Nesting Success of Western Gulls on Bird Rock, Santa Catalina, California

In 1965 and 1966, Charles Harper studied aspects of reproductive biology in a colony of less than thirty pairs of Western Gulls (Larus occidentalis Armani) on Bird Rock, a small islet approximately 530 m off the east side of the isthmus at Santa Catalina Island, California (Harper 1971). In 1974, 1 made observations on breeding success at Bird Rock which were comparable to some of the data reported by Harper. This paper presents results of comparison of the two studies.