6
Seabirds in the North Sea Demobilized and Killed by Polyisobutylene (C 4 H 8 ) n (PIB) KEES C. J. CAMPHUYSEN *, HEIN BARREVELDà, GERHARD DAHLMANN§ and JAN ANDRIES VAN FRANEKER   Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, Texel, The Netherlands àRijksinstituut voor Integraal Zoetwaterbeheer en Afvalwaterbehandeling (RIZA), P.O. Box 17, 8200 AA Lelystad, The Netherlands §Bundesamt f ur Seeschiart und Hydrographie (BSH), P.O. Box 30 12 20, 20305 Hamburg, Germany   Institute for Forestry and Nature Research (IBN-DLO) P.O. Box 167, NL-1790 AD Den Burg, Texel, The Netherlands This paper reports on a mass stranding of seabirds in the North Sea in December 1998. Hundreds of birds were washed ashore alive in Zeeland (SW Netherlands), covered in a whitish, sticky substance, and were transported to a rehabilitation centre. About 10 days later, more (dead) casualties washed ashore further to the north on Texel and along the mainland coast, again covered in a glue-like substance. Common guillemots Uria aalge, northern ful- mars Fulmarus glacialis and common scoters Melanitta nigra were the most numerous birds aected in this incident. Both strandings were temporarily (10 days) and geo- graphically separated (ca. 120 km apart), but were ap- parently caused by a single source of pollution. The meteorology at the time was consistent with the course of a single incident. At least 1100 seabirds were aected by this substance, soon identified as polyisobutylene (C 4 H 8 ) n . PIB is known as a non-toxic, non-aggressive substance. Vol- unteers cleaning the birds in the rehabilitation centre re- ported serious discomfort and dizziness and the soft parts of the PIB-aected birds found dead (bill, eye, throat, feet, webs) appeared to dissolve in a few days time. Both eects cannot be attributed to PIB, and are therefore unexplained. Although the dumping of PIB in the marine environment is not explicitly prohibited under MARPOL, the eects on wildlife observed are enough to plead for counter-mea- sures. Ó 1999 Elsevier Science Ltd. All rights reserved. Keywords: seabirds; strandings; operational discharges; polyisobutylene; (C 4 H 8 ) n ; Fulmarus glacialis; Uria aalge; Melanitta nigra; MARPOL. Seabirds are highly vulnerable to surface pollutants (Goethe, 1968; Croxall, 1977; Clark, 1984; Jenssen and Ekker, 1991; Barker, 1994). With the term surface pol- lutants, a wide range of lipophilic substances is covered, including mineral oils, vegetable oils and various chemicals. Mineral oils pose by far the greatest threat to seabirds in the North Sea (Barclay-Smith, 1931; Bourne, 1968; Dunnet, 1982; Camphuysen, 1989; Heubeck, 1995; Camphuysen, 1995, 1997, 1998), but several incidents with other substances have shown the equally lethal ef- fects of many products (Anonymous, 1975; Swennen, 1977; McKelvey et al., 1980; Engelen, 1987; Timm and Dahlmann, 1991; Rozemeijer et al., 1992; Scholten, 1993; Dahlmann et al., 1994). In The Netherlands, chronic oil pollution is a constant threat to seabirds and oil rates among stranded birds are very high in com- parison with those in other West European countries (Furness and Camphuysen, 1997; Camphuysen, 1998). A comparative study of the types of oil and other chemicals on beached birds in The Netherlands, Ger- many and Denmark showed that ‘ordinary’ fuel oils are responsible for most seabird deaths (Dahlmann et al., 1994). In December 1998, hundreds of seabirds, all covered in a ‘whitish, sticky substance’, were washed ashore in Zeeland (SW Netherlands; Fig. 1). Many casualties were still alive and these were transported to a nearby reha- bilitation centre. A few days later, more (dead) casual- ties were washed ashore 120 km further to the north, again covered in a glue-like substance. Although some of the birds were contaminated by more than one sub- stance (including mineral oils), it was clear that a non- mineral oily substance was responsible for this wreck. This study reports on the number of seabirds aected, on the identity of the substance found on these birds, Marine Pollution Bulletin Vol. 38, No. 12, pp. 1171–1176, 1999 Ó 1999 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0025-326X/99 $ - see front matter PII: S0025-326X(99)00152-6 *Corresponding author. Present address: CSR Consultancy and Dutch Seabird Group, working group Beached Bird Surveys, An- kerstraat 20, 1794 BJ Oosterend, Texel, The Netherlands. E-mail: [email protected]. 1171

Seabirds in the North Sea Demobilized and Killed by Polyisobutylene (C4H8)n (PIB)

Embed Size (px)

Citation preview

Page 1: Seabirds in the North Sea Demobilized and Killed by Polyisobutylene (C4H8)n (PIB)

Seabirds in the North Sea Demobilizedand Killed by Polyisobutylene (C4H8)n(PIB)KEES C. J. CAMPHUYSEN *, HEIN BARREVELDà, GERHARD DAHLMANN§ and JAN ANDRIES VANFRANEKER   Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, Texel, The NetherlandsàRijksinstituut voor Integraal Zoetwaterbeheer en Afvalwaterbehandeling (RIZA), P.O. Box 17, 8200 AA Lelystad,The Netherlands§Bundesamt f�ur Seeschi�art und Hydrographie (BSH), P.O. Box 30 12 20, 20305 Hamburg, Germany  Institute for Forestry and Nature Research (IBN-DLO) P.O. Box 167, NL-1790 AD Den Burg, Texel,The Netherlands

This paper reports on a mass stranding of seabirds in theNorth Sea in December 1998. Hundreds of birds werewashed ashore alive in Zeeland (SWNetherlands), coveredin a whitish, sticky substance, and were transported to arehabilitation centre. About 10 days later, more (dead)casualties washed ashore further to the north on Texel andalong the mainland coast, again covered in a glue-likesubstance. Common guillemots Uria aalge, northern ful-mars Fulmarus glacialis and common scoters Melanittanigrawere themost numerous birds a�ected in this incident.Both strandings were temporarily (10 days) and geo-graphically separated (ca. 120 km apart), but were ap-parently caused by a single source of pollution. Themeteorology at the time was consistent with the course of asingle incident. At least 1100 seabirds were a�ected by thissubstance, soon identi®ed as polyisobutylene (C4H8)n. PIBis known as a non-toxic, non-aggressive substance. Vol-unteers cleaning the birds in the rehabilitation centre re-ported serious discomfort and dizziness and the soft parts ofthe PIB-a�ected birds found dead (bill, eye, throat, feet,webs) appeared to dissolve in a few days time. Both e�ectscannot be attributed to PIB, and are therefore unexplained.Although the dumping of PIB in the marine environment isnot explicitly prohibited under MARPOL, the e�ects onwildlife observed are enough to plead for counter-mea-sures. Ó 1999 Elsevier Science Ltd. All rights reserved.

Keywords: seabirds; strandings; operational discharges;polyisobutylene; (C4H8)n; Fulmarus glacialis; Uria aalge;Melanitta nigra; MARPOL.

Seabirds are highly vulnerable to surface pollutants(Goethe, 1968; Croxall, 1977; Clark, 1984; Jenssen andEkker, 1991; Barker, 1994). With the term surface pol-lutants, a wide range of lipophilic substances is covered,including mineral oils, vegetable oils and variouschemicals. Mineral oils pose by far the greatest threat toseabirds in the North Sea (Barclay-Smith, 1931; Bourne,1968; Dunnet, 1982; Camphuysen, 1989; Heubeck, 1995;Camphuysen, 1995, 1997, 1998), but several incidentswith other substances have shown the equally lethal ef-fects of many products (Anonymous, 1975; Swennen,1977; McKelvey et al., 1980; Engelen, 1987; Timm andDahlmann, 1991; Rozemeijer et al., 1992; Scholten,1993; Dahlmann et al., 1994). In The Netherlands,chronic oil pollution is a constant threat to seabirds andoil rates among stranded birds are very high in com-parison with those in other West European countries(Furness and Camphuysen, 1997; Camphuysen, 1998).A comparative study of the types of oil and otherchemicals on beached birds in The Netherlands, Ger-many and Denmark showed that `ordinary' fuel oils areresponsible for most seabird deaths (Dahlmann et al.,1994).

In December 1998, hundreds of seabirds, all coveredin a `whitish, sticky substance', were washed ashore inZeeland (SW Netherlands; Fig. 1). Many casualties werestill alive and these were transported to a nearby reha-bilitation centre. A few days later, more (dead) casual-ties were washed ashore 120 km further to the north,again covered in a glue-like substance. Although someof the birds were contaminated by more than one sub-stance (including mineral oils), it was clear that a non-mineral oily substance was responsible for this wreck.This study reports on the number of seabirds a�ected,on the identity of the substance found on these birds,

Marine Pollution Bulletin Vol. 38, No. 12, pp. 1171±1176, 1999

Ó 1999 Elsevier Science Ltd. All rights reserved

Printed in Great Britain

0025-326X/99 $ - see front matterPII: S0025-326X(99)00152-6

*Corresponding author. Present address: CSR Consultancy andDutch Seabird Group, working group Beached Bird Surveys, An-kerstraat 20, 1794 BJ Oosterend, Texel, The Netherlands. E-mail:[email protected].

1171

Page 2: Seabirds in the North Sea Demobilized and Killed by Polyisobutylene (C4H8)n (PIB)

and on the e�ect of this substance on (carcasses of)seabirds.

Methods

The scale, causes and backgrounds of seabird strandingsare monitored through `beached bird surveys' (BBS).BBS are conducted by foot, a group of people walkingthe tide line, recording and describing every corpse.Notes included sub-species, age, sex, plumage of eachbird, presence of oil in the feathers, state of the corpse(fresh, old, very old) and completeness of the corpse (cf.Camphuysen and Dahlmann, 1995). BBS in The Neth-erlands have been centrally co-ordinated since the mid-1960s. BBS are organized so that as many as possiblecoastal stretches are regularly visited. Since 1977, cov-erage has been over the entire winter period by `sam-pling' six coastal regions (>10% of coastline covered bysurveys in each region). Regional co-ordinators are re-sponsible for the precise planning of surveys (in parts of

or entire subregions), mainly organized between No-vember and April but also in the rest of the year. Extravolunteers are called out in the case of mass strandings,so that a greater portion of the coastline can be covered.Corpses are marked by clipping the primaries of thewings to avoid (or recognize) double counts during latersurveys. Monthly densities of beached birds are calcu-lated (n per km surveyed) and extrapolated overstretches that were not surveyed in a given month inorder to estimate total numbers that were washedashore.

Weather reports were taken from six-hourly mea-surements of wind (velocity and direction of wind) anddaily temperatures, published monthly by the RoyalDutch Meteorological Institute in De Bilt (KNMI1999a,b).

Small feather samples were taken and stored fortransport in clean, glass containers. Some of the stickymaterial was taken from the feathers and an infrared-spectrum was made with Fourier-Transform-Infrared-

Fig. 1 Stranding areas (solid black lines along the coast) of thepolyisobutylene incident, December 1998, in Zeeland and onTexel.

1172

Marine Pollution Bulletin

Page 3: Seabirds in the North Sea Demobilized and Killed by Polyisobutylene (C4H8)n (PIB)

Spectroscopy (FT-IR). The sticky material was appliedon a Zinc-Selenide window as a thin ®lm and the in-strument was set on a resolution of 9 cmÿ1. In total 25scans in the range of 5000±600 cmÿ1 were made to ob-tain a clear IR-spectrum. Measurements of the samesample were repeated by the TNO-Industry laboratoriesat Delft, the Netherlands. Some of the substance foundin the feathers was soaked in dichloromethane. Thissolution was examined by Gaschromatography-Mass-spectroscopy (GC-Quadrupole-MS) in the full-scanmode, in the m/z-range of 25±450. The gaschromato-graphic separation was obtained by a 25 m Cp-sil-5capillary column. The purpose of this measurement wasto look for the presence of nonyl-phenols, which weresuspected by the bird-centre, deduced from the behav-iour of many birds and their experience with this com-pound in the past (Zoun et al., 1991).

Results

The ®rst birds, all covered with an `unknown, whitish,sticky substance' were recorded on 7 December 1998 inZeeland (Joosse, 1999). Most these birds were still aliveand therefore transported to a rehabilitation centre inMiddelburg (Walcheren). On the next two days, morecontaminated seabirds were captured and transported,but after 12 December very few contaminated birds werefound that were still alive. In all, 327 casualties werereported from the beaches searched, with commonscoters (94) and common guillemots (215) as most nu-merous species. After extrapolation of the observeddensities over the entire a�ected area it was calculatedthat at least 840 birds had washed ashore in Zeeland, ofwhich 66% were common guillemots and 29% werecommon scoters (7 species in total; Table 1).

On 20 December 1998 and the following week, un-usual numbers of northern fulmars (52) and guillemots(61) and some other seabirds washed ashore on Texel.These birds were covered in a similar substance as whathad been reported from Zeeland 10 days earlier. All

birds on Texel were dead and most were intact, althoughmany birds had probably died a few days before thestranding. This stranding comprised a minimum of 290casualties and scattered individuals were found alongthe coast of Noord-Holland and on Vlieland. Speciescomposition di�ered from Zeeland, with 46% identi®edas common guillemots, 29% as northern fulmars and awider spectrum of casualties (11 species; Table 1). Un-usual was the fact that 27% of the northern fulmarswere of arctic origin (33 dark phase birds); the highestproportion on record since 1962 (Camphuysen unpub.data). Otherwise the species found dead represented the`normal' wintering populations of pelagic seabirds andcoastal species in Dutch waters.

Stranded numbers peaked at two rather small loca-tions: Schouwen in Zeeland (>10 kmÿ1) and on the SWhalf of Texel (5±10 kmÿ1). Low densities were foundelsewhere (Fig. 1). The ®rst birds in Zeeland werestranded during a period with southerly winds (roughlyparallel to the coast, 8±11 December 1998), following aprolonged period of onshore winds (W-NW, 4±7 De-cember 1998). The stranding on Texel took place duringand immediately following a short spell of strong north-westerly winds (onshore), interrupting a prolonged pe-riod with south-westerly winds (roughly parallel to thecoast). Mean temperature ¯uctuated around +5°C overthe entire period, and this temperature is typical for arather mild winter at these latitudes.The glue-like substance was sampled in Zeeland, sent

to the Rijksinstituut voor de Zuivering van Afvalwater(RIZA), and was soon identi®ed as poly-isobutylene((C4H8)n; CAS Registry Number 9003-27-4). An IR-spectrum was also produced by FT-IR, with a resolutionof 4 cmÿ1 and a number of 25 scans, in the range of4000±500 cmÿ1 (Fig. 2). Under the same circumstances aspectrum was made of a low molecular-weight poly-isobutylene (PIB), serving as a reference spectrum. TheIR-spectra made by RIZA and TNO clearly showed thepresence of a branched hydrocarbon compound. Bothspectra correspond to the IR-spectrum of the reference

TABLE 1

Seabird numbers estimated to have washed ashore in Zeeland and on Texel (including northern mainland coast), showing distinctly di�erent speciescomposition during the two phases of the polyisobutylene incident.

Zeeland Texel Total

Gavia stellata 8 2 10Podiceps cristatus 5 0 5Fulmarus glacialis 10 114 124

Sula bassana 0 7 7Somateria mollissima 0 2 2

Melanitta nigra 241 4 245Stercorarius skua 0 2 2

Larus canus 0 2 2Larus argentatus 0 4 4Rissa tridactyla 3 9 12

Uria aalge 552 135 687Alca torda 21 9 30

840 290 1130

1173

Volume 38/Number 12/December 1999

Page 4: Seabirds in the North Sea Demobilized and Killed by Polyisobutylene (C4H8)n (PIB)

sample of the low-molecular-weight PIB. Chromato-gram and mass-spectra of the sample did show homo-logue series of ole®nic hydrocarbons, which can beconcluded from the appearance of an abundant m/z 113.These compounds are expected to be present in a low-molecular-weight PIB. This is also an explanation of thesticky properties of the sample. These types of poly-isobutylenes are often used as adhesives and glue. PIB isalso applied in the bubble-gum industry and in lubri-cating oil and it is known as a non-toxic, non-aggressivesubstance. GC±MS analysis did not show any sign of thepresence of nonyl-phenols. Samples taken from birdsstranded on Texel were sent to Hamburg and the anal-ysis con®rmed that PIB was again responsible.

The contamination ranged from a hardly visible traceof fatty, sticky substance over the feather tips (but oftenincluding all feather parts) to a thick layer of glue-likesubstance covering the entire carcass (estimated mass200±300 g). In the latter case, the birds were unable touse the wing and tail feathers and most of these casu-alties had died instantly. The live casualties were verydi�cult to clean. Volunteers from the rehabilitationcentre complained that the treatment of the birds hadcaused them sensations of serious discomfort and diz-ziness (Joosse, 1999; S. Hart pers. comm.).

The birds on Texel stranded together with slightlyoiled seabirds and the corpse disintegration di�eredconsiderably between the two types. Oiled birds slowlyrotted away, as normal, or stayed more or less un-changed during spells of cold weather. In contrast, thesoft parts of birds covered in PIB (beak, feet, webs, eye)

were rapidly disintegrating and apparently `dissolved'within a few days after the stranding. On 37 northernfulmars collected for dissections it became clear that thissubstance reacted in a rather aggressive way on thebirds' skin. Serious lesions were observed on tarsus andtoes and in most birds the webs were either torn orseemed to have rotted away quickly. In initial or lightcases of contamination, skin at feet gave a slimy im-pression with loose upper layers of the skin. In extremecases of contamination, not only the webs between thetoes became completely torn or dissolved, but the e�ectcontinued on the internal tissues dissolving the tendonsin the feet, resulting in the complete loss of parts of thetoes.

Discussion

Scale of the incidentFrom the timing, the prevailing winds during the in-

cident and from the proportions of live birds in only the®rst of two strandings, we deduce that PIB was releasedinto the sea only once. This must have happened just o�the coast of Zeeland on or around 7 December 1998.Given the proportion of common scoters found inZeeland, the slick will have been within 10±15 km fromthe nearest coast (Camphuysen and Leopold, 1994;Leopold et al., 1995). The slick must have drifted N/NEwith the wind, while the ®rst casualties were just able toreach the coast alive. Given the fact that only pelagicseabirds were found dead on Texel on 20 December andthat vast numbers of highly vulnerable seaducks along

Fig. 2 Infrared spectrum of poly-isobutylene found on a commonscoter, Zeeland, December 1998.

1174

Marine Pollution Bulletin

Page 5: Seabirds in the North Sea Demobilized and Killed by Polyisobutylene (C4H8)n (PIB)

that coast remained largely una�ected, we expect thatthe slick had gradually drifted further o�shore. Thanksto the short spell of north-westerly (onshore) winds,some casualties beached on Texel, but otherwise sincethe live stranding on 7±10 December in Zeeland, thewind has been o�shore or at best parallel to the coast formost of December and early January (KNMI, 1999a,b).This means that part of the mortality may have goneunnoticed, because many of the true seabirds that haveencountered the PIB-slick may have been lost into thecentral North Sea. The estimate of 1100 casualties istherefore a minimum impact of the PIB slick.

The e�ect of PIB on birdsThe e�ect of PIB on bird feathers was roughly similar

to that of other fatty substances or mineral oils: theplumage was disrupted, causing leaks in the insulatinglayer of feathers of the birds that have to maintain abody temperature of c. 40°C. Thick layers of PIB hadcompletely immobilized the birds. Many birds musthave been killed instantly, and therefore the overall`condition' of the dissected casualties (fat contents,condition of breast muscle scored on a 9-point scale)was relatively high (Van Franeker, 1999).The secondary e�ects on stranded PIB-contaminated

birds on soft parts were only noticed on corpses exam-ined during dissections and on corpses re-reported insubsequent beached bird surveys. From these observa-tions it appeared that the ®rst lesions on the feet oc-curred within three days, while the feet and bill wouldfall apart within a week after the stranding. The softpart disintegration was di�erent from and more dra-matic than anything we had ever encountered instranded, oiled seabirds over the last 25 years. PIB isknown as a non-aggressive, non-toxic substance andthere is no evidence to assume that these e�ects werecaused by PIB. There were no other substances reportedin the analysis, but there is always the possibility that forexample a compound, not detectable by GC±MS andIR-spectroscopy, was overlooked during the chemicalanalysis of the samples. Most polar and inorganiccompounds are not taken into account by the methodsof analysis applied in this study.

Similar incidentsThere are a number of recent reports of bird strand-

ings related to non-mineral oily substances. For examplein November 1987, several hundreds of seabirds (mainlyeider ducks Somateria mollissima and common guille-mots), covered in a sticky substance, were washedashore on the Dutch Frisian islands. This substance wasfound to contain 90% linseed-oil and at least 370 kg ofthis product was removed from the beach of one of theislands (Engelen, 1987). A later stranding, mainly in-volving common guillemots, was caused by a para�n oilspillage (Scholten, 1993). Nonylphenol was responsiblefor mass mortality in yet another event (Zoun et al.,1991). The sampling programme conducted in 1991±93

brought para�n waxes, palm oil, C12-fatty-acid, dode-cylphenols and lubricating oil, thiophenes, phenols, al-kylated bis-phenols, alkylated aromatics, plasticizer(phthalates) and detergents (di-t-butyl-phosphin) to ourattention as causing seabird mortality (Dahlmann et al.,1994). Para�n waxes are frequently reported and infact, in an attempt to locate PIB not only on strandedbirds but also on the beaches, beach samples taken onTexel during the PIB incident described here containedpara�n waxes. Most large-scale pollution incidents re-ported over the last 10 years were caused by crude oilsand bunker oil residues discharged by or leaked fromvessels. However, the incident described here clearly il-lustrates the potential impact of other substancesdumped into the marine environment.

Polyisobutylene and MARPOLIt is not prohibited to discharge PIB under MARPOL

73/78 (Annex II, Appendix 3). The source of the pollu-tion is unknown, but it is likely that the PIB has beendumped into the sea from a ship. There have been nosightings of a slick during aerial surveys over the Dutchsector of the North Sea that can be related to this inci-dent and it is unknown how much PIB has been releasedinto the sea. The results of this study and previous re-ports highlight the need for more detailed investigationsinto the e�ects on marine wildlife of non-mineral oilsand other fatty substances, currently often legally dis-charged into the marine environment.

Conclusions

The lethal e�ects of non-mineral oils and other fattysubstances on seabirds have been clearly illustrated inseveral mass-strandings in recent years. While several ofthese substances are legally dumped into the marineenvironment, they may be equally harmful to marinewildlife as mineral oils for which rigid counter-measureswere e�ectuated under MARPOL. The e�ects of mostdischarges of chemicals remain unnoticed, because veryfew samples are routinely taken and adequately ana-lysed by expert laboratories. We advocate a morestringent beached bird survey programme, coupled witha systematic sampling programme of substances onbeaches and beached birds. The chemical analysis offeather samples would provide crucial further insightinto the types and e�ects of surface pollutants respon-sible for the death of seabirds and other marine wildlife.

Many volunteers participate in beached bird surveys in The Nether-lands and substantial contributions to the ®eldwork in the 1998/99season were received from F. Arts, A. Bakker, A. Barnhoorn, S.H. vanden Berg, M. Bos, H. Bouma, H. Brugge, K. Buth, C.J. Camphuysen,G. Camphuysen, J. van Dijk, A. Dijksen, K.D. Dijkstra, P. Edelaar,A.P. van den Ende, G. van den Ende, H. van Franeker, J.A. vanFraneker, F. Geldermans, C.J. de Graaf, E. Grootveld, S. Hart, P.Honkoop, J.N. Ijnsen, F. Jachman, J. Jes, M. de Jong, M. van deKasteele, J. Klous, R. Klous, L. van Kooten, J. de Korte, M. Kreleger,D. Kuiken, M.F. Leopold, J. van der Meer, P.L. Meininger, T. Me-ininger, T. Nieho�, C. Nijdam, L. de Nooyer, C.J.M. Philippart, D.Schermer, E. & W. Schumm, T. Sluyter, C.J. Smit, V.W.G Tringa,

1175

Volume 38/Number 12/December 1999

Page 6: Seabirds in the North Sea Demobilized and Killed by Polyisobutylene (C4H8)n (PIB)

L. Tromper, T. van Wanum, L. van de Weele, De Windbreker, C.J.N.Winter. Koos Zandman and Jan Maat (TNO) kindly produced theFR-IR spectra and we wish to thank Piet van Duijn for his analyticalcontributions at RIZA.

Anonymous (1975) Cape colony hit by pollution. Birds, RSPBMagazine 5(8), 11.

Barclay-Smith, P. (1931) The destruction of birds by oil pollution atsea and the progress made since 1915 combatting this. In Proceed-ings of the Seventh International Ornithological Congress, pp. 503±508.

Barker, J. A. (1994) A veterinary view of the oiled bird. SWOSGBulletin 5, 3±6.

Bourne, W. R. P. (1968) Oil pollution and bird populations. In Thebiological e�ects of oil pollution on littoral communities, ed. J. D.Carthy and D. R. Arthur, Proceedings symposium Pembroke, Wales17±19 February 1968. Field Studies Supplement Volume 2, pp. 99±121.

Camphuysen, C. J. (1989) Beached Bird Surveys in the Netherlands1915±1988; Seabird Mortality in the southern North Sea since theearly days of Oil Pollution. Technisch Rapport Vogelbescherming1, Werkgroep Noordzee, Amsterdam, 322 pp.

Camphuysen, C. J. (1995) Olieslachto�ers langs de Nederlandse kustals indicatoren van de vervuiling van de zee met olie. Sula 9 (specialissue), 1±90, I±XX.

Camphuysen, C. J. (1997)Olievervuiling en olieslachto�ers langs deNederlandse kust, 1969±97: signalen van een schonere zee. Sula 11,41±156.

Camphuysen, C. J. (1998) Beached bird surveys indicate decline inchronic oil pollution in the North Sea. Marine Pollution Bulletin 36,519±526.

Camphuysen, C. J. and Dahlmann, G. (1995) Guidelines on standardmethodology for the use of (oiled) beached birds as indicators ofmarine pollution. Ad Hoc working group on Monitoring, Oslo andParis Convention for the Prevention of Marine Pollution. MON 95/7,Agenda item, 7, 13±17 November 1995, Copenhagen.

Camphuysen, C. J. and Leopold, M. F. (1994) Atlas of seabirds in thesouthern North Sea. IBN Research report 94/6, NIOZ-Report1994-8, Institute for Forestry and Nature Research, NetherlandsInstitute for Sea Research and Dutch Seabird Group, Texel.

Clark, R. B. (1984) Impact of oil pollution on seabirds. EnvironmentalPollution (Series A) 33, 1±22.

Croxall, J. P. (1977) The e�ect of oil on seabirds. Rapports et Proces-verbaux R�eunion du Conseil international Exploration de la Mer 171,191±195.

Dahlmann, G., Timm, D., Averbeck, C., Camphuysen, C. J. and Skov,H. (1994) Oiled seabirds ± Comparative investigations on oiledseabirds and oiled beaches in the Netherlands, Denmark andGermany (1990±1993). Marine Pollution Bulletin 28, 305±310.

Dunnet, G. M. (1982) Oil pollution and seabird populations. Philo-sophical Transactions of the Royal Society, London (B) 297(1087),413±427.

Engelen, K. A. M. (1987) Zeevogels op de Waddeneilanden hetslachto�er van lijmachtige substantie. Sula 1, 112±113.

Van Franeker, J. A. (1999) Twee totaal verschillende `fulmar-wrecks'in de winter van 1998/99. Nieuwsbrief NZG 1, 4±5.

Furness, R. W. and Camphuysen, C. J. (1997) Seabirds as monitors ofthe marine environment. ICES Journal of Marine Science 54, 726±737.

Goethe, F. (1968) The e�ects of oil pollution on populations of marineand coastal birds. Helgol�ander Meeresuntersuchungen 17, 370±374.

Heubeck, M. (1995) Shetland beached bird surveys: national andEuropean context. Proceedings Royal Society Edinburgh 103B, 165±179.

Jenssen, B. M. and Ekker, M. (1991) E�ects of plumage contaminationwith crude oil dispersant mixtures on thermoregulation in CommonEiders and Mallards. Archives Environmental Contamination andToxicology 20, 398±403.

Joosse, R. (1999) Smurrie-slachto�ers op de deltakust. Vogelnieuws12(1), 13.

KNMI (1999a) December 1998. In Maandelijks overzicht van het weerin Nederland. Koninklijk Nederlands Meteorologisch Instituut, DeBilt.

KNMI (1999b) January 1999. In Maandelijks overzicht van het weer inNederland. Koninklijk Nederlands Meteorologisch Instituut, De Bilt.

Leopold, M. F., Baptist, H. J. M., Wolf, P. A. and O�ringa, H. (1995)De Zwarte Zee�eend Melanitta nigra in Nederland. Limosa 68, 49±64.

McKelvey, R. W., Robertson, I. and Whitehead, P. E. (1980) E�ect ofnon-petroleum oil spills on wintering birds near Vancouver. MarinePollution Bulletin 11, 169±171.

Rozemeijer, M. J. C., Booij, K., Swennen, C. and Boon, J. P. (1992)Molecular features of environmental contaminants causing disrup-tion of the plumage of sea-birds. NIOZ BEWON Report no. 43,Netherlands Institute for Sea Research, Texel, 27 pp.

Scholten, M. (1993) Guillemot stranding caused by a para�n oilspillage. Marine Pollution Bulletin 26, 173.

Swennen, C. (1977) Laboratory research on seabirds. UnpublishedReport, Netherlands Institute for Sea Research, Texel, The Neth-erlands.

Timm, D. and Dahlmann, G. (1991) Investigations into the source ofnon-mineral oils in the feathers of seabirds. Sula 5 (special issue),15±17.

Zoun, P. E. F., Baars, A. J. and Boshuizen, R. S. (1991) A case ofseabird mortality in the Netherlands caused by spillage of nonyl-phenol and vegetable oils, winter 1988/89. Sula 5, 101±103.

1176

Marine Pollution Bulletin