Monitoring is essential for conservation policy and management. It enables the detection of adverse trends at an early stage, the formulation of hypotheses of the likely causes of these developments, and the evaluation of conservation interventions. In migratory birds, the wellbeing of a population depends on the quantity and quality of the breeding areas, and at the stop-over sites during migration and in the wintering range. Assessment of developments at these sites needs to be evaluated against the wellbeing of the flyway populations in total. Coastal waterbirds in the East Atlantic Flyway are a prime example of such a migratory system in need of flyway wide monitoring.
This report gives an assessment of waterbird population sizes and trends at a flyway scale for coastal populations depending on the estuarine resources of the East Atlantic Flyway. It is a result of cooperation between the Wadden Sea Flyway Initiative, Wetlands International, BirdLife International, and monitoring organizations and institutions at national level along the flyway. It focusses on populations of birds using the Wadden Sea, and other Palearctic and Intra-African populations using the same sites. As such, it forms a part of the response to the call for more cooperation in management and research along the flyway from the World Heritage Committee at the inscription of the Wadden Sea as a World Heritage Site. This assessment falls within the Flyway Monitoring Strategy that was developed to improve the coordination and cooperation for monitoring along the East Atlantic Flyway (van Roomen et al, 2013). For the monitoring of flyway populations, a combination of monitoring of non-breeding and breeding birds is necessary over a huge geographic range from northern and western Europeto the western seaboard of Africa. This requires substantial cooperation between countries and projects, and the input of resources.
As a result of these combined efforts, the availability and robustness of waterbird population trends along the East Atlantic Flyway have strongly increased. The 66 East Atlantic Flyway populations assessed in this study show an equal number of increasing and decreasing trends in recent years. The proportion of populations with more or less stable numbers is rather small, suggesting large environmental changes along the flyway. Considering the 40 flyway populations that occur in internationally important numbers in the Wadden Sea, populations feeding on shellfish, crabs, worms and other invertebrates (benthivores) showed predominantly decreasing trends in recent years while fish eating species (piscivores) are predominantly increasing. Among these benthivores, flyway populations that depend on the international Wadden Sea to a large extent, are predominantly decreasing. This is not the case for populations for which the Wadden Sea is less important. Correlations between local Wadden Sea trends and flyway populations are also very weak. These patterns suggest that adverse environmental changes in the Wadden Sea are stronger than elsewhere on the flyway, and that trends in the Wadden Sea are mainly caused by these local factors, especially since populations which also breed in the Wadden Sea seem to be particularly vulnerable. The patterns found are strong indications that many flyway populations studied are under pressure. Further research and monitoring, especially also on threats along the flyway, are needed to pinpoint causes and to help identify priority conservation measures.
The expertise brought together in the consortium of the Wadden Sea Flyway Initiative, Wetlands International and BirdLife International, is unparalleled in the East Atlantic Flyway. Through the sharing of expertise and resources, a very cost-effective monitoring network has been developed, with great potential for further growth and with direct links to the implementation of conservation measures. Continuation of the collaboration, also with other partners, can effectively improve our knowledge and conservation efforts for migratory waterbirds in the East Atlantic Flyway.