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ICES Oceanography Committee
ICES CM 2004/C:05 Ref. ACME, ACE
Report of the
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
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
4.1 Introduction................................................................................................................................................... 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 Introduction................................................................................................................................................... 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
the North Sea (SGMSNS) ........................................................................................................................................ 29
7 Ecological quality objectives.................................................................................................................................... 29
7.1 Introduction................................................................................................................................................... 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
8.1 Introduction................................................................................................................................................... 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
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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
C.Res.2003/2C05. This resolution is in Annex 2.
1.3 Overview by the Chair
The
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.
ICES WGSE Report 2004 5
Our 2004 meeting attracted twelve
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
Birdlife International, on Friday afternoon and we discussed the contents of the nearly completed
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
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
ICES WGSE Report 2004
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).
ICES WGSE Report 2004 7
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
ICES WGSE Report 2004
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
ICES. 2003. Report of the
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.
ICES WGSE Report 2004 9
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.
3.1 Introduction
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.
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ICES WGSE Report 2004
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
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
ICES WGSE Report 2004 11
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.
3.6 References
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.
ICES. 2002. Report of the
ICES. 2003. Report of the
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ICES WGSE Report 2004
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
ICES WGSE Report 2004 13
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.
4.1 Introduction
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.
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ICES WGSE Report 2004
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).
ICES WGSE Report 2004 15
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
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ICES WGSE Report 2004
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.
4.6 References
Aebischer, N.J., Coulson, J.C. and Colebrook, J.M. 1990. Parallel long-term trends across four marine trophic levels
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.
Croxall, J.P., and Rothery, P. 1991. Population regulation of seabirds: implications of their demography for
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.
Diamond, A.W., and Devlin, C.M. 2003. Seabirds as indicators of changes in marine ecosystems: ecological monitoring
on Machias Seal Island. Environmental Monitoring and Assessment, 88: 153–175.
Durant, J.M., Anker-Nilssen, T., and Stenseth, N.C. 2003. Trophic interactions under climate fluctuations: the Atlantic
puffin as an example. Proceedings of the Royal Society of London Series B, 270: 1461–1466.
Durant, J.M., Anker-Nilssen, T., Hjermann, D.Ø., and Stenseth, N.C. 2004. Regime shifts in the breeding of an Atlantic
puffin population. Ecology Letters, 7: 388-394.
Durant, J.M., Stenseth, N.C., Anker-Nilssen, T., Harris, M.P., Thompson, P.M., and Wanless, S. In press b. Marine
birds and climate fluctuations in the North Atlantic. In Marine ecosystems and climate variation – the North
Atlantic. Ed. by Stenseth, N.C., Ottersen, G., Hurrell, J.W. and Belgrano, A. Oxford University Press, Oxford: 95–
105.
Frederiksen, M., Harris, M.P., Daunt, F., Rothery, P. and Wanless, S. In press. Scale-dependent climate signals drive
breeding phenology of three seabird species. Global Change Biology.
ICES WGSE Report 2004 17
Gjerdrum, C.G., Vallée, A.M.J., St. Clair, C.C., Bertram, D.F., Ryder, J.L. and Blackburn, G.S. 2003. Tufted puffin
reproduction reveals ocean climate variability. Proceedings of the National Academy of Science of the USA, 100:
9377–9382.
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.
ICES. 2003. Report of the
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
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.
5.1 Introduction
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
ICES WGSE Report 2004
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.
ICES WGSE Report 2004 19
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
ICES WGSE Report 2004
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
ICES WGSE Report 2004 21
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
ICES WGSE Report 2004
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
ICES WGSE Report 2004 23
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
ICES WGSE Report 2004
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.
ICES WGSE Report 2004 25
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
5.3 References
Anker-Nilssen, T., Bakken, V., Strøm, H., Golovkin, A., Bianki, V.V., and Tatarinkova, I. (eds.) 2000. The status of
marine birds breeding in the Barents Sea region. Norsk Polarinst. Rapportserie No. 113, Tromsø. 213 pp.
Bakken, V., Runde, O., and Tjørve, E. 2003. Norsk ringmerkingsatlas. Vol. 1. Stavanger Museum, Stavanger. 431 pp.
Barrett, R.T., Anker-Nilssen, T., Gabrielsen, G.W., and Chapdelaine, G. 2002. Food consumption by seabirds in
Norwegian waters. ICES Journal of Marine Science, 59: 43–57.
Birt-Friesen, V.L., Montevecchi, W.A., Cairns, D.K., and Macko, S.A. 1989. Activity specific metabolic rates of freeliving
northern gannets and other seabirds. Ecology, 70: 357–367.
Brooke, M. de L. 2003. The food consumption of the world’s seabirds. Proceedings of the Royal Society of London.
Series B: Biological Sciences. Biology Letters, 271(S4): 246-248.
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.
ICES WGSE Report 2004 27
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
season
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
season
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
ICES WGSE Report 2004
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
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.
7.1 Introduction
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.
ICES WGSE Report 2004 29
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
ICES WGSE Report 2004
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
ICES WGSE Report 2004 31
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.
WGSE therefore suggests that the EcoQO be formulated as:
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
ICES WGSE Report 2004
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.
WGSE therefore suggests that the EcoQO be formulated as:
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
ICES WGSE Report 2004 33
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
ICES WGSE Report 2004
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 ).
ICES WGSE Report 2004 35
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.
7.8 References
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
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
ICES WGSE Report 2004 37
Frederiksen, M., Harris, M., and Wanless, S. 2004. Spatio-temporal pattern of black-legged kittiwake nesting success.
Abstract of paper at Seabird
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
ICES 2003a. Report of the
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
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.
8.1 Introduction
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
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
ICES WGSE Report 2004
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.
ICES WGSE Report 2004 39
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
ICES WGSE Report 2004
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%
ICES WGSE Report 2004 41
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
ICES WGSE Report 2004
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
ICES WGSE Report 2004 43
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
ICES WGSE Report 2004
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.
ICES WGSE Report 2004 45
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
ICES. 2002. Report of the
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
ICES WGSE Report 2004
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
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
ICES WGSE Report 2004 47
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
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:
Linkages to other
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.
ICES WGSE Report 2004
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,
United Kingdom
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
United Kingdom
+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
United Kingdom
+44 1224 655701 +44 1224 621488 mark.tasker@jncc.gov.uk
ICES WGSE Report 2004 49
Annex 2 Terms of Reference
The
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
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
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
ICES WGSE Report 2004
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:
Linkages to other
committees or
groups:
Linkages to other
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.
ICES WGSE Report 2004 51
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
ICES WGSE Report 2004
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
ICES WGSE Report 2004 53
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