Ring-billed Gulls (Larus delawarensis) and Herring Gulls (L. argentatus) nesting on South Manitou Island in Lake Michigan were subjected to at least 9 yr of intense fox predation. Both gull species experienced total or nearly total reproductive failure during all but 1 yr between 1975 and 1983. The number of active nests declined significantly during this period, with Ring-bills showing a more regular rate of reduction. These gull species are unlikely to produce progeny when subjected to regular fox predation. Persistence of the colonies may be the result of a nucleus of experienced, site-tenacious breeders returning to the site year after year.