Opportunity for targeted protection
Spoonbills spend a large part of the summer outside the protected breeding areas. After the breeding season, these iconic migratory birds gather on the mudflats of Lutjewad, along the coast of Groningen. Research by BirdEyes reveals the seasonal movements of spoonbills (Platalea leucorodia leucorodia) in the eastern Dutch Wadden Sea area. They shift their use of space in clear and predictable phases between four key locations. The findings present an opportunity to refine and strengthen existing conservation measures in one of Europe’s most ecologically valuable coastal zones.
Researchers from BirdEyes, the University of Groningen, the University of Amsterdam, and the Royal Netherlands Institute for Sea Research (NIOZ) tracked the behaviour and movements of 31 spoonbills over a period of eleven years. They used GPS loggers equipped with behavioural sensors. The study focused on birds that breed on Schiermonnikoog, one of the most important colonies in the eastern Wadden Sea region.
A time and place for everything
The team discovered that spoonbills spend a significant portion of their summer outside the strictly protected breeding sites, shifting their space use in distinct and predictable phases. Most notably, after the breeding season, both male and female spoonbills converged on the intertidal mudflats of Lutjewad, located on the coast of Groningen, to molt and prepare for their southward flights. “What makes Lutjewad so suitable appears to be its relatively calm environment: little human disturbance compared to the surrounding areas,” explains Dr. Mohamed Henriques. “However, this could change quickly due to the plan to route a new TenneT energy cable south of Schiermonnikoog. Our study provides a baseline to monitor the impact of installing a power line in an area where the birds are especially vulnerable.”
Four key areas
The home range of the population of spoonbills from Schiermonnikoog covered an area of 94.6 km2. By applying dynamic Brownian Bridge Movement Models to describe movement patterns, the researchers identified four key spatial zones that spoonbills use differently throughout the summer. This included the areas around the breeding colonies and the Wadden Sea shore of Schiermonnikoog, the intertidal gullies between the island and the mainland, and parts of the freshwater lake Lauwersmeer. The findings also revealed that males and females use space differently, yet ultimately converge in the post-breeding period. “Our results show that spoonbills treat the Wadden Sea like a living landscape—using different zones for different needs, at different times,” explains co-author Prof. Theunis Piersma. “This gives us a more complete picture of what protection should mean in practice.”
Overall home range, vital areas and core areas (utilisation distributions, UD, with 95%, 75% and 50% probability densities, respectively) and the key zones (delimited by coloured rectangles) of 31 Spoonbills (71 cycles) breeding or born on the island of Schiermonnikoog, in the Dutch Wadden Sea.
Dynamic conservation strategies
Importantly, most of the areas identified—including Lutjewad—are already designated as Natura 2000 sites, National Parks, or UNESCO World Heritage areas. However, the study suggests that some of these zones, while protected on paper, may benefit from more targeted management to reduce seasonal human disturbance. By aligning protection efforts more closely with spoonbills’ seasonal needs, stakeholders have a chance to further strengthen the region’s ecological resilience. “Our findings challenge the assumption that protection of breeding colonies alone is sufficient,” says Prof. Theunis Piersma. “To truly support the full life cycle of these iconic waterbirds, we need conservation strategies that are just as mobile and dynamic as the birds themselves.”
A post-breeding congregation of Spoonbills waiting for low tide to forage on the intertidal flats of the Lutjewad keyzone (photo Arjen de Boer, 15 September 2022).
Henriques M., Piersma T., Vansteelant W.M.G., de Goeij P. & Lok T. (2025). A time and a place for everything: Eurasian Spoonbills divide spring and summer activities across different areas in the eastern Dutch Wadden Sea. Ardea, 113: 3–20. doi:10.5253/arde.2024.a24
Senior author Dr. Tamar Lok, expert in movement ecology and population dynamics and co-author Dr. Petra de Goeij have been investigating spoonbills at Schiermonnikoog for nearly 20 years. Co-author Dr. Wouter Vansteelant is lead researcher of the current spoonbill work in Schiermonnikoog.
Drawing: Jos Zwarts
