Resurrecting seasonal dynamics in waterbirds after wetland restoration: before-after monitoring highlights the role of a single dominant species

We compared a set of uni-varied diversity metrics of a guild of water-related birds (hereafter 'waterbirds') before and after a wetland restoration carried out on uncultivated (reclaimed) lands. Over a period of five years, we observed a restart of seasonal waterbirds dynamics after wetland restoration by flooding of abandoned croplands, with a significant increase in all metrics of diversity, more evident in autumn–winter periods. Seasonal thresholds were evident before (2017–2018) and after (2018–2019) the flooding. These dynamics appeared irregular, probably for a different inter-annual suitability of the flooded meadows due to local ecological factors (e.g., change in meteorological regime and in rush-bed vegetation cover). Rarefaction curves, both for richness and diversity, showed how the waterbird community moved towards a greater complexity. Flooded meadow restoration, particularly favoured wintering species in Mediterranean sites, which explained the strong fluctuations in total abundance. At the species level, Northern Lapwing ( Vanellus vanellus ), absent before restoration, was the most abundant species after flooding, using flooded meadows with its gregarious behaviour. This ‘crowding’ may be explained also for a lack of similar habitats in the surrounding. Other dominant species ( Anas platyrhynchos, Ardea cinerea, Egretta garzetta ) showed a significant increase after restoration. Standardized before-after monitoring on medium term time periods seem suitable to evidence inter-annual season dynamics in diversity metrics of waterbird assemblages.