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Black-headed gull (Chroicocephalus ridibundus)

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

 

The black-headed gull is the most widely distributed seabird breeding in the UK, with similar numbers breeding inland as on the coast. The majority of the breeding population are resident throughout the year, with numbers being greatly bolstered during the winter months by birds from northern and eastern Europe, especially in the east and southeast of England. Black-headed gulls breed throughout the middle latitudes of the Palaearctic and have recently formed a breeding outpost in north eastern North America. The UK holds approximately 6% of the world breeding population. Black-headed gulls tend to nest on open ground and occasionally in low trees and bushes, in colonies of anywhere from a few to over 10,000 apparently occupied nests (AON). Habitats such as wetlands, bogs, marshes and artificial ponds are favoured breeding sites, but dry areas adjacent to water are also used.

Conservation status

Black-headed gull is currently identified as a conservation priority in the following:

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International importance

UK Population

Biogeographic Population

% World Population

138,000 AON*

n/a

5.6

*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)

Prior to Seabird 2000, the population of black-headed gulls in Britain and Ireland had only ever been surveyed incompletely. During Operation Seafarer (1969-70) complete coverage of coastal colonies was achieved, but no inland colonies were counted, and these hold just under half of the UK breeding population. Both coastal and inland colonies were surveyed during the SCR Census (1985-88), but coverage inland was incomplete and so only provided a minimum estimate of the number nesting away from the coast. During Seabird 2000, coverage of colonies in the UK was comprehensive, with the exception of inland colonies in Durham and in western parts of North Yorkshire, where some may have been missed although the numbers involved are not thought to be large. Surveys at the majority of colonies counted apparently occupied nests (AONs). However, at some colonies, flush counts of individuals attending the colony were made which were then divided by two to provide a rough measure of the number of AONs. This is the least accurate method for counting breeding gulls, as such counts will include an unknown percentage of non-breeders and attendance at the colony by both members of a pair is highly variable throughout the day and throughout the breeding season. During Seabird 2000 only 13% of the total population estimate of AONs was determined from flush counts of individuals, which compares favourably to 18% during the SCR Census.

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

UK Population estimate (AON*)

73,607

77,119

77,324

Inland numbers

-

-

60,688

Total Figure

-

-

138,012

% change since previous census   

n/a

+5

0

*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 black-headed gull found in different regions, and a map showing the location and size of colonies, is provided in the Seabird 2000 black-headed 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

bh-gull-uk-ab.jpg

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

 

National census data indicate the number of coastal nesting black-headed gulls in the United Kingdom was relatively stable between 1969-70 and 1998–2002. However, there are differences within the census data for the constituent countries of the UK (see individual country accounts).

Data submitted to the SMP show an increase in the abundance index to the early 1990’s but a decline thereafter until 2003. After this the trend gradually increased until 2014, where it was over 30% above the baseline, but declined back to the baseline value by 2016. By 2018, the abundance index had increased again to 56% above the baseline, the highest value to date.

 

Productivity

bh-gull-uk-prod.jpg

Figure 2. Trend in UK productivity (no. of chicks fledged per pair) of black-headed gull 1987–2018. Based on SMP data; view the methods of analysis.

 

Over the monitoring period, Black-headed gull productivity has fluctuated markedly and is likely to have been affected by predation by American mink1,2 (and, to a lesser extent, by rats Rattus sp.), as well as changes in food supply and periods of inclement weather during breeding seasons. This fluctuating productivity trend is common to black-headed gull colonies throughout the UK. Very low productivity occurred in 1998 and 1991, although between 1996 and 2001 it was often above one chick fledged per pair. Since 2003, productivity values have generally been lower, although have gradually been increasing since 2011, reaching 0.73 chicks fledged per pair in 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*)

18,226

9,554

6,888

Inland numbers

-

-

36,303

Total Figure

-

-

43,191

% change since previous census   

n/a

+48

-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

bh-gull-scotland-ab.jpg

Figure 3. Abundance of black-headed gull at Loch of Strathbeg, Sands of Forvie and Insh Marshes, 1986–2018.

 

The number of black-headed gulls nesting in coastal areas of Scotland declined severely between 1969-70 and 1998–2002. National census data show almost 50% of the population disappeared between Operation Seafarer and the Seabird Colony Register, with a further decline of 28% by the time of Seabird 2000.

Due to colonies being surveyed infrequently, no trend can be generated from data submitted to the SMP. However, counts at three of the largest and most frequently monitored colonies (Loch of Strathbeg, Sands of Forvie and Insh Marshes) show how numbers have changed at each site over the reporting period (Figure 3, 1986–2018). The Sands of Forvie colony had almost disappeared by the mid-1990s but by 2018 had recovered and held over 2,100 AON. However, Loch of Strathbeg and Insh Marshes have declined considerably over the reporting period, now holding a fraction of the numbers they once did. Data from 19 coastal colonies counted in 2018 totalled 2,195 AON (including Forvie and Strathbeg), an increase of 158% compared to the 850 AON recorded at the same colonies during Seabird 2000. However, drawing definite conclusions about the fortunes of black-headed gulls in Scotland is difficult without extensive coverage of inland colonies which held far greater numbers compared to coastal colonies during the last census.

 

Productivity

bh-gull-scotland-prod.jpg

Figure 4. Trend in productivity (no. of chicks fledged per pair) of black-headed gull in Scotland, 1987–2018. Based on SMP data; view the methods of analysis.

 

The productivity of black-headed gulls in Scotland has fluctuated widely over the years. There is no clear trend, although birds appear to have been more successful overall during the latter half of the recording period. However, in 2018 only 0.24 chicks fledged per pair. Productivity is affected by predation by mammals, especially by American mink3 at west coast colonies. Comparisons of productivity at colonies where American mink were controlled against those with no mink control, or where control was unsuccessful, found that on average, between 1997 and 2011, American mink lowered success from 0.79 to 0.32 chicks fledged per pair – an estimated reduction of 59%. However, from 2012 to 2014, success at colonies where American mink were controlled (0.06, 0.44 and 0.00 in each year, respectively) was actually lower than at colonies with no, or unsuccessful, control (0.44, 0.65 and 0.69 in each year, respectively), suggesting other factors (e.g. predation by large gulls, predation by otters Lutra lutra, or due to inclement weather) were impacting on productivity.

 

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*)

53,142

61,968

65,549

Inland numbers

-

-

17,179

Total Figure

-

-

82,728

% change since previous census   

n/a

+14

+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

bh-gull-england-ab.jpg

Figure 5. Trend in abundance index (solid line) of coastal-nesting black-headed gulls in England, 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.

 

Census results for coastal nesting black-headed gulls in England show an increase of 14% in the number of nests recorded between 1969-70 and 1985-88. Results from Seabird 2000 showed little change took place between 1985-88 and 1998–2002. The abundance trend of black-headed gulls from SMP data indicates increases may have continued up until the early 1990s (Figure 5) before declining. Abundance was then relatively stable until 2003 when the index reached its lowest point since monitoring began. However, abundance has overall increased since then and, between 2010 and 2015, reached values equal to, or above, that recorded in the late 1980s and early 1990s. In 2018, the index was 124% above the 1986 baseline, the highest ever recorded.

The breeding population at inland colonies (about 100 were known at the time of Seabird 2000) may have increased too, although an insufficient number are routinely surveyed to deliver a robust trend. Two inland colonies, Belmont Reservoir and Old Moor, that were surveyed in 2018, held a total of 13,555 AON, a very large increase since Seabird 2000, when each held only 70 AON and 200 AON, respectively. Based on the latest national population estimate of black-headed gull (140,000 pairs4), Belmont Reservoir holds c. 8% of the UK breeding population and is probably the largest, inland black-headed gull colony in the UK.

 

Productivity

bh-gull-england-prod.jpg

Figure 6. Trend in productivity (no. of chicks fledged per pair) of black-headed gull in England, 1990-2018. Based on SMP data; view the methods of analysis.


The productivity of black-headed gulls breeding in England fluctuates markedly. Particularly low levels of productivity were recorded prior to 1996, often due to high tides washing out nests. Between 1996 and 2001, colonies fledged an average of over one chick per pair per year but this was followed by a reduced productivity of 0.55 chicks per year per pair between 2002 and 2009. In 2010, black-headed gulls at English colonies had a successful breeding season (fledging an average of 0.9 chicks per pair) which was followed by a very poor season in 2011 (0.1 chicks per pair). In 2012, failure at several colonies was caused by flooding or predation leading to another poor season (0.2 chicks fledged per pair). Since then, productivity has continually increased and is now at 1.13 chicks fledged per pair per year, one of the highest values ever recorded.

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*)

800

1,002

850

Inland numbers

-

-

1,136

Total Figure

-

-

1,986

% change since previous census   

n/a

+25

-15

*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 colonies holding black-headed gulls are monitored regularly in Wales. National census data indicate there was little overall change at coastal colonies between Operation Seafarer and Seabird 2000, although numbers during the Seabird Colony Register were approximately 20% higher. The largest and most frequently monitored colony, at Cemlyn, held 15% of the coastal population during the Seabird Colony Register but 52% during Seabird 2000. Distributional data from Seabird 2000 found fewer but larger colonies than recorded in previous censuses. Four coastal colonies counted in 2018 held 34 AON compared to 450 AON in Seabird 2000, indicating that the coastal black-headed breeding population in Wales may be decreasing. Little is known about the fortunes of inland colonies since Seabird 2000; however, a small sample of seven colonies visited in 2018 held 444 AON compared to 499 AON during Seabird 2000.

 

Productivity

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

 

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*)

1,439

4,595

4,037

Inland numbers

-

-

6,070

Total Figure

-

-

10,107

% change since previous census   

n/a

+219

-12

*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

bh-gull-ni-ab.jpg

Figure 7. Abundance of black-headed gull at Strangford Lough, 1986–2018.

 

Seabird 2000 recorded just over 4,000 pairs of black-headed gulls nesting around the Northern Ireland coastline. This was 12% fewer than recorded by the SCR but almost three times that found by Operation Seafarer. However, the national population must have been far higher between the SCR and Seabird 2000 censuses, as numbers at Strangford Lough (Figure 7), climbed above 7,000 AON at the colonies peak in the mid-1990s, before declining prior to Seabird 2000. Numbers then increased again but, from 2008 to 2012 declined considerably (from 4,351 to 1,015 AON respectively). Since 2013 numbers have stabilised to between 1,200 and 1,300 AON each year. The colonies at Carlingford Lough, Copeland Island and Rathlin need to be counted to better understand the status of the coastal-nesting population of black-headed gulls in Northern Ireland.

Few inland colonies are regularly monitored, although those at Lower Lough Erne and Portmore Lough held 1,517 AON in 2018 compared to 1,033 AON during Seabird 2000. On Lough Neagh, which held 30,000 breeding AON of black-headed gulls on 12 islands in the 1980s, counts of the main breeding islands estimated 11,595 individuals in 2016, 8,120 in 2017 and 8,906 in 20185. In addition, black-headed gulls have abandoned breeding on Shallow Flat and Coney Island Flat, and have decreased in number on Padian Island, Owen Roe and Scaddy Island6.

 

Productivity

Data submitted to the SMP on the productivity of black-headed gulls in Northern Ireland are sparse. At Portmore Lough, 124 AONs produced 159 chicks (1.28 chicks fledged per pair), almost identical to 2017. In 2018, productivity was approximately 1.50 chicks fledged per pair at Blue Circle Island and Swan Island in Larne Lough.

 

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*)

1,320

376

2,066

7,810**

Inland numbers

-

-

1,810

-

Total Figure

-

-

3,876

-

% change since previous census

n/a

-71

+449

+102

*AON = Apparently Occupied Nests

** This population estimate figure is a combination of inland and coastal as information on the split were not available5.

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 number of black-headed gulls in the Republic of Ireland was very low during the Seabird Colony Register, at 376 pairs. Numbers had declined by 71% since Operation Seafarer, possibly due to birds deserting coastal colonies in favour of inland ones. However, by the time of Seabird 2000, coastal black-headed gulls were more numerous than they had been during the first census, at 2,066 pairs with a further 1,810 pairs nesting inland. The recent Republic of Ireland Seabird Census (2015–2018) recorded a total of 7,810 pairs, an increase of 102% compared to 3,876 AON recorded during Seabird 20007. The two coastal lakes of Inch in Donegal and Lady’s Island Lake in Wexford currently host over half of the national population, increasing from 949 AON and 800 AON during Seabird 2000 to 2,526 AON (+166%) and 1,450 AON (+81%), respectively. Inland colonies at Lough Carra (556%), Lough Mask (63%) and Lough Corrib (57%) have been increasing and an additional colony emerged on Lough Derg7.

 

Productivity

Data submitted to the SMP on the productivity of black-headed 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*)

2,759

4,971

6,103

Inland numbers

-

-

7,880

Total Figure

-

-

13,983

% change since previous census   

n/a

+80

+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

During Seabird 2000, 6,103 AON of black-headed gull were recorded around the coast of Ireland. This was higher than during both of the previous censuses, with numbers having more than doubled since Operation Seafarer.

Numbers at Strangford Lough, one of the largest coastal colonies in Northern Ireland have stabilised to between 1,200 and 1,300 AON each year since 2013. Other colonies such as Carlingford Lough, Copeland Island and Rathlin Island need to be counted to better understand the status of the coastal-nesting population of black-headed gulls in Northern Ireland. The recent Republic of Ireland Seabird Census (2015-2018) recorded a total of 7,810 pairs, an increase of 102% compared to 3,876 AON recorded during Seabird 20007. Over half of the coastal-nesting population of black-headed gulls is currently located at two coastal lakes (Lough Inch and Lady’s Island Lake).

Few inland colonies are regularly monitored in Northern Ireland and the Republic of Ireland therefore, it is unclear whether the black-headed gull population is stable or decreasing.

 

Productivity

Data submitted to the SMP on the productivity of black-headed gulls 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

78

2

6

Inland numbers

-

-

0

0

Total Figure

-

-

2

6

% change since previous census   

n/a

n/a

-97

+200

*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 two pairs of black-headed gull were recorded during Seabird 2000, numbers having declined by 97% since the Seabird Colony Register. The first data received for this species since the last national census was in 2017, when an island census found six AON at the Point of Ayres Gravel Pits8. No data were submitted to the SMP in 2018.

 

Productivity

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

 

Channel Islands

Black-headed 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, 303–309.

2 Coulson C.C. 2019. Gulls. HarperCollins Publisher, London.

3 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.

4 Martin, S.J. 2017. Belmont Reservoir Gullery, 2017. Unpublished report to United Utilities plc. and Natural England, Horwich.

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

6 Allen, D. and Mellon, C. 2018. Lough Neagh Islands Conservation Management Plan 2018. Belfast.

7 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.

8 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 Black-headed 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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