We review the history of the nesting population of California Gulls (Larus californicus) at Mono Lake, California. We conclude that a large population was apparently reduced considerably by commercial egging in the nineteenth century. Over the past 75 years, the population appears to have rebounded to at least its initial size. Because of diversions of its tributary streams, Mono Lake has declined rapidly in level over the past 40 years, exposing new islands and connecting older ones to the mainland. We find no convincing evidence that availability of nesting habitat ever limited the size of the population. However, if the late continues to decline at its present rate, only a few islets will remain, and the gull population will be reduced to a small fraction of its present size.