Rapid establishment of waterbird prey populations in newly created wetlands

Introduction: Recent efforts to mitigate negative population trends in waterbirds involve large-scale restoration and creation of wetland habitats. However, it is not well understood how long it takes before prey populations supporting waterbirds develop in newly created wetlands. Objectives: In this study, we contrast benthic macroinvertebrate prey communities in Belgian wetlands created at different times in the past. Methods: We used a space-for-time approach and generalized linear models to study changes in benthic macroinvertebrate community composition and corresponding waterbird abundances as a wetland ages. In function of this, we collected invertebrate data and paired it with longer-term citizen-science data to investigate temporal trends. Results: Our findings reveal that recently created wetlands can support macroinvertebrate prey populations within 2 years after creation with a comparable biomass as observed in older wetlands, but with a different composition. Oligochaetes and nematodes were more abundant in recently created wetlands (abundances declined on average 9.8 and 14.7% per year, respectively) while ostracods and bivalves were more abundant in older wetlands (abundances increased on average 6.5 and 31.6% [at mean age, scales quadratically] per year, respectively). Interestingly, more waterbirds were present in younger compared to older wetlands, presumably due to the higher abundance of oligochaetes, an opportune prey item. Conclusion: Overall, these results suggest that waterbird prey populations can establish relatively quickly after wetland creation and that ecological conditions early during succession are attractive to several bird species such as Northern Lapwing, Ruff, Common Greenshank, or Common Snipe. However, waterbirds require more from their habitat than abundant prey, and wetlands need to support more conservation targets than just waterbirds.