Climate change will add to the pressures facing Black-legged Kittiwakes Rissa tridactyla in the Norwegian Sea, with future extinction probabilities increasing with warming waters. Warm waters reduce recruitment of important prey sources like sand eels, with impacts of warming upon kittiwake populations already observed in the UK.
Climate change is having profound impacts on marine productivity and processes. Warming temperatures are reducing vertical mixing and nutrient upwellings, increasing ice melt, influencing phytoplankton growth rates and affecting water pH through reabsorption of atmospheric carbon (Hoegh-Guldberg and Bruno 2010). These changes are influencing sea bird distribution and population viability largely through changes in the distribution and abundance of prey (Grémillet and Thierry Boulinier 2009).
Rising sea surface temperatures partly explain observed declines of Black-legged Kittiwakes Rissa tridactyla, and is expected to influence the future extinction probabilities of colonies around the Norwegian coast. Population declines seem to be mediated by reduced survival of immature birds, with reduced recruitment with warmer sea surface temperatures (Sandvik et al. 2014).
To determine the impacts of future climate change on the extinction probabilities of these populations, population viability analysis incorporated several sea surface temperature (SST) scenarios. The median time to extinction is predicted to shorten when considering the effects of SST, and shorten even further when considering future ocean warming (Sandvik et al. 2014).
Studies in the North Sea demonstrate similar patterns already occurring, with the single and combined impact of climate change and fishery activity influencing observed population growth, and to a lesser degree, survival (Frederiksen et al. 2004). Kittiwakes rely heavily on juvenile sand eels as a food source in the breeding season. Warm winter sea surface temperatures are however associated with low sand eel recruitment (Arnott and Ruxton 2002), with likely knock on effects for the condition of birds in the following breeding season. Population models suggest the observed declines can be explained by both reduced survival and breeding success (Frederiksen et al. 2004), with climate change expected to exacerbate these declines, especially if fishery activity continues.
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