Olieslachtoffers in Nederland in vroeger tijd: een nieuwe presentatie van oude tellingen

This report intends to summarize the results of the earliest Dutch beached bird-surveys in the years 1947-65 in order to provide the background for comparison with the results from recent years. This was felt to be necessary, since earlier publications (e.g. Mörzer Bruyns 1959, Tanis & Mörzer Bruyns 1962) failed to present these results in an easily comparable way. For a number of rather representative species (e.g. Red-throated Diver, Great Crested Grebe, Fulmar, Gannet, Common Scoter, Eider Duck, Herring Gull, Kittiwake, Razorbill and Guillemot) the data on occurrence of washed-up corpses as well as on oilfouling incidence are presented here. The figures 1-10 show both the trends over the years 1947-65 and the seasonal patterns over the entire period considered. In table 4 the results on frequency of washing up and oil fouling are summarized and compared to the results obtained from 1980-82 (Jonker 1981, 1982, 1983). In 1947-65 there was a relatively high oil-caused mortality in Redthroated Diver, Gannet and Common Scoter, all but the Gannet being coastal birds. Great Crested Grebe, Eider Duck and Herring Gull, three other coastal species, though found in the same (Great Crested Grebe) or higher numbers in recent years, were much more frequently oiled in the 1947-65-samples, so it might be deduced that oil-incidence has declined in these species as well. The more pelagic seabird species were found in about the same numbers as nowadays (Fulmar and Razorbill) or much less frequently (Kittiwake and Guillemot). The precentage of oil fouling in these birds was invariably high, except for the Kittiwake in 1947-65.