Nest-Site Selection and Reproductive Success of Ring-Billed Gulls at Sprague Lake, Washington

Abstract

AssTRAcr-Nest-site selection and reproductive success are reported for ring-billed gulls nesting at Sprague Lake, Washington, in 1981. Gulls nesting in tall grass and rocky beach habitats began laying significantly earlier than other gulls. Incubation times also varied by location, with birds in peripheral areas spending over three days longer to incubate their eggs than those nesting in the main part of the colony. Reproductive success was highest for birds nesting in tall grass, followed by those in rocky beach, sparse vegetation, low dense herb, and peripheral areas, respectively. Nest densities by habitat were determined in 1979, 1980, and 1981. Densities were highest in tall grass, followed by those in rocky beach, sparse vegetation, and low dense herb, respectively. Associated California gulls nested almost exclusively in sparse vegetation. Nests with supernormal clutches (5-6 eggs) were more common in sparse vegetation, low dense herb, and peripheral areas than in tall grass and rocky beach and accounted for 0.9% of the ring-billed gull nests in the colony.