Various aspects of the winter biology of Dunlins (Calidris alpina) have been studied in California by Storer (1951), Recher (1966), Holmes (1966a, b, 1971), Gerstenberg (1972) and Jurek (1973). Recent studies at Bolinas Lagoon provide information that supplements and in certain details, contradicts previously published accounts. This paper reports on age and sex ratios, molt and migration of Dunlins at Bolinas Lagoon.