Bird and Invertebrate Ecology in Field Margins
Field margins have been a prominent focus at the Allerton Project's research and demonstration farm in Leicestershire for more than 25 years. The project is managed by the Game & Wildlife Conservation Trust and carries out research into a wide range of agri-environmental issues, disseminating results to agricultural professionals, regulators, and policy makers through farm visits, training, and publications. The farm area is 333 hectares and reflects the undulating topography, clay soils, and mixed farming system of the wider landscape, with the pasture being let to a neighbouring sheep farmer. The arable land is managed by the Allerton Project's own farm staff, and the rotation is, broadly, wheat, rape, wheat, followed by beans or oats. Thirteen percent of the farm is pasture which is grazed by sheep. There is a small pheasant Phasianus colchicus shoot on the farm with associated management such as habitat creation and management and legal control of predators and provision of grain as food in winter in most years (Stoate et al. 2013).
As was typically the case across lowland Britain in the early 1990s, field boundaries were routinely sprayed either accidentally, as a result of spray drift into the hedge base from applications to the crop, or deliberately in order to control the weeds which established there as a result of destruction of the perennial herbaceous vegetation (Boatman et al. 1994) , Following a baseline year, the management of the farm changed to include the creation and management of hedges and associated herbaceous vegetation in field margins. In subsequent years, management of field margin habitats has been modified in the light of wildlife-oriented research findings. As a result, field margins at Loddington feature traditional hedges, primarily hawthorn Crataegus monogyna and blackthorn Prunus spinosa, perennial grass strips of various widths within agri-environment schemes and, in some cases, annual or biennial seed-bearing crops to provide winter food for birds. Approximately half of the field margins also contain ditches as all the arable fields and some pasture fields are under-drained.
In the early years of the project, research concentrated on field margins, in part because this involves least intrusion into the cropping system and yields are around 20% lower in the field headland than in the rest of the field (Wilcox et al. 2000). However, the focus is also on field margins because most farmland wildlife is associated with them rather than the crop. The emphasis, in terms of both research and management, has been on birds because of their cultural value to society, and on invertebrates that are either food for birds, pollinators, or predators of crop pests which therefore have the potential to benefit crop production.