The Effects of Food Abundance, Sward Structure and Management on Foraging by Yellowhammers on Agricultural Grasslands
		David Buckingham Supervisors: Ken Norris, Will Peach (RSPB) Declines in farmland bird populations over the last 30 years have been most severe in pastoral parts of western Britain. Links between the declines and changing farming practice have been demonstrated for arable farmland, but not for the pastoral sector Recent large-scale habitat selection studies of birds using grasslands do not indicate problems with intensification. However, declining granivorous species are scarce in grassland areas, limiting the sensitivity of such studies Autecological studies have shown that grasslands can be important foraging habitats for granivorous passerines during the breeding season. Conversely, most grasslands are poor wintering habitats for such species There is a pressing need for an insight into what governs this patchy use of grassland by such birds, both to assess and develop agri-environment prescriptions. OBJECTIVES The project aims to identify how birds choose where to feed in agricultural grasslands and to assess the relative value of different grasslands to birds The hypothesis that small birds feed where the sward provides a compromise between food abundance (taller grass) and food accessibility (short grass) will be developed for a representative declining bird species The project will also consider how management practices affect foraging behaviour across a range of different pastoral enterprises, including organic dairies and agri-environment schemes. METHODS In the breeding season we are examining the role of grasslands in providing invertebrate food for those granivorous species that feed their chicks on invertebrates. Yellowhammer (Emberiza citrinella) is being used as the model species for this study. Wild adult yellowhammers are being observed as they feed their chicks at the nest. Invertebrate abundance and sward structure are being sampled to quantify their importance in foraging site choice. In the winter, we are looking at where granivorous birds find seeds in grasslands. Seed abundance and accessibility are being manipulated experimentally on silage fields using standard farming practices. The two main species responding to these treatments are yellowhammers and reed buntings (E. schoeniclus). OUTPUTS The goal of this project is to establish how the utility of grasslands for declining bird species can be improved. This knowledge will be used to guide development of agri-environment options for pastoral farms. Effective, practical agri-environment options for grass management are urgently required in western Britain, where regional specialisation in pastoral farming has led to the loss of the mixed farming systems that birds depend upon. The situation is becoming severe in Northern Ireland, where a near-complete loss of arable farming seems set to drive the yellowhammer population to extinction. The project also seeks to extend the limited range of agri-environment options that can realistically be incorporated into high-productivity dairy systems. The study is funded by ...With support from ...