Olieslachtoffers op de Nederlandse Kust, 2010/2011 = Oiled Seabirds Washing Ashore in the Netherlands, 2010/2011

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 the first cold seasonfor years). However, densities of species that are sensitive to cold weather(waders and waterfowl) did again hardly increase.? The Europese Commissie wrote a 'Commission Decision', in which as an indicator:"Occurrence, origin (where possible) and scale of significant spills (for exampleof oil or oil products) and the effect on marine biota (8.2.2)". The beached birdsurveys are an important contribution to this indicator

Distance doesn't matter: migration strategy in a seabird has no effect on survival or reproduction

Migrating animals show remarkable diversity in migration strategies, even between individuals from the same population. Migrating longer distances is usually expected to be costlier in terms of time, energy expenditure and risks with potential repercussions for subsequent stages within the annual cycle. Such costs are expected to be balanced by increased survival, for example due to higher quality wintering areas or lower energy expenditure at lower latitudes. We compared reproductive parameters and apparent survival of lesser black-backed gulls (Larus fuscus) breeding in The Netherlands, whose winter range extends from the UK to West Africa, resulting in one-way migration distances that differ by more than 4500 km. Individuals migrating furthest arrived later in the colony than shorter distance migrants, but still laid in synchrony with the colony and consequently had a shorter pre-laying period. This shorter pre-laying period affected neither egg volumes nor hatching success. We found no relationship between migration distance and apparent survival probability, corresponding with previous research showing that annual energy expenditure and distance travelled throughout the year is similar across migration strategies. Combined, our results indicate an equal fitness payoff across migration strategies, suggesting there is no strong selective pressure acting on migration strategy within this population