As the global biodiversity is rapidly eroding, the preservation of species and their intra-specific diversity is an urgent challenge. Many seabirds are slipping dangerously close to extinction and seabird numbers have deteriorated faster than most other groups. Molecular methods and population modelling can be used to answer various questions important for the declining species conservation. This project has three main objectives. First, we will develop an accurate method to census seabird colonies and analyse kinships even when the birds are absent. Indeed, one difficulty of working with seabirds is that they are often located in areas difficult to access and study trips are usually of limited duration. Second, we will determine how seabird populations are connected and if meta-populations occur. The grey-faced petrel (Pterodroma macroptera) and the Yelkouan shearwater (Puffinus yelkouan) both have unclear conservation status even if the latter has been recently listed as Vulnerable by the IUCN. Humans have had a marked impact on their range and many local populations have gone extinct or contracted to very small sizes. It is crucial to evaluate gene flow and meta-population occurrence to identify threatened populations. Third, we will analyse how seabird population diversity is distributed and what are the factors that influence their distribution. We will use a range of various molecular techniques, population modelling and biogeographical analyses to reach these objectives. The fellow will obtain the skills necessary to use the full toolkit of molecular methods currently available to ecologists and to perform meta-population modelling analyses. Once learned, these skills will be easily transferred to other conservation programs in Europe. This project will help to define units below the species level (Evolutionary Significant Units, Adaptative Units, Designatable Units) to accurately assess the extinction probability and to help set conservation priorities.