Changes in the gull populations of SW Wales

Abstract

The breeding populations of the Larus gulls in SW Wales are reviewed, using all the available information hut specifically drawing on the data from the islands of Skomer, Skokholm, St Margarets and Caldey. After increasing steadily for many years, Herring Gull numbers have recently declined rapidly. Some populations of Great Black-backed Gulls have been greatly affected by deliberate control measures but the records show a similar pattern to that of Herring Gulls, with large decreases being recorded recently despite the lifting of these controls. The decreases in the populations of these species are coincident with botulism poisoning of adult birds during the breeding season, probably resulting from feeding on refuse tips. There may be a connection between the introduction of black plastic bags for refuse collection and the outbreak of botulism in SW Wales. Lesser Black-backed Gull populations continue to increase at a rate that has been roughly constant for at least 15 years. This species rarely feeds at...