Herring Gull - 1949

Larus argentatus argentatus

This species had already increased considerably by 1894, and was then a common resident, and seems to have continued to increase steadily.  There are colonies of varying size all along coastal cliffs and on the islands (eg 300 pairs Newport Head, 300 pairs Skokholm, 650 pairs Skomer - all in 1946)

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

Herring Gull - 2003-07

Only 40 years ago Herring Gulls could be found breeding in almost every cove and on every cliff around the Pembrokeshire coastline but in the early 2000s they are predominantly confined to the offshore islands. Unfortunately we know rather little about their historic numbers, perhaps because they appeared so common they were never counted.  Indeed the eggs were widely collected for human consumption at least up to the 1960’s.

Herring gulls feed along the coastline, in the fields and formerly at rubbish tips and around the docks. They will readily take any food offered to them.  Their ability to adapt to available food sources enabled them to increase in numbers dramatically, around 10% per year, between the 1950’s and the early 1970’s, when there was abundant waste available on rubbish tips and in the docks at Milford Haven.

The subsequent dramatic decline of c.80% in the early 1980’s was almost totally caused by a botulism outbreak which killed many hundreds of adult birds (Sutcliffe 1986).

It is clear from the map that Herring Gulls still breed all around the coastline of the county, but today mostly in small numbers and often on isolated offshore rocks.  The main concentrations are on the islands and in particular on Caldey, where numbers have recovered from a low of 675 pairs in 1998 to just over 2,000 in 2008, making it one of the largest colonies in the UK.  On the other islands the populations have not recovered: on Skomer and Skokholm it has been relatively stable at just under c. 450 to 600 pairs and 250 to 350 pairs respectively during the last decade.  The islands of Ramsey and the Bishops hold around 300 pairs and there are small colonies of 50 to 200 pairs on St Margaret’s and Grassholm Islands, Dinas Head and along the Castlemartin coastline. The whole county population in 2003-07 was probably in the order of 4,000 pairs, compared with the peak 1969 counts of 12,700.

Steve Sutcliffe

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 69

Orange = breeding probable = 5

Yellow = breeding possible = not included

Total tetrads in which registered = 74 (15.1%)

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.

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Herring Gull - 1994

Breeding resident and winter visitor

Mathew (1894) commented on an increase in the number of breeding herring gulls in the wake of the sea birds preservation act of 1869.  Lockley et al (1949) traced a continued increase, despite large scale collection of gulls eggs; for example, about 3000 eggs were taken in one season at Skokholm, from a colony of 1000 pairs. 

Limitations were put upon the collection of eggs at Skokholm and Skomer and the harvesting of eggs generally declined throughout the county as social conditions changed.  Herring gulls accelerated their rate of increase, a process aided by the abundance of food at local refuse dumps.  In 1969 Operation Seafarer recorded 11740 pairs breeding in Pembrokeshire, including 1350 pairs on Skokholm and 2200 pairs at Skomer.  Most nest on the cliffs of the mainland and islands but roof nesting has been noted at Tenby and the Esso refinery at Herbrandston and suspected elsewhere.

Herring Gulls began to decrease in the lat 1970s, coinciding with the introduction of black plastic bags for refuse collection.  In warm conditions these bags make good incubators for the bacterium Clostridium botulinum which is thought to have poisoned the gulls feeding on the rubbish tips.  By the time the Seabird register survey of 1985-87 was conducted the breeding population had shrunk to 4062 pairs, with 613 pairs at Skomer, and 321 at Skokholm.  Changes in rubbish tip operations are coming into force which will make harmful food less accessible to gulls, and this may reverse the decline.

Herring gulls are not confined to scavenging on rubbish tips, but feed widely across the fields of the county, where earthworms form an important part of their diet.  They also feed around the rocky shores and the estuaries and pick up fish offal at Milford Docks, though fewer catches are landed there than in the past.

Although generally regarded as sedentary, many of our herring gulls disperse from the breeding grounds in the winter, certainly as far as the upper Bristol Channel.  Juveniles can venture further, with recoveries from North Wales, Ireland, France, Holland and Poland, as well as of an Irish-bred bird visiting Pembrokeshire.

Small numbers of Scandinavian birds of the subspecies argentatus were detected in the winters of 1985 to 1987, with records occurring between 11 December and 22 February.

Fieldwork 1984-88 (based on 478 tetrads)

Red = breeding confirmed = 63

Orange = breeding probable = 3

Total tetrads in which registered = 66 (13.8%)

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

Herring Gull - 1970s breeding

Red = breeding confirmed

Orange = breeding probable

Yellow = breeding possible

Herring Gull - 1980s winter atlas

The BTO winter atlas showed that Herring 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 400 birds.

All squares were used for feeding purposes but the largest concentrations were at coastal roost sites 

Graham Rees 

Herring Gull - 1894

Species account from M Mathew, 1894, "The Birds of Pembrokeshire and its islands"

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