Black-headed Gull Chroicocephalus ridibundus

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

 

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Description

Black-headed Gull vignette

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:

EC Birds Directive - migratory species

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

(further information on Conservation Designations for UK Taxa)

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


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.

 


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*)

Inland

Total

73,607 77,119

  77,324

  60,688

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.

 


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 (PDF, 1.1 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 coastal Black-headed gull abundance trend

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

 

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 during the late 1980s, but a decline thereafter until 2003.The trend has been upward since then although has declined in 2015. In 2014, the index was approaching values recorded in the late 1980s and early 1990s albeit with wide confidence limits, however in 2015 it has decreased and is based at 11% above the 1986 baseline. Predation by invasive mammalian predators, especially American mink Neovison vison1, is likely to be the main factor responsible for declines in black-headed gull abundance between 1992 and 2003..

 

Productivity

 

UK black-headed gull productivity trend

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

 

Productivity fluctuates markedly and is affected by predation by American mink2 (and, to a lesser extent, by rats Rattus sp.) as well as changes in food supply and periods of inclement weather during breeding seasons. Total breeding failure usually occurs at colonies visited by American mink. Relatively low productivity in some years between 2002 and 2015 is likely to decrease breeding abundance in subsequent years as fewer birds are available to recruit into the breeding population.

 

 

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

18,226 9,554

  6,888

36,303

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

 

Black-headed gull Scotland abundance 2015

Figure 1: Abundance of black-headed gull at Loch of Strathbeg (Banff and Buchan), Sands of Forvie (Gordon) and Insh Marshes (Badenoch and Strathspey), 1986-2015.

 

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 counted colonies, Loch of Strathbeg (Banff and Buchan) and Sands of Forvie (Gordon) and Insh Marshes (Badenoch and Strathspey) show how numbers have changed at each site in the period 1986-2015. At Sands of Forvie, the colony had almost disappeared during the mid-1990s but recovered and in 2015 held over 1,700 nesting pairs. However, Loch of Strathbeg and Insh Marshes have declined considerably, holding only a fraction of the numbers they once did. Data from 15 coastal colonies counted in 2015 totalled 2,247 AON (including Forvie and Strathbeg), an increase of 52% compared to 1,483 AON 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

 

Black-headed gull Scotland productivity 2015

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

 

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. Productivity is affected by predation by mammals, especially American mink2 at west coast colonies. Comparison of breeding success 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% overall. 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 or otter Lutra lutra, or inclement weather) were impacting on breeding success.

 

 

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

53,142 61,968

65,549

17,179

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

 

Black headed gull England abundance graph 1986-2015

Figure 1: Trend in abundance index (solid line) of coastal-nesting black-headed gulls in England, 1986-2014 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).

 

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 1) before declining. Abundance was then relatively stable until 2003 when the trend reached a low point. However, abundance has generally increased since that time and between 2010 and 2014 has reached values equal to, or above, that recorded in the late 1980s and early 1990s. In 2015, the index was 76% above the 1986 baseline, the highest record since then.

 

Numbers in inland colonies (about 100 were known at the time of Seabird 2000) may have increased too, though few colonies are routinely surveyed as part of the SMP. Four major colonies, holding almost 60% of the inland population of 17,000 pairs, have not been surveyed since Seabird 2000. However, at Belmont Reservoir (Lancashire), where gulls nest on a low lying island which necessitates the use of aerial photography to count the nests, numbers in 2015 were estimated at 11,000 AON compared to just 70 AON during Seabird 20003. Based on the latest national population estimate of black-headed gull (140,000 pairs4), Belmont Reservoir held c.8% of the UK breeding population and is probably the largest, both coastal and inland, black-headed gull colony in the UK.

 

Productivity

 

Black headed gull England productivity graph 1986-2015

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

 

The productivity of black-headed gulls breeding in England fluctuates markedly. Particularly low levels of breeding success were recorded prior to 1996, usually 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 und 2009. In 2010, black-headed gulls at English colonies had a very successful breeding season but this has been a rare occurrence during much of the last decade. In 2012, failure at several colonies was due to flooding or predation (by a variety of animals including herring gull, fox and otter), factors which were less prevalent in 2013, 2014 and 2015, resulting in greater numbers of chicks fledging. Productivity consistently monitored at seven colonies throughout England decreased from 0.89 to 0.66 chicks fledged per pair between 2013 and 2015.

 

 

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

800 1,002

   850

1,136

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 had been little overall change at coastal colonies between Operation Seafarer and Seabird 2000, although numbers during the Seabird Colony Register were roughly 20% higher. The largest and most frequently monitored colony, at Cemlyn (Gwynedd), held 15% of the coastal population during the Seabird Colony Register but 52% during Seabird 2000. Distributional data from Seabird 2000 suggested fewer but larger colonies than recorded in previous censuses. Data from three coastal colonies (about five are known) monitored in 2012 gave 680 pairs, suggesting total numbers may be close to that recorded during Seabird 2000, with the majority nesting at Cemlyn (386 pairs). Cemlyn was also the only coastal colony from which data were received in 2015 when 450 nests were recorded. Little is known about the fortunes of inland colonies since the last national census; two colonies visited in 2015 held 165 AON compared to 150 AON during Seabird 2000 however, numbers are fluctuating with only 60 AON recorded in 2014.

 

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.

 

 

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

1,439 4,595

  4,037

  6,070

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

 

SMP Black-headed gull Strangforg Lough abundance from 1986 to 2015

Figure 1: Abundance of black-headed gull at Strangford Lough (Co. Down), 1986-2015.

 

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 (Co. Down, Figure 1), climbed above 7,000 AON at the colonies peak in the mid 1990s, before then declining prior to Seabird 2000. Over the last decade, numbers at this colony had been increasing again, but from 2008 onward are once more on the wane; just 1,265 AON were recorded in 2015. In total, five coastal colonies surveyed in 2015 held  3,676 nesting pairs  compared to 3,309 during Seabird 2000. So it appears that the coastal population at least has recovered to the number recorded during the last census.

 

Inland colonies, which held a further 6,070 pairs during Seabird 2000, are less well monitored apart from those at Lower Lough Erne (Co. Fermanagh) and Portmore Lough (Co. Antrim) where 1,121 AON were present in 2015 (compared to 1,033 AON during Seabird 2000).

 

Productivity

 

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

1,320 376

2,066

1,810

3,876

% change since previous census    N/a -71 +449

 

* 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 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. Only one coastal colony, at Lady's Island Lake (Co. Wexford), has been counted frequently since the last census. Numbers there have increased from 570 in 2001 to 2,012 AON in 2015. With only a single colony counted recently it is not known whether changes at Lady's Island Lake are representative of the national trend although numbers at this one colony are now slightly above  the total coastal population recorded for the Republic of Ireland during Seabird 2000. No data have been received from any of the inland colonies since Seabird 2000.

 

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.

 

 

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

2,759 4,971

  6,103

  7,880

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 pairs of black-headed gull were recorded nesting around the coast for the whole of Ireland. This was higher than during both of the previous censuses, with numbers having more than doubled since Operation Seafarer. In 2015, six coastal colonies held over 5,700 AON, only slightly lower than the total All-Ireland population as recorded by Seabird 2000 suggesting that numbers may now be higher (there are about 10 other colonies which held a further 1,000 pairs during the last census). Seabird 2000 recorded a further 7,880 pairs from 25 inland colonies. Inland colonies are less well monitored apart from those at Lower Lough Erne and Portmore Lough, both in Northern Ireland, where 1,121 AON were present in 2015 (compared to 1,033 AON during Seabird 2000). Too few colonies are surveyed from which to draw any firm conclusion as to how inland breeder black-headed gulls are faring.

 

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.

 

 

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

N/a 78

2

0

2

% change since previous census    N/a N/a -97

 

* 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. No data have been received for this species since the last national census. It is possible that black-headed gulls no longer breed on the Isle of Man.

 

Productivity

 

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

 

 

Black-headed gull does not breed on the Channel Islands.

 

 


UK phenology, diet, survival rates

 

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

 


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 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 Martin, S. 2015. Belmont Reservoir Gullery, 2015. Unpublished report to United Utilities, Horwich.

4 Musgrove, A., Aebischer, N., Eaton, M., Hearn, R., Newton, S., Noble, D., Parsons, M., Risely, K. and Stroud, D. 2013. Population estimates of birds in Great Britain and the United Kingdom. British Birds 106: 64-100.

 


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