Buffer strip management to deliver plant and invertebrate resources for farmland birds in agricultural landscapes

To address the decline in farmland birds across agricultural landscapes a key approach under agri-environment schemes has been the widespread creation of perennial grass-only buffer strips along field boundaries. However, despite a high dependency on these strips to enhance biodiversity in agricultural landscapes, it appears that benefits for farmland birds during the breeding season have been limited. We investigated the provision of plant and invertebrate resources for farmland birds in buffer strips that were established with three different seed mixes, including the standard grass-only habitat. We hypothesised that resource provision would differ between seed mix types due to differences in original composition. We also investigated three different types of management aimed at influencing sward composition and habitat structure, namely cutting, scarification and the application of graminicide. These approaches were used to influence the accessibility of structurally complex swards to farmland birds. We hypothesised that the abundance of plant and invertebrate resources and access to these resources would be directly related to management type. The abundance of plant resources and sward structure were determined using quadrats and the drop disc method respectively, whilst the invertebrates were assessed using suction sampling. The study demonstrated the value of including forbs (herbaceous plant species) in seed mixes used to establish buffer strips by increasing plant resources for farmland birds, although this was not coupled with an increase in beetle abundance and mass. However, grass-only buffer strips managed with annual cutting were shown to provide similar levels of invertebrate resources to farmland birds as with the more complex seed mixes, but it is likely that access to these resources was restricted by tall homogenous swards and a limited amount of bare ground. The study demonstrated that novel buffer strip management techniques can strongly influence both the resource abundance and resource access by farmland birds. Scarification in particular was shown to be highly effective at opening up the sward to increase access by farmland birds, but was associated with a reduction in plant resources. Given the financial barriers for the use of seed mixes that contain forbs to establish buffer strips, importantly the study has shown that the value of existing grass-only buffer strips for farmland birds can be enhanced through the use of scarification. Consequently, as an alternative to annual cutting, we recommend that scarification is periodically applied to narrow (1–3 m) strips next to the crop edge to enhance the value of grass-only buffer strips for farmland birds.