Larus marinus – GWYLAN GEFNDDU FWYAF – Breeding resident
|Breeding possible||not included in total|
|No of tetrads occupied||30 (of 478)|
|Percentage of tetrads||6.3%|
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.
DAVIS, T.A.W. 1958. Great Black-backed Gulls in England and Wales. Bird study 5: 191-215
MONTAGUE, G. 1866. Ornithological dictionary and supplement (edited by Edward Newman). 3rd edition. London, Swan Sonnenschein and Co.