Field occupancy by breeding lapwings Vanellus vanellus and redshanks Tringa totanus in agricultural wet grasslands

This study is based on a comparative approach to explore how two breeding waders, the lapwing Vanellus vanellus and the redshank Tringa totanus, respond to cattle grazing in terms of timing and intensity of grazing in the Marais Poitevin, French Atlantic coast. Generalised linear mixed models showed that the two main predictors determining suitable grasslands were sward structure and water surface. In the lapwing, a precocious species which nests in short swards, i.e. ≤10 cm, with no/few tussocks, the suitability of grasslands was driven by both previous autumn and early spring effects of grazing. Conversely, the redshank, which nests later and needs taller swards, i.e. 10–40 cm, did not respond to autumn grazing, but seemed to be more sensitive to mid-spring grazing. The lapwing and the redshank responded positively to early spring and mid-spring stocking densities, respectively. These results are discussed in the light of the habitat characteristics and the grazing management situation of the study site.