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Great black-backed gull (Larus marinus)

The following has been adapted from original text by James B. Reid in Seabird Populations of Britain and Ireland (with permission from A&C Black, London).

 

The great black-backed gull has an extensive breeding range across the north Atlantic and adjacent seas. Historically, Britain and Ireland have hosted most of the world population after Iceland and Norway. Great black-backed gulls breed mainly in the Outer and Inner Hebrides and the Northern Isles of Scotland. These regions offer extensive areas of the preferred breeding habitat of well-vegetated rocky coastline with stacks and cliffs. The 20th century saw widespread expansion of the breeding range and numbers on both sides of the Atlantic. In Britain at least, population increase was remarkable given that a period of decline rendered the species virtually extinct as a breeder towards the end of the previous century. The species nests almost exclusively in coastal habitats, but will occasionally nest inland at freshwater sites as well as on the roofs of buildings.

Conservation status

Great black-backed gull is currently identified as a conservation priority in the following:

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International importance

UK Population

Biogeographic Population

% World Population

16,800 AON*

16.0 (Europe excl. Russia)

9.6

*AON = Apparently Occupied Nests

The UK population figure (rounded to the nearest hundred) was derived from data in Mitchell, P.I., Newton, S.F., Ratcliffe, N. and Dunn, T.E. (eds.) 2004. Seabird Populations of Britain and Ireland. Poyser, London. This was also the source of figures for the Biogeographic and World populations.

Note: The UK population figure above includes data from both inland and coastal colonies and hence differs from that tabled below.

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UK population estimates and change 1969–2002 (census data)

No major gaps in survey coverage are known for the three national surveys as most colonies are well established. Great black-backed gulls often nest at low densities in mixed-species colonies, usually with lesser black-backed gulls, but their large size and conspicuous plumage, coupled with a distinctively deep voice, probably reduces the chances of such pairs being overlooked. However, solitary nests or pairs, especially those in remote areas, might easily have been missed. Seabird 2000 represented the first attempt to census all coastal and inland breeding colonies of great black-backed gull although only 20 pairs were found inland.

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

UK Population estimate (AON*)

Inland numbers

Total Figure

18,771

-

-

17,415

-

-

16,735

20

16,755

% change since previous census   

n/a

-7

-4

*AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the first two national censuses, so, to enable direct comparison, the percentage change refers to coastal colonies only.

For census results for individual countries and Ireland, the Channel Islands and the Isle of Man see under relevant sections below.

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Distribution/abundance

The Seabird 2000 census provides the most comprehensive recent assessment of the distribution and abundance of breeding seabirds. Numbers of great black-backed gull found in different regions, and a map showing the location and size of colonies, is provided in the Seabird 2000 great black-backed gull results page.

The locations sampled during the annual Seabird Monitoring Programme provide some information on distribution and are accessible via the Seabird Monitoring Programme online database.

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Annual abundance and productivity by geographical area

With reference to the regional accounts below please note the following:

Breeding abundance: graphs of abundance index with 95% confidence limits are only shown for a region where the trend produced has been deemed accurate (see methods of analysis). Where a trend was thought to be inaccurate, graphs of abundance at major colonies in a region may be shown instead, particularly if such colonies hold greater than 10% of the regional population, are monitored frequently and may thus help illustrate regional population fluctuations outwith national censuses. Occasionally, too few data have been collected regionally to produce either of these.

Productivity: graphs of productivity are only shown if analysis of breeding success data produced a significant result for regional and/or year effects (again see methods of analysis). If results were not significant, then a regional mean productivity value is given. However, on some occasions, too few data are available from which to provide a meaningful average. Furthermore, for 11 species where the quality of monitoring data available was considered high, population viability analysis was undertaken at the UK level and the results of this are also reported.

 

United Kingdom

Breeding abundance

gbb-gull-uk-ab.jpg

Figure 1. Trend in UK abundance index (solid line) of great black-backed gull 1986–2018 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis.

 

The abundance of great black-backed gull changed relatively little between the first census in 1969/70 and Seabird 2000. Data submitted to the SMP show the index peaked around the time of the most recent census (1999/2002) then declined to reach its second lowest point in 2012 (36% below the baseline). It then climbed 9% above the baseline in 2016, although by 2018 had declined steeply to 45% below the baseline, the lowest value since monitoring began. It has been suggested that great black-backed gulls have competitive advantage over other seabird species when scavenging at sea for fishery discards and offal1, and hence have not undergone (at least, until recently) the declines that other scavengers (herring and lesser black-backed gull) have in recent decades which may be due to a reduction in discards and offal2. The species also forages on natural prey (e.g. rabbits and other seabirds) and appears to be quite adaptable to changing dietary opportunities. Declining productivity may have contributed to the downward population trend noted from 1999 to 2005.

 

Productivity

gbb-gull-uk-prod.jpg

Figure 2. Trend in UK productivity (no. of chicks fledged per pair) of great black-backed gull 1986–2018. Based on SMP data; view the methods of analysis.

 

There is no clear trend in great black-backed gull productivity, or statistically significant variation over time; on average approximately 0.89 chicks fledged per nest per year between 1991 and 2018. The effects of predation by American mink on this large and aggressive gull appear to be less severe than for its smaller relatives. However, in some years, it does appear that mink can impact on productivity; in 2014, a comparison of islands off west Scotland with mink control against those with none found that productivity for each group was 3.00 and 0.94 chicks fledged per pair, respectively – a difference of 69%3.

 

Scotland

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (AON*)

15,950

15,315

14,773

Inland numbers

-

-

3

Total Figure

-

-

14,776

% change since previous census   

n/a

-4

-4

*AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the first two national censuses, so, to enable direct comparison, the percentage change refers to coastal colonies only.

 

Breeding abundance

gbb-gull-scotland-ab.jpg

Figure 3. Trend in abundance index (solid line) of great black-backed gull in Scotland, 1986–2018 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis.

 

National census data show that numbers of great black-backed gulls in Scotland changed relatively little between 1969-70 and Seabird 2000, although the trend from SMP annual sampling (Figure 3), shows a decline from 1986 to 1990 followed by an increase until the Seabird 2000 census. Since Seabird 2000, there appears to have been a prolonged decline in the breeding population with the index in 2018 reaching in lowest ever value, at 69% below the 1986 baseline. In 2018, 112 colonies were surveyed (accounting for 10% of the great black-backed gull population in Scotland) and held a total of 907 AON, a 76% decline since Seabird 2000 (3,859 AON). Scotland’s largest colony, Calf of Eday, decreased by 97% between Seabird 2000 and 2018 (from 1,350 AON to 43 AON).

 

Productivity

gbb-gull-scotland-prod.jpg

Figure 4. Trend in productivity (no. of chicks fledged per pair) of great black-backed gull in Scotland, 1991–2018. Based on SMP data; view the methods of analysis.

 

The trend in great black-backed gull productivity for Scotland closely matches that of the UK because 87% of data have been collected at Scottish colonies. Productivity of great black-backed gulls at Scottish colonies reached its lowest point in 2005 (at 0.54 chicks fledged per pair), although there was some fluctuation during this period. Productivity has improved since then and, in 2018, was 1.25 chicks fledged per pair. The decline in productivity between 1991 and 2005 may have contributed to the downward population trend noted since 1999. As with common and herring gulls, most data come from a long-term study of near-shore islands on the west coast of Scotland where American mink, an introduced mammal, can heavily depress productivity, by preying on the eggs and chicks of gulls, terns and other seabirds. In 2014, a comparison of islands where American mink were controlled against those with no, or unsuccessful, mink control found a difference of 69% (success of 3.00 and 0.94 chicks per pair in each group, respectively).

 

England

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (AON*)

1,676

1,534

1,466

Inland numbers

-

-

10

Total Figure

-

-

1,476

% change since previous census   

n/a

-8

-4

*AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the first two national censuses, so, to enable direct comparison, the percentage change refers to coastal colonies only.

 

Breeding abundance

gbb-gull-england-ab.jpg

Figure 5. Abundance of great black-backed gull on Annet and Lundy, 1986–2018.

 

Between Operation Seafarer (1969-70) and the Seabird 2000 census (1998–2002), great black-backed gull numbers in England decreased slightly. The largest concentration of the species is in south-west England, with the Isles of Scilly holding 807 AON during Seabird 2000, over 50% of the English population. A complete survey of the Isles of Scilly in 2015 found 1,017 AON, an increase of 26% since Seabird 2000. On Lundy, where rats Rattus sp. were eradicated between 2002 and 2004, numbers have begun to increase, from 35 AON in Seabird 2000 to 46 AON in 2018 (Figure 5).

 

Productivity

gbb-gull-england-prod.jpg

Figure 6. Trend in productivity (no. of chicks fledged per pair) of great black-backed gull in England, 1998–2018. Based on SMP data; view the methods of analysis.

 

Relatively few data are available on the productivity of great black-backed gulls in England and all data submitted to the SMP have been collected since 1998. Most data come from colonies holding fewer than 10 pairs, the exception being Brownsea Island where the number of nests has increased to double figures in recent years. Great black-backed gulls at this colony have been very successful fledging on average 1.94 chicks per pair between 2010 and 2016.

 

Wales

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (AON*)

905

289

425

Inland numbers

-

-

2

Total Figure

-

-

427

% change since previous census   

n/a

-68

+47

*AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the first two national censuses, so, to enable direct comparison, the percentage change refers to coastal colonies only.

 

Breeding abundance

gbb-gull-wales-ab.jpg

Figure 7. Trend in abundance index (solid line) of great black-backed gull in Wales, 1986–2018 with 95% confidence limits (dotted lines; drawing of upper limit restricted to preserve detail in the abundance index). Based on SMP data; view the methods of analysis.

 

The trend in abundance for great black-backed gulls in Wales has generally been upward over the last 30 years, although with some fluctuation (see pronounced dips in 2000, 2006, 2011 and 2013). During the Seabird 2000 census, the population was 47% larger than recorded during the Seabird Colony Register (SCR) census. However, despite the increase since the SCR, numbers still lie well below those recorded by Operation Seafarer, when 905 AON were recorded. In 2018, 38 colonies held 276 AON compared to 236 AON during Seabird 2000, an increase of 17%.

 

Productivity

On average great black-backed gulls at colonies in Wales fledged 1.26 chicks per year per pair between 1986 and 2018; there was no statistically significant variation over time.

 

Northern Ireland

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (AON*)

240

277

71

Inland numbers

-

-

5

Total Figure

-

-

76

% change since previous census   

n/a

+15

-74

*AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the first two national censuses, so, to enable direct comparison, the percentage change refers to coastal colonies only.

 

Breeding abundance

gbb-gull-ni-ab.jpg

Figure 8. Trend in abundance index (solid line) of great black-backed gull in Northern Ireland, 1986–2018 with 95% confidence limits (dotted lines; drawing of upper limit restricted to preserve detail in the abundance index). Based on SMP data; view the methods of analysis.

 

Most great black-backed gull colonies in Northern Ireland hold only a few pairs and Great Minnis’s Island, on Strangford Lough, is by far the most important, holding over 40% of the population during the Seabird Colony Register census. This colony, which is monitored annually, largely drives the trend shown in Figure 8. It declined by over 50% between 1986 (86 AON) and 2000 (41 AON); and, one year later held only one AON. The colony has gradually increased since then to a peak of 129 AON in 2018, although only 62 AON were counted in 20134. Another 46 AON were recorded at four other colonies in 2018, suggesting that the great black-backed gull population in Northern Ireland has more than doubled since Seabird 2000.

 

Productivity

Data submitted to the SMP on the productivity of great black-backed gulls in Northern Ireland are sparse; thus, no meaningful average productivity value can be given.

 

Republic of Ireland

Population estimates and change 1969–2018 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Republic of Ireland Census

(2015-18)

Population estimate (AON*)

3,166

2,921

2,241

3,078

Inland numbers

-

-

2

3

Total Figure

-

-

2,243

3,081

% change since previous census   

n/a

-8

-23

+38

*AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the first two national censuses, so, to enable direct comparison, the percentage change refers to coastal colonies only.

 

Breeding abundance

Great black-backed gulls nesting in the Republic of Ireland declined by 29% between Operation Seafarer and the Seabird 2000 census The decline was thought to be due to a redistribution of breeding birds, rather than a decline per se, with the species adapting to changing environmental conditions5,6. During the recent Republic of Ireland Seabird Census, a total of 3,081 AON were recorded, an increase of 38% since Seabird 2000 and very similar to the population recorded by Operation Seafarer. The species nests almost exclusively in coastal counties7,6 and is well monitored.

 

Productivity

Data submitted to the SMP on the productivity of great black-backed gulls in the Republic of Ireland are sparse; thus, no meaningful average productivity value can be given.

 

All Ireland

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (AON*)

3,406

3,198

2,312

Inland numbers

-

-

7

Total Figure

-

-

2,319

% change since previous census   

n/a

-6

-28

*AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the first two national censuses, so, to enable direct comparison, the percentage change refers to coastal colonies only.

 

Breeding abundance

The great black-backed gull population for the whole of Ireland declined by 32% between Operation Seafarer and Seabird 2000, although numbers were fairly stable between Operation Seafarer and the Seabird Colony Register census. Northern Ireland holds the smaller proportion of the all-Ireland population and numbers are increasing at its main colony in Strangford Lough. During the recent Republic of Ireland Seabird Census a total of 3,081 AON were counted, an increase of 38% since Seabird 200. The population nests almost exclusively in coastal counties with only two inland sites known to hold a very small number of AON6. There were insufficient data from all-Ireland to allow trends to be generated.

 

Productivity

Data submitted to the SMP on the productivity of great black-backed gulls in colonies throughout Ireland is sparse; thus, no meaningful average productivity value can be given.

 

Isle of Man

Population estimates and change 1969–2018 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register  

(1985-88)

Seabird 2000

(1998–2002)

Isle of Man Census

(2017-18)

Population estimate (AON*)

286

380

396 

85

Inland numbers

-

-

0

0

Total Figure

-

-

396

85

% change since previous census   

n/a

+33

+4

-79

*AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the first two national censuses, so, to enable direct comparison, the percentage change refers to coastal colonies only.

 

Breeding abundance

gbb-gull-iom-ab.jpg

Figure 9. Abundance of great black-backed gull on the Calf of Man, 1986–2017.

 

Between Operation Seafarer and the Seabird Colony Register censuses, great black-backed gulls nesting on the Isle of Man increased by 33% with little further growth by the time of Seabird 2000. A seabird census of the Isle of Man in 2017 found that numbers of great black-backed gulls had fallen dramatically to 85 AON, a decline of 79% since Seabird 20008. Only one colony, the Calf of Man (Figure 9), has been surveyed regularly since Seabird 2000, when it held 146 AON in 1999. In 2010 it had declined to 57 AON, then 38 AON in 2015 and only 22 AON in 2017, representing a 85% decline since Seabird 2000.

 

Productivity

Data submitted to the SMP on the productivity of great black-backed gulls on the Isle of Man are sparse; thus, no meaningful average productivity value can be given.

 

Channel Islands

Population estimates and change 1969–2015 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Channel Islands Census

(2015)

Population estimate (AON*)

200

180

310

446

% change since previous census   

n/a

-10

+72

+44

*AON = Apparently Occupied Nests

Note: Inland colonies were not counted during the first two national censuses, so, to enable direct comparison, the percentage change refers to coastal colonies only.

 

Breeding abundance

During Seabird 2000, 310 pairs of great black-backed gull were recorded in the Channel Islands. This represented an increase of 72% since the Seabird Colony Register, which had recorded similar numbers to that found during Operation Seafarer. During the Channel Islands Seabird Census in 2015-16, 446 AON were recorded, an increase of 44% since Seabird 20009.

 

Productivity

No systematic data on the productivity of great black-backed gulls on the Channel Islands have been submitted to the SMP.

 

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UK phenology, diet, survival rates

Phenology

No systematic data on phenology (timing of life-cycle events) have been collected as part of the SMP.

 

Diet

A trial study to monitor the diet of great black-backed gulls breeding on Skomer was initiated in 2008, modified in 2012, and has been subsequently used since then. In recent years, the prey remains around a sample of 25 nests were recorded after gull chicks fledged (from late July to early August). The sample represented nests from differing habitats and from areas of differing Manx shearwater densities. However, from 2012 onwards, the number of prey categories in the diet survey was increased in order to improve the accuracy of recording. Scattered bones, feather and fur pellets were counted separately from Manx shearwaters and rabbits, to avoid including remains in these categories that may have come from other species (e.g. chicken bones from off-island landfill sites). Invertebrate and crustacean remains were counted separately and a new category ‘vegetation pellet’ was added. Overall, these changes mean that comparisons of prey percentages with previous years should be treated with care but still provide a 'snapshot' of great black-backed gull diet in respective breeding seasons10.

gbb-gull-pie-2016.jpg

gbb-gull-pie-2017.jpg

gbb-gull-pie-2018.jpg

Figure 10. Frequency of occurrence of food items within a five-metre radius cross-shaped transect around 25 great black-backed gull nests on Skomer, 2016 (top chart), 2017 (middle) and 2018 (bottom).

 

A wide variety of food items were recorded from 2016 to 2018 of which 8%, 5% and 5% respectively, were identified as Manx shearwaters. Fish remains (including pellets) comprised 6%, 4% and 5% of prey items recorded from 2016 to 2018, respectively. Bones (other), fur pellets and feather pellets were also among the most numerous items in each year. Refuse items were more prevalent in 2016 (15%) compared to 2017 and 2018 (10% and 5% respectively). Refuse was found in 80% of the nests and represented 5% of the prey items found; which is less than found in 2017 (10%), 2016 (15%) and 2015 (9 %). Birds other than Manx Shearwaters were found at 16% of the nests in 2018 and included: Puffins; Guillemots; Razorbills and Kittiwakes. The increased number of prey categories account for an apparent decline in the percentage of Manx shearwater remains found at nests (from a range of 43–58% between 2008–2011 to 5% between 2017 and 2018)11,12,13.

Manx shearwater remains were recorded at 68% of nest sites studied in 2018 and at 85% of the nests studied in 2016 and 2017. In 2018, a mean of 9.12 Manx Shearwater carcasses were found within a 10m radius of each nest. This value is higher than reported in 2017 (8.56 carcasses per nest) and 2016 (7.52 carcasses per nest). The historical records indicate that on average 7.67 carcasses are found per nest. The number of rabbit carcasses found this year was 1.24 rabbit carcasses per nest. This value is similar to that reported in 2016 (1.32 carcasses per nest) but lower than reported in 2017 (0.44 carcasses per nest)11,12,13.

gbb-gull-carcasses.jpg

Figure 11. The number of Manx shearwater carcasses found per great black-backed gull nest on Skomer, 1959, 1965, 1973, 1992 and 2008–2018.

 

Survival

No systematic data have been collected as part of the Seabird Monitoring Programme.

 

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References

1 Reid, J.B. 2004. Great Black-backed Gull Larus marinus. In: Mitchell, P.I., Newton, S.F., Ratcliffe, N. and Dunn, T.E. eds. 2004. Seabird Populations of Britain and Ireland: 263–276. Poyser, London.

2 Reeves, S.A. and Furness, R.W. 2002. Net loss–seabirds gain? Implications of fisheries management for seabirds scavenging discards in the northern North Sea. Unpublished RSPB Report, Sandy.

3 Craik, J.C.A. 2015. Results of the mink-seabird project in 2014. Unpublished Report, Scottish Association for Marine Science, Oban.

4 Booth Jones, K.A. and Wolsey, S. 2019. The Northern Ireland Seabird Report 2018. British Trust for Ornithology, Thetford.

5 Mitchell, P.I., Newton, S.F., Ratcliffe, N., and Dunn, T.E. eds. 2004. Seabird populations of Britain and Ireland. T. and A.D. Poyser, London, UK.

6 Cummins, S., Lauder, C., Lauder, A. and Tierney, T. D. 2019. The Status of Ireland’s Breeding Seabirds: Birds Directive Article 12 Reporting 2013 – 2018. Irish Wildlife Manuals, No. 114. National Parks and Wildlife Service, Department of Culture, Heritage and the Gaeltacht, Ireland.

7 Balmer, D. E., Gillings, S., Caffrey, B., Swann, R. L., Downie, I. S., and Fuller, R. J. 2013. Bird Atlas 2007–11: the breeding and wintering birds of Britain and Ireland. BTO Books, Thetford.

8 Hill, R.W., Morris, N. G., Bowman, and K. A., Wright, D. 2019. The Isle of Man Seabird Census: Report on the census of breeding seabirds in the Isle of Man 2017-18. Manx BirdLife. Laxey, Isle of Man.

9 Veron, M. and Veron, C. 2016. Seabird Count 2015; monitoring the status of Guernsey’s 10 Taylor, C.J., Boyle, D., Perrins, C.M. and Kipling, R. 2012. Seabird monitoring on Skomer Island in 2012. Unpublished JNCC Report, Joint Nature Conservation Committee, Peterborough.

11 Stubbings, E.M., Büche, B.I., Miquel Riera, E., Green, R.M. and Wood, M.J. 2016. Seabird monitoring on Skomer Island in 2016. Unpublished JNCC Report, Joint Nature Conservation Committee, Peterborough.

12 Stubbings, E.M., Büche, B.I., Riordan, J.A., Moss, J. and Wood, M.J. 2017. Seabird monitoring on Skomer Island in 2017. Unpublished JNCC Report, Joint Nature Conservation Committee, Peterborough.

13 Stubbings, E.M., Büche, B.I., Baker, B. and Wood, M.J. 2018. Seabird monitoring on Skomer Island in 2018. Unpublished JNCC Report, Joint Nature Conservation Committee, Peterborough.

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Partners

Data have been provided to the SMP by the generous contributions of its partners, other organisations and volunteers throughout Britain and Ireland. Partners to the SMP are: BirdWatch Ireland; The British Trust for Ornithology; UK Centre for Ecology and Hydrology; Natural Resources Wales; Department of Environment, Food and Agriculture (Isle of Man); Department of Environment, Heritage and Local Government (Republic of Ireland); States of Guernsey Government; JNCC; Manx Birdlife; Manx National Heritage; The National Trust; National Trust for Scotland; Natural England; Northern Ireland Department of Agriculture, Environment and Rural Affairs; The Royal Society for the Protection of Birds; Scottish Natural Heritage; Seabird Group; Shetland Oil Terminal Environmental Advisory Group; Scottish Wildlife Trust. More about the SMP partners >>

 

Image of Great black-backed gull appears courtesy of Ian Rendall ©, is subject to international copyright law and may not be reproduced in any form whatsoever.

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SMP Report 1986–2018

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