The European Seabirds at Sea Database (ESAS) was established in 1991 as a collaboration between individuals and institutes who had collected data on the distribution of seabirds and marine mammals in north-west European offshore areas. The most recent version of this database contains over two million records which were collected over 25 years. The founding aim of this project was to merge data from different collaborators and use these to publish an atlas depicting vulnerable concentrations of seabirds to oil pollution. Subsequently, these data have been used for a wide variety of research purposes. The collaboration has also developed and defined common standards in data capture, processing and storage.