This report presents the proportion of dead oiled birds washed ashore in TheNetherlands of the total number of birds washing ashore as a result of beachedbird surveys conducted by volunteers of the Dutch Seabird Group (NZG/NSO).Apart from the survey results for winter 2010/11, a summary is provided ofdata collected in summer 2010. The results are presented in a context of datacollected in over 50 earlier seasons (1959/60-2009/10).? The oil rate (fraction of oiled corpses of all birds found dead) is considered anindicator of levels of (chronic) oil pollution in the Southern Bight with mineral oiland other lipophilic substances (Camphuysen 1999). These (species-specific) oilrates are calculated on the basis of hundreds of beached bird surveys betweenNovember and April, carefully checking all dead birds found. The results ofwinter 2010/11 are compared for Common Guillemots with long-term trendscalculated over 1975/76-2009/10.? Along the North Sea coast, over the years, downward trends in oil rates werefound in all species and species groups. The most recent data fitted nicely inthis pattern. Numbers of Common Guillemots Uria aalge (the internationalindicator species for oil pollution in the Oiled-Guillemot-EcoQO) washing ashorehave been fairly small in the past few seasons, but the calculated oil rate wasreliable enough and declined according to expectation based on the long-termtrend.? The rather higher oil rate found in Common Guillemots (particularly in comparisonwith more coastal seabirds such as Common Eiders and scoters) confirmed anearlier finding that at greater distances to the coast, oil pollution is still arelatively common issue. The oil rate found, however, was the third lowest everrecorded in Dutch coastal surveys.? Oil rates in the Wadden Sea area are rather lower than oil rates on North Seabeaches. The results obtained in 2010/11 did fit that picture again, at least forbird species that were numerous enough to provide a reliable sample.? Winter 2010/11 was again a fairly cold winter, (2009/10 was ...