Great Black-backed Gull - 1949

Larus marinus

In Mathew's day there were only a few pairs resident on the islands, and he only mentions the Bishop's Rock and St Margaret's.  It has now greatly increased, and is found on all the islands, and along the whole coast, breeding.  At least 150 pairs Skomer and Middleholm in 1946.

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

Great Black-backed Gull - 2003-07

Great black-backs are top predators on the seabird islands, taking eggs and chicks of other species, and are regular predators of Puffins, Manx Shearwaters and Rabbits. They nest in single pairs or loose colonies, the former preferring prominent places on the top of rocky outcrops, while those in colonies will select dense vegetation on the top of the islands. Over 90% of the Pembrokeshire pairs breed on the offshore islands with rest as scattered individual pairs around most of the county coastline.

Numbers of these gulls have fluctuated widely.  Apparently very small numbers were present in the county in the late 19th Century (Harrison & Hurrell, 1933) but by 1949 they could be found all around the coastline and especially on the islands, where Lockley et al (1949) found 310 pairs on Skomer, Middleholm, Skokholm, Grassholm and St Margaret’s combined. Davis (1958) reported between 490 and 520 pairs in the county following an all Wales survey and they continued to increase with 542 pairs recorded in 1969’s Operation Seafarer (Cramp et al 1974). 

Control measures in the 1960s and 1970s on Skomer and Skokholm, followed by a botulism outbreak in the early 1980’s, reduced numbers to a low of about 140 pairs in the mid-1980s.  There has been a steady but slow recovery since then and the population had risen to around 300 pairs in 2000 but has subsequently remained stable, except on Skomer where it has declined by about a third. The mean breeding success recorded on the Pembrokeshire islands in the ten years to 2005 was 1.15 to 1.29 chicks per pair, by far the highest success rate in the UK during this period. In consequence there has been a steady recovery since the 1980’s and the population in the county had risen to around 300 pairs in 2000 and has subsequently remained stable at around this number.

Steve Sutcliffe

 

Fieldwork 2003-07 (based on 490 tetrads)

Red = breeding confirmed = 21

Orange = breeding probable = 9

Yellow = breeding possible = not included

Total tetrads in which found = 30 (6.1%)

Great Black-backed Gull - 1994

Breeding resident

George Montague (1866) found none breeding in Pembrokeshire while Mathew (1894) knew of only a few pairs resident on some of the islands.  By 1949 Lockley et al were able to note that great black-backed gulls could be found breeding along the whole coast, with a total of 310 pairs on the islands of Grassholm, Skomer, Skokholm, Middleholm and St Margarets, and with others on Ramsey, the Bishops and along the mainland coast.  Davis (1958) during his survey of this species in England and Wales, reported between 490 and 520 pairs in Pembrokeshire.  The population continued to increase; for instance there were 60 pairs on Skomer in 1949 but this had risen to 283 pairs by 1961.  Control measures were applied at Skokholm and Skomer from 1958 to reduce their predatory effects on other seabirds.  This halted and then reversed the increase, and the Skomer population was down to 165 pairs by 1969. At this time Operation Seafarer found a total of 542 pairs breeding in Pembrokeshire, and it is thought that the population may have stabilised at this level.

Great black-back gulls are largely coastal birds, although they find inland rubbish tips readily enough.  A proportion disperse during the winter, some reaching the upper Bristol Channel, with first year birds moving to Cornwall and Ireland; and a Fair Isle-ringed bird has reached Skomer.  A county total of 300 found during the BTO winter gull survey of 1983 suggested that the bulk of the population may stay in Pembrokeshire.

Fieldwork 1984-88 (based on 478 tetrads)

Red = breeding confirmed = 25

Orange = breeding probable = 5

Total tetrads in which registered = 30 (6.3%) 

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

Great Black-backed Gull - 1970s breeding

Red = breeding confirmed

Orange = breeding probable

Yellow = breeding possible

Great Black-backed Gull - 1980s winter atlas

The BTO winter atlas showed that Great 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 60 birds, being concentrated in squares SM 80 & 81.

Graham Rees

Great Black-backed Gull - 1894

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

Click to read more ...