THE DISTRIBUTION AND ABUNDANCE OF LARUS GULLS NESTING ON BUILDINGS INBRITAIN AND IRELAND

During the breeding season of 1994, a survey of Larus gulls nesting on buildings and other malt-made structures in Britain and Ireland teas carried out to determine their distribution and abundance, and to asse ss the changes that had occurred since the last survey in 1976. The tw o main species involved were Herring and Lesser Black-backed Gulls, wi th records received of 11047 pairs and 2544 pairs, respectively. Estim ated numbers may be as high as 16900 pairs of Herring Gulls and 3200 p airs of Lesser Black-backed Gulls, constituting 8.2% and 3.6%, respect ively, of the total breeding populations of these species in Britain a nd Ireland. Since 1976, gulls nesting on buildings have continued to i ncrease, both in terms of the number of breeding pairs (Herring Gulls by 10% per annum; Lesser Black-backed Gulls by 17% per annum) and the number of sites colonized (Herring Gulls by 5% per annum; Lesser Black -backed Gulls by 13% per annum). This increase has been greatest in th e Lesser Black-backed Gull, but that of the Herring Gull is of particu lar interest as its numbers in Britain and Ireland have declined durin g this period. Records were received of 236 pairs of Common Gulls and 11 pairs of Great Black-backed Gulls nesting on buildings. In most are as, coastal towns have now been colonized by roof-nesting gulls and si tes further inland are being colonized, especially by Lesser Black-bac ked Culls. There has been an increased colonization of industrial site s in towns since 1976 and this has led to the formation of much denser colonies than previously found in urban areas. Small colonies of Herr ing Gulls nesting on rooftops increase in size at a higher rate than l arge colonies, although the actual numerical increase is still greater in larger colonies. There is Mo evidence of established colonies of r oof-nesting gulls disappearing naturally and the rapid increase in siz e of small colonies means that they become established very quickly, o ften before they are perceived as a problem. Considerable effort has b een put into attempting to reduce the numbers of gulls nesting in some towns. As yet, however, no successful management methods have been de veloped.