Old and unmowed saltmarsh patches provide attractive habitats for breeding passerines

Although the conservation stakes of saltmarshes are widely documented, these areas are still subjected to strong anthropic pressures, including land reclamation, leading to their conversion into arable lands, and agricultural exploitation (mainly cattle grazing and mowing), which modifies their floral and faunal composition. Through the example of one of the largest French saltmarshes, we first assessed how the age of the saltmarsh patches and the mowing intensity determined the spatial distribution of the different saltmarsh habitats. We then tested how the five commonest breeding passerines were distributed in accordance with the mowing activity and the distribution of these habitats. We found that the oldest and the unmowed patches promote the development of habitats dominated by Elymus pungens and Atriplex portulacoides, and also host the highest abundance of four of the five bird species studied. In the current context of an intense artificialization of the littoral area, this study highlights the importance of maintaining the oldest and the least human-impacted patches of natural habitats to conserve their associated biodiversity.