Marine Birds Thematic Assessment

Marine birds are not in good status

The integrated status of marine bird species was assessed with the help of indicators for: (a) breeding and non-breeding abundance, and (b) breeding productivity for five species groups in four OSPAR Regions. Good environmental status was not achieved for surface-feeding birds (Regions I, II, III, IV), water column-feeding birds (Regions I, II, III, IV), benthic-feeding birds (Regions I, II, III) and wading feeding birds (Regions II, III). Good status was achieved by grazing feeding birds in Regions I, II, and III. The overall status is not good for marine birds in Regions I, II, III, and IV. No assessment could be made of Region V. 

Figure S.1: Integrated status of marine birds in the different Regions of the OSPAR Maritime Area

The confidence of the assessment is high for all regions except Region IV, where it is considered to be medium because of the limited number of species assessed and the reduced temporal data available in this Region.

Table S.1: Confidence of assessing state of marine birds 

OSPAR acts as a coordination platform in the North-East Atlantic for the regional implementation of the EU Marine Strategy Framework Directive (MSFD) that aims to achieve a Good Environmental Status (GES) in European marine environments, as well as for the coordination of other national frameworks. The characteristics of GES are determined by the individual EU member states, based on criteria elements, threshold values and methodological standards set regionally or at EU level.
Norwegian, Icelandic, United Kingdom, Greenlandic and Faroese marine areas are not covered by the MSFD.

The marine birds in the North-East Atlantic include some that spend the majority of their lives at sea (petrels and shearwaters, gannets and cormorants, skuas, gulls, terns and auks) and waterbirds that mostly inhabit intertidal areas or inshore areas close by (waders, ducks, geese, swans, grebes and divers).

The integrated assessment of marine birds in each Region was largely based on two common indicator assessments:

Marine Bird Abundance (B1) and Marine Bird Breeding Productivity (B3).

These Common Indicator Assessments were integrated to provide a status assessment of each species. If at least one indicator assessment fails the threshold, the status is not good; if all indicator assessments achieve the threshold, the status is good. Breeding and non-breeding populations of a species were assessed separately, and thus count as two elements. The assessments of populations were combined to assess the status of five species groups (surface feeders, water column feeders, benthic feeders, wading feeders, grazing feeders). A species group achieved good status if 75% or more of the populations were in good status. The overall status of marine birds in each OSPAR Region is based on a one-out-all-out assessment of the species group assessments: if one species group is in not in good status in one Region, the overall status of the Region is considered not good. Integration was done separately for the OSPAR Regions Arctic Waters (Norwegian section only), Greater North Sea, Celtic Seas and Bay of Biscay and Iberian Coast, whereas insufficient information was supplied to assess the marine bird species in the Wider Atlantic. The integration method is described in detail in the CEMP Guideline.

Additional information about the status of marine bird species is available from the pilot assessments for the candidate indicators:

offshore extension of common indicator (B1), by-catch (B5) and habitat quality (B7) (Table S.2).

This information is given in the text but did not contribute to the integrated status of species.

Table S.2: Indicators used in QSR 2023 for assessing the state of marine birds per OSPAR Region. Entries indicate whether breeding populations (B) and/or non-breeding populations (NB) were assessed. * denotes candidate indicator pilot assessments, which did not contribute to the integrated assessment

The indicator assessments also contributed to the status assessments of three species on the OSPAR list of threatened and / or declining species: the black-legged kittiwake, the roseate tern and Brünnich’s guillemot (also known as the thick-billed murre). Where data were insufficient for indicator assessments, they were supplemented by status assessments for the fuscus sub-species of lesser black-backed gull, the Iberian guillemot (a sub-species of the common guillemot) and the Balearic shearwater (see details below). Assessments have not yet been made for two Arctic species (Steller’s eider and the ivory gull) and one species from the wider Atlantic (the Barolo shearwater (separate from the little shearwater and also known as the Macaronesian shearwater)).

Iberian Guillemots. © Shutterstock

Surface-feeding birds

Surface-feeding birds typically peck food items from the surface or take it during shallow dives within the upper 1 to 2 m of the water column. Their main prey consists of small fish, zooplankton and other invertebrates and also includes discarded incidental by-catch from fisheries.

Based on the indicator assessments for abundance and productivity and the status assessments for the lesser black-backed gull (sub-species fuscus) and the Balearic shearwater, the species group of surface-feeding birds is in not in good status in the Arctic Waters, the Greater North Sea, the Celtic Seas and the Bay of Biscay and Iberian Coast, because the percentage of species in good status is below the threshold of 75% (Table S.3).

The pilot assessment for the candidate indicator on Marine Bird habitat quality (B7) shows that habitat quality in the southern North Sea (part of Region II) is good for the surface feeders: the black-legged kittiwake, the great black-backed gull and the herring gull, since they appear to be undisturbed by offshore wind farms, shipping and bottom-trawling fisheries. In the same area, the threshold for offshore winter abundance was achieved by the black-legged kittiwake, whereas the offshore abundance of great black-backed gull and herring gull was far below the threshold (pilot assessment for B1 offshore).

In the pilot assessment of the candidate indicator Marine bird bycatch (B5) , it was found through population modelling that the incidental by-catch of Cory’s shearwater in the breeding population in the Bay of Biscay and Iberian Coast would exceed a provisional threshold, indicating that the long-term viability of this species is threatened. In the same pilot assessment, the roseate tern (Greater North Sea, Celtic Seas, Wider Atlantic) and the Barolo shearwater (Wider Atlantic) achieved the threshold because there is no indication of incidental by-catch happening. The latter two species are included in the OSPAR List of Threatened and/or Declining Species and Habitats. From this list, the assessments do not show good status for the lesser black-backed gull (subspecies fuscus) in the Arctic Waters, for the Balearic shearwater in the Greater North Sea, the Celtic Seas and the Bay of Biscay and Iberian Coast, and for the black-legged kittiwake in the Arctic Waters, the Greater North Sea, the Celtic Seas and the Bay of Biscay and Iberian Coast. No such assessments are so far available for the ivory gull, the roseate tern and the Barolo shearwater. In the case of the lesser black-backed gull, the assessment based on the indicators Marine bird abundance (B1) and Marine bird productivity (B3) for Arctic Waters was used for the integrated assessment, as well as the status assessment for the northern sub-species fuscus only (two sub-species are breeding in Norway, also in mixed colonies).

Table S.3: Surface-feeding marine birds species group common indicator outcomes (B1, B3) and integrated status. Breeding populations (B) and non-breeding populations (NB) are assessed separately. Green: indicator threshold achieved or status good; Red: indicator threshold not achieved or status not good; OSPAR Listed species are shown in italics; * status solely derived from status assessment

Fulmar. © Shutterstock

Water column-feeding birds

Water column-feeders typically dive in a broad depth range in the water column and take pelagic and demersal fish and invertebrates (e.g., squid, zooplankton). This access to a greater potential range of prey - compared with surface-feeders - has often been used to explain the differing fortunes of these two groups. On the other hand, water-column feeders are perhaps exposed to a greater risk of additive mortality due to incidental by-catch in fishery gears than are surface feeders.

As for surface feeders, the indicator assessments for abundance and productivity do not reveal good status for marine birds feeding in the water column in the Arctic Waters, in the Greater North Sea and in the Celtic Seas, because fewer than 75% of the species assessed were in good status (Table S.4). In addition, the status assessment for the Iberian guillemot (a probably extinct population of common guillemot) does not show good status (see below), which carries over to the species group status in the Bay of Biscay and Iberian Coast, where no other water-column feeders were assessed. The confidence in the regional assessment of water-column feeders in Bay of Biscay and Iberian Coast is low as it is based only the Iberian guillemot assessment.

For the three species (red-throated diver, common guillemot, northern gannet) examined in the southern North Sea under the Marine bird habitat quality (B7) pilot assessment, habitat disturbance by offshore wind farms, shipping and bottom-trawling fisheries was found. Nevertheless, these three species still achieved the threshold in the pilot assessment for offshore winter abundance in the southern North Sea

Table S.4: Water-column feeding marine bird species groups indicator outcomes (B1, B3) and integrated status. Breeding populations (B) and non-breeding populations (NB) are assessed separately. Green: indicator threshold achieved or status good; red: indicator threshold not achieved or status not good; OSPAR listed species are shown in italics; * status solely derived from status assessment

Benthic-feeding birds

Benthic feeders dive to the seafloor and prey on invertebrates (e.g., molluscs, echinoderms).

In Arctic Waters, the Greater North Sea and Celtic Seas, benthic feeders did not achieve the threshold and therefore are not in good status in all three Regions (Table S.5). In addition, a pilot assessment for the common scoter in the southern North Sea showed that its winter abundance is far below the threshold value.

The pilot assessment of the by-catch indicator (B5) dealt with only one benthic feeder. It showed that the distribution of Steller’s eider in northern Norway (Arctic Waters) overlaps spatio-temporally with the practice of gillnet fishing, where incidental by-catch of this species is known to occur. According to the assessment method for species on the OSPAR List of Threatened and/or Declining Species and Habitats (which applies to Steller’s eider), the presence of an overlap implies that the indicator threshold is not achieved for the Steller's eider. However, as there is no status assessment for this species it cannot yet be included in the integrated assessment.

Table S.5: Benthic-feeding marine bird species group indicator outcomes (B1, B3) and integrated status. Breeding populations (B) and non-breeding populations (NB) are assessed separately. Green: indicator threshold achieved or status good; red: indicator threshold not achieved or status not good

Wading birds

Wading feeders walk and wade in shallow water or on mudflats and in the rocky intertidal, but also along the shoreline. They typically prey on invertebrates (molluscs, polychaetes, crustaceans, etc.) although some species (e.g., little egret, spoonbill) also feed on fish.

Wading feeders were assessed in the Greater North Sea and the Celtic Seas only, mostly birds in the non-breeding season (Table S.6). In both Regions the threshold for good status (75% of species in good status) was not achieved. There is no additional information from pilot assessments or status assessments.

Table S.6: Wading feeder marine birds species group indicator outcomes (B1, B3) and integrated status. Breeding populations (B) and non-breeding populations (NB) are assessed separately. Green: indicator threshold achieved or status good; red: indicator threshold not achieved or status not good

Grazing birds

Grazing feeders typically forage on salt marshes adjacent to the shoreline, but also in intertidal areas and shallow waters. They are herbivores, taking various plants (e.g., eelgrass, saltmarsh plants) and algae.

The threshold for good status of a species group was achieved in grazing feeders in the three assessments conducted for the Arctic Waters, the Greater North Sea and the Celtic Seas (but only one species was assessed in the Arctic Waters) (Table S.7). This assessment is based almost entirely on non-breeding populations, without information from pilot assessments or status assessments being available.

Table S.7: Grazing feeders marine birds species group common indicator outcomes (B1, B3) and integrated status. Breeding populations (B) and non-breeding populations (NB) are assessed separately. Green: indicator threshold achieved or status good; red: indicator threshold not achieved or status not good

Overall assessment

The results of the species group assessments are summarised in Table S.8. It is clear that marine birds are not in good status across the OSPAR Regions and species groups, with the striking exception of grazing feeders in all three Regions examined.

In order to investigate possible changes in the status of marine bird species groups, the status of marine bird species and species groups was assessed retrospectively for the year 2010, using the outputs from the Common Indicators Marine bird abundance (B1) and Marine bird productivity (B3). This method of comparison was chosen because in QSR 2010 the status of marine birds was not assessed. Compared with 2010, the assessment for 2020 shows no major differences (Table S.8). Status remained unchanged in all combinations of Region and species group. Further, the percentages of species in good status only slightly differed between 2010 and 2020. This indicates that most marine birds were already not in good status in 2010. However, for the “all species” grouping the proportion of species in good status decreased from 2010 to 2020 in all Regions (Table S.8).

The species groups in this assessment were compiled on the basis of their diet and feeding habits. In this context, if one species group fails to achieve good status it cannot perform its role in the marine environment, i.e. in the food web. Because of the link to food and feeding, the role of one species group cannot be taken on by another species group. As a consequence, if one species group is not in good status, marine birds as an ecosystem component have to be treated as not being in overall good status. Integration from species groups to ecosystem component is not required in EU MSFD Article 8 assessments*, but if needed for other purposes it is recommended to use the one-out-all-out approach, as outlined above. Applying this to the bird assessments shown in Table S.8, marine birds were not in good status both in 2010 and 2020 in the four OSPAR Regions assessed: Arctic Waters, Greater North Sea, Celtic Seas and Bay of Biscay and Iberian Coast.

*OSPAR acts as a coordination platform in the North-East Atlantic for the regional implementation of the EU Marine Strategy Framework Directive (MSFD) that aims to achieve a Good Environmental Status (GES) in European marine environments, as well as for the coordination of other national frameworks. The characteristics of GES are determined by the individual EU member states, based on criteria elements, threshold values and methodological standards set regionally or at EU level.

Norwegian, Icelandic, United Kingdom, Greenlandic and Faroese marine areas are not covered by the MSFD.

Table S.8: Status overview for species groups of marine birds in the five OSPAR Regions (N/A = not assessed) for 2020 compared with 2010 (retrospective assessment using the same methods). Changes in the proportions of species in good status and in the status of species groups are shown as increase/improvement (↑), decrease/degradation (↓) or no change (=). Note that some species assessments are done with data up to 2016, 2017 or 2019 only. Summary information for “all species groups” is given only for illustration, but is not part of the assessment

Threatened and / or declining seabirds

Nine species or sub-species of birds are on the OSPAR List of Threatened and/or Declining Species and Habitats (OSPAR Agreement 2008-06). The status of all nine species / sub-species was assessed in 2003 to 2010 as requiring priority protective action. Since then, five species have been reassessed. All five species are still declining in status and it is highly likely that the Iberian race of common guillemot has become extinct (Table S.9 and Table S.10). Threatened and declining bird species are not distributed evenly across the OSPAR Regions (see Table S.10). Three species are confined to Arctic Waters and the Barolo shearwater (split from the little shearwater, also known as Macaronesian shearwater) breeds in the Azores and is confined to the Wider Atlantic Region. The other species are distributed across multiple regions, with the black-legged kittiwake the most wide-ranging.

Balearic shearwater breed on islands in the Mediterranean but venture into the North-East Atlantic when not breeding. The numbers in breeding colonies are undergoing a severe decline of -14% per year, mainly owing to the poor survival rates of adults when they are away from the colonies at sea. Incidental by-catch in fisheries is believed to be contributing to mortality at sea and is the most significant threat to this species in the OSPAR Maritime Area. 

The Iberian race of common guillemot was almost extinct when it was added to the OSPAR List in 2003. The last known breeding attempts in Portugal were in 2002 and in Galicia in north-west Spain in 2007. The last recorded individuals were seen in Galicia in 2013. Numbers of breeding Iberian guillemots declined by 33% per year between 1960 and 1974. Incidental by-catch mortality resulting from the rapid development of gillnet fisheries appears to be the main factor underpinning the population crash. Pollution derived from large oil spills could also have contributed to their extinction.  

The breeding success of the OSPAR listed sub-species of lesser black-backed gull has been exceptionally low in recent years at the breeding sites in northern Norway. Climate change and pollution remain serious threats and the pressure from predators at breeding colonies appears to be increasing. 

The status of black-legged kittiwake breeding populations is still declining in Arctic Waters and the Greater North Sea and is also declining in the Celtic Seas and the Bay of Biscay. Climate change appears to continue to affect food supply in the Arctic, Greater North Sea and the Iberian coast, as well as in wintering areas partly outside the OSPAR Region. Food supply in the North Sea is also threatened by sandeel fishing in some areas (see: Food webs Thematic Assessment – Response Section – Case study ). A northward contraction in breeding range in the Bay of Biscay and Celtic Seas appears consistent with climate change predictions.

The breeding populations of the thick-billed murre (Brünnich‘s guillemot) in Svalbard, East Greenland and northern Norway are currently declining. Climate change and its indirect effects, such as oceanographic shifts in the wintering grounds resulting in reduced food supplies, are believed to be driving this negative trend. Further threats in some areas include hunting, disturbance by predators, as well as chemical and oil pollution. Populations in Iceland and Franz Josef Land appear to be either stable or increasing.

Table S.9: Status assessments for lesser black-backed gull (sub-species fuscus - 2021), thick-billed murre (Brünnich's guillemot - 2020) 2020), Balearic shearwater, Iberian guillemot and black-legged kittiwake (2022). Most have been recognised by OSPAR as threatened and/or declining (●) Based on Chapter 10 Table 10.1 and Table 10.2 in QSR 2010 (except for cases marked with ○)

Legend:

Trends in status (since the assessment in the background document):
↓       decreasing trend or deterioration of the criterion assessed
↑       increasing trend or improvement in the criterion assessed
↔     no change observed in the criterion assessed
?       trend unknown
N/A   not applicable (i.e. species not present during breeding or non-breeding season).

Status of criterion assessed:

Assessment type:
1 - direct data driven
2 - indirect data driven
3 - third party assessment close-geographic match
4 - third party assessment partial-geographic match
5 - expert judgement

* Assessment of non-breeding population size is based on wintering numbers offshore in the southern North Sea only, using data from NL, BE and DE. This only a very small part of the non-breeding distribution of black-legged kittiwake, which covers large parts of the North Atlantic. Source: Pilot assessment of B1 Marine bird abundance – non-breeding birds offshore (OSPAR, 2023).

Table S.10: Overview of status assessments available for OSPAR threatened and declining marine birds. ? = Not assessed since listing in 2008-10, * probably extinct; blank cells indicate species not present in region (or occurs in low numbers and/or infrequently)