Ian Mitchell Joint Nature Conservation Committee
Long-term climate change is likely to impact significantly on seabird populations. The breeding behaviour of some seabird populations in the UK been linked to large-scale climatic fluctuations in the North Atlantic, such as the North Atlantic Oscillation (NAO) (Thompson and Ollason 2001; Frederiksen et al., 2004b). Projected consequences of global warming in UK waters, such as sea level rises and increased storminess are likely to have a direct impact on seabird populations. For instance, rising sea levels may reduce the amount of breeding habitat available for shoreline nesting species such as terns; winter storms can cause large-scale mortality or 'wrecks' of seabirds and summer storms can wash whole colonies from cliffs.
Rises in sea temperatures have already caused significant changes lower down the food chain that may be having a serious knock-on effect on seabirds. Around the mid 1980s, rises in sea surface temperatures (SST) led to a complete change in species composition and biomass of the plankton community in the North Sea (Beaugrand et al., 2003) and consequently, a reduction in the recruitment of sandeels (Arnott and Ruxton 2002) - a major source of food for breeding seabirds and their young. The size of sandeels caught by (and available to) Atlantic puffins over the Wee Bankie off south-east Scotland decreased significantly over the period 1973-2002 (Wanless et al., 2004). Furthermore, the energy content of sandeels and sprats that adult common guillemots fed to their young in 2004 on the Isle of May, south-east Scotland, was much lower than normal and resulted in lower growth rates of chicks and ultimately the worst breeding season on record for the colony (Wanless et al., 2004). At the same site, over-winter survival of adult black-legged kittiwakes during 1986-2002 was lower following warmer winters (i.e. high SST) and breeding success one year later was significantly reduced - this is thought to be linked to variable recruitment of sandeels (Frederiksen et al., 2004a). There have been recent breeding failures at UK colonies amongst those species that rely on sandeels - the poorest breeding seasons since annual monitoring began in 1986 occurred in Orkney, Shetland and the North Sea coast of Britain in 2004 (Mavor et al., 2005; JNCC undated) and in NW Scotland in 2005 (Mavor et al., 2006; JNCC undated). While no direct link has been shown between SST increases, low sandeel biomass and poor seabird breeding performance, the circumstantial evidence is compelling.
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Please acknowledge this document as: Mitchell, I. (2006). Impacts of Climate Change on Seabirds in Marine Climate Change Impacts Annual Report Card 2006 (Eds. Buckley, P.J, Dye, S.R. and Baxter, J.M), Online Summary Reports, MCCIP, Lowestoft, www.mccip.org.uk
