Human-Made 1,000 Hectare Archipelago "Marker Wadden" Has Positive Impact on Regional and Flyway Populations of Waterbirds of Dynamic Freshwater Ecosystems.

Marker Wadden is a 1000 ha artificial archipelago developed, since 2017, as a novel ecosystem to restore dynamics in a large Dutch freshwater lake with limited natural dynamics. The newly created habitats should, at flyway level, strengthen populations of threatened bird species that depend on dynamic wetlands. The archipelago includes basins with sandbars and mudflats subject to wind tides. Situated at 3 km distance from the mainland, ground predators are lacking. During the first five years of colonization (2017–2021) six pioneer breeding birds represented significant portions (>5%) of national populations. Common Terns (Sterna hirundo) and shorebirds of pioneer habitats were instantly numerous. Ducks and Black-headed Gulls (Chroicocephalus ridibundus) colonized from year two onwards and in year five gulls became the most numerous breeding birds. Staging birds such as ducks (including 13,000 Eurasian Teal [Anas crecca]), shorebirds, and spoonbills (Platalea leucorodia) appeared in internationally important numbers. We conclude that the archipelago indeed has become an important site for breeding and staging birds and at flyway level, especially in the growing season. Therefore, artificial semi-dynamic habitats with mudflats and developed at a sufficiently isolated and large scale, may mitigate losses of natural pioneer habitat in freshwaters. [ABSTRACT FROM AUTHOR]