Variations in Nest Mortality in the European Storm Petrel Hydrobates Pelagicus

Procellariformes breed mainly on inaccessible islands and many species nest underground reducing egg or chick losses caused by predation. Nevertheless, Procellariformes show low reproductive rates. In a four years study of breeding European Storm Petrel, we estimated nest mortality for three stages: incubation, brooding and chick-rearing period, using the Mayfield-40%'s method. The highest value of daily nesting mortality was found during the brooding period (after incubation). Furthermore, daily egg failure varied less between years than daily chick mortality rate, both in the brooding and the chick-rearing stages. These results are in accordance with theoretical differences in both the duration of foraging trips of parents, and daily nest energy requirements among the three stages.