild bird cover option on flexible set-aside and buffer zones for broad spectrum insecticides could restore partridge populations with concomitant benefits for farmland wildlife in general. Six proposals are given, see page 173.
More than any other bird species, the grey partridge could be said to be a barometer of the biodiversity in cereal-based farmland ecosystems (Potts, 1986). It lives mainly in cereal crops, feeds on a wide variety of insects and plants, benefits from mixed farming and is perhaps the most thoroughly monitored species amongst an assemblage of about 8000 (excluding micro-organisms) which live, or lived, in the arable crops of Europe. The species is also highly sensitive to changes in its environment. What is more, despite much lip-service and small-scale attempts to make agriculture more conservation-sensitive, many farming policies still further reduce the numbers of this bird.