Data have been collected on the breeding success of several characteristic coastal breeding bird species in the Wadden Sea each year since 2015. Ten bird species considered representative of specific habitats and food groups are being monitored in a trilateral context. The monitoring scheme on breeding success in coastal breeding birds is run as an ‘early warning system’ to follow the reproductive capacity of the bird populations in the Wadden Sea and understand the processes underlying fluctuations in populations. It is a valuable addition to the monitoring of population numbers and is carried out under a trilateral agreement with Germany and Denmark (TMAP). The data are also included in the OSPAR biodiversity indicator B3 under the Marine Strategy Framework Directive. The 2018 results indicate that little has changed in the poor breeding success observed in previous years, although there were some positive exceptions locally and for some species, partly related to special conservation measures.