Assessing the impact of mowing on Common Redshanks Tringa totanus breeding on saltmarshes: lessons for conservation management

Abstract

SummaryInformed application of habitat management measures is crucial, especially in saltmarshes that function as last refuges for breeding waders in Europe. Despite a reduction in agricultural use of saltmarshes since the establishment of the Wadden Sea National Parks at the end of the 1980s, there remains controversy regarding management measures such as the timing of mowing. We modelled the proportion of nests and chicks that would be jeopardised by mowing at different dates, using long-term breeding data of the Common Redshank Tringa totanus – an endangered and widespread indicator species of saltmarshes – from four study sites in the German Wadden Sea. At two study sites in the western Jadebusen, the proportion of broods that were at risk of being killed when mowing began on 1 July ranged between 78% in early, to 96% in late, breeding years, averaging 87%. Although Common Redshanks in the eastern Jadebusen started breeding one week earlier, the model still predicted a loss of 73% of chicks; while 97% of broods were at risk on the island of Wangerooge. Postponement of mowing to 1 August reduced these proportions to 21%, 11% and 32%, respectively. This study is the first to model the positive effects of delayed mowing of saltmarshes on ground-nesting birds. By implementing adjusted mowing dates in addition to previously suggested reductions in artificial drainage, direct and indirect adverse effects caused by mowing and drainage, such as an increased predation risk, are likely to be reduced, such that a ’favourable conservation status’ according to the EC Habitats Directive may be achieved.