Résumé
Since the Second World War, the international oil trade has developed dramatically, increasing as a consequence the risks of accidents during sea transport. Thus, oil pollutions, chronic or accidental, have become an important threat to the marine environment, especially to seabirds which have become the emblematic victims. In order to understand the impact of these anthropogenic pressures and their implications for the management and conservation of seabirds, it appears important to identify the geographic areas, periods of the year, species, populations, and individuals at risk. In spite of the narrow links between seabirds and the marine environment, all seabird species do not face the same risks from oil pollution. The sensitivity of the species and the individuals varies with their life histories, their diet and their behaviour. At the individual level, the physio-pathologic consequences of oil on seabirds are well known. At the population level, the mortality following oil pollution lowers the survival of individuals directly, which can result in a decline of population size. Oil pollutions can also have short and long term indirect effects on populations, decreasing as a consequence their ability to recover. However, direct cause and effect relationships between oil pollutions and fluctuations in seabird population sizes have been difficult to demonstrate. In order to improve our ability to evaluate the impact of these anthropogenic pressures, we need to better understand the dynamic and functioning of seabird populations by developing and using different methods allowing 1. to estimate the number of birds killed, 2. to determine the geographic origin of affected birds and 3. to evaluate the demographic impact on populations at various spatial scales.