Using phenological drivers of demography in conservation

Understanding density-dependent processes and the conditions that influence their fitness consequences is a key component of population ecology, but the mechanisms determining density-dependent effects in wild populations are rarely understood. Most studies of density-dependent processes have focussed on identifying conditions influencing spatial variation in densities. However, phenological variation among individuals within breeding populations may also influence the strength of local density-dependence, if individual contributions to these processes vary with stage of the reproductive cycle. Synchronous breeding could thus be a major contributor to density-dependent processes within local populations. Identifying links between reproductive synchrony, density-dependence and demography is particularly important in species of conservation concern, for which management to facilitate reproductive synchrony and associated fitness benefits may be possible.

In lowland areas of Europe, wading bird populations have undergone severe and widespread declines, and are increasingly restricted to small numbers of nature reserves. Funding mechanisms have been developed within the EU Common Agricultural Policy to attempt to halt and reverse these declines, through agri-environment schemes (AES), but these attempts have failed despite the very large sums of money involved. There is therefore growing recognition of the need to target actions through a much more profound understanding of the interactions between land management and species demography. AES that deliver suitable breeding habitat can successfully attract breeding waders, but high levels of nest and chick predation by generalist predators (primarily red foxes, Vulpes vulpes) consistently prevent population recovery. Ground-nesting waders are inherently vulnerable to predation, and many species have evolved strategies such as semi-colonial breeding and group mobbing of predators to counteract these impacts, but these behavioural adaptations have not previously been considered in the design of AES, and piecemeal deployment of AES that support very small populations may in fact be exacerbating the population declines. Predation rates on wader nests and chicks are generally lower when nesting densities are high, but there is often a great deal of variation in these relationships. The effectiveness of anti-predator behavioural adaptations may be enhanced when breeding is synchronous, as defence behaviour often intensifies through the breeding cycle, but the contribution of reproductive synchrony to these density-dependent processes is unknown. High levels of predation typically result in reproductive asynchrony, as predated nests are replaced throughout the breeding season. The actions of predators may therefore be reducing the effectiveness of anti-predator strategies; a cycle which can potentially be broken through management to facilitate reproductive synchrony.

To test the role of reproductive synchrony in driving productivity and population growth, and the potential for management to facilitate reproductive synchrony in species of conservation concern, we propose to carry out a large-scale experimental manipulation of predator distribution and reproductive synchrony in breeding wading bird (northern lapwing, Vanellus vanellus, and common redshank, Tringa totanus) populations on lowland wet grasslands, and to quantify the mechanisms through which synchrony can enhance local productivity. This information will be used to model potential rates of population growth that could be achieved by land management strategies that integrate both environmental and behavioural drivers of population growth. Within-population phenological variation could influence density-dependent processes in a wide range of settings, and identifying these links may therefore substantially improve our understanding of key processes in population ecology and conservation management.

At the national level, key beneficiaries of this research will be from government departments (NE, Defra) and NGOs (RSPB, Wildlife Trusts) involved in the development and implementation of agricultural land management and, particularly, the design and delivery of agri-environment initiatives. Over the last two decades, CAP reform and associated developments in agri-environment scheme (AES) funding have fuelled the implementation of strategies for biodiversity conservation within farmed landscapes. However, the effectiveness of many AES options has been compromised by a failure to address the need for landscape-scale management to provide the suite of environmental requirements at appropriate spatial scales. The most recent AES in the UK, Countryside Stewardship (CS) will provide more than £900 million to rural businesses to improve the countryside environment, but the deployment procedures needed to deliver effective landscape-scale conservation are still poorly understood. This proposal aims to develop these procedures for one of the major groups of conservation concern in lowland Europe; migratory breeding waders. The CS programme contains options for the tools that our proposal will deploy (fencing and the provision of tall vegetation), but the deployment strategies that can facilitate population growth in breeding waders have not yet been identified. Through our close collaboration with local RSPB and NE staff, we have developed a network of landowners on whose land we are able to manipulate conditions through targetted deployment of AES options in the CS scheme, and our work will have direct impacts for the type of AES deployment strategy that is adopted in the Broads area for the new CS scheme. In addition, our application of the outputs to other regions of the UK highlighted by RSPB/NE as Wader Conservation Targetting areas means that our study can influence AES deployment strategies throughout other lowland areas of the UK.

Our work will also have impact internationally, as these issues are directly relevant to the aims of international conservation conventions, agreements and organisation (Convention on Migratory Species directorate, EU ORNIS committee, Birdlife International, African-Eurasian Waterbird Agreement). Identifying strategies for maintaining the species protected under these international agreements alongside agricultural development is a major challenge throughout the world. The information on agricultural land management impacts and the consequences for wader populations of different land management options will aid the implementation of national and international action plans for these species, and the development of agri-environment initiatives and land management plans throughout Europe.

We aim to achieve this impact through the creation of a Project Advisory Group, with representatives from NE and RSPB, through an international workshop for policy-makers and researchers on 'Targetting AES delivery and predator management for breeding waders across Europe', and through continuing regular communication with landowners and colleagues in NE, RSPB, Defra, JNCC, AEWA and Birdlife International.