Long-Term Changes (1993-2022) in Wintering Waders of the Largest Mediterranean Coastal Lagoon: Dominance Patterns, Habitat Shifts and Weak Thermal Signals

Coastal lagoons are key wintering habitats for waders, yet long-term changes in their community structure remain poorly understood in Mediterranean systems. We analysed a 30-year dataset (1993–2022, excluding 2021) of wintering waders in the Venice Lagoon to assess trends in abundance, community structure, thermal composition and spatial patterns. Total abundance increased significantly (+3.5% yr⁻¹), while species richness ranged between 12–21 species per winter. Community structure changed markedly, with increasing dominance of a few species, particularly Dunlin, leading to reduced evenness. Species-level analyses showed a prevalence of increasing trends: nine of the 19 species analysed increased significantly, one declined, one was stable and eight showed uncer-tain trends. The Community Temperature Index (CTI) increased significantly (p = 0.001), suggesting a shift towards species with higher thermal affinities, but this pattern was not robust to the exclusion of Dunlin C. alpina, indicating dominance-driven dynamics. Spatial analyses revealed a strong increase in the open lagoon (p < 0.001) and a decline in fish farms (p = 0.008), indicating a shift towards natural tidal habitats. Overall, the assemblage is increasing but structurally simplified, highlighting the need to integrate species- and community-level approaches when interpreting ecological indicators.