Great Black-backed Gull Larus marinus

Status;  International importance;  Population estimates;  Distribution;  Annual abundance/ productivity; Phenology/diet/survival

 

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Description

Great Black-backed Gull vignette

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:

EC Birds Directive - migratory species

Amber listed in Birds of Conservation Concern 4 (2015 update)

(further information on Conservation Designations for UK Taxa)

Amber listed in Birds of Conservation Concern in Ireland 2014-2019 (2014 update)


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.

 


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

Total

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.

 


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 (PDF, 2.1 mb).

 

An interactive map is available on the NBN Gateway, where you can filter to display only the Seabird 2000 data.  For more recent, but less comprehensive, coverage view the distribution on the NBN with all available contributing datasets.

 

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

 

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% CLs 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.   

 



 

Breeding abundance

 

UK Great black-backed gull abundance trend

Figure 1: Trend in UK abundance index (solid line) of great black-backed gull 1986-2015 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis (PDF 158 kb).

 

The abundance of the 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) with a noticeable decline occurring since then. In 2012, the index value reached its lowest point, at around 50% of the peak value, but has again climbed and in 2014 was again on a par with the 1986 baseline. In 2015, the index declined slightly to 2% below the baseline in 1986. 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 due to a reduction in discards and offal2. The species also forages on natural prey (rabbits, 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

 

Great black-backed gull UK productivity graph 1986-2015

Figure 2: Trend in UK productivity (no. of chicks fledged per pair) of great black-backed gull 1986-2015. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

No clear trend for great black-backed gulls is evident in productivity overall, although it was lower in 2003-2006. 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 American mink can have an impact on breeding success; in 2014, a comparison of islands off west Scotland with mink control against those with no, or unsuccessful, mink control found that breeding success for each group was 3.00 and 0.94 chicks fledged per pair, respectively - a difference of 69%3.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*)

Inland

Total

15,950 15,315

14,773

          3

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

 

Scotland Great black-backed gull abundance trend

Figure 1: Trend in abundance index (solid line) of great black-backed gull in Scotland, 1986-2015 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis (PDF 158 kb).

 

National census data show that numbers of great black-backed gulls in Scotland changed relatively little between 1969-70 and Seabird 2000. The trend from the SMP since 1986 shows a decline after the Seabird Colony Register, but abundance had increased by the time of Seabird 2000. However, since 1999 there appears to have been a prolonged decline with the index in 2015 only 53% of 1986 reference levels.

 

Productivity

 

Scotland Great black-backed gull productivity trend

Figure 2: Trend in productivity (no. of chicks fledged per pair) of great black-backed gull in Scotland, 1986-2015. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

The trend in productivity for Scotland closely matches that of the UK because 87% of the data have been collected at Scottish colonies. Productivity of great black-backed gulls at Scottish colonies generally declined toward 2003, although there were some large fluctuations. Particularly low levels of productivity were then recorded up to 2005, but success has improved again since. Declining productivity may have contributed to the downward population trend noted since 1999 but this could be reversed with the recent increase in fledging rate. As with common and herring gulls, most data come from a long-term study of near-shore islands on the west coast where American mink, an introduced mammal which can heavily depress breeding success, prey on the eggs and chicks of gulls, terns and other seabirds. In 2014, 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). Over the period 1996-2013, islands with mink control fledged an average of 1.15 chicks per pair compared to 0.89 from islands with no, or unsuccessful, mink control. On average, breeding success was 24% lower each year (range 3-52%) in the latter group compared to 61% for common gulls and 30% for herring gulls over roughly the same period. This suggests that the effects of predation by American mink on this large and aggressive gull appear to be less severe than for its smaller relatives.  

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*)

Inland

Total

1,676 1,534

1,466

      10

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

 

Great black-back gull Lundy/Annet abundance 2015

Figure 1: Abundance of great black-backed gull on Annet (Isles of Scilly) and Lundy (Devon), 1986-2015.

National census data show great black-backed gull numbers in England have increased slightly over a 30-year period. Thirty-nine English colonies monitored in 2015 were holding 1,047 pairs compared to 867 AON during Seabird 2000. Hence, trends derived from colonies providing data to the SMP are probably unrepresentative and therefore are not shown. The greatest concentration of the species is in south-west England, where the largest colony monitored regularly is on Annet in the Isles of Scilly (Figure 1). This colony has increased in size (235 AON in 2015) since Seabird 2000 when it held c.10% of England's great black-backed gulls. A complete survey of the Isles of Scilly in 2015 resulted in 1,017 AON. This figure is above that recorded for the islands as a whole during Seabird 2000 (807 AON). The next largest colony monitored regularly is on Lundy (Devon) where, following rat Rattus sp. eradication, numbers have increased slightly since Seabird 2000, from 35 to 50 AON in 2013. In 2014 and 2015, gulls were cont counted on Lundy. 

 

Productivity

 

England Great black-backed gull productivity trend

Figure 2: Trend in productivity (no. of chicks fledged per pair) of great black-backed gull in England, 1986-2015. Based on SMP data; view the methods of analysis (PDF 158 kb).

 

Relatively few data are available on the productivity of great black-backed gulls in England and all data submitted to the SMP has been collected since 1998. Most of the data come from colonies holding fewer than 10 pairs (75%), 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 at least two chicks per nest each year between 2011 and 2013.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*)

Inland

Total

905 289

425

     2

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

 

Wales Great black-backed gull abundance trend

Figure 1: Trend in abundance index (solid line) of great black-backed gull in Wales, 1986-2015 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 (PDF 158 kb).

 

The trend in abundance for greater black-backed gulls in Wales has generally been upward over the last 28 years, although with some fluctuation (see pronounced dips in 2000, 2006 and 2011). In 2015, 11 monitored colonies (about 50 are known) held 375 AON compared to 151 AON during Seabird 2000 - an increase of 148%. Census data suggest numbers recorded during Seabird 2000 were 47% higher overall than during the Seabird Colony Register. However, despite apparent increases since the SCR, numbers probably still lie well below those recorded by Operation Seafarer, when 905 pairs were counted.  

 

Productivity

 

On average great black-backed gulls at colonies in Wales fledged 1.16 chicks per year per pair between 1986 and 2015; there was no statistically significant variation over time.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*)

Inland

Total

240 277

71

  5

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

 

NI Great black-backed gull abundance trend

Figure 1: Trend in abundance index (solid line) of great black-backed gull in Northern Ireland, 1986-2015 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 (PDF 158 kb).

 

Most of the colonies of great black-backed gull in Northern Ireland hold only a few pairs. Strangford Lough (Co. Down) is by far the most important colony in the region, holding over 40% of the population during the Seabird Colony Register. This colony, which is monitored annually, largely drives the trend shown in Figure 1. It declined severely after 1986 from 86 AON down to 40 AON when counted for Seabird 2000. One year later only one pair was recorded but the colony has grown since then, with a peak of 102 AON recorded in 2013 although only 82 AON were counted in 2014 and 62 AON in 2015. With another 7 pairs recorded at four other colonies in 2015, numbers are slightly below the total recorded by Seabird 2000 (71 AON), and the trend above suggests that overall, including data from colonies not surveyed recently, numbers may be comparable to that recorded during the SCR census.

 

Only small numbers were found nesting inland during Seabird 2000; it is unknown whether this situation has changed recently.

.

 

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.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*)

Inland

Total

3,166 2,921

2,241

        2

2,243

% change since previous census    N/a -8 -23

 

* 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 have been in long-term decline, numbers fell between Operation Seafarer and Seabird 2000 by 29%. Out of the 180 known colonies at the time of the last census few have been monitored in recent years. However in 2015, a suite of 14 colonies counted  held a total of 448 AON compared to 635 AON recorded at the same colonies during Seabird 20006. The species has increased substantially at these colonies but drawing firm conclusions for the Republic of Ireland population as a whole from such a small sample is inadvisable.

 

Only small numbers were found nesting inland during Seabird 2000. These colonies have not been visited since then.

 

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.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*)

Inland

Total

3,406 3,198

2,312

        7

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 up until the Seabird Colony Register. Few colonies have been monitored over the last decade so the current status of the species is largely unknown. However, given increases in Northern Ireland and at a small suite of colonies monitored in the Republic of Ireland, numbers may have increased overall.

 

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.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*)

Inland

Total

275 376

405

     0

405

% change since previous census    N/a +37 +8

 

* 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 gull Calf of Man abundance 2015

Figure 1: Abundance of great black-backed gull on the Calf of Man (Isle of Man), 1986-2015.

 

Between Operation Seafarer and the Seabird Colony Register, great black-backed gulls nesting on the Isle of Man increased by 37%, but there had been little further growth by the time of Seabird 2000. The current status of great black-backed gull on the Isle of Man is unknown as only one colony, on the Calf of Man, has been surveyed since Seabird 2000. In the late 1980s and early 1990s, land-based counts at this colony regularly recorded between 115-155 AON, over 40% of the great black-backed gull population. Numbers were probably stable up to Seabird 2000 and immediately thereafter with counts of 146 AON (1999), 121 AON (2000) and 114 AON (2001), again all done from land. Thereafter, a decline occurred as survey work in 2010 recorded only 57 AON, with an almost equal split between nests recorded from land and sea. In 2015, the number of breeding great black-backed gull fell to 38 AON.

 

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.

 

 

Population estimates and change 1969-2002 (census data)

 

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998-2002)

Population estimate (AON*)

Inland

Total

200 180

310

     0

310

% change since previous census    N/a -10 +42

 

* 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 42% since the Seabird Colony Register, which had recorded similar numbers to that found during Operation Seafarer. The only data collected in the region since Seabird 2000 are from Burhou which held 27 AON during Seabird 2000 (c.9% of the population). Near annual monitoring between 2005 and 2011 found numbers fluctuated but were relatively stable between 16 and 23 AON. However, a rapid decline has occurred since with four AON recorded in 2012, only one AON in 2013 and six AON in 2014. Whether this decline is similarly occurring at other colonies in the Channel Islands is unknown. No data was submitted to the SMP in 2015.

 

Productivity

 

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

 

 


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 (Dyfed) 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 the gull chicks fledged (from late July to early August). The sample represented nests from differing habitats and from areas of differing 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 in fact 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 seasons4.

 

GBBG diet on Skomer 2013

 

 

Diet pie chart

 

Figure 3: Great black-backed gull diet remains from 25 nests on Skomer (Dyfed), 2013 (top chart), 2014 (middle) and 2015 (bottom).

A wide variety of food items were recorded from 2013 to 2015 of which 20%, 14%,and 8% respectively, were identified as Manx shearwaters. Fish remains (including pellets) comprised 6% and 7% of prey items recorded in 2013 and 2014, respectively, but only 3% in 2015. Bones (other), fur pellets and feather pellets were also among the most numerous items in each year. Rabbit remains were more prevalent in 2013 (10%) compared to 2014 and 2015 (4 and 3%, respectively). 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 less than 20% between 2013 and 2015). The number of shearwater carcasses recorded in 2015 (217) was lower to that recorded in 2014 (259) and in 2013 (266).

 

Manx shearwater remains were recorded at 96% of nest sites studied in 2013 and at 92% of the nests studied in 2014 and 2015, providing means of 9.89 corpses per nest site in each year. A mean of 8.68 corpses per nest site were recorded in 2015 which is lower than in 2014 and 2013 (10.36 and 10.64) but higher than the historical overall mean of 7.51 (1959, 1965, 1973, 1992, 2008-2015).5

Great black-backed gull skomer manx diet

Figure 4: The number of Manx shearwater carcasses found per great black-backed gull nest on Skomer (Dyfed), 1992 and 2008-2015.

 

Survival

 

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

 


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, UK.

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

4 Taylor, C.J., Boyle, D., Perrins, C.M. and Kipling, R. 2012. Seabird monitoring on Skomer Island in 2012. Unpublished report to JNCC, Peterborough.

5 Stubbings, E.M., Büche, B.I., Miquel Riera, E., Green, R.M. and Wood, M.J. 2015. Seabird monitoring on Skomer Island in 2015. Unpublished report to JNCC, Peterborough.

6 Newton, S.  Lewis, L. and  Trewby, M. 2015. Results of a Breeding Survey of Important Cliff‐Nesting Seabird Colonies in Ireland 2015. National Parks and Wildlife Service Ireland.

 

 


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; 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 Environment Agency; 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.