Annual survival of North American Razorbills (Alca torda) varies with ocean climate indices

According to life-history theory, survival in long-lived animals is not expected to vary greatly with environmental conditions. However, recent studies of a number of seabirds have shown that ocean climate indices such as the Pacific Decadal Oscillation index and sea surface temperature are correlated with adult survival.

Here we evaluated whether annual adult survival of Razorbills (Alca torda L., 1758) at two breeding colonies covaried with oceanographic conditions in the North Atlantic during 1995–2006. We also examined pre-breeder survival (from fledging to age 2). The relationship between local adult survival and the North Atlantic Oscillation and two oceanographic variables (Labrador Current temperature profile and Bay of Fundy sea surface temperature) were evaluated using the program MARK.

Capture–mark–recapture data fit the assumptions of the program MARK reasonably well with ĉ values ranging from 1.390 to 2.404. Pre-breeder survival rates were high for Machias Seal Island (Ф = 0.778 ± 0.041) and low for the Gannet Islands (Ф = 0.482 ± 0.033), likely the result of hunting pressure. On Machias Seal Island, constant adult survival (Ф = 0.967 ± 0.028) was the best model; however, time-dependent models that included a climate covariate performed nearly as well.

On the Gannet Islands, adult survival (Ф = 0.890 ± 0.053) was negatively correlated with Labrador Current temperature. Overall, our results show significant differences in survival rates across sites over the same time period and highlight the importance of multisite studies and smaller scale climate indices for local populations. In addition, our study contributes to the growing body of evidence that survival in long-lived animals may vary with environmental conditions more than previously expected