FACTORS INFLUENCING THE ONSET OF SPRING MIGRATION IN MALLARDS

Our knowledge of factors causing intraspecific variation in timing of spring migration in waterfowl is poor, despite its potential importanc e for understanding reproductive patterns and the importance of the no n-breeding period to reproductive success. I used radio telemetry to d ocument initiation of spring migration by female Mallards (Anas platyr hynchos) wintering in Arkansas in 1989. I tested whether age, molt sta tus, or physiological condition explained observed intraspecific varia tion. Migration date was independent of female age or physiological co ndition at time of capture in January, but not molt. Late-molting fema les migrated later than early-molting females. Results were consistent with the hypothesis that spring migration is influenced by the timing of earlier winter life-history events.