CONTROL OF RING-BILLED GULLS AND HERRING GULLS NESTING AT URBAN AND INDUSTRIAL SITES IN ONTARIO, 1987-1990

Large numbers of ring-billed gulls (Larus delawarensis) and much smaller numbers of herring gulls (L. argentatus) have begun to nest at several industrial and urban sites in the Canadian Great Lakes causing a flight safety problem (nesting at end of a runway), disrupting commercial operations (nesting on roads and storage yards), and creating nuisances (noise and smell of the colony and defecations on equipment). Gulls were prevented from nesting by scaring (using tethered birds of prey, moving vehicles, and foot patrols equipped with cracker shells) or by physically excluding them (by installing monofilament lines). At some sites nestbuilding was thwartedby frequently disturbing the nesting substrate through grading, disking, or dragging aboom. Where nesting could not be prevented, reproduction was stopped by collecting eggs repeatedly, or by spraying oil on eggs. Operations at gull colonies were carried out by affected landowners under special permits issued by the Canadian Wildlife Service. Advantages and disadvantages of the different control methods are briefly discussed. Control operations reduced or eliminated local problems but did not reduce the population of adult, urbanized gulls. We predict more problems associated with the expected colonization of other industrial sites by gulls