Background Audouin's Gull (Larus audouinii) is a bird native to the Mediterranean that feeds mostly on fish. Its population has slightly increased in recent years. Ninety percent of the world's total number of this species breeds in the European Union. It is concentrated in two colonies, one of which, the Ebro Delta, is the focus of this project. Some 10-12,000 breeding pairs (60-70% of the world population) are found in this area, making it an SPA of great importance internationally, since the conservation of the species depends to a large extent on the preservation of this unique but threatened environment. The other SPA where the project is taking place is the Llobregat Delta. Up to 800 individuals congregate at any one time in this feeding and resting area. Apart from the threat posed by the concentration of its population, the species is also threatened by its dependency for food on fish waste from the fishing fleet and its attendant fluctuations, competition with the yellow-legged gull (Larus michahellis) and direct predation by other vertebrates. Objectives This project, which is a continuation of a previous one, aimed to improve the conservation of Audouin's Gull in coordination with the authorities of Valencia. It planned to monitor both Audouin's Gull and the yellow-legged gull, while containing the expansion of the latter. In addition, fences would be erected around the breeding grounds to prevent predators from entering, and public use of the SPAs would be appropriately managed, with the necessary vigilance being exercised. Moreover, social attraction techniques would be applied in order to set up a new colony on the Illa de San Antoni/Buda (Ebro Delta) and the interactions between the species with foxes and with red swamp crayfish would be analysed. All these operations would be accompanied by an extensive publicity campaign. Results At the start of the project, the Ebro Delta was home to a population of 10,122 breeding pairs at Punta de la Banya. During the project lifetime this population grew to more than 15,000 breeding pairs, a 50% increase. The project was executed in two different SPAs: Delta del Llobregat and Delta del Ebro. Most of the actions were carried out in the second SPA, but three important actions were undertaken in the Llobregat’s Delta: monitoring of Audouin’s Gull and the yellow-legged gull, flooding of the area of Cal Roc and placing of decoys to facilitate the colonisation of the area. These three actions were implemented satisfactorily, though some actions were no longer necessary following the compensatory measures implemented in the area, namely the creation of several infrastructures: the Airport extension, the river canalisation and the construction of a new Water Treatment Station. The compensatory measures implemented had very interesting effects for the species. The new beach of Ca’l Arana has provided a very good resting area for the gulls that could be possibly accommodate a breeding colony. Measures implemented in the Delta del Ebro have advanced knowledge of the factors that affect the species. A good connection was established between research activities and management actions. A study was carried out on the effect of predators on the gull’s colonies and also on the changes of diet of the Audouin Gull and the consumption of red swamp crayfish. Another key result of the project was the design and installation of specific signposting panels and limitation fencing that allowed a protection of the species during the breeding period. Also an effective methodology for the control of the yellow-legged gull (main competitor of the species for breeding areas and food) was devised. Actions related to the facilitation of new breeding areas (hacking in Sant Antoni de Buda) have still not provided conclusive results. As a result, it was not possible to attain the redistribution of the main colony to other areas. This makes the species quite vulnerable to stochastic events, as they are all concentrated in a specific area. Efforts will continue after the project end to deal with this threat. In a few years time, the success of this action might be assessed. Finally, the project produced a set of interesting publicity materials that were used in several activities aimed at raising the awareness of the local public, specifically farmers. Thanks to the project, this sector has realised the important role that this species plays in the control of the red swamp crayfish – which causes damage to rice crops – and views the species as an ally. Though the large rise of the Audouin Gull population is not exclusively due to the project implementation, the project undoubtedly played a significant role. The approval of the Recovery Plan (published in the Official Bulletin on 15/04/2004) was a major milestone for the project, ensuring an improved conservation status for this species.