Scenarios of habitat management options to reduce predator impacts on nesting waders.
Abstract
Wetland ecosystems throughout the world are threatened by drainage and intensification of agriculture. Consequently, many wetland species of conservation concern are now restricted to fewer and smaller sites, and maintaining these species often requires intensive habitat management. In Western Europe, breeding wader populations have declined severely as a result of wetland degradation, but very high levels of predation on eggs and chicks are now preventing population recovery. Wet grassland management for breeding waders has focussed on providing suitable nesting habitats, but the potential for management of landscape features to influence predation rates remains largely unknown. Using a 7-year study of breeding lapwing Vanellus vanellus and redshank Tringa totanus we first identify features that influence nest predation, and then use this information to compare the magnitude of change in nest predation rates that could potentially result from future landscape management scenarios. As lapwing nest predation rates are higher (i) in fields further from patches of tall vegetation, (ii) close (<50 m) to field edges in wet fields, (iii) further from field edges in dry fields and (iv) in areas of low lapwing nesting density, we modelled a series of realistic scenarios in which the area of tall vegetation and the extent and distribution of surface water were varied across the reserve, to quantify the magnitude of change in nest predation rate that could potentially have been achieved through management. Modelled scenarios of changes in surface water and area of tall vegetation indicated that reduced surface flooding combined with removal of tall vegetation could result in significant increases in lapwing nest predation rates in areas with low nesting densities and nests in field centres. By contrast, a ∼20% reduction in nest predation, corresponding to ∼100 more chicks hatching per year, is predicted in scenarios with expansion of tall vegetation in areas with high lapwing nest density and nests close to field edges. Synthesis and applications. These management scenarios suggest that, for breeding waders in wet grassland landscapes, creating areas of tall vegetation and concentrating surface flooding (to encourage high nesting densities and influence nesting distribution) can potentially help to reduce the unsustainably high levels of nest predation that are preventing population recovery.