The management of set-aside land as brood-rearing habitats for gamebirds.

Abstract

The U.K's five-year set-aside scheme began in 1988 and was designed to move land out of cereal production into various non-crop uses to reduce cereal surplus production within the European Community. However, the grey partridge (Perdix perdix), a bird of open arable landscapes, is often found in cereals throughout the year, especially preferring the habitat offered by these crops for rearing their young. Populations of P. perdix were once a common sight on farmland but one measure of their abundance, their spring breeding densIty, has declined from 25 pairs km² in the early 1950s to less than five pairs by the mid 1980s (Potts 1986). The major reason for this decline has been a reduction in the rates of chick survival. To ensure high levels of chick survival young chicks need a high-protein diet, particularly during the first few weeks after hatching. A high density of invertebrates from cereal crops, especially where there is an associated weed flora, supplies this need (Potts 1986; Green 1984). Most invertebrates will be eaten, but four insect groups are particularly important: plant bugs (Heteroptera, especially Miridae), leaf hoppers (Homoptera: Auchenorrhyncha), sawf1y larvae (Hymenoptera, Symphyta: Tenthredinidae) and Coleoptera (especially Carabidae, Curculionidae and Chrysomelidae) (Sotherton & Moreby 1992). These four groups form the compiled guild of preferred 'chick food items'. The change from land growing cereals, an ecosystem known under certain circumstances to be able to supply a plentiful amount of food for young gamebird chicks and many other farmland birds, into arable fallow or set-aside which is of unknown potential to provide suitable brood-rearing habitat resulted in the motivation for this study. It was intended that the study would look at changes in the flora and fauna of fields in their first fallow year following harvest through to their fifth year of naturally regenerating vegetation and compare these fields to winter wheat, the main crop they replaced. However, due to changes in the Five-year Set-aside Scheme and the widespread introduction of the Rotational Set-aside Scheme in 1993, it was only possible to follow fields for three years. This paper presents the results on invertebrate densities and discusses the implications for gamebird chick survival.