Diet and contamination of the Yelkouan Shearwater Puffinus yelkouan in the Hyères archipelago, Mediterranean Basin, France

Abstract

The Yelkouan Shearwater Puffinus yelkouan is a Procellariiform endemic to the Mediterranean Basin, recently categorised as Near Threatened on the IUCN Red List. We need to identify the threats it faces, which are particularly poorly understood when at sea. Specifically, very little is known about the Yelkouan Shearwater feeding strategy and how it is related to potential threats at sea, such as contaminants which deserve particular attention regarding this shearwater, as the Mediterranean Basin is overall highly contaminated. Here, we analysed Yelkouan Shearwater diet, as well as metal (lead, cadmium, mercury, selenium) and organic contamination. The diet analysis revealed the predominance of fish prey, particularly Clupeids, Engraulids and Scombrids, both in terms of relative occurrence (84.6%) and relative biomass (99.7%). Crustaceans (Euphasiacea and Decapoda) were the major prey type during the pre-laying period (relative number: 88.8%) but contributed little to the biomass ingested. The metal levels we found in contour feathers were below the known adverse effect threshold for seabirds. Organic contamination in livers was also low but we found two eggs with levels of concern of polychlorinated biphenyls (PCB) and dichloro-diphenyl-trichloroethane (DDT) compounds.