Citation: Sandvik, H., K. E. Erikstad and B.-E. Sæther (2012) Climate affects seabird population dynamics both via reproduction and adult survival. Marine Ecology Progress Series, 454, 273–284.
doi: 10.3354/meps09558 [what’s a doi?].
Key words: Climatic responsiveness, population growth rate, recruitment, age at maturity, North Atlantic Oscillation, time lag.
Abstract: Climate variability can affect population dynamics via adult
survival or via offspring production and recruitment. The relative importance of both
processes is still an unresolved matter, especially in long-lived species, where the
time lags between the climate signal and the population response differ greatly
depending on the process involved. We address the issue using 378 time series from
29 seabird species from 187 breeding colonies throughout the North Atlantic.
The effect of climate on population growth rate is estimated as the slope of the
North Atlantic Oscillation (NAO) index at different time lags when used as a
covariate in population models. Using non-linear mixed effects models, we can
demonstrate that climate affects the population dynamics of seabirds, both through
adult survival and through the recruitment of offspring produced. The latter effect
is stronger, and the long time lags involved make it likely that its magnitude is
still underestimated. Because different processes are involved, the sign of the
relationship with the NAO differs between time lags. The relationship between the
NAO and the population growth rate is also highly variable, both within and across
species. In a second analytical step, we address the factors that may cause this
interspecific and inter-colony variation, considering the ecological, demographic
and geographical characteristics of the populations. Among comparatively ‘fast-lived’
seabirds, i.e. species with large clutches, the relationship with the NAO reverses
its sign depending on latitude, while no such trend is apparent among ‘slow’ species.
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