To assess mitigation measures for habitat loss, it is important to understand the function of artificial wetlands as alternative wader habitat. In the Netherlands since 2016, a 1,000-ha freshwater archipelago called Marker Wadden has been constructed 3 km offshore in lake Markermeer. This artificial ecosystem provided a unique opportunity to study the impacts of construction designs and development of habitats on waders. Over a seven-year period, we studied Pied Avocets Recurvirostra avosetta because they used habitats in the constructed basins right from the start for feeding, and they are of conservation concern in the Netherlands. Between 2017 and 2023 we counted staging Pied Avocets and monitored habitat development in basins that varied in the time of construction (age) and design (closed or open, i.e. with breached levees connecting to the surrounding lake). Annual habitat changes were assessed with satellite images, and with pictures taken monthly at 20 fixed locations. With negative binomial zero-inflated models, we tested the effects of habitat characteristics, basin age, size and design, and raptor presence on bird numbers. The maximum number of Pied Avocets declined from >500 in 2017 to <100 in 2023. Basin age captured all habitat variation caused by natural succession and had the strongest negative effect on bird numbers. Open basins, allowing permanent flooding, were used less than closed basins. Avocet numbers remained highest in basins containing a mosaic of water and mud, with no or sparse vegetation. We concluded that Pied Avocets decreased due to two reinforcing processes: vegetation succession and breaching of levees leading to a rise in water level. Future developments targeting Pied Avocet conservation in freshwater wetlands should create and maintain shallow and muddy habitats with the closed basin and size concept as guidelines.