Conservation and Restoration of Coastal Reed Beds in the Context of Global Change: Potential Effects of Habitat Fragmentation for Specialist Marshland Passerines

In the context of coastal marshland reduction due to sea level rise, we evaluated the value of fragmented reed beds located within agricultural polders for the conservation of habitats exploited by marshland passerines characterized by different ecological requirements. Although our study was carried out within sites sampled over different years, analyses of body condition and diet of birds during the breeding period, as well as the local daily survival rate and the body mass evolution of birds during the post-breeding period, reveal trends illustrating that fragmented reed beds within inland meadows can: (i) generate habitats that may be significantly exploited by species with a large ecological plasticity, such as the Reed Warbler that could benefit from edge effects of habitat fragmentation; (ii) offer low attractiveness for specialised species such as the Aquatic Warbler, a migratory species apparently very sensitive to the effects of reed bed fragmentation. These results underline the reed beds fragmentation effects that may impact specialised marshland passerines and which should be taken into account in wetland conservation and restoration plans.