Investigating Conservation Management Interventions for the Benefit of Farmland Breeding Waders of Marginal Agricultural Grasslands in the UK

Abstract

Agriculture is the principal land use throughout Europe and agricultural intensification has been implicated in large reductions in biodiversity, with the negative effects on birds particularly well documented. The Northern Lapwing (Vanellus vanellus) and the (Numenius arquata) are farmland breeding wader species where changes in farming practices has reduced the suitability and quality of breeding habitat, as well as the availability of large, soft-bodied soil prey which these birds depend upon leading to severe declines in population size that warrants them both listed on the Red List of Birds of Conservation Concern in the UK. Lowland areas, where agricultural intensification has generally been most pronounced, have been worst affected. However, more recently declines in marginal upland areas, previously considered refuges for breeding wader populations, have been identified. In this thesis I investigate conservation management interventions for the benefit of farmland breeding waders of marginal agricultural grasslands in the UK. Upland areas receive high levels of rainfall and are characterised by typically peaty soils with a low buffer capacity and a high organic matter content that results in these areas being particularly prone to localised acidification over time. I use field-scale trials to experimentally test the use of lime as a potential novel conservation tool to amend acidic soil pH, thus increasing earthworms (Annelida), an important prey item of Lapwing and Curlew. I show that lime use increases soil pH, although the effect varies with time, and that earthworm numbers increased following lime with the largest effect size observed two years after liming. Above ground, I show that there was no effect of liming on the vegetation of grazed grasslands, and no effect on beetles (Coleoptera) or spiders (Aranea). Additionally, I show that wader densities were 50% higher on lime treatment plots, and that wader intake rate of large prey items was greater on lime treatment than control three years following the application of lime. Furthermore, I show strong woodland edge effects on four wader species over a distance of several hundreds of metres in the Badenoch and Strathspey, an important stronghold for these birds. This is particularly relevant in light of land-use policy of tree planting to mitigate climate change committed to by the UK Government. The results presented here in this thesis will help contribute to the development of conservation strategies for waders. My results suggest that lime use could be an important tool to mitigate localised acidification of enclosed upland grassland where earthworm numbers may have declined, alongside other well established habitat managements for these birds, and that buffer zones should be placed of at least 200m between tree planting and important wader breeding habitat.