Mediterranean seabirds under global threats: a long-term demographic and spatial project within National Parks highlighting the need to preserve shearwater populations.

Seabird populations declined worldwide since 1970. Recent global review showed that invasive species, bycatch, exploitation of marine resources and climate change are the main threats to seabirds. These multiple threats, acting in combination, are also a common situation in the Mediterranean basin. After a brief global context, we will present specific cases on seabird conservation on Port-Cros and Calanques National Park (NP), located in the south east of France. Archipelago of Port-Cros NP is housing the main breeding population of Yelkouan Shearwater, listed endangered in France, while the Scopoli’s Shearwater, vulnerable in France, mainly breed on Calanques NP. Long-term demographic survey and GPS tracking conducted on both archipelagos, supplied by LIFE projects, allowed scientists and managers to obtain crucial information about shearwater biology (e.g., reproduction, survival, moulting strategy), behaviour at colonies (in sexual and nest selection, interactions with introduced species and con-specifics), and behaviour at sea (diving ecology, flight height, feeding sites and global distribution). We showed that the main driver of shearwater population dynamic was the adult survival. This crucial population parameter for a long-lived seabird was relatively low compared to other study sites. At land, shearwater populations are threatened mainly by cats and rats. More recently on Port-Cros NP, wild boars are suspected to weaken the soft substrate where Yelkouan shearwaters dig their burrows. We will discuss about the mesopredator release theory that was not confirmed here by the field results of a concrete cat control management plan. We will show the population dynamics changes of cats, rats and seabirds after several years of management and will discuss of further research questions and concrete management actions targeting islands where shearwater population survival is most at risk. More recently, threats at sea have been investigated through the use of GPS-tracking to estimate space use of seabirds, mortality due to transnational bycatch and recent threat that can emerge from new offshore wind farms. In a recent study, it was revealed that Spanish longliners kill an average of up to 3% of French Scopoli’s shearwater colonies each year. Spanish bycatch is therefore accelerating the decline of the French shearwater populations. As shearwaters are long-distance travelers especially when they undertake extensive foraging trips off breeding colonies and along migration routes, they require an international approach to marine conservation. Concomitantly, our GPS tracking reveals that the area dedicated to deployment of offshore windfarm in “Golfe de Fos” was largely used by both shearwater species to their foraging activities. A GPS program, taking place up to 2028, will allow researchers to investigate for a potential avoidance effect compared with previous years before the turbines were installed.