The 'Conservation Headland' experiment in cereal ecosystems.

Abstract

In 1984, The Cereals and Gamebirds Research Project began working on the problems associated with wild gamebird production on intensively farmed arable land. The Project arose as a result of studies on grey partridges (Perdix perdix L.) carried out in Sussex which began in 1968 to identify the problems encountered by stocks of wild, breeding birds and the factors that had contributed to the observed 80% decline in the national population of partridges which had been monitored over the last forty years (Potts, 1980; 1986).

Earlier studies (Blank et al., 1967; Potts, 1980) had found that the key factor causing changes in a grey partridge population in Hampshire was chick mortality and clearly showed the link between their observed national decline and the increasingly poor levels of chick survival. Also, chick survival was shown to be linked to the availability of sufficient quantities of the preferred insects that are essential in the diet of young chicks (Southwood & Cross, 1969; Potts, 1986). It has been suggested that low densities of preferred insects in cereal fields resulted from the increasingly intensive nature of cereal production over the last forty years and the use of pesticides appeared to be a major contributory factor in reducing populations of preferred insects.

Green (1984) listed the preferred food items of young chicks. These include a group of Coleoptera (Chrysomelidae, small diurnal Carabidae and Curculionidae), larval forms of Lepidoptera and Tenthredinidae (especially species of the genus Dolerus) and many members of the Heteroptera (especially species of the genus Lygocoris). Many of these preferred insects were found to be abundant at the edges of cereal fields where grey partridge broods forage (Green, 1984).

It is now known that various types of pesticides can detrimentally affect these non-target species; both the use of insecticides and insecticidal fungicides (Vickerman, 1977; Vickerman & Sunderland, 1977; Vickerman & Sotherton 1983; Sotherton et al., 1987; Sotherton & Moreby, in press) and the use of herbicides. The use of herbicides has probably been the most important single contributory factor because of their ability to remove cereal field weeds that are the host plants of many of these phytophagous chick-food insects (Southwood & Cross, 1969; Vickerman, 1974; Sotherton, 1982).