Seasonal variations of waterbird ecological networks under different saltpans management

Abstract

Habitat change has increased the loss of wetlands and impacted highly on coastal biodiversity. Consequently, wetland-dependent species such as waterbirds have experienced a decline in their populations. This study proposes an application of bipartite networks using both the sampled sites and species as nodes to assess seasonal variations in waterbirds composition and habitat specialization in response to the abandonment of saltpans. The sampling was carried out in active and abandoned saltpans of the Ria Formosa (Portugal) over four sampling periods to evaluate the temporal change in waterbird communities. Abundance was twice and species richness 14% higher in active saltpans than in abandoned ones. About 60% of the waterbirds indicated a high specificity towards active saltpans. Saltpans showed a high β-diversity and seasonal dynamic of waterbird community composition. Network dissimilarity across the year was dominated by turnover of the edges rather than species turnover. Dynamics in network structure and composition seemed to be related to bird dispersal, migration phenology, and habitat specialist strategies. Overall, this study highlights the importance of preserving the activity of saltpans as it conditions abundance, richness and dynamics of waterbird populations. Continued efforts are needed to reduce threats to coastal wetlands and restore abandoned saltpans worldwide, since these are key habitats for the conservation of resident and migratory waterbirds.