Great Black-backed Gull Larus marinus
Status; International importance;
Population
estimates; Distribution; Annual abundance/
productivity; Phenology/diet/survival
Description
The following was adapted from original text by James
B. Reid in
Seabird Populations of Britain and Ireland (with
permission from A&C Black, London).
The great black-backed gull has an extensive breeding range
across the north Atlantic and adjacent seas, and historically,
Britain and Ireland have hosted most of the world population after
Iceland and Norway. They breed mainly in the Outer and Inner
Hebrides and the Northern Isles of Scotland. These regions offer
extensive areas of the preferred breeding habitat of well-vegetated
rocky coastline with stacks and cliffs. The 20th century
saw widespread expansion of the great black-backed gull breeding
range and numbers on both sides of the Atlantic. In Britain at
least, population increase was remarkable given that a period of
decline rendered the species virtually extinct as a breeder towards
the end of the previous century. The species nests almost
exclusively in coastal habitats, but will occasionally nest inland
at freshwater sites as well as on the roofs of buildings.
Conservation status
Great black-backed gull 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
*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 hence differs from that tabled
below.
UK population estimates and change 1969-2002 (census data)
No major gaps in survey coverage are known for the three
national surveys as most colonies are well established.
Great black-backed gulls often nest at low densities in
mixed-species colonies, usually with lesser black-backed gulls, but
their visually conspicuous plumage and large size, coupled with a
distinctively deep voice, probably reduces the chances of such
pairs being overlooked. However, solitary nests or pairs,
especially those in remote areas, might easily have been missed.
Seabird 2000 represented the first attempt to census all coastal
and inland breeding colonies of great black-backed gull
although only 20 pairs were found inland.
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| UK Population estimate (AON*) |
18,771 |
17,415 |
16,735 |
| % change since previous census |
N/a |
-7 |
-4 |
*AON = Apparently Occupied Nests
Note: Inland colonies were not counted during the two earlier
national censuses so to enable direct comparison the Seabird 2000
figure refers to the coastal population 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 great black-backed gull found in different
regions, and a map showing where colonies are found and how large
they are is provided in the Seabird 2000 great black-backed
gull results page (PDF, 2.1 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
Breeding abundance
Figure 1: Trend in UK
abundance index (solid line) of great black-backed gull 1986-2010
with 95% confidence limits (dotted lines). Based on SMP data;
view the methods
of analysis (PDF 158 kb).
The abundance of great black-backed
gulls changed relatively little between the first census
of their numbers in 1969/70 and Seabird 2000. During 1986 to 2010,
abundance fluctuated between 80% and 115% of the 1986 reference
level, but since the peak index was reached in 1999 it
has decreased by around 20%. However, some regional variation
is apparent: numbers in Wales decreased between 1969/70 and 1985-88
(and increased somewhat by 1998-2002) and numbers in Northern
Ireland decreased between 1985-88 and 1998-2002. It has been
suggested that great black-backed gulls have competitive advantage
when scavenging at sea for fishery discards and offal1, and hence have not
experienced (at least, until recently) the declines that other
scavengers (herring and lesser black-backed gull) have in recent
decades due to declines in discards and offal2. The species also forages on
natural prey (rabbits, other seabirds) and appears to be quite
adaptable to changing dietary opportunities. The cause of the
decline seen in the last decade is unknown.
Productivity
Figure 2: Trend in
UK productivity (no. of chicks fledged per pair) of great
black-backed gull 1986-2010. Based on SMP data; view
the methods
of analysis (PDF 158 kb).
No clear trend is evident in productivity
overall, though it was lower in 2003-2006. The effects of predation
by mink on this large and aggressive gull appear to be less severe
than for its smaller relatives.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AON*) |
15,950 |
15,315 |
14,773 |
| % change since previous
census |
N/a |
-4 |
-4 |
* AON = Apparently Occupied Nests
Note: Inland colonies were not counted during
the two earlier national censuses so to enable direct comparison
the Seabird 2000 figure refers to the coastal population only.
Breeding abundance
Figure 1: Trend in abundance index (solid
line) of great black-backed gull in Scotland, 1986-2010 with 95%
confidence limits (dotted lines). Based on SMP data; view
the methods
of analysis (PDF 158 kb).
National census data show that numbers of great
black-backed gulls in Scotland changed relatively
little between 1969/70 and Seabird 2000. The trend from
the SMP since 1986 (Figure 1) shows a decline after the
Seabird Colony Register, but abundance had increased by
the time of Seabird 2000. Since 1999 there appears to have
been a steeper and prolonged decline with the index
in 2010 40% lower than in 1999.
Productivity
Figure 2: Trend
in productivity (no. of chicks fledged per pair) of great
black-backed gull in Scotland, 1986-2010. Based on SMP data;
view the methods
of analysis (PDF 158 kb).
Productivity of great black-backed gulls at
Scottish colonies generally declined toward 2003 although
there was some large fluctuations. Particularly low levels of
productivity were then recorded up to 2005 but success
has increased again since then. Declining productivity may have
contributed to the downward population trend noted since 1999 but
this could be reversed with the recent increase in fledging
rate.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AON*) |
1,676 |
1,534 |
1,466 |
| % change since previous
census |
N/a |
-8 |
-4 |
* AON = Apparently Occupied Nests
Note: Inland colonies were not counted during
the two earlier national censuses so to enable direct comparison
the Seabird 2000 figure refers to the coastal population only.
Breeding abundance
Figure 1: Abundance of great black-backed gull
on Annet (Isles of Scilly), 1986-2010.
National census data show great black-backed gull numbers in
England have declined only slightly over a thirty-year period.
The greatest concentration of the species is
in south-west England, where few colonies receive regular
monitoring. Hence, trends derived from colonies providing data to
the SMP are probably unrepresentative and not shown. The
largest colony monitored regularly in the south-west, on Annet in
the Isles of Scilly (above), has increased in size since
Seabird 2000. Whether this increase is representative of the
national trend is unknown, although changes at the colony between
1987 and 1999 match those from national census
data.
Productivity
Relatively few data are available on the productivity of
great black-backed gulls in England. There was no statistically
significant variation over time; on average approximately
0.94 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 (AON*) |
905 |
289 |
425 |
| % change since previous
census |
N/a |
-68 |
+47 |
* AON = Apparently Occupied Nests
Note: Inland colonies were not counted during
the two earlier national censuses so to enable direct comparison
the Seabird 2000 figure refers to the coastal population only.
Breeding abundance
Figure 1: Trend in abundance index (solid
line) of great black-backed gull in Wales, 1986-2010 with 95%
confidence limits (dotted lines). Based on SMP data; view
the methods
of analysis (PDF 158 kb).
The trend in abundance for greater black-backed gulls in
Wales has generally been upward over the last 25 years (Figure 1)
although there is a pronounced dip around the period of
Seabird 2000. Census data suggest numbers recorded then were 47%
higher than during the Seabird Colony Register. Over the
longer-term, data suggest numbers are still low compared with
those recorded by Operation Seafarer, when 905 pairs were
found.
Productivity
Few data are available on the
productivity of great black-backed gulls nesting in Wales. On
average pairs fledged 1.20 chicks 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 (AON*) |
240 |
277 |
71 |
| % change since previous
census |
N/a |
+15 |
-74 |
* AON = Apparently Occupied Nests
Note: Inland colonies were not counted during
the two earlier national censuses so to enable direct comparison
the Seabird 2000 figure refers to the coastal population only.
Breeding abundance
Figure 1: Abundance of great black-backed gull
at Strangford Lough, 1986-2010.
Most of the colonies of great black-backed gull in Northern
Ireland hold only a few pairs. Strangford Lough (above) is by far
the most important colony in the region holding as it did over 40%
of the population during the Seabird Colony Register. This colony
declined severely after the SCR, and held just 40 pairs when
counted for Seabird 2000; one year later only one pair was
recorded. Numbers have increased at Strangford since 2001, although
are still only about three quarters of what they were in
the mid 1980s.
Productivity
Very few systematic productivity data have been collected
for great black-backed gulls in Northern Ireland 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 (AON*) |
3,166 |
2,921 |
2,241 |
| % change since previous
census |
N/a |
-8 |
-23 |
* AON = Apparently Occupied Nests
Note: Inland colonies were not counted during
the two earlier national censuses so to enable direct comparison
the Seabird 2000 figure refers to the coastal population only.
Breeding abundance
Great black-backed gulls nesting in the Republic of Ireland have
been in long-term decline, numbers falling between Operation
Seafarer and Seabird 2000 by 29%. Few colonies have been monitored
over the last decade so the current status of the species is
unknown although six colonies holding 488 pairs during
Seabird 2000, held 681 pairs in 2010.
Productivity
Very few systematic productivity data have been collected
for great black-backed gulls in the Republic of Ireland 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 (AON*) |
3,406 |
3,198 |
2,312 |
| % change since previous
census |
N/a |
-6 |
-28 |
* AON = Apparently Occupied Nests
Note: Inland colonies were not counted during
the two earlier national censuses so to enable direct comparison
the Seabird 2000 figure refers to the coastal population only.
Breeding abundance
The great black-backed gull population for the whole
of Ireland declined by 32% between Operation Seafarer and
Seabird 2000, although numbers were fairly stable up until the
Seabird Colony Register. Few colonies have been monitored over
the last decade so the current status of the species is
unknown.
Productivity
Very few systematic productivity data have been collected
for great black-backed gulls throughout Ireland 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 (AON*) |
275 |
376 |
405 |
| % change since previous
census |
N/a |
+37 |
+8 |
* AON = Apparently Occupied Nests
Note: Inland colonies were not counted during
the two earlier national censuses so to enable direct comparison
the Seabird 2000 figure refers to the coastal population only.
Breeding abundance
Figure 1: Abundance of great
black-backed gull on the Calf of Man, 1986-2010.
Between Operation Seafarer and the Seabird Colony
Register great black-backed gulls nesting on the Isle of
Man increased by 37%, but there had been little further growth by
the time of Seabird 2000. The current status of great
black-backed gull on the Isle of Man is unknown as only one
colony, on the Calf of Man, has been surveyed since then. In the
late 1980s and early 1990s this colony regularly held over 50% of
the regional population but in 2010 only 57 pairs were
recorded. The decline in great black-backed gull numbers at this
colony is in common with declines recorded there for herring
and lesser black-backed gulls.
Productivity
Very few systematic productivity data have been collected
for great black-backed gulls on the Isle of Man 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 (AON*) |
200 |
180 |
310 |
| % change since previous
census |
N/a |
-10 |
+42 |
* AON = Apparently Occupied Nests
Note: Inland colonies were not counted during
the two earlier national censuses so to enable direct comparison
the Seabird 2000 figure refers to the coastal population only.
Breeding abundance
During Seabird 2000, 310 pairs of great black-backed gull were
recorded in the Channel Islands. This represented an increase of
42% since the Seabird Colony Register, which had recorded similar
numbers to that found during Operation Seafarer. No data have
been collected in the region since 1998-2002 so the current
status of the species is unknown.
Productivity
No systematic data on productivity have been
collected as part of the SMP.
UK phenology, diet, survival rates
No systematic data have been collected as part of the Seabird
Monitoring Programme.
References
1 Reid, J.B. 2004. Great Black-backed
Gull Larus marinus. In: Mitchell,
P.I., Newton, S.F., Ratcliffe, N.
and Dunn, T.E. (eds.) 2004. Seabird
Populations of Britain and Ireland:
263-276. Poyser, London.
2 Reeves, S.A. and R.W. Furness. 2002. Net
loss–seabirds gain? Implications of fisheries management for
seabirds scavenging discards in the northern North Sea. Unpublished
RSPB Report, Sandy, UK.
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 great black-backed gull appears courtesy of Ian
Rendall ©, is subject to international copyright
law and may not be reproduced in any form whatsoever.