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Common gull (Larus canus)

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

 

The common gull breeds across the Palaearctic and in North America. They breed on coasts and at inland sites, and spend the winter inland, on estuaries and at sea. Terrestrial foods include earthworms, beetles and other insects, while discarded fishery wastes supplements natural food at sea. In the UK their breeding distribution is virtually confined to Scotland and Northern Ireland. It is a colonial breeder, but will also nest solitarily. During Seabird 2000, over half of the total population in the UK was breeding inland. Despite the inland bias in the distribution, this was the first time that all inland-breeding mew gulls had been censused. There is no reason to suggest that the coastal and inland nesting populations are in anyway separate. Therefore, it is essential that inland colonies are surveyed as thoroughly as those on the coast if an accurate assessment of the current status of the species is to be made.

Conservation status

Common gull is currently identified as a conservation priority in the following:

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International importance

UK Population

Biogeographic Population

% World Population

48,700 AON*

9.3 (ssp. canus)

9.1

*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 hence differs from that tabled below.

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

Only coastal-nesting common gulls were counted fully during both Operation Seafarer (1969-70) and the SCR Census (1985-88), so comparison between Seabird 2000 population estimates and the previous censuses are based only on coastal colonies. During the SCR Census (1985-88) the total inland population was estimated to be 60,000 pairs. This was based largely on the fact that in 1988-89 some 40,000 pairs were nesting at just a few colonies in the Mortlach Hills (Moray) and Correen Hills (Gordon). Common gulls nest in many inland areas of Scotland and in more remote areas of England and Northern Ireland. Given the relatively small number of observers involved, coverage of such areas during Seabird 2000 is difficult to assess but it is likely that all areas were covered at least once during the period of the census. If, however, the species is mobile between sites within this count period, some breeding sites could have been missed and other groups of birds double-counted. There has never been a census of this species over one year that would enable this possibility to be assessed.

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

UK Population estimate (AON*)

12,295

15,357

20,883

Inland numbers

-

-

27,831

 

Total Figures

-

-

48,714

% change since previous census   

n/a

+25

+36

*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 Common gull found in different regions, and a map showing the locations and size of colonies, is provided in the Seabird 2000 Common 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

The annual sample of common gull colonies is insufficient to produce reliable trend information for the UK as a whole. Note that the only comparable data from national censuses relate to coastal-nesting common gulls. Coastal nesting birds increased by 24% between 1969-70 and 1985-88, with a further increase of 36% to Seabird 2000. The reason for this increase in coastal nesters is not known; it is, however, possible that it may have been an artefact due to less complete survey coverage during the earlier censuses. With Scotland holding approximately 98% of the UK population, the trend there can be used as a proxy for the UK situation post Seabird 2000 and suggests that numbers have declined since the then. In 2018, 139 coastal sites held 1,550 AON, 48% less than during Seabird 2000. This number comprises only 10% of the total coastal breeding sites counted during Seabird 2000, although does give an indication of the current status of the UK coastal common gull breeding population. However, drawing definite conclusions about the fortunes of common gulls in the UK is difficult without extensive coverage of inland colonies which held far greater numbers compared to coastal colonies during the last census. The fourth seabird census (Seabirds Count) will provide a comprehensive picture of trends in the UK common gull breeding population when it reports in 2021. American mink Neovison vison are known to have severe negative effects at a local level, taking both eggs, chicks and adults, and causing colony abandonment1,2, but it is unknown whether this is the main reason for the apparent decline nationally.

During Seabird 2000 over half (57%) of the total common gull population in Britain and Ireland bred inland, although, as inland colonies are surveyed infrequently, no trend can be generated from data submitted to the SMP. However, some large inland common gull colonies in Scotland are known to have declined severely, although the reasons are unknown.

 

Productivity

common-gull-uk-prod.jpg

Figure 1. Trend in UK productivity (no. of chicks fledged per pair) of common gull 1989–2018. Based on SMP data; view the methods of analysis.

 

The sample of productivity data used in the generation of the above trend may not be representative at a UK level, as most data up to 2013 came from a study of the effects of American mink control on productivity of gulls and terns in western Scotland2,3. This showed the significant negative effects of mink, although results in some years may be partially clouded by predation of common gull eggs by larger gulls. Common gull productivity data collected from this study between 1996 and 2013 found colonies with successful mink control fledged an average of 0.71 chicks per pair per year, compared to 0.30 at colonies with no, or unsuccessful, mink control; on average productivity was 57% (range 27–77%) lower at colonies in the latter group. In 2014, success at these two groups of colonies was 0.68 and 0.19 chicks fledged per pair, respectively – a difference of 72%3. Productivity of common gull has declined since 1998 from 0.71 to 0.17 chicks fledged per pair, with its lowest index value in 2016 (0.17). Since then, it increased in 2017 but this figure should be treated with caution due to the small amount of data submitted to the SMP. In 2018, average productivity for common gull in the UK was 0.50 chicks fledged per pair which was higher than the long-term productivity average of 0.40 (1989–2018).

 

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*)

12,229

15,134

20,467

Inland numbers

-

-

27,646

Total Figure

-

-

48,113

% change since previous census   

n/a

+24

+35

*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

common-gull-scotland-ab.jpg

Figure 2. Trend in abundance index (solid line) of coastal-nesting common gulls in Scotland, 1986-2018 with 95% confidence limits (dotted lines). Based on SMP data; view the methods of analysis.

 

58% of common gulls recorded during the last census (Seabird 2000) were considered to be nesting within the coastal region (≤5 km from the coastline)4. Coastal nesting common gulls in Scotland have been increasing since 1969-70 according to national census data. Numbers recorded during Seabird 2000 were 35% higher than during the Seabird Colony Register and 67% higher than during Operation Seafarer. The abundance trend using the SMP sample agrees with the national census data over the same period, although suggests a slightly higher abundance at the time of Seabird 2000. Since 2005, the trend has been downward, with a slight recovery in 2009, the index in 2018 stands at 39% below the 1986 baseline. A 58% decline was found at a sample of 132 coastal sites (1,207 AON) in 2018. These represent only 10% of all sites in Scotland counted during Seabird 2000 but do provide an indication of the current status of Scotland’s breeding common gull population.

Numbers at some large inland colonies, not part of the above analysis, have declined severely, for unknown reasons. For example, the first systematic survey of colonies at the Correen Hills and Mortlach Hills in 1988-89 found 24,500 and 16,200 AON, respectively. By 1995, the Correen Hills colony had declined to 6,400 AON, and by 1998, had become extinct. The Mortlach Hills colonies followed a similar fate, having declined since 1998 when they held 18,136 AON; 6,565 AON were recorded in 2003 and 6,240 AON in 2007/08. It is doubtful whether decreases in both these areas have been compensated by increases at other colonies or by the establishment of new colonies. Two major colonies (Tom Mor and Tips of Corsemaul) which were not present during Seabird 2000 held just 4,156 and 2,084 in 2007 and 2008 respectively. Both colonies were surveyed again in 2015 but had declined by 61% and 23% respectively.

 

Productivity

common-gull-scotland-prod.jpg

Figure 3. Trend in productivity (no. of chicks fledged per pair) of common gull in Scotland, 1989–2018. Based on SMP data; view the methods of analysis.

 

Productivity of common gulls in Scotland has declined since the late 1990s with poor breeding seasons in 2009, 2011, 2013, 2016 and 2018. Between 1996 and 2003, most information on common gull productivity came from a study of the effects of American mink Neovison vison control on gulls and terns nesting on west coast islands2 and may, therefore, not be representative of Scotland as a whole. American Mink can have a significant depressive effect on productivity. Common gull data collected from this area between 1996 and 2013 found colonies with successful mink control fledged an average of 0.71 chicks per pair per year, compared to 0.30 at colonies with no, or unsuccessful, mink control; on average productivity was 57% (range 27–77%) lower at colonies in the latter group. In 2014, productivity at these two groups of colonies was 0.68 and 0.19 chicks fledged per pair respectively – a difference of 72%3.

 

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*)

8

31

33

 Inland numbers

-

-

11

 Total Figure

-

-

44

% change since previous census   

n/a

+287

+6

*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

Few common gulls nest in England, with eight AON being recorded during Operation Seafarer and 31 during the Seabird Colony Register (SCR). During Seabird 2000, 15 colonies were found with total numbers close to that recorded by the SCR. Information from colonies counted on an annual basis suggests that the common gull breeding population in England increased in the decade following Seabird 2000 but may have declined more recently. For example, between 2003 and 2018 records were received from a sample of between five and nine colonies, where numbers ranged from 20 AON (2004 and 2005) to 64 AON (2008), although only 18 pairs were reported from eight of these colonies in 2018.

 

Productivity

With only a handful of pairs nesting in England, few meaningful data on productivity are received. Monitored pairs tend to be in colonies containing terns which receive most of the targeted effort toward recording breeding performance. Complete failure is, however, usually noticed and recorded but successful years may not be recorded. Hence, productivity data for this species may be biased toward recording zeros, so the estimated average productivity of 0.50 and 0.29 chicks fledged per nest per year for 2017 and 2018 respectively (there was no significant difference over time) may be low due to this potential bias.

 

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*)

2

0

0

Inland numbers

-

-

0

Total Figure

-

-

0

% change since previous census   

n/a

-100

n/a

*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

Common gull no longer breeds in Wales. Two pairs were recorded during Operation Seafarer but none were found during the last two censuses. 

 

Productivity

This species ceased to breed in Wales before the SMP started so no data on productivity are available.

 

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*)

56

192

383

Inland numbers

-

-

174

Total Figure

-

-

557

% change since previous census   

n/a

+243

+99

*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

common-gull-ni-ab.jpg

Figure 4. Abundance of common gull at Strangford Lough, 1986–2018.

National census data show that the number of coastal nesting common gulls in Northern Ireland increased between Operation Seafarer and Seabird 2000. The largest colonies are found on the Copeland Islands and at Strangford Lough. Common gull numbers at Strangford Lough (Figure 4) increased steadily from the late 1980s to 1999. A sharp decline occurred between 1999 and 2002 (access restrictions due to foot and mouth disease prevented counting in 2001) as numbers fell from 138 to 28 AON. Numbers then increased rapidly to a peak of 532 AON in 2010 but declined again to 229 AON in 2015. A total of 293 AON were recorded during the 2018 breeding season and a further 105 AON were estimated at four other colonies that year. In 2009, 850 common gull AON were recorded on the Copeland Islands, although numbers had declined to 452 AON in 2012. The population of coastal nesting common gulls in Northern Ireland may have increased since Seabird 2000, although without a more recent count from the Copeland Islands, there is some uncertainty.

Inland colonies, which held 174 AON during Seabird 2000, have not been surveyed to any great extent in recent years although 121 AON were recorded at the largest one on Lower Lough Erne in 20185.

 

Productivity

Data submitted to the SMP on the productivity of common 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*)

688

109

586

 779

Inland numbers

-

-

474

1,169

Total Figures

-

-

1,060

1,948

% change since previous census   

n/a

-531

+438

+82

*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, 586 common gull AON were recorded in the Republic of Ireland, five times as many as recorded by the Seabird Colony Register census, but still 100 pairs fewer than were found during Operation Seafarer. The recent Republic of Ireland Seabird Census recorded 1,948 AON, an increase of 82% since Seabird 2000, with over 60% of the population now nesting at inland sites (45% during Seabird 2000). Much of this increase in AON is due to higher survey effort rather than driven by site-based population changes6.

 

Productivity

Data submitted to the SMP on common gull productivity 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*)

744

301

969

Inland numbers

-

-

648

Total Figure

-

-

1,617

% change since previous census   

n/a

-60

+222

*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 Irish coastal nesting common gull population decreased by 60% between the Operation Seafarer and Seabird Colony Register (SCR) censuses. Between the SCR and Seabird 2000 censuses it increased by 222% to 969 AON, 30% higher than the Operation Seafarer census.

During Seabird 2000, Northern Ireland held approximately 30% of the whole of Ireland breeding population of common gulls. The largest colonies in Northern Ireland are found on the Copeland Islands and at Strangford Lough. At Strangford Lough, 293 AON were recorded in 2018 compared to 82 AON during Seabird 2000, indicating that the national population may have increased during this period. However, without a more recent count from the Copeland Islands, there is some uncertainty. Inland colonies, which held 174 AON during Seabird 2000, have not been surveyed to any great extent in recent years, although 121 AON were recorded at the largest one on Lower Lough Erne in 20184.

The recent Republic of Ireland Seabird Census (2015-2018) recorded 1,948 AON, an increase of 82% since Seabird 2000. Much of this increase in AON is due to higher survey effort rather than driven by site-based population changes6. Inland colonies, which held 474 AON during Seabird 2000, now hold 1,169 AON, an increase of 147%. Over 60% of the common gull population now breeds at inland sites (45% during Seabird 2000)5. There were insufficient data from all-Ireland to allow trends to be generated.

 

Productivity

Data submitted to the SMP on the productivity of common gulls from colonies throughout Ireland are 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*)

n/a

5

6

3

Inland numbers

-

-

0

0

Total Figure

-

-

6

3

% change since previous census   

n/a

n/a

+20

-50

*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

Only a few pairs of common gull nest on the Isle of Man. Five AON were recorded during the Seabird Colony Register census and six during Seabird 2000. During the 2017 Isle of Man Seabird Census, two AON were found at the Point of Ayres Gravel Pits and one on the lighthouse wall at the Point of Ayre7, representing a 50% decline in the population since Seabird 2000.

 

Productivity

No systematic data on the productivity of common gulls on the Isle of Man have been submitted to the SMP.

 

Channel Islands

Common gull does not breed on the Channel Islands.

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UK phenology, diet, survival rates

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

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References

1 Craik, J.C.A. 1997. Long-term effects of North American Mink Mustela vison on seabirds in western Scotland. Bird Study, 44, 303–9.

2 Craik, J.C.A. 1995. Effects of North American Mink Mustela vison on the breeding success of terns and smaller gulls in west Scotland. Seabird, 17, 3–11.

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

4 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.

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

6 Cummins, S., Lauder, C., Lauder, A. & 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 Hill, R.W., Morris, N. G., Bowman, K. A., and 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.

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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 Mew 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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Categories:

SMP Report 1986–2018

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