Lesser Black-backed Gull Larus fuscus
Status; International importance;
Population
estimates; Distribution; Annual abundance/
productivity; Phenology/diet/survival
Description
The following was adapted from
original text by John Calladine in
Seabird Populations of Britain and Ireland (with
permission from A&C Black, London).
The lesser black-backed gull breeds in north and west Europe and
has increased in numbers throughout its range during much of the
20th century. During this time, they have become less
migratory and can now be found within much of their breeding range
throughout the year. The species nests colonially, often with
other gulls, especially the herring gull. Colonies are found on
islands offshore and within inland freshwater bodies, coastal
cliffs, sand dunes, salt marshes, moorland and on the rooftops of
buildings. Seemingly, many sites that are either inaccessible to
ground predators (e.g. islands and urban rooftops) or
where ground predators are particularly scarce (e.g.
narrow peninsulas or on moorland managed as sporting estate) can
prove attractive for nesting. Though often sharing breeding areas
with herring gulls, their nest sites and feeding strategies
generally differ; lesser black-backed gulls can forage over larger
distances and they tend to nest within more vegetated areas.
Conservation status
Lesser 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)
Prior to Seabird 2000, the population of lesser black-backed
gulls in the UK has only ever been surveyed incompletely.
During Operation Seafarer (1969-70), complete coverage of coastal
colonies was achieved but no inland colonies were counted. 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. Seabird 2000 thus represented the first attempt to census
all coastal and inland breeding colonies. While coverage was
good in most areas, inland Durham was not surveyed (although this
probably had little overall impact since only two nests were
recorded there in 1987). Furthermore, the several
hundred pairs that are believed to be nesting on the rooftops of
Edinburgh proved practically impossible to survey. Elsewhere,
coverage of roof-nesting gulls was good, and was aided by
aerial surveys in places like south Wales, Gloucester, Glasgow and
Inverness. Apparently occupied nests (AON) were counted at the
majority of colonies. However, at some colonies flush counts
of individuals attending the colony were made and then divided
by two to provide a rough approximation of the number of AON. This
is the least accurate method for censusing 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, 91% of counts were of nests, the rest were
derived from counts of birds, apparently occupied sites or
territories. In colonies mixed with herring gulls the determination
of the proportion of a count to assign to a particular
species was determined from sample head counts
representative of the colony as a whole.
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| UK Population estimate (AON*) |
48,217 |
62,321 |
87,413 |
| % change since previous census |
N/a |
+29 |
+40 |
*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 lesser 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 lesser 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 lesser black-backed
gull 1986-2010 with 95% confidence limits (dotted lines).
Based on SMP data; view the methods
of analysis (PDF 158 kb).
Abundance (of coastal and inland nesters
combined) increased from 1986 to 1993, stabilised, then decreased
between 2000 to 2003, and thereafter remained fairly stable. In the
longer term, census results of coastal-nesting birds indicated a
29% increase from 1969-70 (48,000 pairs) to 1985-88 (62,000 pairs).
The number of roof-nesting birds increased dramatically between
surveys conducted in 1976 (325 AON), 1993-95 (2507 AON) and
1999-2002 (10,853). The UK trend in roof-nesters since Seabird 2000
is unknown due to insufficient coverage, though colonies in SW
England have increased.
As regards coastal nesters, increases from
1969 to the early 1990s were probably a result of increased food
availability from fishery discards1 and from landfill sites. At
the same time culls of lesser-blacked backed gulls (and herring
gulls) were introduced on some nature reserves where gulls were
predating upon and competing with other seabirds, especially terns,
though such culling ceased in the 1980s and 1990s2. Other culls have been
locally instigated to reduce the risk of contaminating water
sources. However, culls have probably not substantially affected UK
populations. The causes of population decline since 1993 are
unknown, though may essentially be a reversal of the factors
responsible for earlier population increases, namely a decrease in
the availability of domestic refuse and reduced discards from
fisheries2. A major
driver of recent population decline is likely to have been a
reduction in adult survival rate; estimates on Skomer (the only UK
data point for survival) declined between 1993 and 2002.
As regards roof-nesters, the causes of the
population increase are unknown, though may have been
facilitated by an abundance of locally available food (e.g.
from fast-food street litter and domestic/commercial rubbish
bins), and safe (predator-free) nesting sites.
Productivity
Figure 2: Trend in
UK productivity (no. of chicks fledged per pair)
of lesser black-backed gull 1986-2010. Based on SMP
data; view the methods
of analysis (PDF 158 kb).
The trend of productivity shown is
heavily influenced by data from very large colony on Skomer, SW
Wales. Here, productivity has fluctuated widely, though has
often been low, for unknown reasons. There have been few successful
years over the recording period.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AON*) |
12,031 |
19,524 |
21,565 |
| % change since previous
census |
N/a |
+62 |
+10 |
* 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
Between the Seabird Colony Register and
Seabird 2000 coastal-nesting lesser black-backed gull numbers
increased by 10%. Prior to this a large increase was recorded
with numbers during the SCR 62% higher than during Operation
Seafarer. Roof-nesters increased greatly between surveys in
1993-953 (1356 AON) and
Seabird 2000 (3846 AON), though there is little information on
their status since then. The sample obtained from the SMP is
probably unrepresentative of Scotland as a whole, so is not shown.
On the Isle of May, the largest colony in Scotland that is
frequently counted, numbers increased from the late 1980s to
the mid 1990s, with a particularly steep increase between 1992 and
1993. This increase was associated with the cessation of gull
control measures undertaken in 1984-88 to reduce gull
predation on other seabirds4. A decline then
occurred but numbers increased again from 2005. However,
in Scotland as a whole there may have been a decline in
coastal nesters since Seabird 2000, as 23 colonies counted in 2010
held 9,004 pairs compared with 10,762 pairs during
Seabird 2000.
Productivity
Figure 2: Trend
in productivity (no. of chicks fledged per pair)
of lesser black-backed gull in Scotland, 1986-2010. Based
on SMP data; view the methods
of analysis (PDF 158 kb).
Productivity of lesser black-backed gulls in Scotland has
been variable over the recording period although there is an
underlying increasing trend. Predation by mink at colonies in
south-west Scotland is the main cause of low productivity in some,
but not all, years. Higher productivity in recent years maybe a
result of efforts to remove this destructive species at
affected colonies.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AON*) |
24,434 |
22,306 |
44,133 |
| % change since previous
census |
N/a |
-9 |
+98 |
* 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 lesser black-backed gull at South Walney,
1986-2010.
National census data show show numbers of
coastal-nesting lesser black-backed gulls in England had changed
little between Operation Seafarer and the Seabird Colony Register
but had doubled by the time of Seabird 2000 to just over 44,000
pairs. The national population has probably declined over the
last decade e.g. 20 colonies surveyed in 2010 held 15,233
pairs compared with 22,000 pairs during Seabird
2000. At South Walney (above), one of the largest
colonies in England, numbers have almost halved since the last
national census. Roof-nesters increased greatly between surveys in
19765 (127 AON),
1993-953 (954 AON) and
Seabird 2000 (6550 AON). Since then, comprehensive information is
unavailable, though increases have been recorded in some towns in
SW England.
Productivity
Few data on the productivity of lesser black-backed gulls at
English colonies 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 (AON*) |
11,529 |
20,043 |
20,682 |
| % change since previous
census |
N/a |
+74 |
+3 |
* 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 lesser 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).
In Wales, numbers of coastal-nesting lesser black-backed gulls
increased by 74% between Operation Seafarer and the Seabird Colony
Register. It appears, from data collected by the SMP (Figure 1),
which includes roof-nesters, that this increase continued beyond
the 1985-88 census up until 1993, although the trend is
somewhat variable until 1989. After 1993, the general
picture is of slow decline, continuing beyond Seabird 2000
when total numbers were similar to that recorded by the SCR.
At present, the index is close to its lowest point since
1986. Roof-nesters increased between surveys in 19765 (198 AON), 1993-953 (201 AON) and Seabird 2000
(394 AON).
Productivity
Figure 2: Trend
in productivity (no. of chicks fledged per pair)
of lesser black-backed gull in Wales, 1986-2010. Based on
SMP data; view the methods
of analysis (PDF 158 kb).
The trend in productivity shown
above is heavily influenced by data from the very large Skomer
colony. Here, productivity has fluctuated widely, though
has often been low, for unknown reasons. In 2010, lesser
black-backed gulls on Skomer had their most successful breeding
season in the period of the SMP fledging 0.89 chicks per pair.
Population estimates and change 1969-2002 (census data)
| |
Operation Seafarer
(1969-70)
|
Seabird Colony Register
(1985-88)
|
Seabird 2000
(1998-2002)
|
| Population estimate (AON*) |
223 |
448 |
1,033 |
| % change since previous
census |
N/a |
+101 |
+131 |
* 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 lesser black-backed gull at Strangford Lough,
1986-2010.
The lesser black-backed gull breeds at
approximately 30 colonies in Northern Ireland although few are
monitored in any year, so a representative annual trend is not
available. Numbers between each of the national censuses
doubled by the time of the Seabird Colony Register then more than
doubled again by Seabird 2000. Numbers at six of the main
colonies held 864 pairs in 2007 compared with 606 pairs during
Seabird 2000 suggesting a recent increase. At Strangford Lough, one
of the more frequently monitored colonies, lesser black-backed
gulls have been increasing since 2003 and are now
higher than at any other time. The relatively small number of
roof-nesters in Northern Ireland increased from a survey in
1993-953 of 8 AON
to 63 AON in Seabird 2000.
Productivity
Few systematic data on the breeding performance of lesser
black-backed gulls have been collected 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*) |
1,460 |
1,219 |
2,062 |
| % change since previous
census |
N/a |
-20 |
+69 |
* 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
Seabird 2000 recorded just over 2000 pairs
of lesser black-backed gulls in the Republic of Ireland. This
was an increase of 69% since the Seabird Colony Register and 41%
higher than that recorded by Operation Seafarer. Few sizeable
colonies have been monitored recently but on Lambay, one of the
largest colonies in the country, numbers had been relatively stable
since Seabird 2000; 321 pairs were counted in 2007 compared to 309
pairs in 1999. However, survey work in 2010 recorded 476 pairs. It
is not known whether changes at this colony are indicative of
changes in the national population. In Seabird 2000, 21 pairs
nested on roofs.
Productivity
Few systematic data on the breeding performance of lesser
black-backed gulls have been collected 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*) |
1,683 |
1,667 |
3,095 |
| % change since previous
census |
N/a |
-1 |
+86 |
* 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 lesser black-backed gull coastal-nesting
population for the whole of Ireland was stable between the first
two national censuses but increased by 86% between the Seabird
Colony Register and Seabird 2000. Since then, counts from the more
frequently monitored colonies suggested there had been little
change up to 2009 although large increases have been detected
at Strangford Lough and Lambay in 2010 which now hold over 800
pairs between them. It is not known whether this increase has
occurred more widely. Roof-nesters increased from 8 pairs in
1993-953 to 84 in
Seabird 2000.
Productivity
Few systematic data on the
productivity of lesser black-backed gulls have been collected
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*) |
54 |
99 |
114 |
| % change since previous
census |
N/a |
+83 |
+15 |
* 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 lesser black-backed gull on the Calf of Man,
1986-2010.
The small population of lesser black-backed gulls on the Isle of
Man more than doubled between Operation Seafarer and Seabird 2000
from 54 to 114 pairs. Only one colony has been surveyed since
then, on the Calf of Man, where numbers fell from a peak count
of 65 pairs in 1993 to 19 pairs in 2006. Numbers there have since
recovered with 54 AON recorded in 2010.
Productivity
No systematic data on productivity 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 (AON*) |
304 |
778 |
1,734 |
| % change since previous
census |
N/a |
+156 |
+123 |
* 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
With no data available since Seabird
2000 the current status of lesser black-backed gulls in the
Channel Islands is unknown. However, national census data
show that the population had been increasing over the
long-term up until 1998-2002 at least, when numbers were nearly six
times those recorded in 1969/70.
Productivity
No systematic data on productivity have been collected as part
of the SMP.
UK phenology, diet, survival rates
Phenology
No systematic data on phenology (timing of life-cycle events)
have been collected as part of the SMP.
Diet
No systematic data on diet have been collected as part
of the SMP.
Survival rate
The single estimate of adult survival rate from the SMP
comes from the large population breeding on Skomer, SW
Wales. Survival rate there declined between 1994 and 2003, but
increased thereafter. This decline in survival rate
coincided with a rapid decline in the number breeding on
Skomer. It is not known to what extent changes in survival
have effected the UK population as a whole.
Figure 3. Estimated adult survival rate
of lesser black-backed gull on Skomer, Pembrokeshire,
1987-2009.
References
1 Furness, R.W., Ensor, K. & Hudson, A.V.
1992. The use of fishery waste by gull populations around the
British Isles. Ardea 80: 105-113.
2 Calladine, J. 2004. Lesser Black-backed Gull
Larus fuscus. In: Mitchell, P.I.,
Newton, S.F., Ratcliffe, N. and Dunn, T.E. (eds.) 2004. Seabird Populations of
Britain and Ireland:226-241. Poyser,
London.
3 Raven, S.J. and Coulson, J.C. 1997. The distribution and
abundance of Larus gulls nesting on buildings in Britain
and Ireland. Bird Study 44, 13-34.
4 Wanless, S., Harris, M.P., Calladine, J. and Rothery, P.
1996. Modelling responses of Herring Gull and Lesser Black-backed
Gull populations to reduction of reproductive output: implications
for control measures. J. Appl. Ecol. 33, 1420-32.
5 Monaghan, P. 1977. The status of large gulls nesting on
buildings. Bird Study 24, 89-104.
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 lesser black-backed gull appears
courtesy of Ian Rendall ©, is subject to
international copyright law and may not be reproduced in any form
whatsoever.