a1 Department of Bacteriology, Stobhill General Hospital, Glasgow G21 3UW
a2 Department of Zoology, University of Glasgow, G12 8QQ.
During much of the present century, the population of herring gulls in Britain has increased rapidly (Cramp, Bourne & Saunders, 1973; Chabrzyk & Coulson, 1976; Monaghan & Coulson, 1977). Accompanying this changes was an increased utilization by these birds of human waste as a food supply, particularly sewage and refuse emanating from our towns and cities (Monaghan, 1983; Horton et al. 1983). This, coupled with their habits of roosting on agricultural land and water storage reservoirs and of breeding on inhabited buildings, has given rise to concern over the role of these birds in the spread of disease to man and domestic animals (e.g. Fenlon, 1981; Reilly et al. 1981; Butterfield et al. 1983; Monaghan et al. 1985; Girdwood et al. 1986).
(Accepted April 12 1988)
p1 Department of Microbiology, University of Reading, Whiteknights, Reading RG6 2AJ.