Managing agri-environment grass fields and margins for Orthoptera and farmland birds

• Main Author: Smith, W. D.
• Published: University of Reading 2006
• Subjects: 591.7
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538719

Grasshoppers and bush-crickets, collectively known as Orthoptera, are a critical invertebrate prey group for a number of declining farmland birds, including the cirl bunting (Emberiza cirlus). This study focuses on one species of Orthoptera, the meadow grasshopper (Chorthippus parallelus). The key objective was to provide an evidence base in order to identify the agri-environment scheme prescriptions and management practices of greatest value to C. parallelus. This information will help formulate management recommendations that will enhance C. parallelus abundance in agro-ecosystems, which in turn will contribute to the conservation of farmland birds. Comparisons between agri-environment pasture, 2m and 6m arable margins, longterm set-aside and intensively grazed pasture revealed that 6m margins and longterm set-aside tended to support significantly higher densities of adult C. paralle/us. The abundance of nymphs, however, did not appear to differ between the habitats surveyed. The abundance of C. parallelus adults and nymphs was influenced by a combination of sward architecture and botanical composition. Sward height was particularly important. Early stage nymphs preferred short swards, and as individuals matured sward height preferences shifted towards taller swards. Sward heights on agrienvironment pastures appear to be too short to benefit adult C. parallelus, whilst swards on arable margins are too tall to benefit nymphs. Mowing in July significantly reduced the abundance of C. parallelus adults and late stage nymphs, whereas mowing in May appeared to benefit early stage nymphs. The most critical and simplest improvement on current management practices would be to delay the mowing of grasslands and arable margins, which commonly occurs in July or August, until later in the season. It is proposed here that mowing should not be undertaken before September. Furthermore, results suggest that grazing on agrienvironment pastures should be lighter if higher abundances of C. parallelus are required to benefit farmland bird populations.