Welsh Journals

Lesser Black- Great Black- Herring Gull backed Gull backed Gull 1928 250 pairs 700 pairs 31 pairs 1934 270 750 45 1940 300 800 61 1949 572 350 72 JJ 1955 400 300 c.30 JJ 1959 510 390 30 JJ 1961 No count 350 12 JJ The large decrease in nesting Lesser Black-backed Gulls which seems to have occurred between 1940 and 1949 is difficult to explain but there was much egg-collecting, especially in the war years. The Observatory report for 1940 states, over 3,CCO eggs of the Herring, Greater and Lesser Black-backed Gulls were collected this summer for food." It is usually the Lesser Black-backed Gulls in their compact colonies which suffer most from these ac- tivities. A similar drop, from 350 pairs in 1939 to 100 pairs in 1949, has been found on Lundy by Boyd (1956), and this has been similarly explained by egg collecting. The drop in breeding pairs of Great Black-backed Gulls is probably a direct result of control measures. There seems to be little room for a further increase in breeding gulls on Grassholm, whereas Skokholm and Skomer appear to have room for many more pairs. It would be worth while to make annual counts to determine the trend towards saturation of Skomer by these breeding gulls, if indeed the trend should be allowed to con- tinue. The damage done to other, rarer birds and their young by Herring and Lesser Black-backed Gulls is certainly less than that by the Great Black-backed Gull, but if their increase continues the total damage might be serious. Consideration should be given to the idea of cropping gulls eggs on an organised basis. Tinbergen (1953) has shown that a system in which people pay for the priv- ilege of collecting gulls' eggs has been successful in controlling gulls in Holland, and provided a useful source of food. This might well be tried here. REFERENCES BOYD, H. J. (1956). Lundy Field Society Report 1956. BUXTON, J., and LOCKLEY, R. M. (1950). Island of Skomer. London. LOCKLEY, R. M. (1947). Letters from Skokholm. London. TINBERGEN, N. (1953). The Herring Gull's World. London.