Black Guillemot Cepphus grylle

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

 

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Description

Black Guillemot vignette

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:

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

(further information on Conservation Designations for UK Taxa)

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

 


International importance

 

UK Population % Biogeographic Population % World Population
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.

 


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

(1982-91)

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.

 


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 (PDF, 2.2 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% 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.   

 



 

Breeding abundance

 

UK black guillemot abundance trend

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

 

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 52-67% 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 1.01 chicks fledged per pair per year between 1986 and 2014. No productivity data for 2015 was submitted to the SMP.

 

 

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

 

Scotland black guillemot abundance trend

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

 

The total population of the black guillemot 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. The disparity between the high abundance value for 1986 and subsequent fall in 1987, after which the index was reasonably stable for almost 20 years, is probably due to fewer than usual colonies being monitored in 1986, and hence a potentially unrepresentative sample, although the number of sampled colonies in any year is never large. The abundance index increased slowly since 2008 but fell to 35% below the 1986 baseline in 2015.

 

Productivity

 

The productivity of black guillemots derived from regularly monitored colonies in Scotland (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 productivity data has been collected since 2015.

 

 

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 (Cumbria). Fourteen individuals were counted during the Seabird Colony Register, but numbers had halved by Seabird 2000. Ten individuals were recorded in 2011 and 2012, nine in 2013 with only six recorded in 2014. No data was collected in 2015.

 

Productivity

 

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

 

 

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 counted in Wales during Seabird 2000, mostly around Anglesey (Gwynedd), 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.

 

 

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 36 colonies in April 2014 which held an estimated 80% of the country's population during Seabird 20002. The total recorded, at 908 individuals, was 8% less than 990 individuals recorded in the same areas during Seabird 2000. It also appears that some distributional shift has occurred as 102 birds were recorded at sites which apparently held no birds during Seabird 2000.

 

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.

Close study of a colony at Bangor Marina (Co. Down, 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, herring gulls 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 quite low and very few nests are deserted. Overall, breeding success at this colony was 0.98 chicks per nest in 2015, slightly above the long-term average of 0.94 (1986-2015), although this has lessened in recent years. The reason for the decline in success is uncertain and is currently an area of investigation4. These breeding success data are higher than at another small colony in Belfast Harbour, where only 0.53 young per pair were fledged between 2000 and 2009 (when black guillemots last attempted to breed at the site).

 

 

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 3,367
% change since previous census    N/a N/a N/a

 

 

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), so the status of the national population is not known.

 

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, on Rockabill (Co. Dublin), between 2000 and 2014. No productivity data was submitted to the SMP in 2015.

 

 

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 surveys done 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 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. However, in Northern Ireland, numbers appear to have been relatively stable during the years since Seabird 2000. Survey work at 14 colonies in April 2013 recorded 892 individuals, which was similar to 927 individuals recorded at the same colonies during Seabird 20001. Further extensive survey work was carried out at 36 colonies in April 20142. The total recorded, at 908 individuals, was 8% fewer than 990 individuals recorded in the same areas during Seabird 2000. There was evidence that a distributional shift had occurred during the intervening years. For example, in 2013, numbers in Co. Down had increased (from 149 to 333) in contrast to a decline in Antrim (278 to 159)1 and, in 2014, 102 birds were recorded at sites which apparently held no birds during Seabird 2000.

 

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 was submitted to the SMP from either country in 2015.

 

 

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 303 602
% change since previous census    N/a N/a +99

 

 

Breeding abundance

 

Between the Seabird Colony Register and Seabird 2000 the numbers of black guillemots on the Isle of Man almost doubled from 303 to 602 individuals. Very little monitoring has been carried out since then, so the current status of the species is largely unknown.

 

Productivity

 

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

 

 

Black guillemot does not breed on the Channel Islands.

 

 


UK phenology, diet, survival rates

 

Phenology

 

Black guillemot Bangor abundance 2015

Figure 1: Median date of laying of the first egg of black guillemots nesting at North Pier, Bangor Marina (Co. Down), 1986-2014. Reproduced with kind permission of J. Greenwood.

 

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 1 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 forward5. 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.

 


References

 

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

2 Leonard, K. and Wolsey, S. (eds.). 2015. Northern Ireland Seabird Report 2014. 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 Greenwood, J. 2015. Breeding sites and breeding success in 2014 of black guillemots at Bangor Marina. In: Leonard, K. and Wolsey, S. (eds.). 2015. Northern Ireland Seabird Report 2014. British Trust for Ornithology, Thetford.

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

 


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