Adult survival estimates from two Atlantic Puffin (Fratercula arctica) colonies in the Gulf of Maine

摘要

We report survival probabilities for 148 breeding adult Atlantic Puffins (Fratercula arctica) monitored through capture-mark-resight at two colonies for 11 years (1992-2003). The colonies, Eastern Egg Rock and Seal Island, are similar to 42 km apart in the Gulf of Maine. Support for competing models in the program MARK suggests constant survival of 0.95 +/- 0.01 (SE) that is independent of colony. Our high survival probability is consistent with published estimates for Atlantic Puffins and other long-lived seabirds. No time-variance contrasts with many long-term seabird studies, which often report high survival in most years, broken occasionally by low-survival events. However, a post-hoc observation of survival estimates from the time-dependent model suggests that there may have been at least two low-survival events in our time-series; sparse data may have precluded detection by our models. In this study, each bird received an individually engraved, plastic, field-readable leg band, as well as the standard metal band. Using an index of band readability, we show that plastic bands wore rapidly, resulting in accumulating losses of engraved characters through time. Degradation and loss of marks is a common source of overdispersion in capture-mark-re-encounter data and results in underestimated sampling variances. In the presence of a 70% reduction in band readability over eight years, an estimate of the adjusted overdispersion factor ((c) over cap = 1.14) identified very little overdispersion in our data. Overdispersion was avoided by double banding and intensively resighting metal bands.