Working Group on Seabird Ecology (WGSE). ICES CM 2004/C:05 ...

ICES Oceanography Committee 

ICES CM 2004/C:05 Ref. ACME, ACE 

Report of the 

<strong>Working</strong> <strong>Group</strong> on Seabird Ecology (WGSE) 

29 March–2 April 2004 

Aberdeen, UK 

This report is not to be quoted without prior consultation with the General Secretary. The document is a report of an 

Expert <strong>Group</strong> under the auspices of the International Council for the Exploration of the Sea and does not necessarily 

represent the views of the Council.

International Council for the Exploration of the Sea 

Conseil International pour l’Exploration de la Mer 

Palægade 2–4 DK–1261 Copenhagen K Denmark 

Telephone + 45 33 38 67 00 · Telefax +45 33 93 42 15 

www.ices.dk · info@ices.dk

Contents 

1 Introduction................................................................................................................................................................ 5 

1.1 Participation .................................................................................................................................................... 5 

1.2 Terms of Reference......................................................................................................................................... 5 

1.3 Overview by the Chair .................................................................................................................................... 5 

1.4 Note on bird names ......................................................................................................................................... 6 

1.5 Acknowledgements......................................................................................................................................... 6 

2 Factors influencing trends in abundance of seabirds in the Baltic Sea....................................................................... 6 

2.1 Introduction..................................................................................................................................................... 6 

2.2 Factors known or assumed to be responsible for the trends observed............................................................. 6 

2.2.1 Climate ............................................................................................................................................... 6 

2.2.2 Bycatch in fishing gear ........................................................................................................................ 6 

2.2.3 Fishery discards and offal.................................................................................................................... 7 

2.2.4 Oil pollution......................................................................................................................................... 7 

2.2.5 Predation by native and introduced predators...................................................................................... 7 

2.2.6 Coastal zone development ................................................................................................................... 8 

2.2.7 Marine wind farms............................................................................................................................... 8 

2.2.8 Sand and gravel extraction................................................................................................................... 8 

2.2.9 Hunting ............................................................................................................................................... 8 

2.2.10 Other factors ........................................................................................................................................ 8 

2.3 Discussion....................................................................................................................................................... 9 

2.4 References....................................................................................................................................................... 9 

3 Progress in measuring impacts of at-sea wind farms on seabirds............................................................................. 10 

3.1 Introduction................................................................................................................................................... 10 

3.2 Recent advances in measuring impacts of existing wind farms on seabird................................................... 10 

3.3 Recent progress in understanding bird migration at sea................................................................................ 10 

3.4 Recent progress in site-selection procedures ................................................................................................ 11 

3.5 Progress and future plans of monitoring possible impacts of wind farms on seabirds.................................. 11 

3.6 References..................................................................................................................................................... 12 

4 Climatic effects on seabird population performance................................................................................................ 14 


4.2 Relations between seabird population performance and climate .................................................................. 15 

4.2.1 Phenology .......................................................................................................................................... 15 

4.2.2 Breeding success................................................................................................................................ 16 

4.2.3 Survival ............................................................................................................................................. 16 

4.3 Scale issues ................................................................................................................................................... 16 

4.4 Conclusions................................................................................................................................................... 16 

4.5 Summary....................................................................................................................................................... 17 

4.6 References..................................................................................................................................................... 17 

5 A comparison of seabird communities and prey consumption in the east and west north atlantic........................... 18 


5.1.1 Population estimates .......................................................................................................................... 18 

5.2 Results........................................................................................................................................................... 20 

5.2.1 Breeding populations (adapted from ICES 2003).............................................................................. 20 

5.2.2 Seasonal changes in numbers and biomass of seabirds in ICES and NAFO areas ............................ 22 

5.2.3 Consumption estimates...................................................................................................................... 24 

5.2.4 Comparison to earlier models............................................................................................................ 25 

5.3 References..................................................................................................................................................... 26 

6 Consumption of prey by seabirds in the North Sea as input for the Study <strong>Group</strong> on Multispecies Assessments in 

the North Sea (SGMSNS) ........................................................................................................................................ 29 

7 Ecological quality objectives.................................................................................................................................... 29 


7.2 Proportion of oiled common guillemots among those found dead or dying on beaches............................... 30 

7.3 Mercury concentrations in seabird eggs (and feathers)................................................................................. 31 

7.4 Organochlorine concentrations in seabird eggs ............................................................................................ 31 

7.5 Plastic particles in stomachs of seabirds ....................................................................................................... 32 

7.6 Local sandeel availability to black-legged kittiwakes................................................................................... 33 

7.6.1 Objective............................................................................................................................................ 33 

7.6.2 Can black-legged kittiwake breeding success be monitored accurately?........................................... 33 

ICES WGSE Report 2004 3

7.6.3 Does black-legged kittiwake breeding success correlate with sandeel abundance? .......................... 34 

7.6.4 Are human impacts important?.......................................................................................................... 36 

7.6.5 Can a clearly defined objective be set?.............................................................................................. 36 

7.6.6 Can this EcoQ apply to much of the North Sea? ............................................................................... 36 

7.7 Seabird population trends as an index of seabird community health ............................................................ 37 

7.8 References..................................................................................................................................................... 37 

8 Summary of the size, distribution, and status of seabird populations in the North Sea for the period 2000–2004, 

and any trends over recent decades in these populations, for input to REGNS in 2006........................................... 38 


8.2 Population distribution and size.................................................................................................................... 38 

8.2.1 UK (ICES IVa-c) ............................................................................................................................... 39 

8.2.2 Netherlands (ICES IVc)..................................................................................................................... 39 

8.2.3 Norway (ICES IVa and IIIa).............................................................................................................. 39 

8.2.4 Sweden (ICES IIIa)............................................................................................................................ 39 

8.2.5 Belgium (ICES IVc) .......................................................................................................................... 39 

8.2.6 Denmark (ICES IVb and IIIa) ........................................................................................................... 39 

8.2.7 Germany (ICES IVb)......................................................................................................................... 39 

8.3 Population trends .......................................................................................................................................... 39 

8.4 Future development of this term of reference ............................................................................................... 46 

8.5 Additional references .................................................................................................................................... 46 

9 Recommendations.................................................................................................................................................... 47 

9.1 Chair of WGSE............................................................................................................................................. 47 

9.2 Proposal for next meeting ............................................................................................................................. 47 

10 Annexes.................................................................................................................................................................... 49 

Annex 1 List of participants ............................................................................................................................. 49 

Annex 2 Terms of Reference............................................................................................................................ 50 

Annex 3 English and scientific names of birds mentioned in this report ......................................................... 52 

4 

ICES WGSE Report 2004

1 INTRODUCTION 

1.1 Participation 

The meeting participants are listed in Annex 1. 

1.2 Terms of Reference 

The Terms of Reference for the 2004 meeting of the <strong>Working</strong> <strong>Group</strong> on Seabird Ecology (WGSE) are given in 

C.Res.2003/2C05. This resolution is in Annex 2. 

1.3 Overview by the Chair 

The <strong>Working</strong> <strong>Group</strong> met for five days (29 March to 2 April 2004), and was attended by twelve nominated 

representatives from seven countries (Annex 1). It was able to address all terms of reference, though in varying detail, 

and the results are reported here. 

We reviewed factors influencing trends in abundance of seabirds in the Baltic Sea. This review followed from our 

review of the status and trends of Baltic Sea birds carried out in 2003. Although our group lacked representatives from 

many Baltic countries, and so was unable to make detailed evaluation of local literature and knowledge, the review 

clearly shows that many human impacts affect Baltic seabirds, including fishery bycatch, provision of discards, habitat 

change and increases in numbers of predators on ground-nesting birds. Increasing rates of oil tanker traffic represent a 

potential hazard in the immediate future. 

We briefly reviewed progress over the last twelve months in the study of seabirds in relation to marine wind farms. 

Although several marine wind farms are now commissioned, there are still no established means to assess the numbers 

of bird collisions. Methods to assess this are still at a developmental stage, but advances have been made in assessing 

the relative suitability of sites that could be developed as wind farms in relation to their importance for seabirds. 

We reviewed effects of climate on seabird population performance, a topic that has received much increased research 

attention recently and one where long term data sets on seabird ecology provide excellent opportunities to investigate 

relationships with food supply and with environmental factors such as oceanography and climate. While the presence of 

many effects of climate can be established, further work to assess the relative importance of climate and other factors, 

such as predators or fisheries, remains to be undertaken, perhaps focusing on specific situations where detailed data 

exist such as in parts of the North Sea. 

A longstanding investigation into the energy consumption by seabirds in the ICES and NAFO Regions was brought to a 

stage where we present total biomass and energy consumption estimates for each season of the year. A striking feature 

contrasting between the regions is the higher proportion of small seabirds in the NAFO Region, higher consumption 

from a lower trophic level than occupied by seabirds in the ICES Region, and the relatively greater importance of longdistance 

migrant seabirds taking resources from the NAFO Region. These patterns deserve further investigation in 

relation to foodweb structure in the two regions. 

Our Term of Reference f) required WGSE to prepare data on the consumption of different prey by seabirds in the North 

Sea, in a format specified by SGMSNS. WGSE received only very brief guidance from SGMSNS on the format 

required, via a member of WGSE who had already attended WGMME and obtained some details there. However, he 

pointed out that WGMME had not worked on this ToR as it was unclear what was needed, and it appeared that this 

work was now being taken forward by an EC contract ‘BECAUSE’ rather than through ICES. WGSE would be happy 

to work on this ToR intersessionally in future if ICES wishes to continue with this work. 

A major part of this year’s WGSE work was discussion of the six EcoQOs that involve seabird ecology. Five of these 

utilize seabirds to assess the status of other topics (oil, plastic, mercury, organochlorines, sandeels) and only one focuses 

on seabird populations themselves. WGSE made good progress with all of these EcoQOs except the one focused on 

seabird populations, where there is a need for more consideration of metrics and objectives. 

Term of Reference h) was to start to prepare for input of data on seabird populations to REGNS in 2006. This topic was 

warmly received by WGSE, who felt that such an approach was very much in line with our own thinking and was 

highly desirable. So we have begun this process with enthusiasm. Although compiling appropriate data sets may require 

considerable effort intersessionally, we have started by providing an outline of the sorts of time-series of seabird data 

that are available and that we think would be useful in the approach we envisage being taken by REGNS. 


Our 2004 meeting attracted twelve <strong>Working</strong> <strong>Group</strong> members. The considerable efforts have been rewarded by a sense 

of achievement and new understandings from the data brought together, and also of the great benefits and synergies of 

group working to clear objectives. 

Following the new ‘sandwich’ arrangement, WGSE offered stakeholders the possibility to join us before and after the 

<strong>Working</strong> <strong>Group</strong> meeting. We were joined by Dr Euan Dunn, of the Royal Society for the Protection of Birds (RSPB)/ 

Birdlife International, on Friday afternoon and we discussed the contents of the nearly completed <strong>Working</strong> <strong>Group</strong> 

Report and the proposed Terms of Reference for WGSE 2005. We note the relative impracticality for representatives of 

organisations located at distance from the meeting venue to be able to discuss issues both before and after meetings. 

Also the ‘sandwich’ approach was announced only shortly before our meeting so that interested parties would have had 

little time to arrange to attend. However, WGSE welcomes participation in this form and is pleased to receive scientific 

information from any source. 

1.4 Note on bird names 

Throughout the text we provide the common English names of bird species. A full list of species names together with 

their scientific binomial appears in Annex 3. 

1.5 Acknowledgements 

The <strong>Working</strong> <strong>Group</strong> wishes to thank the Fishery Research Service, Aberdeen, for providing a room for our meeting, and 

keeping the coffee machine topped up. We particularly thank Simon Greenstreet, Ray Johnstone and Dick Ferro for 

providing facilities, Tony Fox, Simon Greenstreet, Ommo Hüppop, Bill Montevecchi and Dick Veit for providing 

information and reviewing content of sections of the report, and Bill Turrell for joining us for a very useful discussion 

of the approach being developed in REGNS. 

2 FACTORS INFLUENCING TRENDS IN ABUNDANCE OF SEABIRDS IN THE BALTIC SEA 

Term of Reference: Review the factors influencing trends in abundance of seabirds in the Baltic Sea. 

2.1 Introduction 

The status and trends of seabirds in the Baltic Sea have been reviewed at the 2003 meeting of WGSE (ICES, 2003). 

Given that there have been major declines in numbers of certain populations and species and increases in numbers in a 

few species, it is important to review likely causes for these trends. Because of a bulk of local literature in different 

languages in all countries bordering the Baltic Sea and also a substantial amount of unpublished information it is quite 

difficult to get a good country-wide coverage of these factors. The presence at WGSE of representatives from countries 

bordering the Baltic Sea needs to be higher to fill these apparent gaps in detail. This section is thus to specify some of 

the main factors known to influence seabird population trends in the Baltic Sea without being necessarily 

comprehensive. Also, many more details will be summarised later by others in a report to be produced for HELCOM. 

2.2 Factors known or assumed to be responsible for the trends observed 

2.2.1 Climate 

Winters of different strength have a substantial influence on distributions and numbers of waterbirds along the coast but 

also in offshore areas (e.g., Kube 1996; Vaitkus 2001; Garthe et al. 2003). Species with relatively restricted habitat 

selection, especially those living in shallow waters (e.g., common goldeneye and Steller's eider), respond to cold 

winters and thus ice formation much more quickly than species exhibiting a more flexible habitat selection such as 

velvet scoter and long-tailed ducks (Zydelis, 2001). The climatic trend is thus of major importance for explaining trends 

in birds spending their winter in the Baltic Sea, with many species and substantial proportions leaving the eastern Baltic 

already in normal winters and many more leaving even the generally warmer southern and western parts in cold winters. 

Unfortunately, hardly any large-scale surveys have been conducted in offshore areas in cold winters so far so that the 

extent of changes outside the coastal areas remains partly speculative. 

2.2.2 Bycatch in fishing gear 

The scale of additional mortality imposed upon different seabird populations from the use of different passive fishing 

gears throughout the Baltic Sea is currently unknown. It is known that bycatch of many species occurs throughout the 

6 


egion, but its size and importance has not been assessed. A number of national or regional investigations has been 

undertaken, focusing on gill-net fisheries, e.g., in Finland (Hario 1998), Latvia (Urtans and Priednieks 2000), Lithuania 

(Dagys and Zydelis 2002), Poland (Stempniewicz, 1994), and Germany (Kirchhoff, 1982; Schirmeister, 2003). The 

numerical effects of such activities vary with the type of gears used and the temporal and spatial overlap between 

fishery activities and seabird distribution and abundance. The impacts at the population level will vary according to the 

demographic patterns and the populations concerned: long-lived species with low reproductive rates suffer greater 

effects on overall abundance than short-lived species with high reproductive potential. A well-documented example is 

the study of common guillemots ringed in Sweden. Bycatches of this species appear to be the single most serious threat 

to the population, and the proportion of recoveries of ringed birds in fishing gear, compared with other finding 

circumstances, has significantly increased during a 28-year period (Österblom et al., 2002). 50% of guillemots found 

dead were caught in fishing nets, most notably in drift gillnets for salmon and set gillnets for cod. Österblom et al. 

(2002) concluded that the observed increased use of cod gillnets in the Baltic Sea may have contributed to the observed 

decrease in guillemot adult survival rate. 

2.2.3 Fishery discards and offal 

Scavenging on discards and offal is a widespread phenomenon in the Baltic Sea as it is in other shelf areas of Europe, 

but the number of bird species involved is generally lower and strongly biased towards gulls, especially herring gulls 

(Garthe and Scherp, 2003). Herring gulls were clearly the most numerous scavenging species in all areas and all seasons 

studied, followed by great black-backed gulls, lesser black-backed gulls and mew gulls. High percentages of discarded 

gadids (cod, whiting), clupeids (herring, sprat), scad, rockling and offal were consumed by seabirds during experimental 

discarding on fishing boats, whereas percentages of flatfish consumed were extremely low. By combining official 

discard and offal statistics and experimental discarding, Garthe and Scherp (2003) estimated that 6,500 t of fish discards 

and 16,000 t of offal were consumed annually by seabirds in the Baltic Sea. The proportion of discards in herring gull 

pellets was on average 1.6% (range: 0–4.5%) and 17.5% (range: 9.4–25.5%), respectively, at two study sites in the 

southwestern Baltic Sea. Even if these percentages are not extremely high it seems likely that herring gulls in particular 

but also great black-backed gulls in winter and lesser black-backed gulls in summer should have benefited from this 

surplus food. 

2.2.4 Oil pollution 

Zydelis and Dagys (1997) consider oil pollution due to ship traffic as the most important threat to wintering seabirds 

and waterbirds in the coastal zone of Lithuania. Oil rates of beached birds were up to 34% in years without any major 

accidents and up to 90% in years with such accidents. As oil exploration is assumed to increase in the eastern Baltic Sea 

chronic oil pollution is thought to be a major factor for the forthcoming years. Particular emphasis is put to strongly 

increasing traffic of oil tankers transporting oil from the eastern Baltic Sea coast into the North Sea and NE Atlantic. 

Major accidents occur from time to time. In March 2001, 1,750 birds were found dead after the 'Baltic Carrier' oil spill 

with estimates up to ten times higher: 

(www.europa.eu.int/comm/environment/civil/marin/reports_publications/final_reports/baltic_carrier.pdf). In June 

2003, an oil spill from the “Fu Shan Hai” hit Christiansø, where 164 birds were found dead; total mortality was 

estimated as up to ten times higher, with about 50% being common guillemots (www.danbbs.dk/~lynx/chroe_obs/). 

2.2.5 Predation by native and introduced predators 

Predation by mammalian ground predators is one of the main reasons for declines in breeding gulls and terns (as well as 

shorebirds) along the Baltic Sea coasts. Different predators are involved, native (e.g., red fox Vulpes vulpes) as well as 

introduced (e.g., American mink Mustela vison) species. In addition to other local factors, predation and disturbance by 

American minks has been one the main factors responsible for the decline of black-headed gulls in Latvia (e.g., Viksne 

and Janaus, 1993; Viksne et al., 1996). Mew gulls in Schleswig-Holstein (northern Germany) suffer from repeated 

breeding failure due to intense predation above all from red foxes (Kubetzki, 2001). Further east along the German 

Baltic Sea coast, foxes and some other mammals caused severe reduction in breeding success and breeding populations 

of many coastal species (Dierschke et al., 1995; Hartmann and Stier, 2003). 

Large-scale losses of breeding habitats such as small islands which are hardly accessible to predators have strongly 

enhanced the predation pressure on the remaining breeding colonies. These colonies are usually easily accessible for 

predators (Kubetzki, 2001). After the experimental removal of minks from islands in SW Finland some species returned 

to their former breeding sites (Nordström et al., 2003). However, removal of native species is a much bigger issue at 

least for most of the southern Baltic Sea coast (Garthe et al., 2003). 


2.2.6 Coastal zone development 

Many coastal zones of the Baltic Sea have been developed extensively so that most natural habitats have been 

destroyed. This is most obvious in countries where economic development occurred earlier. Protected areas are often 

the only places where breeding seabirds and also coastal birds can still reproduce though indirect effects such as 

predation pressure can be very intense. Herring gulls and mew gulls seem to circumvent the problem of lacking natural 

breeding habitats by founding new colonies on buildings with flat-roofs, basically doing that in the much-exploited 

western part of Germany and hardly so in the less-exploited eastern part (Kubetzki, 2001; Garthe et al., 2003). Most 

other breeding species respond simply by decreasing in population sizes along with the disappearing breeding habitats. 

2.2.7 Marine wind farms 

This issue is reviewed in Section 3 of this WG report and also in the WG reports of 2002 and 2003 (ICES, 2002; 2003) 

so that information will not be reported here. However, as the first wind farms have just been set up, they cannot have 

been influenced the trends of seabirds in the Baltic Sea area. 

2.2.8 Sand and gravel extraction 

Sand and gravel extraction is carried out at some locations in the Baltic Sea with plans for many more sites to be 

exploited. No information is available so far as how such activities may influence seabirds. However, there is at least 

some overlap between major sea duck (and other seabird) concentrations and extraction sites so that at least food 

availability for benthivorous seabirds might possibly be affected. The observed long-term trend for Baltic Sea seabirds 

is nevertheless unlikely to have been caused by the current level of sand and gravel extraction. 

2.2.9 Hunting 

Hunting is still performed in Denmark at a large scale. The most recent figures for annual bags of sea ducks in Denmark 

are given by Clausager (2003); he estimated 86,400 common eiders in the season 2000/2001 and 77,400 in the season 

2001/02, the values for other sea ducks are less high: common scoter 4,100 and 2,800, respectively, velvet scoter 2,800 

and 1,800, respectively, and long-tailed duck 4,700 and 1,600, respectively. 

2.2.10 Other factors 

Though generally difficult to show, there seems to be changes in fish availability affecting reproductive performance of 

common guillemots breeding at Stora Karlsö, Sweden. Chick fledging body mass has decreased over the period 1989– 

2000 as has the body condition of sprats, their main food. The sprat population itself has changed considerably over the 

past decades due to changes in the Baltic Sea ecosystem (Österblom et al., 2001). 

Further effects are possibly due to eutrophication, litter and other pollution although these are relatively rarely 

documented. In general, however, there is a slightly positive trend as pollution seems to be reduced in the Baltic Sea 

(Rheinheimer, 1998). Organochlorine levels in common guillemots eggs from the Baltic have decreased considerably 

during the last decades (Bignert et al., 1995). 

Furthermore, disturbance by ship traffic and recreational activities play certainly a role, well-documented examples are 

rare though (e.g., Mikola et al., 1994). Protected areas turn into refugees if the surrounding areas are intensively 

exploited, e.g., by recreational boat traffic (Dierschke, 1998). 

Another aspect which has influenced those seabirds feeding on land is change in agricultural practice. Both the 

reduction of meadows and the increased use of winter crops has reduced food availability for mew Gulls and blackheaded 

gulls breeding at or near the German Baltic Sea coast (Berndt, 1980; Kubetzki, 2001). 

Finally, it needs to be clearly stated that some of the reasons for population changes have not been (fully) understood. A 

dramatic decline in the number of wintering eiders from ca. 800,000 to ca. 370,000 occurred in Danish waters between 

1990 and 2000 (Desholm et al., 2002). Given that Danish waters constitute the most important wintering area of eiders 

from the Baltic/Wadden Sea flyway, these reports strongly suggest major declines have taken place in this population 

over the last decade. There seems to be no common explanation for the observed decline in the Baltic/Wadden Sea 

eiders. Local decreases in discrete breeding populations have been related to periods of very low duckling survival 

caused by viral infections, mass adult mortality due to avian cholera and reduced adult annual survival rates. In 

8 


addition, mass mortality events on the wintering grounds have occurred in the Wadden Sea potentially affecting 

breeding populations throughout the range (Desholm et al., 2002). 

2.3 Discussion 

The Baltic Sea is strongly influenced by human activities all around the coast, likely more than most other seas. This 

has led to a full range of different anthropogenic factors which affect breeding seabirds on land and at the coast as well 

as resting and wintering seabirds along the coast and further offshore. Many of these factors are inter-connected as has, 

e.g., been demonstrated for the decreases in mew gulls and black-headed gulls (see above). 

2.4 References 

Berndt, R.K. 1980. Bestand und Bestandsentwicklung von Silber-, Sturm- und Lachmöwe (Larus argentatus, canus und 

ridibundus) in der Seenplatte des Östlichen Hügellandes (Schleswig-Holstein) 1970–1979. Corax 8: 131–149. 

Bignert, A., Litzen, K., Odsjö, T., Olsson, M., Persson, W., and Reutergardh, L. 1995. Time related factors influence 

the concentrations of DDT, PCBs and shell parameters in eggs of Baltic guillemots (Uria aalge), 1961–1989. 

Environmental Pollution, 89: 27–36. 

Clausager, I. 2003. Vingeindsamling fra jagtsæsonen 2002/03 i Danmark. DMU rapport 452, 72 pp. 

Dagys, M., and Zydelis, R. 2002. Bird bycatch in fishing nets in Lithuanian coastal waters in wintering season 2001– 

2002. Acta Zoologica Lituanica, 12: 276–282. 

Desholm, M., Christensen, T.K., Scheiffarth, G., Hario, M., Andersson, Å., Ens, B., Camphuysen, C.J., Nilsson, L., 

Waltho, C.M., Lorentsen, S.-H., Kuresoo, A., Kats, R.K.H., Fleet, D.M., and Fox, A.D. 2002. Status of the 

Baltic/Wadden Sea population of the Common Eider Somateria m. mollissima. Wildfowl, 53: 167–203. 

Dierschke, V. 1998. Anthropogene und natürliche Störreize für Küstenvögel im Windwatt von Hiddensee. Seevögel 19, 

Sonderheft: 53–56. 

Dierschke, V., Helbig, A.J., and Barth, R. 1995. Ornithologischer Jahresbericht 1994 für Hiddensee und Umgebung. 

Berichte Vogelwarte Hiddensee, 12: 41–96. 

Garthe, S., and Scherp, B. 2003. Utilization of discards and offal from commercial fisheries by seabirds in the Baltic 

Sea. ICES Journal of Marine Science, 60: 980–989. 

Garthe, S., Ullrich, N., Weichler, T., Dierschke, V., Kubetzki, U., Kotzerka, J., Krüger, T., Sonntag, N., and Helbig, 

A.J. 2003. See- und Wasservögel der deutschen Ostsee - Verbreitung, Gefährdung und Schutz. Report to the 

Federal Agency for Nature Conservation, Bonn. 

Hario, M. 1998. Review of incidental catches of seabirds in fisheries in Finland. CAFF Technical Report 1: 20–24. 

Hartmann, E., and Stier, N. 2003. Raubsäuger in Küstenvogelschutzgebieten Mecklenburg-Vorpommerns – einer 

Gefahr für Bodenbrüter? Vogelkundliche Berichtung Niedersachsen, 35: 83–90. 

ICES. 2002. Report of the <strong>Working</strong> <strong>Group</strong> on Seabird Ecology. ICES CM 2002/C:04. 


Kirchhoff, K. 1982. Wasservogelverluste durch die Fischerei an der schleswig-holsteinischen Ostseeküste. Vogelwelt, 

103: 81–89. 

Kube, J. 1996. The ecology of macrozoobenthos and seaducks in the Pomeranian Bay. Meereswissenschaftliche 

Berichte, 18: 1–128. 

Kubetzki, U. 2001. Zum Bestandsrückgang der Sturmmöwe (Larus canus) an der schleswig-holsteinischen Ostseeküste 

– Ausmaß, Ursachen und Schutzkonzepte. Corax, 18: 301–323. 

Mikola, J., Miettinen, M., Lehikoinen, E., and Lehtilae, K. 1994. The effects of disturbance caused by boating on 

survival and behaviour of Velvet Scoter Melanitta fusca ducklings. Biological Conservation, 67: 119–124. 

Nordström, M., Högmander, J., Laine, J., Nummelin, J., Laanetu, N., and Korpimäki, E. 2003. Effects of feral mink 

removal on seabirds, waders and passerines on small islands in the Baltic Sea. Biological Conservation, 109: 359– 

368. 

Österblom, H., Bignert, A., Fransson, T., and Olsson, O. 2001. A decrease in fledging body mass in Common Guillemot 

Uria aalge chicks in the Baltic Sea. Marine Ecology Progress Series, 224: 305–309. 

Österblom, H., Fransson, T., and Olsson, O. 2002. Bycatches of Common Guillemots (Uria aalge) in the Baltic Sea 

gillnet fishery. Biological Conservation 105: 309–319. 

Rheinheimer, G. 1998. Pollution in the Baltic Sea. Naturwissenschaften, 85: 318–329. 

Schirmeister, B. 2003. Verluste von Wasservögeln in Stellnetzen der Küstenfischerei – das Beispiel der Insel Usedom. 

Meer und Museum, 17: 160–166. 

Rheinheimer, G. 1998. Pollution in the Baltic Sea. Naturwissenschaften, 85: 318–329. 

Stempniewicz, L. 1994. Marine birds drowning in fishing nets in the Gulf of Gdansk (southern Baltic): numbers, 

species composition, age and sex structure. Ornis Svecica, 4: 123–132. 

Urtans, E., and Priednieks, J. 2000. The present status of seabirds by-catch in Latvia coastal fishery of the Baltic Sea. 

ICES C.M. 2000/J:14. 

Vaitkus, G. 2001. Spatial dynamics of regional wintering populations of seabirds in the gradient of winter climatic 

conditions. Acta Zoologica Lituanica, 11: 273–279. 


Viksne, J., and Janaus, M. 1993. What is going on with the Black-headed Gull (Larus ridibundus) at the eastern coast of 

the Baltic? Ring 15: 154–158. 

Viksne, J., Janaus, M., and Stipniece, A. 1996. Recent trends of the Black-headed Gull (Larus ridibundus L.) population 

in Latvia. Ornis Svecica 6: 39–44. 

Zydelis, R. 2001. Some remarks on effect of climatic parameters on wintering waterbirds in the eastern Baltic. Acta 

Zoologica Lituanica 11: 303–308. 

Zydelis, R., and Dagys, M. 1997. Winter period ornithological impact assessment of oil related activities and sea 

transportation in Lithuanian inshore waters of the Baltic Sea and in the Kursiu Lagoon. Acta Zoologica Lituanica, 

Ornithologia, 6: 45–65. 

3 PROGRESS IN MEASURING IMPACTS OF AT-SEA WIND FARMS ON SEABIRDS 

Term of Reference: review progress in studies of seabirds in relation to marine wind farms. 


During the last two years, the possible impacts of at-sea wind farms have been described in two relatively long sections 

by the ICES WGSE (ICES, 2002; 2003). This year, we concentrate our efforts to report on progress obtained during the 

last 12 months. The sub-sections of this report are structured accordingly. We furthermore expect major progress from 

on-going studies to be reported at a workshop to be held in Billund, Denmark, on 21–22 September 2004, organised by 

Elsam Engineering, Energi E2, the Danish Forest and Nature Agency, and the Danish Energy Authority. Full details of 

the event can be found on the web-site http://www.hornsrev.dk/Engelsk/nyheder/conference_hornsrev.pdf. 

3.2 Recent advances in measuring impacts of existing wind farms on seabird 

There have been investigations into effects of wind farms on seabirds in the Danish wind farms at Horns Rev (North 

Sea) and Nysted (Baltic Sea) but up to date information could not be obtained to be included in this report. 

3.3 Recent progress in understanding bird migration at sea 

Information on the nature of bird migration at sea provides an important basis to predict collision risks and avoidance of 

sea areas where wind farms are installed. Consequently in advance of the expected high numbers of wind farms built 

offshore the German coast, progress had been made in order to increase our knowledge of bird movements at sea in 

areas where wind farms are planned. 

Detailed results of recent investigations have been reviewed in our last report (ICES, 2003). Within the frame of 

ecological research on windfarms in Germany (project “BEOFINO”, 2002–2004), the Institute of Avian Research, 

Wilhelmshaven and Helgoland, is performing the sub-project “Effects on bird migration” (Hüppop and Exo, 2004). In 

summer 2003 the research platform FINO-1 was erected 45 km north of Borkum. It is equipped with both a vertically 

and a horizontally rotating radar, a remotely operated video-camera, a directional microphone (for recording bird calls), 

an ultrasound detector (for recording bat sounds) and an thermal imaging camera to get information on species 

composition and flock sizes during night. Especially the vertical radar collected continuous data of the migrating 

activities. Additionally, at several sites on the coast and on Helgoland observations of the visible bird migration are 

made. 

By combination of these methods information is expected on migration direction and intensity in its seasonal, diurnal, 

weather- and visibility affected and species-specific variability. Additionally, at several coastal sites the observations of 

the visible bird migrations are continued to get information on phenology and spatial patterns of bird migration on the 

species level. 

First data collected from the vertically rotating radar have been evaluated and show the flight altitudes corresponding to 

those reported by Hüppop et al., 2002 (see ICES, 2003). At least one third of the individuals was migrating below 

200 m, in the critical height range of the wind farms. Most radar signals were detected at night, when birds also flew 

higher. The continuous operation of the vertical radar allowed some first quantification of reverse migration for the 

southeastern North Sea, i.e., the amount of birds passing the area presumably more than once. From mid October until 

the end of the year (covering almost exclusively short and median distance migrants) roughly 30% of all echoes 

recorded during darkness belonged to birds migrating against the general migration direction. Reverse migration was 

mainly observed after pronounced increases in ambient temperature. 

10 


During autumn migration surprisingly high numbers of bird strikes were recorded on FINO 1, almost exclusively 

songbirds (mainly thrushes) with good body condition. 

Following completion of the Environmental Impact Assessments of the offshore windfarms at Horns Rev and Rødsand 

in Denmark, a programme of avian investigations was established. These included detailed studies during the preconstruction 

(ca. three years), construction (ca. ½ year) and post-construction phase (2–3 years). The objective was to 

gather base-line data pre-construction on feeding distributions, migration trajectories, flight heights and relative volume 

of key species in time and space, taking into account annual variation in wind direction and strength, visibility, 

disturbance (construction, operation and maintenance) and time of day. Reports on many of these base-line studies have 

already been published (see the overview of reports available at 

http://www.dmu.dk/1_Om_DMU/2_afdelinger/3_vibi/publikationer1.asp). Now that construction of both sites have 

been completed, monitoring of changes in bird migration patterns as a result of the presence of the windfarms is 

currently underway and these observations will be reported in due course when the data have been fully analysed. 

3.4 Recent progress in site-selection procedures 

One of the problems concerning marine wind farms is the issue of selecting suitable sites. Without fundamental 

information on the effects of wind farms on seabirds – due to a lack of truly marine wind farms until very recently – one 

approach is to select areas that are least sensitive. Garthe and Hüppop (2004) developed a "wind farm sensitivity index" 

(WSI) for seabirds. They chose nine factors, derived from species’ attributes, to be included in the WSI: flight 

manoeuvrability, flight altitude, percentage of time flying, nocturnal flight activity, sensitivity towards disturbance by 

ship and helicopter traffic, flexibility in habitat use, biogeographic population size, adult survival rate, and European 

threat and Conservation status. Each factor was scored on a five-point-scale from one (low vulnerability of seabirds) to 

five (high vulnerability of seabirds). Five of these factors could be dealt with by real data but four could only be 

assessed by subjective considerations based on at-sea experience; in the latter cases, experts independently modulated 

suggestions of the authors. 

Species differed strongly in sensitivity index (Table 3.4.1). Black-throated diver and red-throated diver ranked highest 

(= most sensitive), followed by velvet scoter, sandwich tern and great cormorant. Lowest values were calculated for 

black-legged kittiwake, black-headed gull and northern fulmar. Derived from the frequency distribution of the WSI 

applied to the southeastern North Sea, Garthe and Hüppop (2004) suggest a “level of concern” and a “level of major 

concern” which are visualised spatially and could act as a basis for the selection of marine wind farm locations (Figure 

3.4.1). The wind farm sensitivity index might be useful in Strategic Environmental Assessments. Results from smallscale 

Environmental Impact Assessments about wind installations should be set into a more global perspective provided 

for example by large mapping projects and detailed behavioural studies. 

3.5 Progress and future plans of monitoring possible impacts of wind farms on seabirds 

ICES (2002) highlights the need for dedicated research in order to assess the potential impact of the construction of an 

offshore wind farm and to understand how such a construction is likely to affect the birds associated with a site, 

dedicated research is required. The coupling of bird census data with geographical, hydrographic and biological 

measurements is essential to begin to understand how an offshore construction such as a wind farm is likely to affect an 

area and how the seabirds associated with a site are most likely to respond. Natural variability issues have also to be 

addressed and existing census techniques have been evaluated for their potential to provide data that can be used to 

describe habitat characteristics and area usage by seabirds. In 2002, the Crown Estate (UK) initiated a Steering <strong>Group</strong> 

called COWRIE (Collaborative Offshore Wind Research into the Environment) to deal with the environmental 

implications of offshore wind farms. 

One of the research contracts awarded was to undertake a comparison of ship and aerial sampling methods for the 

mapping of the distribution and abundance of marine birds, and to assess their applicability to offshore windfarm EIAs. 

The contract was awarded to NIOZ (Royal Netherlands Institute for Sea Research), funding a research consortium 

consisting of the Danish National Environmental Research Institute, the Wildfowl and Wetlands Trust and the Research 

Unit for Wildlife Population Assessment, St. Andrews University. The consortium undertook a major review of 

techniques and recommended the most appropriate methods to be adopted in UK waters in relation to offshore 

windfarm EIAs (Camphuysen et al., in prep.). A workshop gathering interested parties and experts was held in 

Aberdeen in November 2003 to discuss the pre–workshop report, the final report of which will be posted on the 

COWRIE web site when finalised. Background information can be found on the COWRIE web site at 

http://www.thecrownestate.co.uk/15_our_portfolio_04_02_16/33_energy_and_telecoms_04_02_09/34_wind_farms_04 

_02_07/35_cowrie_04_02_07/35_cowrie_marine_bird_survey_methodology_04_02_07.htm 


The two observation tools discussed by Camphuysen et al. (in prep.) in this study, aerial and ship-based surveys, 

potentially provide similar data for as long as basic seabird counts are concerned (accurate numbers, accurate maps). 

Census techniques are similar (distance techniques using parallel bands of known width), but the level of detail on 

species level is considerably less during aerial surveys. Aerial surveys are quick and relatively cheap, whereas shipsurveys 

are more time-consuming. Data obtained during aerial surveys may be combined with environmental 

parameters in a correlative approach, whereas the advantage of a ship is that such parameters can often be collected 

simultaneously. The slower approach with vessels allows detailed observations on seabird behaviour (habitat utilisation, 

feeding conditions) and diurnal/tidal fluctuations in seabird abundance and distribution (Camphuysen et al. in prep.). 

The existing Danish wind farms in Horns Rev (North Sea) and Nysted ( = Rødsand; Baltic Sea) will exhibit substantial 

demonstration effects for offshore wind farms in general. Both wind farms may be considered being the most 

representative for the seas they are located at; Horns Rev is situated off the west coast of Denmark in a marine habitat, 

Nysted is placed at a shallow inshore site in the southwestern Baltic Sea. Elsam Engineering plans to continue with bird 

surveys for at least two years after the commissioning of the two wind farms. For Nysted, this applies to aerial counts as 

well as further developments of methods for study of migrations. For Horns Rev it is planned to continue with aerial 

counts for two years and migration observations for at least one year, according to the results achieved. For both sites, 

efforts are being made to develop collision detection methods, but these are not yet effective as a monitoring tool. 


Camphuysen, C.J., Fox, A.D., Leopold, M.F., and Petersen, I.K. in prep. Towards standardised seabirds at sea census 

techniques in connection with environmental impact assessments for offshore wind farms in the U.K. COWRIE- 

BAM-02–2002. 

Garthe, S., and Hüppop, O. 2004. Scaling possible adverse effects of marine wind farms on seabirds: developing and 

applying a vulnerability index. Journal of Applied Ecology 41: in press. 

Hüppop, O., Exo, K.-M., and Garthe, S. 2002. Empfehlungen für projektbezogene Untersuchungen möglicher bau- und 

betriebsbedingter Auswirkungen von Offshore-Windenergieanlagen auf Vögel. Berichte zum Vogelschutz. 39: 

77–94. 

Hüppop, O., and Exo, M. 2004. Offshore-Windenergieanlagen und Vögel in Nord- und Ostsee. Jahresbericht des 

Instituts für Vogelforschung, 6: 19–20. 



12 


Table 3.4.1. Score of the nine vulnerability factors and the resulting species sensitivity index (SSI) values for each of 

the 26 seabird species. For details see Garthe and Hüppop (2004). 

Bird species Flight 

manoeuvra- 

bility 

Flight 

altitude 

Percentage 

flying 

Nocturnal 

flight 

activity 

Disturbance 

by ship and 

helicopter 

traffic 

Habitat use 

flexibility 

Biogeogr. 

population 

size 

Adult 

survival 

rate 

European SSI 

threat and 

conservation 

status 

Black-throated diver 5 2 3 1 4 4 4 3 5 44,0 

Red-throated diver 5 2 2 1 4 4 5 3 5 43,3 

Velvet scoter 3 1 2 3 5 4 3 2 3 27,0 

Sandwich tern 1 3 5 1 2 3 4 4 4 25,0 

Great cormorant 4 1 4 1 4 3 4 3 1 23,3 

Common eider 4 1 2 3 3 4 2 4 1 20,4 

Great crested grebe 4 2 3 2 3 4 4 1 1 19,3 

Red-necked grebe 4 2 1 1 3 5 5 1 1 18,7 

Great black-backed gull 2 3 2 3 2 2 4 5 2 18,3 

Black tern 1 1 4 1 2 3 4 4 4 17,5 

Common scoter 3 1 2 3 5 4 2 2 1 16,9 

Northern gannet 3 3 3 2 2 1 4 5 3 16,5 

Razorbill 4 1 1 1 3 3 2 5 2 15,8 

Atlantic puffin 3 1 1 1 2 3 2 5 5 15,0 

Common tern 1 2 5 1 2 3 3 4 1 15,0 

Lesser black-backed gull 1 4 2 3 2 1 4 5 2 13,8 

Arctic tern 1 1 5 1 2 3 3 4 1 13,3 

Little gull 1 1 3 2 1 3 5 2 4 12,8 

Great skua 1 3 4 1 1 2 5 4 2 12,4 

Common guillemot 4 1 1 2 3 3 1 4 1 12,0 

Mew gull 1 3 2 3 2 2 2 2 4 12,0 

Herring gull 2 4 2 3 2 1 2 5 1 11,0 

Arctic skua 1 3 5 1 1 2 4 3 1 10,0 

Black-headed gull 1 5 1 2 2 2 1 3 1 7,5 

Black-legged kittiwake 1 2 3 3 2 2 1 3 1 7,5 

Northern fulmar 3 1 2 4 1 1 1 5 1 5,8 


Figure 3.4.1. Areas in the German sector of the North Sea where wind energy utilization is considered to be of “less concern”, 

“concern” or “major concern” to seabirds. Areas not studied in at least one of the four seasons are left blank. From Garthe and 

Hüppop (2004). 

4 CLIMATIC EFFECTS ON SEABIRD POPULATION PERFORMANCE 

Term of reference: review relationships between seabirds and oceanographic features, with particular reference to 

effects of climate change. 


WGSE in 2003 (ICES, 2003) proposed to review relationships between seabirds and oceanographic features, with 

particular reference to effects of climate change. In 2004, WGSE was unable to complete this term of reference, but a 

brief review of the effects of climate on seabird population performance was produced. This review collates background 

information that would be useful for future attempts to predict the effects of climate change. Seabirds are obviously 

affected by numerous natural and anthropogenic factors, such as fisheries, introduced predators, etc., but this review 

deals only with effects of climate. The conclusions reached here on climatic effects should not be taken to imply that 

other factors are not important in determining seabird population growth rate. 

The subject of how various aspects of seabird population performance are affected by climate or oceanography, and 

how populations may react to current and future climate change, has recently attracted much interest. In order to predict 

the effects of climate change it is necessary to understand current relationships between climate and seabird 

performance, and this section intends to provide a preliminary, incomplete review of the recent literature in this field. 

Schreiber (2002) recently reviewed how seabirds are affected by the ENSO (El Niño Southern Oscillation), and because 

this large-scale climatic event mainly affects the Pacific Ocean as well as tropical regions, but has little effect in the 

north-eastern Atlantic, it will not be considered in detail here. Another limitation of this review is that effects on the atsea 

or breeding distribution of seabirds are not covered. Durant et al. (in press) recently provided a more detailed review 

of relationships between seabirds and climate fluctuations in the North Atlantic. 

14 


It might be considered useful to distinguish between effects of climate and (usually severe) weather on seabirds. 

However, such a distinction is to some extent artificial, as climate determines the frequency of severe weather events. 

This distinction is therefore not adopted here. 

Climate can affect seabirds both directly and indirectly. Direct effects of temperature are unlikely to be important for 

seabirds in most cases, although chicks of some species may be vulnerable to overheating and dehydration in warm 

summers, and such effects may partly determine the limits of a species' breeding range (Oswald et al. 2004). Strong 

winds are probably more important for many species, mainly because they cause increased turbulence and thus make 

prey capture more difficult. Increased flight costs may also be important for some species. In polar and cold temperate 

regions, strong onshore winds may also cause hypothermia of chicks, especially if heavy rain occurs at the same time. 

The same may occur in winter for adult cormorants (Phalacrocoracidae), which do not have completely waterproof 

plumage and must dry out on land. Flooding caused by heavy rain sometimes causes egg or chick losses for burrownesting 

seabirds, snow cover may prevent access to nest sites or burrows at high latitudes, and ice cover may allow 

predators access to otherwise “safe” islands. On the whole, however, indirect effects of climate are likely to be more 

important than direct ones. These indirect effects often work through the food supply to seabirds. Many marine 

foodwebrs are very sensitive to small changes in sea temperature, and even changes as small as 0.5–1° C in annual 

means, which are probably too small to affect birds directly, can cause fundamental shifts in the availability of main 

seabird prey species. For example, recruitment of lesser sandeels in the North Sea has been found to be low at high 

winter sea temperatures (Arnott and Ruxton, 2002). Correlative studies of relationships between climate and seabird 

performance generally do not discriminate between indirect and direct effects, and elucidating the mechanisms behind 

observed relationships will often require further studies. Because physiological requirements of organisms at different 

trophic levels can be very different, indirect effects can sometimes create counter-intuitive correlations, such as high sea 

temperatures being unfavourable for polar or temperate seabirds (see examples below). 

What we want to draw conclusions about is whether climate affects, or is likely in the future to affect, the population 

size of seabirds. However, because population size usually changes rather slowly and is affected by a multitude of 

processes, it is generally more instructive to search for causal correlations between, e.g., climate and individual 

components of population performance, which together determine population size. Seabirds are long-lived organisms, 

and as a consequence their population growth rate is more sensitive to changes in the survival probability of adult 

breeders than in other parameters (Croxall and Rothery, 1991). Nevertheless, successful reproduction and recruitment 

are obviously also necessary to maintain a population, and collecting and analysing data on reproduction is often more 

simple than on survival. Phenology, or the timing of reproduction, is not in itself an aspect of population performance, 

but given the often close relationship with breeding success and the ease with which data can be collected for many 

species, it can nevertheless be useful to test for how phenology is related to climate. Once the relevant data have been 

collected, it is reasonably simple to test for correlations with aspects of climate thought to be important (for 

considerations about how to select appropriate climate variables, see Section 4.3 below). Most studies have focussed on 

the relationship between climate and timing of breeding or breeding success, presumably because more data are 

available on these parameters and analyses are simpler. However, a few studies have started looking at the complex, but 

potentially very important, relations between climate and adult or juvenile survival. 

4.2 Relations between seabird population performance and climate 

4.2.1 Phenology 

Several studies have found clear relationships between inter-annual variation in the timing of breeding in seabirds and 

some measure of climate. In most cases, breeding was earlier following milder winter conditions, either locally or 

regionally. The classical study of Aebischer et al. (1990) showed that timing of egg-laying in black-legged kittiwakes 

was related to the frequency of westerly weather on an annual basis. Gjerdrum et al. (2003) found that breeding in 

tufted puffins was earlier when local sea surface temperature (SST) during chick-rearing was high, although it is unclear 

how birds were assumed to adjust their phenology to achieve this. In Atlantic puffins, Diamond and Devlin (2003) 

interpreted the earlier breeding in Maine, USA than in N Norway as a consequence of higher May SST in Maine, with 

the slope of the relationship being similar to the one found in N Norway by Barrett (2001). Frederiksen et al. (in press) 

found that breeding of three seabird species was earlier following mild winters, measured as local late winter SST or the 

North Atlantic Oscillation (NAO) winter index. In Atlantic puffins in Norway, breeding was also earlier following mild 

winters (i.e., when the NAO index was high), except during 1987–1994 (Durant et al., 2004). There are some 

indications that breeding phenology can be influenced by very large-scale processes; in roseate terns breeding in the 

tropical Indian Ocean, Ramos et al. (2002) found that timing of breeding was correlated with an index of ENSO, even 

though this index was based on measurements from the Pacific Ocean. Long-term trends in phenology seem to vary 

between study sites, with breeding getting progressively earlier in tufted puffins in the Pacific (Gjerdrum et al., 2003), 

but later in North Sea black-legged kittiwakes and common guillemots (Aebischer et al. 1990; Frederiksen et al., in 

press). 


4.2.2 Breeding success 

It is a general finding in birds that early breeding is advantageous, so it is hardly surprising that several of the abovementioned 

studies found that breeding success was related to the same climatic factors as phenology (Aebischer et al., 

1990; Ramos et al., 2002). Durant et al. (2003) found that breeding success in Atlantic puffins was related to SST in a 

sigmoid fashion, while NAO had no effect. However, in tufted puffins there was a curvilinear relationship, with 

breeding success being low at both the highest and lowest values of SST (Gjerdrum et al., 2003), and Diamond and 

Devlin (2003) found no relationship between SST and breeding success. Despite low chick growth rates, horned puffin 

breeding success in Alaska was high during year of ENSO-related low food availability (Harding et al., 2003). Inchausti 

et al. (2003) found varying relationships between SST and breeding success for eight seabird species at the sub- 

Antarctic Kerguelen and Crozet Islands: species foraging north of the Polar Front (wandering albatross, sooty albatross) 

had high breeding success when SST was high, whereas those foraging south of the Polar Front (light-mantled sooty 

albatross, blue petrel, thin-billed prion, white-headed petrel) showed the reverse relationship, and breeding success of 

species foraging close to the islands (black-browed albatross, grey petrel) was independent of SST (Inchausti et al., 

2003). In southern fulmars, breeding success was low when sea ice concentration around the colony was low, as was 

recruitment of new adults to the breeding population (Jenouvrier et al., 2003). In the closely related northern fulmar, 

Thompson and Ollason (2001) found that breeding success was weakly negatively correlated with the NAO index, 

indicating low breeding success following mild winters; they also found that the proportion of a birth cohort recruiting 

to the breeding population depended on a global measure of summer temperatures in the northern hemisphere. 

As an example of a direct effect, breeding success of Manx shearwaters on Rum was strongly affected by rainfall during 

the breeding season, and was particularly low when heavy rainfall was frequent (Thompson and Furness, 1991). 

4.2.3 Survival 

Relating survival to climatic or oceanographic variables has proved to be considerably more challenging, or at least, 

only few published studies to date have shown such correlations. In blue petrels in the southern Indian Ocean, winter 

survival was strongly related to lagged variation in the Southern Oscillation Index, with survival being low during years 

when SST was higher than normal (Barbraud and Weimerskirch, 2003). Climate interacted with population size so that 

when a series of warm years occurred when population size was high, survival became very low and the population 

crashed (Barbraud and Weimerskirch, 2003). In high-Antarctic southern fulmars, Jenouvrier et al. (2003) also found a 

negative effect of winter SST on adult survival and attributed this to climatic effects on food availability. Jones et al. 

(2002) found that survival of least auklets in the Pacific was related to an index of winter ocean climate throughout the 

species’ range. 

4.3 Scale issues 

It seems reasonable to assume that the geographical scale at which seabirds are affected most directly by climate, and 

thus where the strongest correlations are found, should be the one at which the birds interact with their environment. 

Using climate variables measured at the “wrong” scale, or in the wrong place, is likely to lead to underestimation of the 

strength of interactions between seabirds and climatic factors. Nevertheless, very few studies have explicitly considered 

the issue of scale. Jones et al. (2002) found that adult survival of least auklets was correlated with climatic fluctuations 

at the meso-scale, but not with a basin-wide index. Frederiksen et al. (in press) found that correlations between 

phenology and climate in three North Sea seabirds depended on the species-specific non-breeding distribution. In two 

dispersive species, common guillemot and black-legged kittiwake, phenology was related to the NAO index, whereas a 

resident species, the European shag, bred earlier when local late-winter SST was high. 

In this context, it is important to consider carefully which climate variables one tries to relate seabird performance to. 

Using “standard” indices of large-scale processes, such as NAO and ENSO, may be tempting, because they are easily 

available and seem to allow more general conclusions to be drawn. However, birds are more likely to react to conditions 

at the time and place they actually encounter them, and the strongest correlations should therefore be expected at this 

scale. Because climate variables at different scales are often intercorrelated, using the “wrong” variables may lead to 

partially misleading conclusions about causal relationships. However, in pelagic seabirds, the areas used outside the 

breeding season are often huge and not known in detail, and using large-scale indices is probably the best available 

approach to correlating, e.g., overwinter survival of these species with climate. 

4.4 Conclusions 

The field of seabird-climate interactions is a very dynamic one, and this short review does not claim to provide a full 

overview of all the published research; particularly, there is a bias towards very recent papers. However, it is clear that 

an increasing number of researchers are both looking for and finding correlations between various aspects of seabird 

16 


performance and climatic variables, and it is likely that at least some failures to find such correlations are related to the 

use of inappropriate measures of climatic variation. Most of the authors of the studies reviewed here either explicitly or 

implicitly interpret climate effects on seabirds as being indirect, i.e., mainly working through effects on food 

availability or quality. If seabird breeding success and survival are indeed affected by climate, as much of the evidence 

reviewed here seems to suggest, we should expect current and future climate change to have substantial effects on 

population size, as well as on breeding and wintering distribution. In the North Sea, there is strong evidence for a 

“regime shift” taking place in the late 1980s, when increasing SST led to fundamental changes in plankton 

communities. Such effects are likely to have been propagated through the foodwebr to top predators such as seabirds, 

and we should expect to find changes in population parameters taking place around that time, perhaps with a delay of 

some years. Whether such changes are strong enough to cause sustained declines or increases of seabirds in the North 

Sea and adjoining areas remains to be seen. 

4.5 Summary 

• Climate is one of many factors affecting seabird population performance; others such as fisheries and introduced 

predators may be more or less important depending on the context; 

• Effects may be either direct, physiological impacts on birds, or indirect effects often through food supply; 

• Seabird population size and growth rate are determined by the balance of reproduction and survival; reproductive 

success is often strongly influenced by timing of breeding (phenology); 

• Predicting the effects of climate change on seabird populations requires an understanding of how current climate 

affects population performance; 

• Most studies looking for climatic effects on seabird populations have found such effects; 

• Studies looking for relationships between climate and population performance often cannot distinguish between 

direct and indirect effects; 

• Many studies have found correlations between phenology and climate, most often with breeding being earlier 

following mild winters; 

• Relationships between breeding success and climate are variable, e.g., different studies have found positive, 

negative and no effects of sea temperature on success; 

• There are few studies of effects of climate on survival; some of these have found survival to be low in warm 

winters; 

• Climatic variables should be measured at the most appropriate scale, i.e., one corresponding to how seabirds 

perceive and use their environment. 


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and weather. Nature, 347: 753–755. 

Arnott, S.A., and Ruxton, G.D. 2002. Sandeel recruitment in the North Sea: demographic, climatic and trophic effects. 

Marine Ecology Progress Series, 238: 199–210. 

Barbraud, C. and Weimerskirch, H. 2003. Climate and density shape population dynamics of a marine top predator. 

Proceedings of the Royal Society of London Series B, 270: 2111–2116. 

Barrett, R.T. 2001. The breeding demography and egg size of North Norwegian Atlantic puffins Fratercula arctica and 

razorbills Alca torda during twenty years of climatic variability. Atlantic Seabirds, 3: 97–112. 

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conservation. In Bird population studies. Relevance to conservation and management. Ed. by Perrins, C.M., 

Lebreton, J.-D. and Hirons, G.J.M. Oxford University Press, Oxford: 272–296. 

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on Machias Seal Island. Environmental Monitoring and Assessment, 88: 153–175. 

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puffin as an example. Proceedings of the Royal Society of London Series B, 270: 1461–1466. 

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puffin population. Ecology Letters, 7: 388-394. 

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Harding, A.M.A., Piatt, J.F. and Hamer, K.C. 2003. Breeding ecology of horned puffins (Fratercula corniculata) in 

Alaska: annual variation and effects of El Niño. Canadian Journal of Zoology, 81: 1004–1013. 


Inchausti, P., Guinet, C., Koudil, M., Durbec, J.-P., Barbraud, C., Weimerskirch, H., Cherel, Y., and Jouventin, P. 2003. 

Inter-annual variability in the breeding performance of seabirds in relation to oceanographic anomalies that affect 

the Crozet and the Kerguelen sectors of the Southern Ocean. Journal of Avian Biology, 34: 170–176. 

Jenouvrier, S., Barbraud, C., and Weimerskirch, H. 2003. Effects of climate variability on the temporal population 

dynamics of southern fulmars. Journal of Animal Ecology, 72: 576–587. 

Jones, I.L., Hunter, F.M., and Robertson, G.J. 2002. Annual adult survival of least auklets (Aves, Alcidae) varies with 

large scale climatic conditions in the North Pacific Ocean. Oecologia, 133: 38–44. 

Oswald, S., Huntley, B., and Hamer, K.C. 2004. Exploring the impact of climate on the distribution of great skuas 

breeding in the UK. Abstract, 8 th International Seabird <strong>Group</strong> Conference, Aberdeen, 2–4 April 2004. 

Ramos, J.A., Maul, A.M., Ayrton, V., Bullock, I., Hunter, J., Bowler, J., Castle, G., Mileto, R., and Pacheco, C. 2002. 

Influence of local and large-scale weather events and timing of breeding on tropical roseate tern reproductive 

parameters. Marine Ecology Progress Series, 243: 271–279. 

Schreiber, E.A. 2002. Climate and weather effects on seabirds. In Biology of marine birds. Ed. By Schreiber, E.A. and 

Burger, J. CRC Press, Boca Raton, Florida: 179–216. 

Thompson, K.R., and Furness, R.W. 1991. The influence of rainfall and nest site quality on the population dynamics of 

the Manx shearwater Puffinus puffinus on Rhum. Journal of Zoology, London, 225: 427–437. 

Thompson, P.M., and Ollason, J.C. 2001. Lagged effects of ocean climate change on fulmar population dynamics. 

Nature 413: 417–420. 

5 A COMPARISON OF SEABIRD COMMUNITIES AND PREY CONSUMPTION IN THE EAST 

AND WEST NORTH ATLANTIC 

Term of reference: complete the work carried out in 2003 to compare seabird communities and prey consumption 

between the east and west North Atlantic. 


The WGSE 2002 meeting completed a summary of the breeding seabird numbers by species, total seabird energy 

requirements and approximate food consumption equivalents, in all ICES areas (approximately described as the ‘east 

North Atlantic’). Given the pronounced differences in seabird community composition and species abundances, and in 

fish stocks and fisheries, between the west and east North Atlantic, WGSE 2003 thought that it might be instructive to 

compare and contrast the patterns of seabird community composition and energy requirements between ICES and 

NAFO areas (approximately ‘east’ and ‘west’ North Atlantic), in relation to broad differences in the histories of fish 

stocks and fisheries in these areas. We here complete the comparison of the seabird communities and their consumption 

on both sides of the North Atlantic. The relationships to fish stocks and fisheries need to be followed up. 

5.1.1 Population estimates 

The estimates of numbers presented here are primarily of birds nesting on the coast and feeding wholly or partially at 

sea, but the numbers of gulls may also include a small fraction of non-marine, inland-breeding segments of the 

populations. They are based on the input by members of the WGSE who were asked to provide the best estimates of the 

numbers of seabirds currently breeding in their respective countries. Some of these are now several years old, and 

predate recent national updates. The background data are presented in earlier WGSE reports. Although a number of 

known caveats have been considered here, discrepancies from an updated analysis of the database would probably be 

small. 

Data from the huge colonies of, e.g., northern fulmars, guillemots, little auks and Atlantic puffins in Canada, Greenland, 

Iceland, Svalbard and the Barents Sea should not be considered as definitive. Some are quoted as “guesstimates” and 

await more detailed censuses. Furthermore, while data for many species were presented to the nearest hundred, ten or 

even individual pairs, others were presented as ranges, some as large as 100,000–1,000,000 pairs. For the sake of 

simplicity, all such ranges were tabulated as mid-points between the two extremes. 

18 


Calculation of numbers of birds in the non-breeding part of population 

Whereas the numbers of breeding adults were generally known or estimated based on field data, numbers 

of nestlings and pre-breeders were estimated empirically using a classification of whether the species lay 

single or multiple-egg clutches, and calculations based numbers of breeding pairs (bp) plus numbers of 

immatures (calculated for single-egg species = (bp x 0.7) + (bp x 0.7); multi-egg species = (bp x 0.6) + 

(bp x 1). These estimates assumed that numbers of non-breeding birds (immatures and deferred breeders) 

were equivalent to 35% or 30% of the breeding population and that the fledging success of single-egg and 

multi-egg clutch species was 0.7 and 1.0 chicks/pair, respectively (Cairns et al. 1991). 

These calculations are very crude, and do not take into consideration population trends or life histories of 

the different species. In the calculations of seasonal changes in total numbers (and hence biomass and 

food consumption) of birds in a population (i.e., breeding pairs + immatures), the resulting figures have 

been used for the whole year, and no correction has been made to account for the fact that reproduction 

takes place during summer and mortality takes place during the year. As a result, the autumn population 

sizes will be underestimated and spring population sizes will be overestimated. For single-egg species 

these under- and overestimates will each be about 10%, and for multi-egg species about 20%. 

Of the many species of divers, ducks and geese, some of which may be equally defined as seabirds as some of the gulls, 

only the eider duck is included as a breeding species due to its total dependence on the sea for food, and to their very 

large numbers in some areas. Other waterfowl which breed inland but feed in the sea in large numbers at other times of 

the year are, however, considered where relevant. Data sources were Anker-Nilssen et al. (2000), Delany and Scott 

(2002), Durinck et al. (1994), Gilchrist (pers. com.), Gilliland (pers.com.), Hagemeijer and Blair (1997), Kershaw and 

Cranswick (2003) Merkel et al. (2002), Mosbech and Boertmann (1999), Nygård et al. (1988) and Savard (pers.com.). 

At the other end of the scale, some rare species whose total numbers do not total more than a few hundred (e.g., gullbilled 

tern, Sabine’s gull) are not included in the calculations. 

In addition to birds that breed in specific ICES and NAFO areas, there are, at times, large numbers that breed outside 

the areas but are present at certain times of the year as migratory or wintering populations. Furthermore birds breeding 

within the ICES and NAFO areas may also move to other areas during migration or to spend the winter. We have 

attempted to account for these movements by estimating the occurrence by month for each species in each subarea and 

making rough estimates of the numbers of individuals present. The resulting numbers were summed by season by 

dividing the year into four quarters. The summer season in ICES and NAFO was chosen separately so the summer 

included all the species breeding seasons as far as possible. The resulting seasons differed by two month between ICES 

and NAFO because of the climatic and hence phenological diffences. In the ICES region winter was defined as Nov- 

Jan, spring Feb-Apr, summer May-July and autumn Aug-Oct. In NAFO, winter was defined as Jan-Mar, spring Apr- 

June, summer July-Sep and autumn Oct-Dec. Migration tendency and routes of the various species in ICES areas were 

taken from Anker-Nilssen et al. (2000), Bakken et al. (2003), Lyngs (2003), Petersen (1982), and Wernham et al. 

(2002). These estimates were limited to the commonest species breeding within a given area, i.e., species whose 

biomass constituted > 2% of the original estimate of the total biomass of seabirds breeding in that area (based on Tables 

2.1–2.5, ICES 2002). For NAFO, the seasonal movements of seabirds are based mainly on Diamond et al. (1993), 

Huettmann (pers. com.) and Lyngs (2003). 

5.1.2 Consumption 

The annual consumption by seabirds in a given area was estimated using calculated species-specific energy demands, 

numbers of individuals of that species within that area, number of days present and a mean energy density of food set at 

5.5 kJ/g (see box below). Like the calculations of bird numbers, this was modelled separately for the four seasons and 

summed for the year. 

Daily and hence seasonal energy demands were calculated using the methods described in Barrett et al. (2002) – see 

box below. 


Energy expenditure 

Basal metabolic rates were estimated using Gabrielsen’s (1994) allometric equations for Procellariiformes 

(BMR=377.9m 0.705 , m in kg) and for seabirds using flapping flight in cold waters (the remaining species 

BMR=455.1 m 0.746 , m in kg). Field metabolic rates of breeding birds within the breeding season were 

estimated for Procellariiformes using the allometric equation, FMR=18.4m 0.599 (m in g) from Nagy et al. 

(1999) and for the remaining species using the allometric equation for seabirds using flapping flight in cold 

waters (FMR=11.455m 0.727 ), m in g; Birt-Friesen et al. 1989). For seaducks, the equations for ‘all seabirds’ 

were used. 

For the non-breeding part of the breeding population (chicks, immatures and deferred breeders) during the 

breeding season and for all birds outside the breeding season, FMR was set as 2.5 x BMR (Gales and Green 

1990, Gabrielsen G.W. pers. comm.). The energy expenditure for breeding seabirds was thus calculated 

separately within the breeding season (using the largest FMR values) and outside the breeding season, and 

for non-breeding birds throughout the period they occupied the area in question using the lower FMR 

values. These were then summed to give the overall energy expenditure of a given species within a given 

season. 

The length of the breeding season was set as the incubation period + fledging period (in days, as given in 

Cramp and Simmons, 1977, 1983; Cramp, 1985) + 20 days (see Appendix 5.1 for an example from ICES 

Va, Iceland). 

In the model used in 2002 (ICES 2002), a mean energy density of 6.0 kJ/g (wet mass) and a digestion efficiency of 75% 

were used in the calculations of food consumption. When comparing the results with those using a model in which 

species-specific diet composition (fatty fish, lean fish or invertebrates) and digestion efficiency is entered (e.g., Barrett 

et al., 2002), it becomes evident that a mean energy density of 6.0 kJ/g is too high. A value of 5.5 kJ/g results in a closer 

harmonization of the final consumption figures in the two models. Because diet composition is largely unknown in 

many species in most of the ICES and NAFO areas, an overall energy density of 5.5 kJ/g and a digestion efficiency of 

75% were thus used in the present model. 

5.2 Results 

5.2.1 Breeding populations (adapted from ICES 2003) 

Approximately 67 million pairs of seabirds breed along the coasts of the NAFO and ICES areas of the North Atlantic. 

Note that this does not include the ca. 3.5–4 million pairs (mostly Brünnich’s guillemots) that breed in the eastern 

Canadian Arctic, west of NAFO 0. 

Of this 70+ million pairs, approx. 40 million breed in the NAFO subareas compared to approx. 27 million pairs in the 

ICES subareas (ICES 2002, 2003). However, the total biomass of seabirds that breed in the western North Atlantic (ca. 

30,000 t) is approximately half that of the eastern North Atlantic (ca. 60,000 t) (ICES 2002, 2003). This anomaly is due 

to the huge numbers of the small-sized little auks and Leach’s storm-petrels which dominate the breeding communities 

in NAFO 1 and NAFO 2 and 3 respectively. 

Auks dominate the seabirds breeding on both sides of the Atlantic (Tables 5.1 and 5.2). In Western Greenland (NAFO 

1), 33 million pairs of little auks comprise ca. 80% of total breeding population and ca. 65% of total biomass of all 

seabirds in the NAFO subareas. In the ICES subareas, puffins, little auks, common and Brünnich’s guillemots make up 

22%, 18%, 9% and 9% (by number) of the total populations. In biomass, the contribution by little auks falls to 5% while 

that of the larger species is between 13–16%. As in the western Atlantic, the majority (> 70%) of the auks in the ICES 

areas breed in the northernmost subareas, north of the 5° C July isotherm. 

The procellariiformes are also very unevenly distributed with a dominance (60–65% of ICES procellariiformes by no. 

and biomass) in the southern part of the ICES subareas (VIIIa-c, IXa and X – mostly Cory’s shearwaters) and 80% of 

NAFO procellariiformes by number but only 20% by biomass in Newfoundland and Labrador (NAFO 2 and 3). The 

relatively minor biomass in NAFO 2 and 3 is due to the small size of the Leach’s storm-petrel (it weighs ca. 50 g) that 

dominates the NAFO breeding population by number. Northern fulmars and Manx shearwaters also made up large 

proportions of numbers (41%) and biomass (30%) of the seabirds breeding in the Faeroes and the western borders of the 

UK. Fulmars are also very numerous on Iceland (ICES Va, estimated to be 1.5 mill. pairs). 

20 


Table 5.1. Relative species composition of seabirds breeding in the ICES subareas as % of total number and total biomass of 

breeding pairs for each subarea (from ICES, 2003). 

Species 

composition 

% by number Barents and 

Norwegian Seas 

I,IIa,IIb Va,XIVa,b IVa-c,VIId,e IIIa-d Vb,VIa,b,f,g,j VIIIa-c, 

IXa,X 

E. Greenland 

and Iceland 

North Sea and 

English 

Channel 

Baltic Sea, 

Skagerrak, and 

Kattegat 

Faeroes and 

western UK 

Petrels 9 15 12 0 41 64 

Pelecaniformes < 1 < 1 4 7 5 1 

Eiders 2 3 2 40 < 1 0 

Gulls 16 6 40 41 14 30 

Terns 1 2 4 8 < 1 4 

Auks 70 73 38 4 39 < 1 

% by biomass 

Petrels 12 21 12 0 30 61 

Pelecaniformes 2 2 16 16 22 3 

Eiders 6 8 3 60 < 1 0 

Gulls 14 6 30 21 11 36 

Terns < 1 < 1 1 1 < 1 1 

Auks 65 62 38 2 37 < 1 

France, 

Iberia, and 

Azores 

Table 5.2. Relative species composition of seabirds breeding in the NAFO areas as% of total number and total biomass of breeding 

pairs for each subarea (from ICES, 2003). 

Species composition 0 1 2 and 3 4 5 6 

% by number 

Eastern Baffin 

Island 

West 

Greenland 

East NFL and 

Labrador 

Gulf of St. 

Lawrence and 

Scotian Shelf 

Gulf of 

Maine 

Petrels 15 < 1 80 9 11 0 

Eiders < 1 0 < 1 10 15 0 

Pelicaniformes 0 0 < 1 21 20 1 

Gulls 5 < 1 2 37 45 70 

Terns 0 < 1 < 1 6 7 29 

Auks 79 99 16 17 2 0 

% by biomass 

Petrels 13 1 19 < 1 < 1 0 

Eiders 2 < 1 4 19 27 0 

Pelicaniformes 0 < 1 7 43 27 4 

Gulls 2 2 8 25 45 88 

Terns 0 < 1 < 1 < 1 < 1 8 

Auks 83 96 62 12 < 1 0 

Long Island to 

Cap Hatteras 


The pelecaniformes (cormorants, shags and gannets) seem to be more important in NAFO 4 and 5 (where they make up 

20% by number and 30–45% by biomass respectively) than in any other NAFO or ICES subarea. In the eastern North 

Atlantic they constitute only 5–7% by number and 16–22% by biomass in the areas compassing the North Sea and 

English Channel (IVa-c, VIId,e) and the Faeroes and western UK (Vb, VIa,b,f,g,j) (Table 5.1) 

Constituting 40% and 41% by number and 60% and 21% by biomass of the population, eiders and gulls respectively 

dominate the seabirds breeding in the shallow, inland Baltic Sea and its approaches (ICES III). Approximately 45% of 

all the ICES eiders (ca. 1 million pairs) breed in subarea III. Eiders also reach their largest proportions (10% and 15% 

by number and 19% and 27% by biomass in the inshore NAFO subareas 4 (St. Lawrence and Nova Scotia) and 5 (Gulf 

of Maine and Georges Bank) respectively. In these same subareas gulls constitute ca. 40% by number and 25–45% by 

biomass. 

The only subarea in the NAFO and ICES areas where gulls dominate the seabird breeding community is NAFO 6 (south 

Maine to Virginia). Of nearly 250 000 pairs of seabirds breeding in this subarea, 70% are gulls (mainly laughing gulls 

and herring gulls). They and terns make up nearly the entire community (88% and 8% of the total biomass). In the 

groupings of ICES subareas used in this report, gulls make up 6–40% of the numbers and 6–36% of the biomass. 

Nowhere do terns constitute > 10% of the numbers or 1% of the biomass. 

In addition to the large differences in breeding populations in the W and E Atlantic, there are much larger differences 

between the two regions due to huge seasonal movements of birds from the Southern Atlantic through NAFO areas than 

through ICES areas. These, and large seasonal migratory movements of birds between and within ICES and NAFO 

areas are described and discussed in the next section. 

5.2.2 Seasonal changes in numbers and biomass of seabirds in ICES and NAFO areas 

In general, the seabird community in the NAFO areas is dominated by huge numbers of individuals feeding at low 

trophic levels, two of which are of small-sized planktivorous species (Wilson’s storm petrel, little auk). 

Due to temporary movements of birds from the southern Atlantic into northern waters, and the migration of North 

Atlantic seabirds across fishing areas, there are considerable seasonal changes in numbers and biomasses of seabirds 

occupying the various parts of the North Atlantic (Tables 5.3–5.6). Such movements include those of large numbers of 

birds out of the northernmost subareas (ICES I and IIb, NAFO 0 and 1) into milder subareas in autumn and winter. For 

example, the large increase in NAFO 2 and 3 (E. Newfoundland and Labrador) in autumn and winter is due to millions 

of eiders, auks and kittiwakes entering the areas from colonies outside the NAFO areas (in the eastern Canadian Arctic), 

colonies in NAFO 0 and 1 (E. Baffin Island and W. Greenland) and in ICES IIa, IIb and Va (Barents Sea, Norwegian 

Sea and Iceland). Similarly, nearly seven million seaducks winter in the Baltic Sea (ICES IIIa-d) but leave again in 

spring to breed inland. These include 4.3 million long-tailed ducks, 1.2 million common scoters and 1 million velvet 

scoters. In the western Atlantic, 4.5–5 million non-breeding birds (mostly great shearwaters, sooty shearwaters, 

Wilson’s storm-petrels) enter the southern NAFO areas from the southern oceans in summer, and 1.5 million ring-billed 

gulls move out to the coast in the same areas in winter (Table 5.7, ICES 2003). 

It should be noted, however, that the quantification of the movements of seabirds across the fishing areas is based on 

very poor data as very little is known about the actual numbers of the different species in the different areas at a given 

time. Many of the figures used here are not more than educated guesses! 

Table 5.3. Approximate numbers of seabirds (millions of individuals) occupying ICES subareas in winter, spring, summer, and 

autumn. 

ICES subarea Winter Spring Summer Autumn 

I,IIa,IIb Barents and Norwegian Seas 15.1 22.8 26.8 27.3 

Va,XIVa,b E. Greenland and Iceland 21.4 33.9 38.6 33.1 

IVa-c,VIId,e North Sea and English Channel 8.9 8.3 8.8 8.8 

IIIa-d Baltic, Skagerrak and Kattegat 10.2 9.8 3.9 5.8 

Vb,VIa,b,f,g,j Faeroes and W. UK 10.3 12.6 13.2 13.6 

VIIIa-c,IXa,X France, Iberia, Azores 1.3 2.1 1.0 1.4 

Total 67.1 89.5 92.4 90.1 

22 


Table 5.4. Approximate numbers of seabirds (millions of individuals) occupying NAFO areas in winter, spring, summer, and autumn. 

NAFO areas Winter Spring Summer Autumn 

0 Eastern Baffin Island 0 4.6 4.6 3.8 

1 West Greenland 19.6 117.6 115.6 19.6 

2 and 3 East NFL and Labrador 110.9 23.8 21.2 128.7 

4 Gulf of St. Lawrence and Scotian Shelf 2.0 3.7 4.4 4.3 

5 Gulf of Maine 0.9 18.9 3.5 10.0 

6 Long Island to Cap Hatteras 2.6 3.6 3.6 6.0 

Total 136.0 172.2 152.9 172.3 

The total biomass of seabirds occupying ICES subareas (Table 5.5) in different seasons varies between 54,000 tonnes 

(winter) to 64 000 tonnes (spring), whereas the total biomass of seabirds occupying NAFO subareas (Table 5.6) in 

different seasons is even more variable, ranging from 34 000 tonnes (winter) to 46 000 tonnes (spring and autumn). 

Note, however, that the numbers (and biomass) figures are based on the maximum number of a given species in any 

given season only, and do not consider their length of stay within the given season. Short stays in two or more areas will 

thus be reflected in the total numbers and biomasses in those areas, e.g., in the migration seasons spring, and autumn. 

Table 5.5. Approximate biomass (tonnes x 1000) of seabirds occupying ICES subareas in winter, spring, summer, and autumn. 

ICES subarea Winter Spring Summer Autumn 

I,IIa,IIb Barents and Norwegian Seas 10.5 15.2 17.0 17.0 

Va,XIVa,b E. Greenland and Iceland 15.3 20.3 20.6 19.9 

IVa-c,VIId,e North Sea and English Channel 7.1 6.8 6.9 7.0 

IIIa-d Baltic, Skagerrak and Kattegat 11.2 11.1 5.1 7.0 

Vb,VIa,b,f,g,j Faeroes and W. UK 7.6 9.3 9.5 9.5 

VIIIa-c,IXa,X France, Iberia, Azores 2.2 1.3 0.9 0.9 

Total 53.9 64.0 60.0 61.4 

Table 5.6. Approximate biomass of seabirds (tonnes x 1000) in NAFO occupying NAFO areas in winter, spring, summer, and 

autumn. 

NAFO areas Winter Spring Summer Autumn 

0 Eastern Baffin Island 0 4.7 4.7 3.4 

1 West Greenland 8.1 23.2 20.8 8.1 

2 and 3 East NFL and Labrador 21.7 8.1 5.7 23.9 

4 Gulf of St. Lawrence and Scotian Shelf 1.6 3.7 3.1 3.5 

5 Gulf of Maine 1.0 4.2 2.7 3.4 

6 Long Island to Cap Hatteras 1.6 2.4 2.4 3.7 

Total 34.1 46.4 39.5 46.0 


Table 5.7. Approximate numbers (individuals x 1000) and biomass (tonnes) of birds that breed outside NAFO subareas but enter 

NAFO 5 and 6 (from ICES. 2003, Table 3.4). 

Species Number Biomass 

Greater shearwater 1900 2100 

Sooty shearwater 410 320 

Wilson’s storm-petrel 600 20 

Long-tailed duck 230 190 

Black scoter 60 60 

Surf scoter 120 150 

Velvet scoter 100 130 

Red-breasted merganser 60 40 

Red-necked phalarope 250 10 

Grey phalarope 240 10 

Bonaparte’s gull 60 10 

Ring-billed gull 1500 600 

Total 5530 3640 

5.2.3 Consumption estimates 

Seabirds occupying the NAFO and ICES areas of the North Atlantic consume an estimated 11.5 million tonnes of food 

per year with 45% being taken in the western sector and 55% in the east. This total is ca. 10–20% of the total 

consumption by the world’s seabirds (max. CI range = 56–133 million tonnes) estimated by Brooke (2003). Although 

this percentage seems relatively high, it may reflect both the elevated consumption by seabirds at high latitudes and the 

conservative approach of Brooke’s estimate. 

The near equality of the overall consumption on both sides of the Atlantic is despite the fact that nearly twice the 

number of seabirds occupies the NAFO areas and is a reflection of the huge numbers of small species in the west. 

The total food consumption estimates for both the ICES subareas and for the NAFO subareas peak in the summer 

season at levels 44% and 54% higher than the respective winter consumption estimates. The elevated energy demand in 

summer is primarily caused by increased reproduction activity, but also the larger numbers of birds (and hence higher 

biomass) in summer on both sides of the Atlantic. In the ICES area there are 37% more birds (and an 11% higher 

biomass) and in the NAFO area 12% more birds (and 16% higher biomass) in summer than in winter. In the NAFO area 

the extra food consumption caused by reproduction and the summer visitors from the southern hemisphere outweigh by 

far the extra consumption by wintering visitors entering the NAFO area from the ICES area and the eastern Canadian 

Arctic (guillemots and seaducks) and leaving the NAFO area for the summer. 

Note that while numbers and biomass of seabirds in a given area in a given season are based on maximum numbers in 

that season, the food consumption of seabirds occupying the ICES subareas (Table 5.8) and the NAFO subareas (Table 

5.9) are calculated based on the number of days each species stays in a given subarea and thus do not directly 

correspond to the biomass in Tables 5.5 and 5.6. 

24 


Table 5.8. Approximate food consumption (tonnes x 1000) by seabirds occupying ICES subareas in winter, spring, summer, and 

autumn. 

ICES subarea Winter Spring Summer Autumn Total 

I,IIa,IIb Barents and Norwegian Seas 270 360 570 450 1650 

Va,XIVa,b E. Greenland and Iceland 380 470 690 530 2080 

IVa-c,VIId,e North Sea and English Channel 180 170 220 180 750 

IIIa-d Baltic, Skagerrak and Kattegat 270 250 140 160 810 

Vb,VIa,b,f,g,j Faeroes and W. UK 190 220 290 240 950 

VIIIa-c,IXa,X France, Iberia, Azores 40 20 30 20 110 

Total 1340 1490 1940 1580 6350 

Table 5.9. Approximate food consumption (tonnes x 1000) by seabirds occupying NAFO areas in winter, spring, summer, and 

autumn. 

NAFO areas Winter Spring Summer Autumn Total 

0 Eastern Baffin Island 0 100 130 60 300 

1 West Greenland 230 670 1110 230 2240 

2 and 3 East NFL and Labrador 730 230 180 800 1940 

4 Gulf of St. Lawrence and Scotian Shelf 50 70 80 60 250 

5 Gulf of Maine 20 75 100 40 230 

6 Long Island to Cap Hatteras 40 50 60 60 200 

Total 1070 1190 1650 1260 5160 

5.2.4 Comparison to earlier models 

Seasonal movements. Taking seasonal movements of birds between NAFO and ICES areas into account increased the 

original estimate of food consumption in the ICES areas (ICES 2002) by 17% (from 5.4 to 6.3 mill. tonnes) and in the 

NAFO areas by 75% (from 2.9 to 5.2 mill. tonnes) (Table 5.10). In the ICES areas this is most evident in ICES IIIa-d 

(Baltic, Skagerrak and Kattegat) where taking into account the population of wintering seaducks doubled the annual 

consumption estimate for that subarea. The most striking differences in the NAFO areas are due to the huge seasonal 

influxes of birds from the southern oceans (into NAFO 5 and 6), northern ICES areas and the eastern Canadian Arctic 

(into NAFO 2 and 3) mentioned above. 


Table 5.10 Estimates of food consumption (tonnes x 1000) by seabirds in ICES and NAFO subareas when not considering seasonal 

movements of birds into, out of and through the subareas (a) and when doing so (b). 

ICES subareas 

I,IIa,IIb Barents and Norwegian Seas 1520 1650 

Va,XIVa,b E. Greenland and Iceland 1800 2080 

IVa-c,VIId,e North Sea and English Channel 690 750 

IIIa-d Baltic, Skagerrak and Kattegat 410 810 

Vb,VIa,b,f,g,j Faeroes and W. UK 870 950 

VIIIa-c,IXa,X France, Iberia, Azores 80 110 

Total ICES 5420 6 350 

NAFO subareas 

0 Eastern Baffin Island 220 300 

1 West Greenland 1650 2240 

2 and 3 East NFL and Labrador 700 1940 

4 Gulf of St. Lawrence and Scotian Shelf 180 250 

5 Gulf of Maine 100 230 

6 Long Island to Cap Hatteras 50 200 

Total NAFO 2910 5160 


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Cairns, D.K., Chapdelaine, G., and Montevecchi, W.A. 1991. Prey exploitation by seabirds in the Gulf of St. Lawrence. 

Canadian Special Publications Fisheries Aquatic Sciences, 113: 277–291. 

Cramp, S. (ed.) 1985. The birds of the Western Palearctic, Vol IV. Oxford University Press. 960 pp. 

Cramp, S. and Simmons, K.E.L. (ed.) 1977. The birds of the Western Palearctic, Vol I. Oxford University Press. 722 

pp. 

Cramp, S. and Simmons, K.E.L. (ed.) 1983. The birds of the Western Palearctic, Vol III. Oxford University Press. 913 

pp. 

Delany, S., and Scott, D. (eds.) 2002. Waterbird population estimates – third ed. Wetlands International Global ser. No. 

12, Wageningen, Netherlands. 226 pp. 

Diamond, A.W., Gaston, A.J., and Brown, R.G.B. 1993. Studies of high-latitude seabirds. 3. A model of the energy 

demands of the seabirds of eastern and Arctic Canada. CWS Occasional Papers, 77: 1–39. 

Durinck, J., Skov, H., Jensen, F.P., and Pihl, S. 1994. Important marine areas for wintering birds in the Baltic Sea. EU 

DG XI research contract no. 2242/90–09–01. Ornis Consult report 1994, 110 pp. 

Ellis, H.I., and Gabrielsen, G.W. 2002. Energetics of free-ranging seabirds. In Biology of marine birds. Ed. by 

Schreiber, E.A. and Burger, J. CRC Press, Boca Raton, Florida: 359–407. 

Gabrielsen, G.W. 1994. Energy expenditure in arctic seabirds. D. Phil. thesis, Univ. Tromsø, Norway. 

Gales, R.P., and Green, B. 1990. The annual energetics cycle of little penguins Eudyptula minor. Ecology, 71: 2297– 

2312. 

Hagemeijer, W.J.M., and Blair, M.J. (eds.). 1997. The EBCC atlas of European breeding birds. Poyser, London. 903 pp. 

ICES 2002. Report of the working group on seabird ecology. ICES CM 2002/C:04. 

ICES 2003. Report of the working group on seabird ecology. ICES CM 2003/C:03. 

26 

ICES WGSE Report 2004 

Total 

a 

Total 

b

Kershaw, M., and Cranswick, P.A. 2003. Numbers of wintering waterbirds in Great Britain, 1994/1995–1998/1999: I. 

Waterfowl and selected waterbirds. Biological Conservation, 111: 91–104. 

Lyngs, P. 2003. Migration and winter ranges of birds in Greenland. Dansk Ornitologisk Forenings Tidsskrift, 97: 1– 

165. 

Merkel, F. R., Mosbech, A., Boertmann, D. M., and Grøndahl, L. 2002. Winter seabird distribution and abundance off 

southwest Greenland, 1999. Polar Research, 21:17–36. 

Mosbech, A.., and Boertmann, D. 1999. Distribution, abundance and reaction to aerial surveys of post-breeding king 

eiders (Somateria spectabilis) in western Greenland. Arctic, 52: 188–203. 

Nagy, K.A., Ginard, I.A., and Brown, T.K. 1999. Energetics of free-ranging mammals, reptiles and birds. Annual 

Reviews Nutrition, 19: 247–277. 

Nygård, T., Larsen, B.H., Follestad, A., and Strann, K.-B. 1988. Numbers and distribution of wintering waterfowl in 

Norway. Wildfowl, 39: 164–176. 

Petersen, A. 1982. [Icelandic seabirds]. In Fuglar. Ed. By Gardarsson, A. Rit Landverndar, 8. 216 pp. 

Wernham, C.V., Toms, M.P., Marchant, J.H., Clark, J.A., Siriwardena, G.M., and Baillie, S.R. (eds.). 2002. The 

Migration Atlas: movements of the birds of Britain and Ireland. Poyser, London. 884 pp. 


Appendix 5.1. An example of the consumption model input data for breeding populations (body mass, length of breeding season, 

field metabolic rate (FMR, outside the breeding season and during the breeding season). This example is from ICES Va (Iceland). 

Note that body mass (and hence FMR) will vary geographically. This is accounted for in the different areas. 

Body 

mass 

g 

Breeding 

population 1 

pairs 

Total no. 

of indivs. 

Period 

present 

in 

area 

Length 

of 

breeding 

season 

d 

FMR 

outside 

breeding 


kj/d 

FMR 

during 

breeding 

Northern fulmar 810 1500000 5100000 Jan-Dec 120 814 1016 

Manx shearwater 450 8500 28900 Mar-Oct 150 538 715 

Leach's petrel 50 115000 391000 Mar-Oct 150 114 192 

Storm petrel 25 75000 255000 Mar-Oct 150 70 127 

Northern gannet 3200 25000 85000 Mar-Oct 150 2709 4048 

Great cormorant 2500 3150 11340 Mar-Oct 100 2254 3383 

Shag 1800 6600 23760 Mar-Oct 100 1764 2664 

Common eider 2200 300000 1080000 Jan-Dec 50 2049 3083 

Great skua 1400 5400 19440 Apr-Sep 100 1462 2219 

Arctic skua 350 7500 27000 May-Sep 80 520 810 

Black-headed gull 250 27500 99000 Apr-Sep 80 404 634 

Mew gull 380 550 1980 Apr-Sep 80 553 860 

Herring gull 1000 7500 27000 Mar-Oct 90 1138 1738 

Lesser black-backed gull 800 30000 108000 Apr-Sep 90 963 1478 

Great black-backed gull 1650 17500 63000 Mar-Oct 100 1653 2501 

Glaucous gull 1800 12500 45000 Apr-Sep 100 1764 2664 

Black-legged kittiwake 400 631000 2271600 Mar-Oct 90 574 893 

Arctic tern 110 250000 900000 May-Aug 70 219 349 

Common guillemot 1000 990000 3366000 Feb-Nov 70 1138 1738 

Brünnich's guillemot 950 580000 1972000 Feb-Nov 70 1095 1674 

Razorbill 700 380000 1292000 Mar-Oct 70 872 1341 

Black guillemot 400 15000 54000 Jan-Dec 90 574 893 

Atlantic puffin 450 2760000 9384000 Mar-Oct 110 627 972 

1 References 


Gardarsson, A. 1995. Numbers and distribution of common murre Uria aalge, thick-billed murre U. lomvia and 

razorbill Alca torda in Iceland. Bliki, 16: 47–65. 

Gardarsson, A. 1996a. Numbers and distribution of breeding kittiwake Rissa tridactyla in Iceland. Bliki, 17: 1–16. 

Gardarsson A. 1996b. Numbers of breeding cormorants Phalacrocorax carbo in Iceland in 1975–1994. Bliki, 17: 35– 

42. 

Gardarsson A. 1979. A census of breeding cormorants (Phalacrocorax carbo) and shags (Phalacrocorax aristotelis) in 

Iceland in 1975. Natturufraedingurinn, 49:126–154. 

Gudmundsson G.A. 1998. The importance of wetlands for birds. (Þýðing votlendis fyrir fugla). In Icelandic wetlands; 

protection and exploitation. (Íslensk votlendi; verndun og nýting. Ed. by Olafsson, J.S. Haskolautgafan, 

Reykjavik: 167-172. 

Gardarsson A. Personal communication. 

Icelandic Institute of Natural History 2000. Red list of threatened species in Iceland 2, birds. 

Lund-Hansen, L.C. and P. Lange 1991. The numbers and distribution of Great Skua Stercorarius skua breeding in 

Iceland 1984–1985. Acta Naturalia Islandica 34, 16pp. 

28 


kj/d

6 CONSUMPTION OF PREY BY SEABIRDS IN THE NORTH SEA AS INPUT FOR THE STUDY 

GROUP ON MULTISPECIES ASSESSMENTS IN THE NORTH SEA (SGMSNS) 

Term of Reference: provide the Study <strong>Group</strong> on Multispecies Assessments in the North Sea (SGMSNS) with data on 

the consumption of different prey by seabirds in the North Sea, in a format specified by SGMSNS. 

In response to a request from SGMSNS in 2003, the WGSE considered in March 2003 whether seabird consumption of 

prey in the North Sea could be presented in a form suitable for incorporation into an MSVPA model. That meeting 

concluded that there would be considerable work required to achieve such an aim, and certain assumptions and 

simplifications would be necessary, but that such work would be possible providing the form of the data requirement of 

SGMSNS could be clearly specified. Our Term of Reference f) required WGSE to prepare data on the consumption of 

different prey by seabirds in the North Sea, in a format specified by SGMSNS. Unfortunately, WGSE received no 

guidance from SGMSNS prior to our meeting in Aberdeen, on the format in which data should be provided for input to 

Multispecies Assessments in the North Sea and only rather limited information while we were meeting in Aberdeen. 

We were advised, however, that this Term of Reference had been superseded by the funding of an EC contract 

‘BECAUSE’ which will be carrying out essentially this same work, and therefore that this Term of Reference should 

perhaps no longer be included in our work programme. Although we tried to obtain confirmation of this fact from the 

Chair of SGMSNS and from ICES, we were unable to get any clear response on this point. We therefore assumed that 

this Term of Reference should be left until clarification of the situation could be obtained. WGSE would be happy to 

work on this tor intersessionally if the decision we made in Aberdeen was based on incorrect advice. 

7 ECOLOGICAL QUALITY OBJECTIVES 

Term of Reference: reconsider the formulation of the EcoQOs listed below, determine whether a more specific EcoQO 

is needed in terms of its specification to the metric, time and geographical area, and as necessary propose more specific 

EcoQO(s) [OSPAR 2004/1]: 

i) EcoQ element (f) Proportion of oiled common guillemots among those found dead or dying on beaches, 

ii) EcoQ element (g) Mercury concentrations in seabird eggs and feathers, 

iii) EcoQ element (h) Organochlorine concentrations in seabird eggs, 

iv) EcoQ element (i) Plastic particles in stomachs of seabirds, 

v) EcoQ element (j) Local sandeel availability to black-legged kittiwakes, 

vi) EcoQ element (k) Seabird population trends as an index of seabird community health. 


The Fifth North Sea Conference in 2002 agreed that six Ecological Quality Elements relating to seabirds in the North 

Sea would be further developed. These elements were: 

• 4(f) Proportion of oiled common guillemots among those found dead or dying on beaches, 

• 4(g) Mercury concentrations in seabird eggs and feathers, 

• 4(h) Organochlorine concentrations in seabird eggs, 

• 4(i) Plastic particles in stomachs of seabirds, 

• 4(j) Local sandeel availability to black-legged kittiwakes, 

• 4(k) Seabird population trends as an index of seabird community health. 

An Ecological Quality Objective was agreed for the first of these Elements: 

‘The proportion of [oiled common guillemots] should be 10% or less of the total found dead or dying in all areas of the 

North Sea’ 

Within the OSPAR framework, The Netherlands agreed to act as a lead country for Element 4(f) on oiled common 

guillemots and the UK for Element 4(j) on sandeels and kittiwakes. Progress made in the development of these EcoQ 

Elements was reported to OSPAR’s Biodiversity Committee in early 2004 (OSPAR 2004a, b). This Committee agreed a 

number of points about these Ecological Quality Elements that are reflected in the considerations below. 


WGSE has responded over the last few years to several terms of reference relating to Ecological Quality Objectives. In 

responding this year, we have tried where possible to avoid repeating the responses of previous years. We note that 

some papers produced, for example in the context of OSPAR, do not appear to have taken account of all of our reports 

(or even those of ICES ACE). We urge those using our responses to read those previous responses alongside this year’s 

work. 

7.2 Proportion of oiled common guillemots among those found dead or dying on beaches 

This is the only seabird EcoQ Element for which an EcoQO has been set for the North Sea pilot project. However, this 

EcoQO is concerned with driving and monitoring the reduction of oil pollution in the North Sea rather than ensuring 

that common guillemot Uria aalge populations are safeguarded. However, there is no doubt that reducing oil pollution 

would reduce anthropogenic mortality of common guillemots and of all other biota adversely affected by oil pollution. 

In this context it should be noted that the 10% objective for the Ecological Quality Element was initially suggested by 

WGSE as a pragmatic target – accepting that the “no-human effect” level would be 0%, but acknowledging that this 

zero level would presently be an unrealistic target, based on experience of oil spill reduction efforts around Orkney and 

Shetland. 

OSPAR (2004b) describes progress with this pilot project. The provision of a manual for volunteers to use when 

collecting information on the proportion of oiled birds has ensured standardisation of this aspect. An international data 

collation system is in place. Two aspects not explicitly addressed in the wording of the EcoQO (but included in 

previous background advice) relate to regional divisions in the North Sea and frequency of surveys. A “grand total” 

percentage of oiled birds would not be appropriate as they may be biased by disproportionately sized samples in some 

areas. In addition, knowledge of the location of high (or low) proportions of oiled birds may help to better target any 

management or mitigation measures. Based on historical precedent, and therefore practicality, ICES (2003a) and 

OSPAR (2004b) suggested a set of fifteen coastal sections of the North Sea (Table 7.1). Equally, previous advice has 

suggested that monthly samples be taken in each section for the winter months between November and April in each 

year. Any lower sampling rates carry the risk that external factors could severely bias the result and that variance 

around the mean oiling rate would be higher than ideal. WGSE notes that surveys for oiled guillemots are not yet 

occurring on all of these coastal sections or at these times. 

Table 7.1. Suggested coastal sections for recording and reporting of proportions of oiled common guillemots (after OSPAR 2004b). 

Section Boundaries Country 

1 Shetland UK 

2 Orkney Orkney and north coast of Scotland UK 

3 East Scotland Duncansby Head to Berwick on Tweed UK 

4 Northeast England Berwick on Tweed to Spurn Head UK 

5 East England Spurn Head to North Foreland UK 

6 Eastern Channel Line between North Foreland and Belgian/French border to line from 

Cherbourg to Portland 

UK, F 

7 Western Channel Line between Cherbourg and Portland to line from Lizard to Ouessant UK, F 

8 Eastern Southern Bight Belgian/French border to Texel B, NL 

9 Southern German Bight North Sea coast Frisian Islands Texel to Elbe NL, FRG 

10 Western Wadden Sea Mainland and Wadden Sea coast Frisian Islands Texel to Elbe NL, FRG 

11 Eastern Wadden Sea Mainland coast and Wadden Sea coast Elbe to Esbjerg FRG, DK 

12 Eastern German Bight North Sea coast Wadden Sea Islands Elbe to Fanø FRG, DK 

13 Danish west coast Mainland coast Esbjerg – Hanstholm DK 

14 Skagerrak/ Oslofjord East of line between Hanstholm to Kristiansand, north of a line from 

Skagen to Gothenburg 

15 SW Norway Kristiansand to Stadt N 

30 


N, DK, S

WGSE and ACE recommended in 2003 (ICES 2003a, 2003b) that trends might be most easily reported as five-year 

running mean percentages oiled. In line with this, ICES (2003a) advised that a period of at least five years in which an 

average of 10% or less oiled common guillemots has been recorded should occur before the conclusion that the 

objective has been reached could be justified statistically. 

WGSE therefore suggests that the EcoQO be reformulated as: 

The average proportion of oiled common guillemots should be 10% or less of the total found dead or dying in 

each of 15 areas of the North Sea over a period of at least five years. Sampling should occur in all winter months 

(November to April) of each year. 

7.3 Mercury concentrations in seabird eggs (and feathers) 

This EcoQ relates to mercury concentration (mg/kg) in eggs of common terns Sterna hirundo and Eurasian 

oystercatchers Haematopus ostralegus, two common and widely distributed species characterised by different foraging 

strategies and food chains. In previous years, WGSE has suggested that an EcoQO might be established for mercury 

concentrations in a combination of bird feathers and eggs. Recognising a comment from OSPAR BDC that EcoQOs 

ought to focus on features that can potentially be influenced by further human management, and recognising the need to 

reduce the complexity of the EcoQO system, WGSE suggests reducing this EcoQ to focus on bird eggs alone (see also 

Section 7.4, below). Seabird eggs are already used to monitor mercury on southern North Sea coasts as part of the 

TMAP project in the Wadden Sea (using JAMP guidelines OSPAR, 1997). 

WGSE recommends sampling sites near estuaries, important cities or industrial areas in order to cover hot spots of 

mercury emissions and especially of riverine inputs (e.g., Becker et al., 2001). We suggest sampling at sites near the 

estuaries of the Rivers Elbe, Weser, Ems, Rhine/Scheld, Thames, Humber, Tees, and Forth. However, with respect to 

atmospheric inputs, the northern parts of the North Sea should be covered as reference areas where lower mercury 

levels are to be expected compared to the estuaries listed above. We suggest sampling sites in similar (but nonindustrial) 

habitats in southwestern Norway and the Moray Firth. An alternative would be to aim to reduce levels to the 

lowest recorded in current monitoring schemes (oystercatcher: 0.1 mg kg −1 ; common tern 0.2 mg kg −1 , Becker et al., 

2001). Costs (and time) could be saved by combining sampling with EcoQ h) on organochlorine concentrations in 

seabird eggs. Sampling should be annual with a sample size of ten eggs (one per nest) per area and species (OSPAR, 

1997). Less frequent sampling would increase the period needed to understand if the EcoQO has been met or not. 

WGSE therefore suggests that the EcoQO be formulated as: 

The average concentrations of mercury in the fresh mass of ten eggs from separate clutches of common tern and 

Eurasian oystercatcher breeding adjacent to the estuaries of the Rivers Elbe, Weser, Ems, Rhine/Scheld, 

Thames, Humber, Tees, and Forth should not significantly exceed concentrations in the fresh mass of ten eggs 

from separate clutches of the same species breeding in similar (but not industrial) habitats in southwestern 

Norway and in the Moray Firth. 

7.4 Organochlorine concentrations in seabird eggs 

WGSE reviewed this metric in 2003 (ICES, 2003a). WGSE did not add to or amend this review in 2004, but noted that 

the OSPAR Biodiversity Committee had commented that it would prefer to have an EcoQ that tracked organochlorines 

where further management action remained to be taken, rather than an EcoQ that tracked the speed at which PCBs and 

DDT flushed out of the environment (OSPAR 2004c). WGSE noted this, but point out that knowledge of the rate at 

which “banned” substances leave biota is of interest and relevance, particularly in ensuring that bans remained 

effective. 

The objective of this EcoQ is to record any change in ecosystem contamination with organochlorines by using seabirds 

as accumulative indicators. Many organochlorines (PCBs, DDT, chlordanes) have been banned for long time, but the 

strong spatial trends of concentrations in seabird eggs at the southern North Sea in recent times and local erratic 

increases indicate continuing inputs into the marine environment (e.g., increased levels of PCBs and DDTs at 

Julianapolder, Dutch Wadden Sea, and at Elbe estuary; chlordanes at Julianapolder; Becker et al., 2001). 

Remobilisation of contaminants from sediments by sea currents or by dredging harbours and dumping of the spoil might 

be possible causes for these trends and fluctuations. Furthermore, currently unpublished data from the Wadden Sea 

monitoring project (TMAP) on contaminants in bird eggs show significant increases of PCBs, DDTs, and chlordanes in 

the western part of the Wadden Sea from 1998 to 2003. Other compounds such as HCB or HCHs, which are in use and 

emitted (high levels of HCB at the Dollart, and the Elbe estuary; high levels of HCHs at Julianapolder and the Elbe 


estuary), further demonstrate the relevance of this EcoQ and of further monitoring as an early warning system that could 

help authorities to take appropriate measures to protect the marine environment. 

Time series of organochlorine contamination levels of longer than 40 years exist for various parts of the North Sea (e.g., 

Alcock et al., 2002),. Seabird eggs have been used to monitor organochlorines in parts of the North Sea region for many 

years, e.g., within in the TMAP in the Wadden Sea (Becker et al., 2001). These data have been used in North Sea QSRs 

(e.g., Bakker et al., 1999). 

WGSE suggested in 2003 that practical EcoQOs could be < 20 ng total PCBs g −1 egg fresh mass, < 10 ng DDT and 

metabolites g −1 egg fresh mass, < 2 ng HCB g −1 egg fresh mass, < 2 ng HCH g −1 egg fresh mass for eggs of common tern 

and Eurasian oystercatcher from both the southern and the northern North Sea. 

WGSE suggests further refining the geographic specificity of monitoring (and therefore of the EcoQO) by focusing on 

areas of high riverine input and other hot spots of organochlorine inputs. WGSE thus suggests sampling sites should be 

chosen adjacent to the Rivers Elbe, Weser, Ems, Rhine/Scheld, Thames, Humber, Tees, and Forth. However, with 

respect to the ongoing atmospheric inputs (especially of PCBs), as reference areas also the northern parts of the North 

Sea should be covered where lower organochlorine levels are to be expected. We suggest sampling sites in similar (but 

non-industrial) habitats in southwestern Norway and the Moray Firth. The common and widely distributed species 

selected offer adequate colony sites for sampling under these requirements (see the TMAP in the Wadden Sea as 

example, Becker et al., 2001). Combining sample sites with EcoQ g) on mercury concentrations in seabird eggs (see 

Section 7.3) would save time and cost. 


For each site, the average concentrations in fresh mass of the eggs of common tern and Eurasian oystercatcher of 

PCBs should not exceed 20 ng g −1 ; of DDT and metabolites should not exceed 10 ng g −1 ; and of HCB and HCH 

should each not exceed 2 ng g −1 . Sampling should be of ten eggs of each species from separate clutches of birds 

breeding adjacent to the estuaries of the Rivers Elbe, Weser, Ems, Rhine/Scheld, Thames, Humber, Tees, and 

Forth, and in similar (but not industrial) habitats in southwestern Norway and in the Moray Firth. 

7.5 Plastic particles in stomachs of seabirds 

WGSE reviewed this EcoQ in 2002 and 2003 (ICES, 2002, 2003a). These reports, and ACE (ICES, 2003b), endorsed 

the conclusions of Van Franeker and Meijboom (2002, 2003) that stomach contents analysis of beach-washed northern 

fulmars Fulmarus glacialis offer a reliable monitoring tool for changes in the abundance of plastic litter at sea. 

Following these recommendations, a study running from May 2002 to December 2004 has been established as part of 

the EC-funded Save the North Sea project (EU Interreg IIIB J-No 1–16–31–7–502–02) and material is being collected 

in seven countries around the North Sea and in adjacent waters 1 . This project should provide further data on the 

suitability of this EcoQ. With an international network of collaborators now (temporarily) in place, and with an agreed 

standard methodology now fully operational, WGSE strongly recommends the continuation of the work after the 

current end of the Save the North Sea programme in December 2004. 

The northern fulmar was chosen over other seabird species due to its well-documented propensity to accumulate plastic 

particles in its stomach (Van Franeker, 1985; Moser and Lee, 1992). It is also an abundant species with a “guaranteed” 

annual supply of sufficient (some tens to hundreds) of beach-washed corpses in most North Sea countries. No other 

species meets both of these conditions in the North Sea (Save the North Sea project, unpubl. data 2002–2003). An 

important further advantage of the northern fulmar is the availability of a data set from the early 1980s, which enables 

the development of time-related trends (Van Franeker, 1985). 

We continue to recommend that the metrics should be the number and mass of plastic particles of each defined type 

(“industrial plastic particles”, “user-plastic particles”, and mass of “inert chemical material”) in the stomachs of samples 

of 50 to 100 beach-washed northern fulmars collected during winter from areas of the North Sea where such sampling 

can be achieved as part of beached-bird surveys. WGSE recommended that the proportion of oiled common guillemots 

should be monitored in fifteen sections of the North Sea coast (see Table 7.1) and consider it logical that the same 

sections of coast be used to monitor plastic particle contamination. 

1 see http://marine-litter.gpa.unep.org/regional/Nederland/nl_results.htm 

32 


The present level is that around 60% of northern fulmars in the southern North Sea samples have more than ten plastic 

particles in the stomach. In line with previous discussions, the objective should be to achieve a target of as little plastic 

in fulmar stomachs as possible (the “natural level” of this metric should be nil). A value of less than 2% of northern 

fulmars having ten or more plastic particles in the stomach seems a reasonable and pragmatic choice of target. 

With regard to the geographical variation in levels of marine litter, the WGSE noted that residence times of plastic in 

northern fulmar stomachs are not known, though likely to be at least in the order of many weeks or months. These long 

periods achieve an integration of plastic contamination over extended periods prior to the death of the birds collected. If 

northern fulmars move into the North Sea en masse from less contaminated areas of the North Atlantic, then the 

numbers of plastic items may be reduced in samples taken from North Sea beaches where plastic contamination is 

probably higher. Only if northern fulmars tend to remain within one area of the North Sea, they may have levels of 

plastic contamination representative of local pollution. A study of geographical variation in northern fulmar 

contamination around the North Sea is therefore helpful only in quantifying the spatial pattern of litter distribution if 

large influxes of “foreign” birds can be identified. The protocol currently deployed in the Save the North Sea project 

includes systematic observations of colour phase, biometrics, and age from which the geographical origin and age 

profile of stranded material may be evaluated. With that, influxes and other anomalies can be identified. 

Van Franeker and Meijboom (2002) also recommend that funds should be made available for analysis of the chemical 

composition of the inert “chemical” substances found in a proportion of the northern fulmars. WGSE agrees that the 

“chemical material” found in many northern fulmar stomachs should receive further analysis to determine its nature, 

likely origins, and toxic hazard. Potential technical problems with this specific aspect or any financial implications 

should not, however, hinder the successful implementation of the EcoQ element (i) where quantities of plastic are the 

important parameter to be monitored. 

With regard to the oiled seabird EcoQO, WGSE and ACE recommended in 2003 (ICES, 2003a, 2003b) that trends 

might be most easily reported as five-year running mean percentages oiled. In line with this, ICES (2003a) advised that 

a period of at least five years in which an average of 10% oiled common guillemots has been recorded should occur 

before the conclusion that the objective has been reached could be justified statistically. There are no baseline data on 

the plastic particles in northern fulmars, so we cannot examine annual variability yet. WGSE therefore recommend 

further investigations into the amount of variability in plastic loadings between years. For the moment and in line with 

the oiled seabirds EcoQO, we suggest a period of five years, over which a value of less than 2% of northern fulmars 

having ten or more plastic particles in the stomach in samples of at least 50 corpses should occur before the conclusion 

that the objective has been reached could be justified statistically. 


A value of less than 2% of northern fulmars having ten or more plastic particles in the stomach in samples of 

50+ beach-washed fulmars found in winter (November to April) from each of fifteen areas of the North Sea over 

a period of at least five years. 

7.6 Local sandeel availability to black-legged kittiwakes 

7.6.1 Objective 

The objective of this EcoQ was somewhat misunderstood by OSPAR (2004d), who stated that it is “to ensure that 

fishing activities do not reduce the supply of food for the breeding black-legged kittiwakes Rissa tridactyla beyond an 

acceptable level”. The objective is to use the black-legged kittiwake as an indicator species for the community of 

species that depend on sandeels as an important food resource, the inference being that if black-legged kittiwakes are 

unable to breed successfully, then it is likely that sandeel abundance will be low and likely to have adverse effects on 

many animal species. This use of black-legged kittiwakes as a sentinel assumes that a) the breeding success of blacklegged 

kittiwakes can easily be monitored with a high level of accuracy, and b) that black-legged kittiwake breeding 

success correlates well with sandeel abundance. These prerequisites are evaluated below, together with the requirements 

for a useful EcoQO that human impacts are important influences, that clearly defined objectives can be set, and that the 

geographical range over which the EcoQ can be used is adequate. 

7.6.2 Can black-legged kittiwake breeding success be monitored accurately? 

Black-legged kittiwakes build very conspicuous nests in colonies on cliff faces. The numbers of chicks in nests can 

easily be counted, and standardized protocols for monitoring black-legged kittiwake breeding success are well 

established and widely used (Walsh et al., 1995; e.g., Mavor et al., 2002). Many amateur and professional ornithologists 


contribute data to the seabird productivity monitoring programme in Britain and Ireland. These data show clear patterns 

of variation; black-legged kittiwake breeding success tends to be similar between colonies counted independently 

within geographical regions, indicating that causes of variation tend to affect all colonies within a region (Frederiksen et 

al., 2004). Averaging data on productivity over several colonies within a geographical region reduces variance in the 

data contributed by colony-specific factors such as local predation impacts, weather, or disturbance effects. 

7.6.3 Does black-legged kittiwake breeding success correlate with sandeel abundance? 

To answer this question, we need data on black-legged kittiwake breeding success and on the local abundance of 

sandeels within the foraging range from breeding colonies being monitored. Breeding black-legged kittiwakes forage 

over a range typically up to 60 km from their colony, and there are few studies of sandeel abundance in such small 

areas. However, the Shetland sandeel stock abundance was estimated from 1975–1994 by VPA, and from 1985–2000 

by research survey. The breeding success of black-legged kittiwakes at colonies in Shetland correlates with the 

abundance estimates of the Shetland sandeel stock (total stock biomass) (Figures 7.6.1–7.6.3). Preliminary results from 

the IMPRESS study in east Scotland also show a strong correlation between black-legged kittiwake breeding success at 

colonies in east Scotland and the annual measurement by trawl survey of 1+ sandeel abundance on the sandeel grounds 

east of Fife (Figure 7.6.4). Although a linear regression provides a good fit (R 2 = 0.839), a logistic regression improves 

the fit even further (R 2 = 0.927). The results from the IMPRESS study are not yet in the public domain and require 

further evaluation, especially of the relative importance of 0 group and 1+ sandeels in affecting black-legged kittiwake 

ecology. Further details will be presented in late 2004 in the IMPRESS final report, but are not yet available to WGSE. 

Kittiwake breeding success at 

Foula 

1.6 

1.4 

1.2 

1 

0.8 

0.6 

y = 0.4735Ln(x) - 4.3601 

R 2 0.4 

0.2 

0 

= 0.602 

0 50000 100000 150000 200000 

Shetland sandeel total stock biomass (tonnes) 

Figure 7.6.1. Breeding success of black-legged kittiwakes in Foula, Shetland from 1975–1994, in relation to the estimated abundance 

of sandeels at Shetland (VPA estimate of total stock biomass in tonnes; data from ICES). The fitted line is a logarithmic regression. 

Kittiwake breeding success 

Shetland 

1.2 

1 

0.8 

0.6 

y = 0.3673Ln(x) - 3.4806 

R2 0.4 

0.2 

0 

= 0.7351 

0 50000 100000 150000 

Shetland sandeel total stock biomass (tonnes) 

Figure 7.6.2. Breeding success of black-legged kittiwakes in selected Shetland colonies monitored by JNCC from 1986–1994, in 

relation to the estimated abundance of sandeels at Shetland (VPA estimate of total stock biomass in tonnes; data from ICES). The 

fitted line is a logarithmic regression. 

34 


Kittiwake breeding success at 

Foula 

1.6 

1.4 

1.2 

1 

0.8 

0.6 

y = 0.3149Ln(x) + 0.8485 

R2 0.4 

0.2 

0 

= 0.4394 

0 0.5 1 1.5 2 2.5 3 

Sandeel abundance index (Cook) 

Figure 7.6.3. Breeding success of black-legged kittiwakes at Foula from 1985 to 2000, in relation to the index of sandeel abundance 

at Shetland, developed by R.M. Cook (ICES, 2001, Table 13.12.3), based on research survey catch data. The fitted line is a 

logarithmic regression. 

Demersal trawl sandeel abundance index in the Wee Bankie/Marr Bank study. 

Each year from 1997 to 2003, between late May and early July, nineteen evenly spaced demersal trawl stations 

were sampled by the Scottish Fisheries Research Vessel “Clupea”. A Jackson Rockhopper demersal trawl was 

towed for 30 min at a speed of approximately 4 km .h −2 at each station. Net geometry monitoring equipment 

(SCANMAR, Norway) recorded the width and height of the trawl opening every 30 sec. The ship’s position, 

determined by Differential Global Positioning System (DGPS), was recorded simultaneously. Thus for each 

trawl sample, the area of seabed swept and the volume of water filtered by the gear could be calculated. The 

total catch of sandeels in each sample was quantified, as numbers per 0.5 cm size class. Length-stratified subsamples 

were weighed to determine length-weight relationships for each year. These were used to estimate 

weight-at-length from numbers-at-length in every trawl sample. Summing across all length classes derived 

estimates of total catch number and biomass. Dividing the number and weight of fish in each catch by the area 

of seabed swept by the trawl on each occasion converted these to density estimates (no. km −2 and kg km −2 ) for 

each trawl station in each year. These density estimates were then multiplied by the area of seabed associated 

with each trawl station (Figure Box 7.1) to produce estimates of the total number and biomass of sandeels in 

each trawl station sub-area. Summing these sub-area population estimates across all trawl station sub-areas 

provided estimates of the total numbers and biomass of sandeels in the whole study area in each year. These 

abundance and biomass estimates should be considered as indices only, since only a small proportion of the 

water column was filtered by the gear (headline height approximately 2.8 m). It is also really only an index of 

1-group and older sandeels, since the 10 mm codend mesh-size permitted 0-group sandeels to pass through. 

Degrees Latitude 

56.5 

56.4 

56.3 

56.2 

56.1 

236.3 

191.4 329.1 

330.0 

269.1 

189.7 

190.6 

191.4 

190.1 

191.0 

284.6 

285.6 

191.4 

191.0 

333.4 

239.1 

56 

215.8 191.8 191.8 287.5 

-3 -2.8 -2.6 -2.4 -2.2 -2 -1.8 -1.6 -1.4 -1.2 -1 

Degrees Longitude 

Figure Box 7.1. Chart showing the sea area associated with each demersal fishing station (numbers show area in km 2 ). 


Kittiwake Breeding Success (chicks.pair -1 ) 

1 

0.8 

0.6 

0.4 

0.2 

0 

1997 

1998 

2002 

1999 

2001 

2003 

2000 

R 2 = 0.839, P

7.7 Seabird population trends as an index of seabird community health 

As pointed out by WGSE (ICES, 2003a), more detailed analyses of the empirical data on seabird population trends and 

individual colony trends are required to fully evaluate the expected performance of the proposed EcoQ on seabird 

population trends in the North Sea as an index of seabird community health. However, the main rationale for this EcoQ 

is the general public concern for declining seabird populations. This makes it practical to define a certain level of 

population decrease that, when exceeded, should trigger investigations to explore the most likely causes for the decline 

and considerations of possible countermeasures. 

At any one time, natural variability would lead half the seabird populations at these latitudes to increase and the other 

half to decrease, but our ability to detect changes over the short term depends both on the magnitude and variability of 

changes in time and space as well as the method(s) used. However, monitoring of breeding seabirds aims to cover at 

least 10% of the total population of the targeted species and methods are considered highly standardised and reasonably 

robust. The target level previously suggested for an EcoQO (≤ 20% decline over ≥ 20 years) is also justified by the fact 

that seabirds are generally long-lived and reproduce slowly. Consequently, rapid changes in their numbers are not 

expected and might indicate that some human-induced factor(s) is affecting the population to an extent that is not 

associated with a healthy seabird community and require(s) immediate management actions. The reference level for 

seabird population trends would typically be less than half the maximum target rate (i.e., in the order of ≤ 10% decline 

over ≥ 20 years). 

One possible option to make this EcoQ/EcoQO more specific is to identify the most suitable target species and key sites 

that could be used as a proxy for the whole North Sea seabird community, since obtaining sufficiently frequent and 

accurate counts of the whole North Sea population of breeding seabirds is not a practical proposition. A set of principles 

for making such a selection of appropriate species and populations would have to take into account the distribution of 

seabirds throughout different parts of the North Sea and include the most representative in terms of their ecology, 

numbers, distribution, and feasibility for monitoring (accessibility and counting accuracy). However, there are many 

different ways of grouping species according to their ecology (e.g., by feeding habitat and/or dietary preferences), and 

changes in the populations of species within different groups might indicate changes in the health of different 

components of the ecosystem. 

Although categorising species with respect to their ecology is certainly informative when exploring the reasons for 

widespread changes in populations, we propose not to apply an a priori categorisation for the purposes of monitoring in 

any region of the North Sea. Rather, monitoring should encompass the full suite of species that occur in significant 

numbers, and which can be practically monitored to the levels required for effective analysis. When this is not possible, 

we do however recommend that special consideration is taken to ensure that the selection of species includes as many 

ecotypes as possible. If changes are detected in more than one species of seabird population, then exploration of the 

possible reasons may be directed at possible common causes in the ecosystem as well as reasons that may apply to only 

individual species. 

WGSE discussed the completeness of the EcoQs considered above. With the exception of the EcoQ on population 

trends, all EcoQs suggest the use of seabirds as a proxy indicator of another environmental feature (degree of oil 

pollution, mercury, organochlorine and plastic particle contamination, local sandeel stocks). WGSE discussed the 

possible development of EcoQs on seabird diversity and on total seabird biomass and noted the possibilities of 

developing such EcoQs. Such metrics could also be considered at the both the regional (country) scale and for the 

whole North Sea area. 

WGSE recognises the importance of seabird population parameters but cannot yet recommend an EcoQO. WGSE 

would be prepared to consider these possibilities further at future meetings. 


Alcock, R.E., Boumphrey, R. Malcolm, H.M., Osborn, D., and Jones, K.C. 2002. Temporal and spatial trends of PCB 

congeners in UK gannet eggs. Ambio, 31: 202–206 

Bakker, J.F., Bartelds, W., Becker, P.H., Bester, D., Dijkshuizen, D., Fredericks, B., and Reineking, B. 1999. Marine 

Chemistry. Ed. by de Jong, F., Bakker, J.F., van Berkel, C.J.M., Dankers, N.M.J.A., Dahl, K., Gätje, C., Marencic, 

H. and Potel, P. In 1999 Wadden Sea Quality Status Report. Wadden Sea Ecosystem No. 9. Common Wadden Sea 

Secretariat, Trilateral Monitoring and Assessment <strong>Group</strong>, Wilhelmshaven, Germany: 85–117. 

Becker, P.H., Munoz Cifuentes, J., Behrends, B., and Schmieder, K.R. 2001. Contaminants in bird eggs in the Wadden 

Sea. Temporal and spatial trends 1991–2000. Wadden Sea Ecosystem No. 11. Common Wadden Sea Secretariat, 

Trilateral Monitoring and Assessment <strong>Group</strong>, Wilhelmshaven, Germany. 


Frederiksen, M., Harris, M., and Wanless, S. 2004. Spatio-temporal pattern of black-legged kittiwake nesting success. 

Abstract of paper at Seabird <strong>Group</strong> conference, Aberdeen, 2–4 April 2004. 

ICES 2001. Report of the working group on the assessment of demersal stocks in the North Sea and Skagerrak. ICES 

CM 2001/ACFM:07. 

ICES 2002. Report of the <strong>Working</strong> <strong>Group</strong> on Seabird Ecology. ICES CM 2002/C:4. 

ICES 2003a. Report of the <strong>Working</strong> <strong>Group</strong> on Seabird Ecology. ICES CM 2003/C:03. 

ICES 2003b. Report of the Advisory Committee on Ecosystems. ICES Co-operative Research Report No. 262. 

Mavor, R.A., Pickerell, G., Heubeck, M., and Mitchell, P.I. 2002. Seabird numbers and breeding success in Britain and 

Ireland, 2000. Joint Nature Conservation Committee, Peterborough. UK Nature Conservation, No. 26. 

Moser, M.L., and Lee, D.S. 1992. A fourteen-year survey of plastic ingestion by Western North Atlantic seabirds. 

Colonial Waterbirds, 15: 83–94. 

OSPAR 1997. JAMP guidelines for monitoring contaminants in biota. 9/6/97, Oslo. 

OSPAR 2004a. Progress in the development of the EcoQ element for local sandeel availability to black-legged 

kittiwakes. Paper BDC 04/02/09 to OSPAR Biodiversity Committee, Bruges, 16–20 February 2004. 

OSPAR 2004b. Proportion of oiled guillemots amongst those found dead or dying on beaches (North Sea Pilot Project 

on Ecological Quality Objectives). Paper BDC 04/02/10 to OSPAR Biodiversity Committee, Bruges 16–20 

February 2004. Including Camphuysen C.J. 2003. North Sea pilot project on Ecological Quality Objectives, Issue 

4. Seabirds, EcoQO element F: Proportion of oiled Common Guillemots among those found dead or dying on 

beaches. Oiled-Guillemot EcoQO. Report to Biodiversity Committee (BDC) 2004 and OSPAR Convention for the 

Protection of the Marine Environment of the North-east Atlantic 2005. Commissioned by the North Sea 

Directorate, Ministry of Transport, Public Works and Water Management. CSR Report 2004–011. 

OSPAR. 2004c. Summary record of Biodiversity Committee, Bruges, 16–20 February 2004. Paper BDC04_SR. 

OSPAR. 2004d. Inventory of influence of human activities on EcoQOs and identification of sectors and other 

stakeholders. Paper BDC 04/2/5 to OSPAR Biodiversity Committee, Bruges,16–20 February 2004. 

Van Franeker, J.A., 1985. Plastic ingestion in the North Atlantic fulmar. Marine Pollution Bulletin 16: 367–369. 

Van Franeker, J.A., and Meijboom, A. 2002. LITTER NSV, Marine litter monitoring by northern fulmars; a pilot study. 

Wageningen, Alterra, Green World Research. Alterra-rapport 401. 72 pp. 

Van Franeker J.A., and Meijboom, A. 2003. Marine litter monitoring by northern fulmars: progress report 2002. Alterra 

rapport 622, Alterra Green World Research, Wageningen, 49pp. 

Vlietstra, L.S., and Parga, J.A. 2002. Long-term changes in the type, but not amount, of ingested plastic particles in 

short-tailed shearwaters in the southeastern Bering Sea. Marine Pollution Bulletin, 44: 945–955. 

Walsh, P.M., Halley, D.J., Harris, M.P., del Nevo, A., Sim, I.M.W., and Tasker, M.L. 1995. Seabird monitoring 

handbook for Britain and Ireland. JNCC / RSPB / ITE / Seabird <strong>Group</strong>, Peterborough. 

8 SUMMARY OF THE SIZE, DISTRIBUTION, AND STATUS OF SEABIRD POPULATIONS IN 

THE NORTH SEA FOR THE PERIOD 2000–2004, AND ANY TRENDS OVER RECENT 

DECADES IN THESE POPULATIONS, FOR INPUT TO REGNS IN 2006. 

Term of Reference: start preparations to summarise the size, distribution and status of seabird populations in the North 

Sea for the period 2000–2004, and any trends over recent decades in these populations, for input to REGNS in 2006. 


The status of seabirds in the North Sea (defined as ICES Areas III a-d and IV a-c) and threats to their populations were 

addressed by WGSE in 2001and 2002 (ICES 2001, 2002). Population trends, in some cases very approximate, were 

identified over the last two or three decades. WGSE has been asked to start preparations to summarise the size, 

distribution and status of seabird populations in the North Sea for the period 2000–2004, identifying any trends over 

recent decades, for input to the Regional Ecosystem <strong>Group</strong> for the North Sea. The time period and geographical scope 

of focus are slightly different from those earlier terms of reference. In the present context the North Sea refers to ICES 

IV a-c and III a, and it was agreed that the period of interest should be extensive and certainly initially should include 

all years/decades for which seabird population data exist. 

8.2 Population distribution and size 

About 2.5 million pairs of seabirds breed around the coasts of the North Sea. The seasonal distributions, current and 

historical, of these populations are quite well-known. Some progress was made in tabulating the current status (i.e., 

size) and trends of seabird populations in some parts of the North Sea (examples in Tables 8.1–8.4); the principal task at 

the outset was identified as initiating the preparation of an audit of the available information. A preliminary, incomplete 

summary of availability of data on breeding population size by country follows. 

38 


8.2.1 UK (ICES IVa-c) 

Data on population sizes of all seabirds in the UK with the exception of nocturnal Procellariiformes exist for the periods 

1969–70, 1985–87 and 1998–2002. Annual data are available for many colonies for a variety of years in the latter half 

of the 20th century, especially since 1986. Various other data are available for selected species, e.g., northern gannet 

and northern fulmar, throughout the 20th century. 

8.2.2 Netherlands (ICES IVc) 

Annual population data for colonies of gulls and the great cormorant exist for the Netherlands since ca. 1900. Over the 

same period decadal count data are available for terns. 

8.2.3 Norway (ICES IVa and IIIa) 

Data exist for cliff-breeding seabirds since ca. 1970. Derived population estimates exist for most species (Norwegian 

Institute for Nature Research, unpublished). 

8.2.4 Sweden (ICES IIIa) 

Few data are available for Swedish seabird populations on the North Sea coast. The latest information is contained in 

Svensson et al. (1999), and indicates generally that populations have either remained fairly stable since the 1980s or 

have increased. 

8.2.5 Belgium (ICES IVc) 

No information was available to us for seabird populations in Belgium. 

8.2.6 Denmark (ICES IVb and IIIa) 

Population data exist for at least the great cormorant, razorbill and gulls since ca. 1920/s30, annually from ca.1980. 

Data (not annual) for the black guillemot and black-legged kittiwake also date from ca. 1980. In 2002, WGSE reported 

on population trends from the 1980s to 1990s in a more extensive area around the North Sea (see Grell 1998, ICES 

2002). 

8.2.7 Germany (ICES IVb) 

Various long-term data sets exist for populations of seabirds in Germany, in some cases dating from ca.1900. WGSE 

reported information on North Sea populations in 2002 (ICES 2002). 

8.3 Population trends 

WGSE recognised that seabird population ecology is perhaps better known than that of most other groups of marine 

organisms and that many kinds of population ecological data have been collected over many decades for a variety of 

species and regions. Given the wealth of data that are available, and are of potential use in integrative studies, WGSE 

adopted an inclusive definition of population trends and identified a range of population parameters for consideration in 

future development of this term of reference. These are indicated in Table 8.5 with a brief explanation of their 

significance and an example of a recent published study. 


Table 8.1. Some breeding population sizes of seabird (number of pairs) in ICES area IVa. Data are from Lloyd et al. (1991), Mitchell 

et al. (2004) and the Norwegian Seabird database (Norwegian Institute for Nature Research, unpublished). 

40 

UK Norway 

1985–87 1998–2002 Annual change 2003 

Northern fulmar 341,644 318,548 −1% 1,500 

Manx shearwater nc 7 − 

European storm-petrel nc 8,929 − 

Leach’s storm-petrel nc 35 − 

Northern gannet 17,188 27,334 +4% 

Great cormorant 1,274 967 −2% 

European shag 11,909 9,042 −2% 5,000 

Arctic skua 2,450 1,876 −2% 

Great skua 5,498 9,060 +3% 5 

Mediterranean gull 0 0 − 

Black-headed gull 5,386 4,385 −1% 

Mew gull 1 11,026 14,589 +2% 50,000 

Lesser black-backed gull 2,490 1,404 −4% 98,000 

Herring gull 24,036 15,754 −3% 33,000 

Great black-backed gull 9,862 8,834 −1% 8,500 

Black-legged kittiwake 190,359 144,974 −2% 6,000 

Sandwich tern 462 172 -7% 

Roseate tern 0 0 - 

Common tern 1,210 1,022 −1% 7,000 

Arctic tern 26,527 33,246 +2% 5,100 

Little tern 27 29 +1% 

Common guillemot 338,331 416,435 +2% 150 

Razorbill 29,268 30,380 0% 300 

Black guillemot 21,008 22,873 +1% 380 

Atlantic puffin 2 115,698 117,722 0% 14,000 


Table 8.2. Some breeding population sizes of seabird (number of pairs) in ICES area IVb. Data are from Lloyd et al. (1991), Mitchell 

et al. (2004), Hälterlein and Behm-Berkelmann (1991), and Südbeck (unpublished). 

UK Germany 

1985–87 1998–2002 Annual 

change 

1990 2001–2002 Annual 

change 

Northern fulmar 13,450 14,118 < +1% 20 100 +14% 

Manx shearwater 0 0 − 

European storm-petrel 0 0 − 

Leach’s storm-petrel 0 0 − 

Northern gannet 22,371 46,662 +6% 0 130 − 

Great cormorant 861 1061 +2% 

European shag 5,402 3,218 −4% 

Arctic skua 0 0 − 

Great skua 0 0 − 

Mediterranean gull 0 0 − 4 2 − 

Little gull 1 0 − 

Black-headed gull 5,932 3,167 −5% 57,497 78,440 +3% 

Mew gull 1 189 321 +4% 4,740 6,692 +3% 

Lesser black-backed gull 5,580 8,848 +4% 3,155 28,382 +22% 

Herring gull 41,936 30,397 −2% 44,446 36,170 −2% 

Yellow-legged gull 11 − 

Great black-backed gull 31 101 +10% 3 14 +15% 

Gull-billed tern 46 55 +2% 

Black-legged kittiwake 213,236 148,593 −3% 3,700 8,000 +7% 

Sandwich tern 6,249 4,500 −3% 9,319 8,233 < −1% 

Roseate tern 49 47 < −1% 

Common tern 2,207 2,965 +2% 7,377 − 

Arctic tern 4,869 4,626 < −1% 6,428 − 

Common/Arctic tern 16,159 − 

Little tern 364 187 −5% 479 692 +4% 

Common guillemot 115,066 176,001 +3% 1,800 2,200 +2% 

Razorbill 13,704 20,639 +3% 6 17 +10% 

Black guillemot 3 3 0% 

Atlantic puffin 2 54,385 149,943 +8% 


Table 8.3. Some breeding population sizes of seabird (no. of pairs) in ICES area IVc. Data are from Lloyd et al. (1991), Mitchell et 

al. (2004), and Dijk et al. (1999, 2003). 

UK Netherlands 

1985–87 1998–2002 Annual 

change 

Northern fulmar 455 144 −8% 

Manx shearwater 0 0 − 

European storm-petrel 0 0 − 

Leach's storm-petrel 0 0 − 

Northern gannet 0 0 − 

1997 2002 Annual 

change 

Great cormorant 0 40 − 17,409 22,000 +5% 

European shag 0 0 − 

Arctic skua 0 0 − 

Great skua 0 0 − 

Mediterranean gull 0 43 − 376 230 −9% 

Little gull − 3 2 0% 

Black-headed gull 21,169 33,260 +3% 140,000 135,500 < −1% 

Mew gull 23 22 < −1% 6,200 6,000 0% 

Lesser black−backed gull 5,051 8,972 +5% 57,200 90,000 +9% 

Herring gull 6,443 3,485 −4% 67,000 76,500 +3% 

Yellow−legged gull 0 5 15 +25% 

Great black−backed gull 0 4 0% 8 20 +20% 

Gull−billed tern 0 

Black−legged kittiwake 2,543 1,598 −3% 

Sandwich tern 3,864 4,615 +1% 11,913 17,300 +8% 

Roseate tern 0 1 

Common tern 1,467 1,211 −1% 18,000 17,700 < −1% 

Arctic tern 4 8 +5% 17,063 15,500 −2% 

Little tern 1,456 1,087 −2% 515 450 −3% 

Common guillemot 0 0 − 

Razorbill 0 0 − 

Black guillemot 0 0 − 

Atlantic puffin 0 0 − 

42 


Table 8.4. Some breeding population sizes of seabird (number of pairs) in ICES area IIIa. Data are from the Norwegian Seabird 

database (Norwegian Institute for Nature Research, unpublished). 

Norway 

2003 

Northern fulmar 20 

Northern gannet 

Great cormorant 

European shag 

Arctic skua 

Great skua 

Mediterranean gull 

Little gull 

Black−headed gull 

Mew gull 20,000 

Lesser black−backed gull 40,000 

Herring gull 20,000 

Yellow−legged gull 

Great black−backed gull 2,500 

Gull−billed tern 

Black-legged kittiwake 

Sandwich tern 

Roseate tern 

Common tern 3,000 

Arctic tern 100 

Little tern 

Whiskered tern 

Black tern 

Common guillemot 

Razorbill 

Black guillemot 30 

Atlantic puffin 2 


Table 8.5. The availability of time series data of life history parameters of seabird populations in the North Sea. 

Parameter Availability Reference example 

Populations 

- breeding population size +++ Mavor, R.A., Pickerell, G., Heubeck, M., and Mitchell, P.I. 2002. 

Seabird numbers and breeding success in Britain and Ireland, 2001. 

Joint Nature Conservation Committee, Peterborough (UK Nature 

Conservation No. 26.) 

Breeding population size (numbers of pairs or occupied nests) is probably the most widely available parameter and there is often a 

legal requirement to collect such data for species of conservation concern. However, monitoring seabird breeding numbers alone, 

will not only fail to provide any indication as to the cause of a measured change in numbers, but also may present a less than optimal 

approach to detecting change, since specific life history parameters may vary more strongly in response to changes in food supply 

than would breeding numbers. Detailed time series exist for British seabird colonies from 1986–2004. For a few species and 

specific colonies, time series exist for 1900–2004 on a decadal basis and in some cases an annual basis. 

- incidence of non-breeding + Harris M.P., Wanless S., and Rothery P. 1986. Counts of breeding 

and non-breeding Guillemots Uria aalge at a colony during the 

chick rearing period. Seabird, 9: 43–46. 

Seabirds may forego breeding in years of low prey abundance and as such this parameter is an indicator of the state of 

environmental conditions prior to the breeding season. A few time series may exist but are not readily available. 

- adult survival ++ Ratcliffe N., Catry P., Hamer K.C., Klomp N.I., and Furness R.W. 

2002. The effect of age and year on the survival of breeding adult 

Great Skuas Catharacta skua in Shetland. Ibis, 144: 384–392. 

In general, seabirds represent extreme K-selected species, in which adult survival is generally high, and annual reproductive output 

low. A significant reduction in adult survival by causes a stronger response of population size than a change in most other 

parameters. Several time series exist, mostly for about 1985–2004. 

- recruitment 

% of cohorts that recruit + Becker P.H., H. Wendeln, and J. González-Solis 2001. Population 

dynamics, - recruitment, individual quality and reproductive 

strategies in Common Terns Sterna hirundo marked with 

transponders. Ardea, 89: 241–252. 

Juvenile mortality is in most species quite substantial and relatively few juveniles recruit into the breeding population. Fluctuations 

in juvenile mortality may result from poor fledging condition or adverse environmental conditions after the breeding season. 

Recruitment rates into breeding populations (rejuvenating the breeding stock) indicate survival of young birds and as it were 

“overwintering” success. In many long-lived seabirds, recruitment into the breeding population takes place after several years (up to 

12 years in some species). A relatively minor or at best a delayed response might be expected of population size. A few time series 

exist for about 1990–2004. 

- recruitment age + Frederiksen, M., and T. Bregnballe. 2001. Conspecific reproductive 

success affects age of recruitment in a great cormorant 

Phalacrocorax carbo sinensis colony. - Proceedings of the Royal 

Society of London, series B, 268: 1519–1526. 

In many long-lived seabirds, recruitment into the breeding population takes place after several years (up to 12 years in some 

species). Shifts in recruitment age may point at density dependent changes in the likelihood prospecting young birds can enter the 

population. Annual recruitment rates into the breeding population may indicate the quality of the colony and year in terms of, e.g., 

food supply. Some data exist, but may not provide complete time series. 

- immigration rate + Moss R., Wanless S., and Harris M.P. 2002. How small Northern 

Gannet colonies grow faster than big ones. Waterbirds, 25: 442– 

448. 

The scope for immigration into established breeding colonies may result from density dependent mechanisms influenced by for 

example per capita food supply and available nesting space. Some data exist, and there may be some time series, but often based on 

modelling rather than purely empirical data. 

- per capita emigration rate + Frederiksen M., and Petersen A. 2000. The importance of natal 

dispersal in a colonial seabird, the Black Guillemot Cepphus grylle. 

Ibis, 142: 48–57. 

The need to emigrate out of an established breeding colony may result from density dependent mechanisms influenced by for 

example poor food supply and predation rates. Modelling can be used to estimate these rates for certain well studied colonies. 

44 


Table 8.5. Continued. 

HUNTING STATUS +++ Spaans A.L. 1998. Breeding Lesser Black-backed Gulls Larus 

graellsii in The Netherlands during the 20 th century. Sula, 12: 173– 

182. 

The most marked changes in seabird populations in the North Sea over the past 150 years have resulted from the relaxation of 

harvesting (seabirds as food), hunting (sports, food), and persecution (seabirds as pests). These impacts, summarised as ‘hunting 

status’ may well mask environmental factors that impact seabird populations. Knowledge of statutory protection and periods of 

persecution are generally well known since 1900. 

Reproduction and food provisioning 

- reproductive success +++ Mavor, R.A., Pickerell, G., Heubeck, M., and Mitchell, P.I. 2002. 

Seabird numbers and breeding success in Britain and Ireland, 2001. 

Joint Nature Conservation Committee, Peterborough (UK Nature 

Conservation No. 26.). 

Breeding success can be measured in various ways and substantial data are collected over a wide range of species (numerous 

colonies, study plots) for at least several decades. Success can be measured in various ways, not detailed here, and is indicative of 

breeding conditions and food supply. Detailed data exist as time series for many colonies since 1986, and for a few species and 

colonies for earlier decades. 

- laying date ++ Greenwood, J.J.D. 1983. The laying date of Razorbills Alca torda. 

Ibis, 124: 108. 

Laying is usually timed such that chicks are to be fed when food supply is at its maximum. Short summer seasons (e.g., at high 

latitudes) lead to shorter windows). As early as possible breeding is often advantageous and changes in laying dates may result from 

climatic fluctuations. Time series exist for certain species and colonies for probably several decades. 

- clutch size ++ Bolton M., Monaghan P., and Houston D.C. 1993. Proximate 

determination of clutch size in lesser black-backed gulls: the roles 

of food supply and body condition. Canadian Journal of Zoology, 

71: 273–279. 

Favourable breeding conditions will lead to a maximal clutch size, poor conditions may give rise to smaller clutches. Note that many 

seabirds lay only a single egg per season. Time series exist for certain species and colonies for probably several decades. 

- egg size ++ Furness R.W. 1984. Influences of adult age and experience, nest 

location, clutch size and laying date on the breeding success of the 

Great Skua Catharacta skua. Journal of Zoology, 202: 565–576. 

High quality parents produce better and larger eggs than conspecifics of less individual quality. Favourable breeding conditions 

permit birds to produce better (larger) eggs. Time series exist for certain species and colonies for probably several decades. 

- chick growth rate ++ Drent R.H., Klaassen, M., and Zwaan B. 1992. Predictive growth 

budgets in terns and gulls. In Population dynamics of Lari in 

relation to food resources. Ed. by Spaans A.L. Ardea 80: 5–17. 

Favourable breeding conditions (e.g., abundant food supply) make chicks grow better. Time series exist for certain species and 

colonies for some years, but rarely over several decades. 

- mass of fledglings ++ Barrett, R.T., and Rikardsen, F. 1992. Chick growth, fledging 

periods and adult mass loss of Atlantic Puffins Fratercula arctica 

during years of prolonged food stress. Colonial Waterbirds, 15: 24– 

32. 

Body mass at fledging may be considered an indicator of favourable growth. Time series exist for certain species and colonies for 

some years, but rarely over several decades. 

- adult nest and brood attendance; 

provisioning rate 

+ Coulson, J.C., and Johnson, M.P. 1993. The attendance and absence 

of adult Kittiwakes Rissa tridactyla from the nest site during the 

chick stage. Ibis, 135: 372–378. 

Poor food supplies during breeding lead to prolonged absences of parent birds at the nest and to low provisioning rates. Time series 

exist for certain species and colonies for some years, but rarely over several decades. 

BODY CONDITION OF BREEDERS + Wendeln, H. 1997. Body mass of female Common Terns (Sterna 

hirundo) during courtship: relationships to male quality, egg mass, 

diet, laying date and age. Colonial Waterbirds 20: 235–243. 

The body condition of breeding birds is an indicator of both quality of the bird and the conditions it is breeding in. Data sets are 

limited for most species and there are few monitoring programmes available. Time series exist for certain species and colonies but 

data are mostly just for some years. 


Table 8.5. Continued. 

BREEDING SEASON FOOD / DIET ++ Votier, S.C., Furness, R.W., Bearhop, S., et al. 2004. Changes in 

fisheries discard rates and seabird communities. Nature 427: 727– 

730. 

Diet composition data for breeding birds are available for numerous populations, sometimes for series of years. Shifts in diet result 

from shifts in prey resources usually. Some detailed time series exist for up to 30 years, but for most species such time series 

are rather short. 

NON-BREEDING POPULATIONS ++ Kirby J.S., Gilburn A.S. and Sellers R.M. 1995. Status, distribution 

and habitat use by Cormorants Phalacrocorax carbo wintering in 

Britain. Ardea 83: 93–102. 

Seabirds disperse or migrate after the breeding season and wintering (or non-breeding) populations in the North Sea include both 

resident seabirds as well as ‘winter visitors’ and ‘migrants’. Mid-winter censuses of waterfowl (including seaduck) are available for 

long periods with a high geographical resolution. Estimates of non-breeding populations of pelagic seabirds are available on the 

basis of composite databases of offshore surveys. Although there are some time series for about 20 to 30 years, many of the 

data sets are of relatively low count accuracy. 

NON-BREEDING DIET + Wurm S. and Hüppop O. 2003. Fischereiabhängige Veränderungen 

in der Ernährung Helgoländer Großmöwen im Winter. Corax 

19(Sonderheft 2): 15–26. 

Seabirds disperse or migrate after the breeding season and are therefore more difficult to approach and handle. Dietary information 

may still be collected at roosts and other sites where seabirds congregate on land, but for most pelagic species it is very difficult to 

collect dietary information. Few long time series are likely to be available. 

NON-BREEDING DISTRIBUTION ++ Stone, C.J., A. Webb, C. Barton, N. Ratcliffe, T.C. Reed, M.L. 

Tasker, C.J. Camphuysen and M.W. Pienkowski. 1995. An atlas of 

seabird distribution in north-west European waters. Joint Nature 

Conservation Committee, Peterborough. 

Seabirds disperse or migrate after the breeding season and wintering (or non-breeding) populations in the North Sea include both 

resident seabirds as well as ‘winter visitors’ and ‘migrants’. Mid-winter censuses of waterfowl (including seaduck) are available for 

long periods with a high geographical resolution (coastal wetlands). Non-breeding distributions of pelagic seabirds are available in 

the form of composite maps of non-breeding distribution based on series of years work, often in areas that differ between seasons. 

Comparisons may be made between decades, but annual data are unlikely to be of sufficient resolution to provide annual 

time series. 

TIMING OF MIGRATION ++ Camphuysen C.J. and Dijk J.van 1983. Zee- en kustvogels langs de 

Nederlandse kust, 1974–79. Limosa, 56: 81–230. 

Coastal seawatching results provide information on the timing and strength of seabird passage during spring and autumn migration. 

The median date of passage does change from year to year, possibly in response to climatic fluctuations. There are probably some 

quite long time series though possibly not readily extracted from readily available data sets. 

+++ large scale, long time series; ++ moderate data; + few data 

8.4 Future development of this term of reference 

Further progress with this term of reference will begin with completion of an audit of available data and possible 

creation of a metadatabase of available time series on aspects of seabird population ecology, and compilation of 

breeding population database. 

8.5 Additional references 

Dijk, A.J. van, Kleefstra, R., Zoetebier, D., and Meijer, R. 1999. Kolonievogels en zeldzame broedvogels in Nederland 

in 1997. SOVON Monitoringrapport 1999/09, SOVON, Beek-Ubbergen. 

Dijk, A.J. van, Hustings, F., Koffijberg, K., Weide, M. van der, Zoetebier, D. and Plate, C., 2003. Kolonievogels en 

zeldzame broedvogels in Nederland in 2002. SOVON-monitoringrapport 2003/02. SOVON, Beek-Ubbergen. 

Grell, M.B. 1998. Fuglenes Danmark. Gads Forlag, Viborg. 825 pp. (In Danish). 

Hälterlein, B. and Behm-Berkelmann, K. 1991. Brutvogelbestände an der deutschen Nordseeküste im Jahre 1990 – 

Vierte Erfassung durch die Arbeitgemeinschaft “Seevogelschutz”. Seevögel 12: 47–51. 

ICES. 2001. Report of the <strong>Working</strong> <strong>Group</strong> on Seabird Ecology. ICES CM 2001/C:05. 


Lloyd, C., Tasker, M. L., and Pertridge, K. 1991. The status of seabirds in Britain and Ireland. T and A D Poyser, 

London. 355 pp. 

Mitchell, P.I., Newton S.F., Ratcliffe, N., and Dunn T.E. 2004. Seabird Populations of Britain and Ireland. T and AD 

Poyser, London. 

46 


Norwegian Institute for Nature Research. Norwegian Seabird Database. Unpublished, Trondheim. 

Südbeck, P. unpublished data from NiedersächsischesLandesant für Ökologie, Landesant für den Nationalpark 

Schleswig-HolsteinischesWattenmeer; Verein Jordsand, 2002. 

Svensson, S., Svensson, M., and Tjernberg, M. 1999. Svensk fågelatlas. Vår Fågelvärld, supplement 31, Stockholm, 

550 pp. 

9 RECOMMENDATIONS 

9.1 Chair of WGSE 

The WGSE unanimously recommends that Dr Stefan Garthe, FTZ, University of Kiel, Hafentörn, D-25761Büsum, 

Germany, should be invited to Chair WGSE from 1 January 2005. 

9.2 Proposal for next meeting 

The <strong>Working</strong> <strong>Group</strong> on Seabird Ecology makes the following proposals: 

The <strong>Working</strong> <strong>Group</strong> on Seabird Ecology [WGSE] (Chair: Dr Stefan Garthe*, Germany) will meet in Texel, The 

Netherlands from 29 March–1 April 2005 to: 

a) Continue to summarize the size, distribution and status of seabird populations in the North Sea for the period 

2000–2004, and any trends over recent decades in these populations, for input to REGNS in 2006; 

b) Develop EcoQOs for seabird populations; 

c) Review the impacts of recent major oil spills on seabirds (“Erika”, “Prestige”, “Tricolor”); 

d) Review the consequences for foraging conditions of sea ducks of the Spisula decline in the southern North Sea; 

e) Examine the foodweb relationships of seabirds indicated by food consumption estimates in the Northeast and 

Northwest Atlantic regions. 

Supporting information 

Priority: This is the only major forum for work being carried out by ICES in relation to marine birds. If 

ICES wishes to maintain its profile in this area of work, then the activities of WGSE must be 

regarded as of high priority. 

Scientific 

justification and 

relation to Action 

Plan 

Action Plan Nos. 1.2, 1.8, 2.2, 2.3, 4.15. 

a) This Term of Reference continues the work requested by ICES to provide data sets for the 

integrated assessment of the North Sea under the coordination of REGNS; 

b) Although WGSE has recommended several EcoQOs using seabirds as a means of measuring 

contaminants or ecological conditions in the North Sea (oil pollution, mercury, 

organochlorines, plastic, sandeel availability to predators), EcoQOs for seabirds have not been 

fully developed. Here we propose a discussion of the possible metrics and objectives for seabird 

populations themselves, such as rates of change in breeding population size, seabird community 

composition, biomass or diversity measures; 

c) Although it is a well-established opinion that chronic oil pollution tends to impose a greater 

mortality on seabirds than that caused by the infrequent major oil spill events, the recent spills 

from the “Erika”, “Prestige” and “Tricolor” appear to have killed very large numbers of 

seabirds. We consider that it would be instructive to review the studies carried out on these 

three major incidents and the monitoring of seabird populations likely to have been affected by 

these spills; 

d) Stocks of Spisula in the southern North Sea have decreased considerably in recent years, and 

the abundance of Ensis has increased. Sea ducks, especially scoters, have switched to feeding 

on Ensis despite the apparent low suitability of that food. We propose reviewing the changes in 

foodweb relationships of these ducks and their winter ecology that have resulted from the 

changes in shellfish stocks; 

e) WGSE has worked for several years on assessing the seabird community composition, 

trophic relations and energy consumption of seabirds in the ICES and NAFO Regions. Having 


Resource 

requirements: 

identified major differences in trophic ecology of seabirds between ICES and NAFO Regions, 

we propose continuing this work by examining these patterns further, and in particular relating 

the differences to possible differences in lower trophic levels, seabird habitats or oceanography 

between the east and west North Atlantic. 

In order to carry out work on the proposed Terms of Reference there may be a need to add 

some new members to the WGSE, particularly individuals with expertise in sea duck ecology in 

the southern North Sea. Facilities for WGSE to work in Texel are anticipated to be excellent. 

Participants: The <strong>Working</strong> <strong>Group</strong> should be able to achieve most of the above objectives. However, some 

members may not be able to attend through lack of funding. Funding of these members from 

Member Countries would be very welcome. 

Secretariat Facilities: The usual excellent support from the Secretariat will be appreciated. 

Financial: No financial implications for ICES. 

Linkages to advisory 

committees: 

Linkages to other 

committees or 

groups: 


organisations: 

48 

Both ACFM and ACE would find the information on consumption by seabirds of relevance to 

the forthcoming multispecies modelling of the North Sea, and to assessing environmental needs 

of seabirds and effects of seabirds on fish stocks. 

WGSE is keen to continue the process of integration of seabird ecology into the workings of 

ICES, and warmly welcomes the initiative of REGNS. 

Information on seabird communities, population trends and environmental impacts should also 

be of interest to OSPAR and HELCOM. 


10 ANNEXES 

Annex 1 List of participants 

Name Address Telephone Telefax E-mail 

Tycho Anker- NINA, Tungasletta 2 

+47 7380 1443 +47 7380 1401 tycho@nina.no 

Nilssen NO-7485 Trondheim 

Norway 

Rob Barrett Tromsø University Museum 

Zoology Department 

N-9037 Tromsø 

Norway 

+47 77645013 +47 77645520 robb@tmu.uit.no 

Peter Becker Institut für Vogelforschung 

Vogelwarte Helgoland, 

An der Vogelwarte 21 

D-26386 Wilhelmshaven 

Germany 

+49 4421 96890 +49 4421 968955 peter.becker@ifv.terramare.de 

Kees 

Royal Netherlands Institute for +31 222 369488 +31 222 319674 camphuys@nioz.nl 

Camphuysen Sea Research 

PO Box 59 

1790 AB Den Burg 

Texel 

The Netherlands 

Gilles 

Service Canadien de la Faune +1 4186496127 +1 4186485511 gilles.chapdelaine@ec.gc.ca 

Chapdelaine Environment Canada CWS 

1141, route de l’Eglise, Ste-Foy 

Quebec G1V 4H5 

Canada 

Morten CEH Banchory 

+44 1330 826338 +44 1330 823303 mfr@ceh.ac.uk 

Frederiksen Hill of Brathens 

Glassel 

Banchory AB31 4BW 

United Kingdom 

Bob Furness University of Glasgow, 

+44 1413303560 +44 1413305971 r.furness@bio.gla.ac.uk 

(Chair) Graham Kerr Building, 

Glasgow G12 8QQ, 


Stefan Garthe FTZ, University of Kiel 

Hafentörn 

D-25761 Büsum 

Germany 

+49 4834 604 116 +49 4834 604 199 garthe@ftz-west.uni-kiel.de 

Anders Dept. of Arctic Environment +45 4630 1934 +45 4630 1914 amo@dmu.dk 

Mosbech National Environmental 

Research Institute 

Frederiksborgvej 399 

PO Box 358 

DK-4000 Roskilde 

Denmark 

Daniel Oro Institut Mediterrani d'Estudis 

Avançats IMEDEA 

CSIC-UIB 

Miquel Marques 21 

07190 Esporles 

Spain 

+34 971611731 +34 971611761 d.oro@uib.es 

Jim Reid Joint Nature Conservation 

Committee 

Dunnet House, 

7 Thistle Place 

Aberdeen AB10 1UZ 


+44 1224 655702 +44 1224 621488 jim.reid@jncc.gov.uk 

Mark Tasker Joint Nature Conservation 

Committee 

Dunnet House, 7 

Thistle Place 

Aberdeen AB10 1UZ 


+44 1224 655701 +44 1224 621488 mark.tasker@jncc.gov.uk 


Annex 2 Terms of Reference 

The <strong>Working</strong> <strong>Group</strong> on Seabird Ecology [WGSE] (Chair: R.W. Furness, UK) will meet in Aberdeen, U.K. from 29 

March–2 April 2004 to: 

a) review the factors influencing trends in abundance of seabirds in the Baltic Sea; 

b) review progress in studies of seabirds in relation to marine wind farms; 

c) review relationships between seabirds and oceanographic features, with particular reference to effects of climate 

change; 

d) consider the selection of seabird species and populations that would be appropriate to use in an EcoQO relating to 

seabird population trends in the North Sea as indices of seabird community health; 

e) complete the work carried out in 2003 to compare seabird communities and prey consumption between the east 

and west North Atlantic; 

f) provide the Study <strong>Group</strong> on Multispecies Assessments in the North Sea (SGMSNS) with data on the consumption 

of different prey by seabirds in the North Sea, in a format specified by SGMSNS; 

g) reconsider the formulation of the EcoQOs listed below, determine whether a more specific EcoQO is needed in 

terms of its specification to the metric, time and geographical area, and as necessary propose more specific 

EcoQO(s) [OSPAR 2004/1]: 

i) EcoQ element (f) Proportion of oiled common guillemots among those found dead or dying on beaches, 

ii) EcoQ element (g) Mercury concentrations in seabird eggs and feathers, 

iii) EcoQ element (h) Organochlorine concentrations in seabird eggs, 

iv) EcoQ element (i) Plastic particles in stomachs of seabirds; 

v) EcoQ element (j) Local sandeel availability to black-legged kittiwakes, 

vi) EcoQ element (k) Seabird population trends as an index of seabird community health. 

h) start preparations to summarise the size, distribution and status of seabird populations in the North Sea for the 

period 2000–2004, and any trends over recent decades in these populations, for input to REGNS in 2006. 

WGSE will report by 30 April 2004 for the attention of the Oceanography Committee, ACME, and ACE. 

Supporting information 

Priority: This is the only major forum for work being carried out by ICES in relation to marine birds. If ICES wishes 

to maintain its profile in this area of work, then the activities of WGSE must be regarded as of high priority. 

Scientific 

justification: 

50 

a) WGSE reviewed data on population trends of seabirds in the Baltic Sea in the 2003 meeting. Given that 

there have been major declines in numbers of certain populations and species, it is important to review 

likely causes of these declines, and factors that may have contributed to the increase in numbers in a 

few species; 

b) With a rapid development of marine wind farms in many European countries, the <strong>Group</strong> should review 

progress in the areas that have been identified as major gaps in knowledge; two of the most important 

of these are the development of methods to measure bird collision risk, and the behavioural responses 

of birds to marine wind farms (such as avoidance causing possible loss of foraging habitat, barriers to 

movement, and use of marine wind farms as new habitat for resting or feeding); 

c) There has been a large increase in work on the extent to which at-sea distributions of seabirds are 

determined by oceanographic factors. This has been partly by at-sea survey work, and partly by the 

application of data loggers on foraging seabirds. Recent research also indicates effects of climate 

change on seabird distribution, demography and ecology. It would be useful to review this progress. 

d) The proposed EcoQO ‘Seabird population trends in the North Sea as an index of seabird community 

health requires further work with empirical data on seabird population trends and individual colony 

trends in order that the historical trajectories and performance of the various possible metrics can be 

evaluated, especially in relation to the use of particular focal species and selected key sites as a proxy 

for the whole North Sea species’ populations (since obtaining accurate and frequent whole-North Sea 

counts of seabird breeding populations is not a practical proposition). During the 2003 WGSE meeting 

we had neither the necessary data, nor the time to perform these analyses. 

e) WGSE 2002 meeting completed a summary of the breeding seabird numbers by species, and total 

seabird energy requirements, and approximate food consumption equivalents, in all ICES areas 

(approximately described as the ‘east North Atlantic’). Given the pronounced differences in seabird 


Relation to strategic 

plan: 

Resource 

requirements: 

community composition and species abundances, and in fish stocks and fisheries, between the west and 

east North Atlantic, WGSE03 confirmed that it is instructive to compare and contrast the patterns of 

seabird community composition and energy requirements between ICES and NAFO areas 

(approximately ‘west’ and ‘east’ North Atlantic), in relation to broad differences in the histories of fish 

stocks and fisheries in these areas. 

f) WGMSNS require a compilation of data on quantities of foods consumed by seabirds in the North Sea 

for input to an MSVPA model. These data will be compiled in the format required by WGMSNS. 

g) This is to respond to an OSPAR request. 

h) This is required as the working groups input to the thematic writing panels working under the coordination 

of REGNS to develop an integrated assessment of the North Sea. For the purposes of this 

study the North Sea comprises ICES Area IV and IIIa and does not include intertidal areas. As far as 

possible, significant seasonal variation should be described.. Where possible, the causes of any trends 

should be outlined. 

The above will help achieve the following within the initial ICES strategic plan 

Goal 1. Develop a challenging core science programme to fulfil the ICES Mission. 

Goal 2. Provide sound, credible, timely, and understandable advice that is relevant to today’s and future 

societal needs. 

Goal 5. Raise public understanding of marine ecosystems and their relevance to society. 

Objective 1. Understand the physical, chemical, and biological functioning of marine ecosystems. 

Objective 2. Understand and quantify human impacts on the marine environment, including living marine 

resources. 

Objective 3. Develop the scientific basis for sustainable use and protection of the marine environment, 

including living marine resources. 

Objective 4. Provide advice on the sustainable use and protection of the marine environment, including 

living marine resources. 

Objective 5. Co-ordinate and support interdisciplinary and international marine science programmes. 

Objective 6. Broaden the diversity of the scientists that participate in ICES activities. 

Objective 11. Make the scientific products of ICES more accessible to the public 

There will be a major conference on Seabirds in Aberdeen starting on Friday 2 April 2004. Since all active 

members of the group are at present funded outside core funding within the Member Countries (many are 

privately funded), meeting in Aberdeen immediately before this conference will minimise travel costs of 

members, as most are likely to be attending the conference. 

Participants: The present members of the group should be able to achieve most of the above objectives. However, some 

may not be able to attend through lack of funding. Funding of these members from Member Countries 

would be very welcome. 

Secretariat 

Facilities: 

N/A 

Financial: No financial implications for ICES. 

Linkages to 

advisory 

committees: 


committees or 

groups: 


organisations: 

Cost Share ICES 100% 

Both ACFM and ACE would find the information on consumption by seabirds of relevance to the 

forthcoming multispecies modelling of the North Sea, and to assessing environmental needs of seabirds and 

effects of seabirds on fish stocks. 

WGSE is keen to continue the process of integration of seabird ecology into the workings of ICES. 

Several national governments have encouraged the development of at-sea wind farms to increase the 

proportion of electricity generated from renewable resources. Review of the impacts of at-sea wind farms on 

seabirds will be of interest to several statutory agencies and NGOs. 

Information on seabird communities, population trends and environmental impacts should also be of interest 

to OSPAR and HELCOM. 


Annex 3 English and scientific names of birds mentioned in this report 

52 

English name Scientific name 

Red-throated diver Gavia stellata 

Black-throated diver Gavia arctica 

Great northern diver Gavia immer 

Slavonian grebe Podiceps auritus 

Great crested grebe Podiceps griseigena 

Red-necked grebe Podiceps grisegena 

Little grebe Tachybaptus ruficollis 

Wandering albatross Diomedea exulans 

Black-browed albatross Thalassarche melanophrys 

Sooty albatross Phoebetria fusca 

Light mantled sooty alb. Phoebetria palpebrata 

Blue petrel Halobaena caerulea 

Thin-billed prion Pachyptila belcheri 

Northern fulmar Fulmarus glacialis 

Southern fulmar Fulmarus glacialoides 

Grey petrel Procellaria cinerea 

Cory’s shearwater Calonectris diomedea 

Great shearwater Puffinus gravis 

Little shearwater Puffinus assimilis 

Audubon’s shearwater Puffinus lherminieri 

Balearic shearwater Puffinus mauretanicus 

Manx shearwater Puffinus puffinus 

Sooty shearwater Puffinus griseus 

Bulwer’s petrel Bulweria bulwerii 

European storm-petrel Hydrobates pelagicus 

White-faced storm-petrel Pelagodroma marina 

Leach’s storm-petrel Oceanodroma leucorhoa 

Madeiran storm-petrel Oceanodroma castro 

Wilson’s storm-petrel Oceanites oceanicus 

Black-capped petrel Pterodroma hasitata 

Zino’s petrel Pterodroma madeira 

White-headed petrel Pterodroma lessoni 

Fea’s petrel Pterodroma feae 

Northern gannet Morus bassanus 

Great cormorant Phalacrocorax carbo 

Double-crested cormorant Phalacrocorax auritus 

European shag Phalacrocorax aristotelis 

Mute swan Cygnus olor 

Whooper swan Cygnus cygnus 

Common shelduck Tadorna tadorna 

Pintail Anas acuta 

Eurasian teal Anas crecca 

Eurasian wigeon Anas penelope 

Mallard Anas platyrhynchos 

Greater scaup Aythya marila 

Pochard Aythya ferina 

Tufted duck Aythya fuligula 

Common eider Somateria mollissima 

King eider Somateria spectabilis 

Steller’s eider Polysticta stelleri 

Harlequin duck Histrionicus histrionicus 

Long-tailed duck Clangula hyenalis 

Black scoter Melanitta nigra 

Velvet scoter Melanitta fusca 

Surf scoter Melanitta perspicillata 

Common goldeneye Bucephala clangula 

Red-breasted merganser Mergus serrator 


English name Scientific name 

Goosander Mergus merganser 

Smew Mergellus albellus 

Eurasian coot Fulica atra 

Eurasian oystercatcher Haematopus ostralegus 

Red-necked phalarope Phalaropus lobatus 

Grey phalarope Phalaropus fulicarius 

Arctic skua Stercorarius parasiticus 

Pomarine skua Stercorarius pomarinus 

Great skua Stercorarius skua 

Mediterranean gull Larus melanocephalus 

Little gull Larus minutus 

Black-headed gull Larus ridibundus 

Sabine’s gull Larus sabini 

Mew ( = Common) gull Larus canus 

Bonaparte’s gull Larus philadelphia 

Laughing gull Larus atricilla 

Ring-billed gull Larus delawarensis 

Audouin’s gull Larus audouinii 

Slender-billed gull Larus genei 

Lesser black-backed gull Larus fuscus 

Glaucous gull Larus hyperboreus 

Iceland gull Larus glaucoides 

Herring gull Larus argentatus 

Yellow-legged gull Larus cachinnans 

Great black-backed gull Larus marinus 

Ivory gull Pagophila eburnean 

Black-legged kittiwake Rissa tridactyla 

Gull-billed tern Gelochelidon nilotica 

Roseate tern Sterna dougallii 

Forster’s tern Sterna forsteri 

Common tern Sterna hirundo 

Arctic tern Sterna paradisaea 

Little tern Sterna albifrons 

Least tern Sterna antillarum 

Sandwich tern Sterna sandvicensis 

Royal tern Sterna maxima 

Caspian tern Sterna caspia 

Black tern Chlidonias niger 

Black skimmer Rynchops niger 

Common guillemot Uria aalge 

Brunnich’s guillemot Uria lomvia 

Razorbill Alca torda 

Black guillemot Cepphus grylle 

Little auk Alle alle 

Least auklet Aethia pusilla 

Atlantic puffin Fratercula arctica 

Tufted puffin Fratercula cirrhata 

Horned puffin Fratercula corniculata

Working Group on Seabird Ecology (WGSE). ICES CM 2004/C:05 ...

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