Black Guillemot Cepphus grylle
Status; International importance;
Population
estimates; Distribution; Annual abundance/
productivity; Phenology/diet/survival
Description
The following was 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, mink, stoats and otters. 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 in to 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 3 (2009 update)
(further information on Conservation Designations for UK Taxa)
Amber listed in
Birds of Conservation Concern in Ireland 2 (2007
update)
International importance
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 amount.
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. Counts were conducted
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 where colonies are found and how large they are
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
Breeding abundance
The UK annual sample of black guillemots is small though appears
to be representative of the population as a whole.
Abundance derived from the SMP annual sample has
been generally stable over the recording period, generally
fluctuating between 52-67% of the 1986 index. Census results
too indicate that the UK population changed little (+3%) between
the SCR and Seabird 2000.
Productivity
Relatively few data are available on productivity but black
guillemots, the only species of auk in the UK which lays two eggs,
on average fledged approximately 1.01 chicks per pair per year;
there was no statistically significant variation over time.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (Ind*) |
N/a |
37,172 |
37,505 |
| % change since previous
census |
N/a |
N/a |
<+1 |
* Ind = Individuals
Breeding abundance
Figure 1: Trend in abundance index (solid
line) of black guillemot in Scotland, 1986-2010 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. The
abundance index above, based on the SMP sample, indicates the
status of the species has probably changed little since then. High
abundance values for 1986 and 1990 are probably due to fewer than
usual colonies being monitored in those years (and hence a
potentially unrepresentative sample, although the number of sampled
colonies in any year is never large).
Productivity
The productivity of black guillemots in Scotland showed no
statistically significant variation over time. On average 0.98
chicks were fledged per pair per year.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (Ind*) |
N/a |
14 |
7 |
| % change since previous
census |
N/a |
N/a |
-50 |
* Ind = Individuals
Breeding abundance
England holds only a few breeding black guillemots. Fourteen
individuals were counted during the Seabird Colony Register but
numbers had halved by Seabird 2000. Only six individuals were
recorded in 2010.
Productivity
No systematic productivity data have been collected for black
guillemots in England as part of 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 (Ind*) |
N/a |
26 |
28 |
| % change since previous
census |
N/a |
N/a |
+8 |
* Ind = Individuals
Breeding abundance
Only 28 black guillemot individuals were counted in Wales during
Seabird 2000, a similar number to that found during the
Seabird Colony Register. Sites are not monitored frequently so the
current status of the population is unknown.
Productivity
No systematic productivity data have been collected for black
guillemots in Wales as part of 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 (Ind*) |
N/a |
533 |
1,174 |
| % change since previous
census |
N/a |
N/a |
120 |
* Ind = Individuals
Breeding abundance
In Northern Ireland, black guillemots increased by 120% between
the Seabird Colony Register and Seabird 2000 to 1,174
individuals. Only a few sites have been monitored since then,
with numbers at the largest colony, Rathlin Island, declining from
203 to 101 individuals between 2000 and 2007. Whether this
decline has occurred at other colonies in Northern
Island is unknown.
Productivity
The productivity of black guillemots in Northern Ireland
showed no statistically significant variation over time. On
average 1.04 chicks were fledged per pair per year.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (Ind*) |
N/a |
N/a |
3,367 |
| % change since previous
census |
N/a |
N/a |
N/a |
* Ind = Individuals
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 done in April and early May recorded
3,367 individuals. Few colonies are currently monitored so the
status of the national population is not known. At Rockabill,
however, numbers have halved over the last decade.
Productivity
Few systematic data on the productivity of black guillemots in
the Republic of Ireland have been collected as part of 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 (Ind*) |
N/a |
N/a |
4,541 |
| % change since previous
census |
N/a |
N/a |
N/a |
* Ind = Individuals
Breeding abundance
With no surveys done in the Republic of Ireland during the first
two national censuses the 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 current population for the whole of Ireland
is unknown, though the latest estimate from Seabird 2000
is 4,541 individuals.
Productivity
The productivity of black guillemots throughout Ireland
showed no statistically significant variation over time. On
average 1.10 chicks were fledged per pair per year.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (Ind*) |
N/a |
303 |
602 |
| % change since previous
census |
N/a |
N/a |
+99 |
* Ind = Individuals
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 productivity have been collected as part
of the SMP.
This species does not breed on the Channel
Islands.
UK phenology, diet, survival rates
No data have been collected as part of the Seabird Monitoring
Programme.
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; Countryside Council for Wales; Department of
Agriculture, Fisheries and Forestry (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.