Food Supply and Reproductive Performance of the American Oystercatcher in Virginia

Abstract

The relationship between food supply and reproductive performance was determined in a 3-year study of the American Oystercatcher, Haematopus palliatus, in Virginia. Clutch size, clutch-initiation dates, interclutch intervals, fledging success, distance to food, and quality and density of food were examined for 41 territories. Food supply varied more among territories than did clutch size, clutch-initiation dates, or interclutch intervals. Annual and interannual fledging success was extremely variable. Although no measure of food supply contributed significantly to variation in clutch size, the size of nearby feeding areas was positively correlated with average egg size and fledging success and was negatively correlated with the date of first clutch initiation. Earlier laying females had greater fledging success. Of the measures of food supply only the size of the nearby feeding area contributed significantly to variation in fledging success. Growth rates and rates of provisioning young were similar among broods of different sizes. In general, the match between food supply and reproductive performance was poor. As predation was the major cause of chick losses, I suggest that better territories for oystercatchers are those that allow parents to watch for predators of the young, and forage at the same time.