SURVIVAL RATE OF THE LONG-TAILED JAEGER AT ALERT, ELLESMERE ISLAND, NUNAVUT.

In long-lived animals, survival rate is a key demographic parameter affecting population dynamics. The objective of this study was to estimate the apparent survival rate of adult Long-tailed Jaegers (Stercorarius longicaudus) breeding at one of the most northerly sites on earth, northern Ellesmere Island, Canada. Because of the large temporal fluctuations in numbers of lemmings, their primary food source during the summer, we also investigated the effect of annual variations in lemming abundance on survival rate. Analysis was based on 336 individuals marked as adults over 11 years with metal and color bands and capture-mark--recapture techniques. There was strong support for a model with two age classes, as survival of newly marked birds was 18% lower than that of previously marked ones. This difference could be due to a true age effect (if a high proportion of young adults was present in our initial samples) or, perhaps more likely, to the presence of transient individuals in the population. The estimated probability of apparent annual survival of local birds (corrected for color-band loss) was 0.91, comparable to values for other seabirds, and was constant overtime. We detected a weak trend for a decrease in apparent survival rate of newly marked birds in years of high lemming abundance but no effect on the survival of previously marked birds. This suggests that conditions at sea during the nonbreeding season may be more important in affecting annual survival. A new longevity record of 22 years was established for the species. [ABSTRACT FROM AUTHOR]