Regional and annual variation in black-legged kittiwake breeding productivity is related to sea surface temperature

Spatiotemporal variation in seabird demographic parameters is often pronounced and
may be an important source of information on the state of marine ecosystems. Black-legged kittiwakes
Rissa tridactyla in Britain and Ireland show strong regional structure in breeding productivity,
and both temporal and spatial variation are probably related to abundance of the principal prey of
breeding kittiwakes, the lesser sandeel Ammodytes marinus. Annual regional estimates of sandeel
abundance do not exist, prohibiting direct tests of this hypothesis. We examined relationships
between kittiwake breeding productivity and 2 potential proxies of sandeel abundance, winter sea
surface temperature (SST) and abundance of Calanus copepods, within and among 6 regions in
Britain and Ireland from 1986 to 2004. Means and trends in winter SST differed among regions, with
higher means and less pronounced increasing trends in western (Atlantic) regions than in eastern
(North Sea) regions. A negative relationship between breeding productivity and winter SST in the
previous year was found within 2 regions (East Scotland and Orkney), as well as in a cross-regional
analysis. Results were inconclusive for Calanus abundance, with a positive relationship in East Scotland
and negative in Orkney. These results demonstrate that although a single environmental driver
(SST) is related to both within- and between-region variation in a key demographic parameter,
regional heterogeneity in SST trends as well as the importance of other factors may lead to highly
variable responses. Understanding this heterogeneity is critical for predicting long-term effects of
climate change or other anthropogenic drivers on marine ecosystems.