Olievervuiling en olieslachtoffers in Nederland, 1997/98

Between July 1997 and June 1998, 170 beached bird surveys were conducted by 58 volunteers, covering 1031 km. A total of 2735 corpses of seabirds and (marine) mammals were reported. Numbers of land birds and coastal birds were small, obviously as a result of the very mild winter, one of the mildest in the last 40 years (Fig. 1). True seabirds beached in 'normal' numbers. Oil polluted beached were reported 25 times (Tabel 4). Numbers of dead Red-throated Divers were again low, as were the numbers of Great Crested Grebes, in both cases because of the mild winter conditions. Fulmars crashed in larger than normal numbers in autumn (Fig. 3). Of all Fulmars found in winter, 30.5% were oil contaminated. Of all Gannets, 58.3% were oiled and another 5% were entangled in fishing gear. Eiders were among the most numerous birds found dead, but a minority were oiled (winter, 9% oiled within the Wadden Sea, 8% along the North Sea coast). Scoters were not found in large numbers, but it should be noted that Terschelling was not visited this year, while the largest concentration of Common Scoters wintered just off this island. Oystercatchers, as the most numerous waders, were scarce, as is typical in mild winters (Fig. 7). The seasonal pattern in strandings of most Lrincvgulls was similar as found in earlier years (Fig. 8-11), but the post-fledging mortality in Black-headed Gulls and Herring Gulls was higher than usual. The winter oil-rates for the Larus group were 4% in de Delta area (n=52), 21% along the mainland coast (n= 52), 21% along the North Sea side of the Wadden Sea islands (n= 34) and 5% within the Wadden Sea (n= 37). The North Sea coast as a whole had 14.5% (n= 138) as an oil rate for the Lrrav-gulls, while an oil rate of 45.3% (n= 139) was observed in the Kittiwake, Of Razorbills (n= 117) and Guillemots (n= 472) respectively 61.5% and 69.9% were oil contaminated. In all, the oil rates were again lower than before and the observed values fit well into the downward trend which has been found earlier (Camphuysen 1997; Table 6, Figs. 15-22). Odd findings in 1997/98 were Rough-legged Buzzard Buteo lagopus and Common Buzzard B. buteo, a Tiger Finch Amandava amandava and a Lama huanacos and last but not least a caged skeleton of African Parrot (not oiled).