Seabird Abstracts

The effect of climate on adult survival in five species of North Atlantic seabirds

Sandvik H, Erikstad KE, Barrett RT & Yoccoz NG (2005) J Animal Ecol 74(5):817-831

1. In long-lived species, adult survival is an important life-history trait. Better knowledge of the effects of non-catastrophic climate variation on the adult survival of long-lived seabirds in therefore needed. However, documentation of such effects is still rare.

2. Using capture-mark-resighting data, we modelled the annual survival rates of five species of seabirds, the Common Guillemot (Uria aalge), Brünnich's Guillemot (Uria lomvia), Razorbill (Alca torda), Atlantic Puffin (Fratercula arctica), and Black-legged Kittiwake (Rissa tridactyla). The data spanned 14 years of observation at a colony on Hornřya, off Northern Norway in the western Barents Sea.

3. A method of taking into account ring-loss of marked individuals is proposed. This approach made it possible to keep many observations which otherwise would have to be discarded.

4. The estimated survival rates were higher and less variable than most estimates for the same species from other colonies. There was extensive resighting homogeneity. Ignoring this effect would have underestimated breeding life span by more than 50% in some species.

5. The analysis presented is the first study to document a correlation between the North Atlantic Oscillation (NAO) index and adult survival in North Atlantic seabirds. Other environmental variables considered were surface sea temperatures (SST) and prey stocks. In most species, models incorporating climatologically variables were considerably better supported than models with constant survival, time-dependent survival or prey effects. SSTs tended to explain more of the variability in seabird survival than did the NAO.

6. The importance of prey availability was evident in some of the species, but climate was generally a better predictor of survival. Nevertheless, the evidence suggests that meteorological parameters affect seabird mortality only indirectly, possibly through the food chain. This conclusion rest on the observations the most NAO effects are lagged and that survival rates decreased with increasing SSTs.

Key-words: adult mortality, Barents Sea, fish stock biomass, North Atlantic Oscillation, sea surface temperature.


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