Lesser Black-backed Gull – 2003-07 breeding

Larus fuscus – GWYLAN GEFNDDU LEIAF – Breeding summer visitor, passage migrant, winter visitor

Comparison with previous atlas:

1984-882003-07
Breeding confirmed2430
Breeding probable16
Breeding possibleexcluded from totalexcluded from total
No of tetrads occupied25 (of 478)36 (of 490)
Percentage of tetrads5.2%7.3%

Formerly the main colonies were confined to the islands of Skomer and Skokholm with a few on Caldey, St Margaret’s and Ramsey and occasionally on the mainland cliffs. Mathew (1894) knew of colonies of 20 – 30 pairs but there were around 2,000 by the middle of the century (Lockley et al 1949). The population increased dramatically from the early 1950’s, to peak at around 20,000 pairs on Skomer and 5,000 on Skokholm in the mid-1980’s. 

This increase was fuelled largely by a ready source of food in the form small fish that were a discarded by-catch of the scampi fishery in the nearby Smalls grounds.  New legislation introduced in the mid-1980’s changed the mesh size of the nets so that fewer small fish were caught and this food supply was lost to the gulls in a very short period. The result has been almost very low breeding success, including total failure in some years, from 1989 to the present day and a resultant steady decline in the number of gulls. Numbers of Lesser Black-backed Gulls breeding on the mainland coast have increased in several places in the last 20 years, with a gradual spread in distribution during this time, but the population here is small.

Over 95% of Lesser Black-backed Gulls in the county breed on Skomer, Skokholm and Caldey Islands.  They are found in large colonies wherever there is good cover for chicks and prefer a bracken/gorse/thick grass habitat.  In 2007 the county population was around half of the peak at c. 13,000 pairs and continuing to decline because there are so few immature birds entering the breeding population.  

Steve Sutcliffe

Records extracted from the Pembrokeshire Bird Reports, which may contain more detail than shown here.

More about the Lesser B-B Gull in Pembrokeshire

Lesser Black-backed Gull – 1994

Larus fuscus – GWYLAN GEFNDDU LEIAF – Breeding summer visitor, passage migrant, winter visitor

1984-88
Breeding confirmed24
Breeding probable1
Breeding possibleexcluded from total
No of tetrads occupied25 (of 478)
Percentage of tetrads5.2%

Mathew (1894) knew of colonies of 20-30 pairs which Lockley et al (1949) used as a datum to note a considerable subsequent increase in breeding numbers with 1000 pairs at Skomer and 800 pairs at Skokholm; they added that they bred at Caldey, St Margaret’s, Ramsey, Sheep Island and some mainland cliffs such as those at Pwll Deri.

Lesser Black-backed Gulls continued to increase and the Skomer colony had reached 3657 pairs by 1970 with 2500 at Skokholm.  During this period Harris (1965) noted that they predominantly foraged on the agricultural mainland and mainly ate beetles.  The population increased rapidly thereafter and numbered about 20,300 pairs by 1983, with 15500 at Skomer and 4557 at Skokholm.  Studies showed that about 80% of their food consisted of small fish, mostly young blue whiting and poor cod (Todd 1986).  Although birds continued to frequent agricultural land, and a few visited rubbish tips, the greatest proportion flew out to sea to the south-west to feed upon fish discards from the trawlers in the southern Celtic Deep, as far away as 80-100km.  There has been a reduction in numbers since then, the Seabird Register survey of 1985-1987 finding 16560 pairs.  Census results from Skomer illustrate how the population has changed.

The colonies at Skokholm and SKomer experienced large scale breeding failure in 1989 and 1990, and low productivity in 1991 and 1992, with eggs hatching but few young being reared.  A shortage of fish seems to have been the cause, due to changes in fishing practice.  The bulk of the population have now switched to foraging in mainland fields, and studies at the colonies show that they are bringing back insufficient food.  They are also spending long periods away from the nest, which has led to increased predation of eggs and young by other adults.  If fish remains unobtainable the population may dwindle to a level that can be sustained by food gleaned from agricultural sources.  They visit all parts of Pembrokeshire to feed in the pastures, being particularly attracted to fields where slurry is being sprayed, which are being ploughed or which have just been cut for silage.

Most lesser black-backed gulls nest on the plateaux and slopes of the islands, with comparatively few on the cliffs, but a few use the roofs of buildings at the old Esso oil refinery at Herbrandston.  Roof nesting was suspected in the past at Kensington hospital (St Bride’s) and at the former county cinema in Haverfordwest.

Many leave Pembrokeshire after breeding, ringing showing that they can reach Spain and Portugal by October, some penetrating to Morocco and the Canary islands during the course of the winter.  Others pass through Pembrokeshire on spring and autumn passage.  The bulk of the breeding birds return during March.

Rather few lesser black-backed gulls used to winter in Pembrokeshire, with 10-13 seen in 1937 (Lloyd’s diaries) and usually less than ten in a winter during the 1950s.  Winter numbers had increased to about 1500 by 1971 and to 7000 by 1987, most roosting at Llysyfran reservoir.  Whether these are local birds in unclear.

In most winters up to five birds of the Scandinavian races are identified between 16 November and 22 March, the majority seeming to fit the description of subspecies intermedius, which have darker mantles than the British race.  A group of 30 of this subspecies seen at the Gann on 18 January 1987 was accompanied by a very convincing black-backed subspecies fuscus.

Donovan J.W. & Rees G.H, 1994, Birds of Pembrokeshire

HARRIS, M.P. 1965. The food of some Larus gulls. Ibis 107: 43-53

LLOYD, B. 1925—1939. Diaries. National Library of Wales.

TODD, P.R. 1986. Gull populations on Skomer. Unpublished report to the Dyfed Wildlife Trust.

Update 

The means of field identification of the different races of LBBGs has developed beyond the assessment of the shades of the upperparts, prevalent during the 1990s. It would seem prudent therefore to discard past racial identifications in favour of more rigorous examination of future occurrences.

Graham Rees, August 3, 2013

More about the Lesser B-B Gull in Pembrokeshire

Herring x Lesser Black-backed Gull hybrids

Harris, M.P. 1970. Abnormal migration and hybridization of Larus argentatus and L. fuscus after interspecies fostering experiments. Ibis 112: 488-498.

Summary

Between 1962 and 1966 eggs of Larus argentatus and L. fuscus were interchanged andalmost 900 young were reared by the wrong species. Many of these cross-fostered young were later recovered or retrapped on and away from the colonies.

The British population of argentatus is sedentary and ringed birds are not recovered outside Britain, whereas fuscus normally migrates. Many cross-fostered argentatus migrated to France, Spain and Portugal, areas where fuscus is common, but they did not migrate as far as the control fuscus. It is possible that these cross-fostered argentatus had followed their foster parents when these migrated, but this is unlikely as the cross-fostered fuscus also migrated although their foster parents would have remained in Britain.

Despite wide ecological and behavioural overlaps, interbreeding between L. argentatus and L.fuscus is exceedingly rare. However, as a result of cross-fostering experiments, 31 and 40 mixed pairs were found on Skokholm in 1968 and 1969 respectively. Although some of the birds involved were unringed it is probable that all the adults in mixed pairs had been cross-fostered. Other cross-fostered birds were found mated with their own species and it appears that the sex of the imprinted birds was important. Female gulls will usually only mate with males of their own species, or in the case of the cross-fostered birds, with males of their foster species. Males will mate with either species.

Evidence is given that suggests that the colour of the mantle and wings is important in species recognition at long range, and the colour of eye-ring and join of the mandibles for recognition at short range. The role of voice is uncertain but general behaviour is probably unimportant.

The original paper can be purchased here 

 A later paper is downloadable here Dr M. P. Harris, C. Morley & G. H. Green (1978): Hybridization of Herring and Lesser Black-backed Gulls in Britain, Bird Study, 25:3, 161-16

More about the Lesser B-B Gull in Pembrokeshire

Lesser Black-backed Gull – 1980s winter

Larus fuscus – GWYLAN GEFNDDU LEIAF – Breeding summer visitor, passage migrant, winter visitor

The BTO winter atlas showed that Lesser Black-backed Gulls were present in most 10km squares during the winters of 1981-82, 1982-82 and 1983-84.

The darker the colour, the higher the relative total count for each 10km square, the darkest blue represents over 46 birds. Over 2,000 were recorded roosting at Llys y fran reservoir during this period.

Graham Rees. Pembrokeshire County Bird Recorder 1981-2007

Data collected by volunteers for the BTO. Lack, P. 1986 Atlas of wintering birds in Britain and Ireland. T & A.D. Poyser.

More about the Lesser B-B Gull in Pembrokeshire

British Lesser Black-backed Gull – 1949

Larus fuscus graellsii

“A common resident. Not so numerous as the Herring Gull” – Mathew, who says it bred 1894 in colonies of only 20-30 pairs, and if this was correct, it has increased considerably since.  In 1946 approx 800 pairs were breeding Skokholm, and 1000 pairs Skomer.  Breeds also Caldey, St Margaret’s, Ramsey and islands, Sheep Island, and some mainland cliffs (eg Pwll Deri)

R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society

More about the Lesser B-B Gull in Pembrokeshire

Lesser Black-backed Gull – 1894

Larus fuscus – A common resident.

Not so numerous as the Herring Gull, this species is nevertheless, well represented in Pembrokeshire, and nests upon the various islands, selecting the ground on the topmost slopes of the cliffs, and there breeding in small societies of from twenty to thirty pairs, apart from the other Gulls, in places where it is perfectly easy to walk among the nests, and to admire the beautiful clutches of eggs. This Gull is also a greedy stealer and devourer of other birds’ eggs, young rabbits, &c, and like the Herring Gull, comes far inland, visiting the meadows in the spring, at which season we always saw some in our fields at Stone Hall, in company with the Common and Herring Gulls.

Mathew M.A. 1894, Birds of Pembrokeshire and its Islands

More about the Lesser B-B Gull in Pembrokeshire

Lesser Black-backed Gull

Larus fuscus – GWYLAN GEFNDDU LEIAF – Breeding summer visitor, passage migrant, winter visitor

Lesser Black-backed Gull – 2003-07 breeding

Larus fuscus – GWYLAN GEFNDDU LEIAF – Breeding summer visitor, passage migrant, winter visitor Comparison with previous atlas: 1984-88 2003-07 Breeding confirmed 24 30 Breeding probable 1 6 Breeding possible excluded from total excluded from total No of tetrads occupied 25 (of 478) 36 (of 490) Percentage of tetrads 5.2% 7.3% Formerly the main colonies […]

Lesser Black-backed Gull – 1994

Larus fuscus – GWYLAN GEFNDDU LEIAF – Breeding summer visitor, passage migrant, winter visitor 1984-88 Breeding confirmed 24 Breeding probable 1 Breeding possible excluded from total No of tetrads occupied 25 (of 478) Percentage of tetrads 5.2% Mathew (1894) knew of colonies of 20-30 pairs which Lockley et al (1949) used as a datum to note a […]

Herring x Lesser Black-backed Gull hybrids

Harris, M.P. 1970. Abnormal migration and hybridization of Larus argentatus and L. fuscus after interspecies fostering experiments. Ibis 112: 488-498. Summary Between 1962 and 1966 eggs of Larus argentatus and L. fuscus were interchanged andalmost 900 young were reared by the wrong species. Many of these cross-fostered young were later recovered or retrapped on and away from the colonies. […]

Lesser Black-backed Gull – 1980s winter

Larus fuscus – GWYLAN GEFNDDU LEIAF – Breeding summer visitor, passage migrant, winter visitor The BTO winter atlas showed that Lesser Black-backed Gulls were present in most 10km squares during the winters of 1981-82, 1982-82 and 1983-84. The darker the colour, the higher the relative total count for each 10km square, the darkest blue represents over 46 […]