Discussion

MH points out that in the interpretation of figures on trends from the International Beached Bird Surveys (IBBS) one has to be cautious. For instance, the peak in proportions oiled in 1987 in HS’s presentation coincided with relatively low densities of auks all around the North Sea. In winters were you get large wrecks of unoiled auks, like in the 1980s, the proportion of corpses oiled (%-age oiled) inevitably drops while it is high in winters with relatively low densities. So changes in the %-age oiled may reflect changes in the amount of oil at sea, but also changes in other mortality factors. It is preferable to use %-ages oiled in conjunction with densities. MLT and LC commented on the trends presented by HS that in fact there was no decline in the proportion of oiled seabirds in the western North Sea, but that in recent data only information from a few northerly (relatively clean) coasts were used. Since the Royal Society for the Protection of Birds had stopped its effort to organise the IBBS, only few counts of beaches in England were organised, but these indicated that the %-ages oiled are still high. A working paper on the possibilities to establish a ’European Beached Bird Survey’ (EBBS), as an extended IBBS, submitted by CJC (see page 45), was introduced and discussed. Differences in methods and planning of BBS in the various countries make an exchange of data difficult (HS), but when trends are calculated from each of these programmes, and when (local) influences are taken into account, most results are remarkably similar (CJC). A coordinated approach could thus mean a strictly uniform method and planning, or a uniform analysis. MH considers it wise to look at the North Sea as one unit and to standardize BBS as much as possible. LC remarks that before planning any coordinated international scheme it should be found out whether or not the scheme would provide the right data and information to influence policy makers rather than to fulfill scientific needs. JD remarks that politicians, at least within the EEC, are certainly interested in this sort of information. AB notes that besides studying beached birds (or individual animal welfare) population studies should be conducted and linked (conservation needs). CIC explains that, although quite recently there actually was found a link between an increase in numbers stranded in the southern North Sea and – in this case – recruitment failures in Scottish colonies, in generally this is extremely difficult. Massive increases in populations obscure the effect of extra winter mortality due to oil. MLT adds that there is more than monitoring birds on the beach and numbers in colonies. One also needs to know other population parameters, e.g. is observed mortality caused by oil pollution additional to normal winter mortality? A crucial question is: is monitoring on the beach telling you what the mortality level is in the whole North Sea? Problems to be tackled with BBS are what is the biological problem (numbers killed, conservation) and what is the environmental problem (state of the sea, monitoring oil pollution). Before going to politicians presenting a nice monitoring programme using BBS it should be discussed if, and how, BBS does provide the required information. AB suggests to use the vulnerability of populations as an argument to use with politicians. BW adds that it should be made clear why and how BBS results give results which is not obtained in an other way (like aerial surveillance).