High survival of immatures in a long-lived seabird:: Insights from a long-term study of the Atlantic Puffin (Fratercula arctica)

Survival from fledging to maturity is an important life-history parameter in long-lived species such as seabirds. However, because of the long period of unobservability following fledging, few studies have reported reliable estimates of survival rates for immatures. We estimated survival to maturity of two cohorts of Atlantic Puffin (Fratercula arctica) fledglings from Hornoya in northern Norway using capture-mark-recapture methodology. By considering only juveniles that actually left their nest burrows, we arrived at unbiased estimates Of Survival rates for immatures. Contrary to many previous studies, annual Survival of immatures was not depressed in relation to adult survival. 13), the age of five years, more than two-thirds of all fledglings are still estimated to be alive. Averaged over this period, ani-Mal survival of immatures is estimated as 0.933 (95% confidence interval: 0.806-0.993). This compares to an annual adult Survival of 0.943 (0.909-0.965) during the same period. The survival estimates also imply that the cohorts Studied are overwhelmingly philopatric. Dispersal of immatures must be extremely rare or absent. The annual estimates of resighting reveal a clear age-related pattern, including a peak at three years of age and a Subsequent minimum at six years of age. Possible biological explanations for this behavior are given.