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Black guillemot (Cepphus grylle)

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

 

The black guillemot or 'tystie' is a circumpolar species, concentrated around the North Atlantic, Barents Sea, Baltic and smaller numbers around the Chukchi Sea in northern Alaska and north-eastern Siberia. Approximately half of the UK's population breeds around the Northern Isles, with the remainder confined mainly to the coasts and islands of north and west Scotland. Their distribution within the core range is determined by the availability of suitable nest cavities that are safe from land predators such as rats Rattus sp., American mink Neovison vison, stoats Mustela erminea and otters Lutra lutra. Between censuses in 1969-70 and 1985-91, there was an expansion in the range of black guillemots, in particular the colonisation of new sites around the Irish Sea, including man-made structures (e.g. harbour walls, jetties, piers), and into north-east Scotland.

The species is one of the more problematic seabirds to survey. It tends to breed away from the large seabird cliff colonies and prefers small rocky islands and low-lying, indented stretches of rocky coast. Nests are hidden in rock crevices and under boulders, which makes them extremely difficult to census during the breeding season (see below).

Conservation status

Black guillemot is currently identified as a conservation priority in the following:

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International importance

UK Population

Biogeographic Population

% World Population

38,700 Individuals

n/a

5.8

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.

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

During Operation Seafarer (1969-70), counts were conducted along with other cliff-nesting seabirds during June. At this time of year, black guillemots are often inconspicuous. Operation Seafarer therefore underestimated the population by an unknown number. Between 1982 and 1991, as part of the SCR Census, a survey of the number of adult black guillemots was conducted between late March and early May prior to the breeding season. Surveys were carried out between 06.00 – 09.00 BST when adults congregate close inshore for courtship and mating. Such counts have been found to be the most repeatable and accurate way of assessing population size. A pre-breeding survey was repeated during Seabird 2000 throughout Britain and Northern Ireland, and thus, provided the first opportunity to examine changes in the population of black guillemots in many areas since 1982-91. The main reason for this is that the spatial scales at which counts were conducted during the SCR Census and Seabird 2000 were highly compatible.

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

UK Population estimate (Individuals)

n/a

37,745

38,714

% change since previous census

n/a

n/a

+3

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 guillemot found in different regions, and a map showing the locations and size of colonies, is provided in the Seabird 2000 black guillemot 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

black-guillemot-uk-ab.jpg

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

 

The UK annual sample of black guillemots is small though appears to be representative of the population as a whole. Abundance derived from the sample of colonies monitored as part of the SMP has been generally stable since 1987, normally fluctuating between 50–75% of the 1986 index, although has appeared to be increasing in recent years. Census results also indicate that the UK population changed little (+3%) between the SCR and Seabird 2000 (no comparable data are available from Operation Seafarer).

 

Productivity

The productivity of black guillemots derived from regularly monitored colonies in the UK (mostly located in Orkney and in Co. Down) showed no statistically significant variation over time. On average, productivity was approximately 1.05 chicks fledged per pair per year between 1986 and 2018. No productivity data for 2018 were submitted to the SMP.

 

Scotland

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (Individuals)

n/a

37,172

37,505

% change since previous census

n/a

n/a

<+1

 

Breeding abundance

black-guillemot-scotland-ab.jpg

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

 

The black guillemot population in Scotland was stable between the Seabird Colony Register and Seabird 2000 censuses – c. 37,000 individuals were recorded in each census. The abundance index above, based on the SMP sample shows an increasing trend since Seabird 2000. However, most data collected annually are from colonies in Shetland with few data from sites along other parts of the Scottish coastline and the number of sampled colonies in any year is never large. In 2018, data from 47 colonies were submitted to the SMP and showed a 33% increase in individuals since Seabird 2000. This may give an indication of the current status of the black guillemot population in Scotland.

 

Productivity

Productivity of black guillemots, which is derived from regularly monitored colonies mostly located in Orkney and Shetland, showed no statistically significant variation over time. On average, productivity was approximately 1.01 chicks fledged per pair per year between 1986 and 2012. No data was submitted to the SMP since 2012.

 

England

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (Individuals)

n/a

14

7

% change since previous census

n/a

n/a

-50

 

Breeding abundance

England holds only a few breeding black guillemots, all located at St. Bee’s Head. Fourteen individuals were counted during the Seabird Colony Register, but numbers had halved by Seabird 2000. Ten individuals were recorded in 2011 and 2012, since then numbers have been decreasing with only two individuals recorded in 2017 and four in 2018.

 

Productivity

No systematic data on the productivity of black guillemots in the small population in England have been submitted to the SMP.

 

Wales

Population estimates and change 1969–2002 (census data)

 

Operation Seafarer    

(1969-70)

Seabird Colony Register    

(1985-88)

Seabird 2000    

(1998–2002)

Population estimate (Individuals)

n/a

26

28

% change since previous census

n/a

n/a

+8

 

Breeding abundance

Only 28 black guillemot individuals were recorded in Wales during Seabird 2000, mostly around Anglesey, a similar number to that found during the Seabird Colony Register. No sites of any size are monitored frequently so the current status of the population is unknown.

 

Productivity

No systematic data on the productivity of black guillemots in Wales have been submitted to the SMP.

 

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 (Individuals)

n/a

533

1,174

% change since previous census

n/a

n/a

+120

 

Breeding abundance

In Northern Ireland, black guillemots increased by 120% between the Seabird Colony Register and Seabird 2000 to 1,174 individuals, probably as a result of increased use of man-made structures for nest sites. Habitat such as harbour walls and piers provided important nesting sites, and it was estimated such habitat held over twice as many nesting black guillemots during Seabird 2000 than it did during the SCR; this equated to an estimated 22% of the national population1. Extensive survey work was carried out at 23 colonies in April 2017 and 2018 which held an estimated 80% of the country's population during Seabird 20002. A total of 879 individuals were recorded, 11% less than during Seabird 2000 when 989 individuals were recorded, indicating that the breeding population of black guillemot in Northern Ireland may be in decline.

 

Productivity

The productivity of black guillemots in Northern Ireland shows no statistically significant variation over time. On average 0.98 chicks were fledged per pair per year at monitored colonies between 1986 and 2015. No data productivity data has been submitted to the SMP since 2014.

A study of a colony at Bangor Marina, where most pairs nest in specially provided holes and nest boxes, has revealed losses of eggs to children and predation of eggs and chicks by brown rats Rattus norvegicus, herring gulls Larus argentatus and domestic/feral cats Felis catus. Gulls have also been seen removing sitting adults, although this has been mitigated against by reducing the size of entrance holes3. Thus, losses of young due to predators are now quite low and very few nests are deserted. Overall, productivity at this colony was 1.08 chicks per nest in 2018, slightly above the long-term average of 0.98 (1986–2018).

 

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 (Individuals)

n/a

n/a

3,367

3,917

% change since previous census

n/a

n/a

n/a

+16

 

Breeding abundance

Seabird 2000 was the first national census to record numbers of pre-breeding adult black guillemots in a systematic way in the Republic of Ireland. Counts carried out in April and early May recorded 3,367 individuals. Few colonies are currently monitored during the recommended month (April), or at the recommended time of day (the first few hours after dawn). The recent Republic of Ireland Seabird Census recorded 3,917 individuals; however, this is an interim assessment. The survey covered the majority of the suitable habitat around the Republic of Ireland’s coastline however, it is still incomplete. The data gaps will to be addressed through additional surveys during the 2019 and 2020 breeding seasons4.

 

Productivity

The productivity of black guillemots in the Republic of Ireland shows no statistically significant variation over time. On average, black guillemots fledged 1.22 chicks per pair per year at the only colony monitored, Rockabill, between 2000 and 2014. No productivity data have been submitted to the SMP since 2014.

 

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 (Individuals)

n/a

n/a

4,541

% change since previous census

n/a

n/a

n/a

 

Breeding abundance

With no coverage in the Republic of Ireland during the first two national censuses, the long-term trend in the black guillemot population for the whole of Ireland is currently unknown. However, numbers in Northern Ireland more than doubled between the Seabird Colony Register and Seabird 2000. The population for the whole of Ireland during Seabird 2000 was 4,541 individuals. Since then, very few colonies have been monitored during the recommended month (April), or at the recommended time of day (the first few hours after dawn), so no conclusions can be drawn as to current population trend for the whole of Ireland. In Northern Ireland, extensive survey work was carried out at 23 colonies in April 2017 and 2018 which held an estimated 80% of the country's population during Seabird 20002. A total of 879 individuals were recorded, 11% less than during Seabird 2000 when 989 individuals were recorded. A black guillemot census in the Republic of Ireland is underway but only provisional counts of 3,917 individuals have been provided to the SMP. The data gaps will be addressed through additional surveys during the 2019 and 2020 breeding seasons4.

 

Productivity

The productivity of black guillemots throughout Ireland showed no statistically significant variation over time. On average 1.06 chicks were fledged per pair per year at monitored colonies between 1986 and 2014. No productivity data has been submitted to the SMP by either of the two countries since 2014.

 

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

(2015-18)

Population estimate (Individuals)

n/a

303

602

211

% change since previous census

n/a

n/a

+99

-65

 

Breeding abundance

Between the Seabird Colony Register and Seabird 2000, numbers of black guillemots on the Isle of Man almost doubled from 303 to 602 individuals. A black guillemot census was carried out on the Isle of Man during April 2018 and recorded a total of 211 individuals, a decline of 65% since Seabird 2000. Individuals were found at 27 sites, including 11 sites that did not hold any birds during the Seabird Colony Register Census6.

 

Productivity

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

 

Channel Islands

Black guillemot does not breed on the Channel Islands.

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UK phenology, diet, survival rates

Black guillemot median laying date Bangor Marina.jpg

Figure 3. Median date of laying of the first egg of black guillemots nesting at North Pier, Bangor Marina, 1986–2014. Reproduced with kind permission of J. Greenwood.

 

A detailed study of black guillemots nesting at Bangor Marina has allowed data on the date of laying of the first egg to be collected. In 2014, the median date of laying for the first egg was 26th May. From Figure 3, it can be seen that 2014 was a late year for the onset of egg-laying. There is evidence that the onset of egg-laying is associated with seawater temperature with warmer springs bringing the date forward6. On average, it was calculated that the breeding season became earlier by 2.5 days for every 1°C increase in April sea-surface temperature.

 

Diet

No systematic data on black guillemot diet have been collected as part of the SMP.

 

Return rate and survival rate

No systematic data have been collected as part of the SMP.

 

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References

1 Leonard, K. and Wolsey, S. 2014. Northern Ireland Seabird Report 2013. British Trust for Ornithology, Thetford.

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

3 Greenwood, J. 2014. A review of black guillemots breeding at Bangor, Co. Down, 1985-2013. In: Leonard, K. and Wolsey, S. eds. 2014. Northern Ireland Seabird Report 2013. British Trust for Ornithology, Thetford.

4 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.

5 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.

6 Greenwood, J. 2007. Earlier laying by black guillemots Cepphus grylle in response to increasing sea-surface temperature. Bird Study, 54, 378–379.

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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 guillemot 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

Published: .

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