Heat stress in a high-latitude seabird: effects of temperature and food supply on bathing and nest attendance of great skuasCatharacta skua

Abstract

Birds such as great skuas Catharacta skua adapted for successful breeding at high latitudes may experience problems of heat dissipation in mild climates. Great skuas spend time bathing at freshwater sites close to breeding territories and here, we examine impacts of heat stress on bathing, foraging and nest attendance of adults during three breeding seasons with marked variation in the availability of prey (1-group sandeels Ammodytes marinus). Adults exhibited diurnal variation in bathing activity that matched heat-stress conditions. Moreover more birds bathed on days of higher average heat stress, suggesting that bathing plays a role in thermoregulation. Bathing numbers were lower in years of poor food availability, when adult attendance at territories was low, probably because lower attendance reduced the opportunity for parents to bathe without leaving chicks unattended. Chicks are normally guarded by female parents and fed by males but under conditions of low food availability territorial attendance of breeding pairs was particularly low on days of high heat stress, with chicks regularly left unattended at air temperatures exceeding 148C. Unattended chicks are at risk of being killed by neighbouring conspecifics and survival of chicks to fledging was low in the two years of low sandeel stocks. Our study indicates that for great skuas, indirect effects of climate change on prey stocks and direct effects on heat stress experienced by adults may be additive.

Seabirds and climate change: roadmap for the future

“…For example, sea level rise may inundate low-lying breeding colonies, but most low-lying breeding sites are located in the tropics where seabird−climate studies are comparatively rare. Physiological stress due to overheating on colonies is also possible (Gaston et al 2002, Oswald et al 2008), but has not been adequately addressed to date, with most authors focusing on water instead of air temperature (but see Lynch et al 2012, Smith & Gaston 2012, Watanuki & Ito 2012. Climate change-induced increases in wind fields could affect foraging success; in the case of procellarid seabirds which rely on wind for flight capacity, this change may improve foraging success with positive demographic consequences .…”

Recent impacts of anthropogenic climate change on a higher marine predator in western Britain

“…Gjerdrum et al 2003, Frederiksen et al 2006. Rising temperatures may also have direct physiological effects on both predatory fish (Perry et al 2005) and seabirds (Oswald et al 2008), in some cases exacerbating the impacts of changes in primary productivity (Hamer 2010, Oswald et al in press). Intense fishing pressure on predatory fish can also have cascading effects on marine food webs (Watermeyer et al 2008, Baum & Worm 2009) and the greatest threat to fish stocks is likely to be the combined effects of climate change and overfishing (Brander 2007).…”

Observed and predicted effects of climate change on species abundance in protected areas

“…The apparent sensitivity of seabirds to warming matches empirical observations which describe how recent increases in sea-surface temperature have reduced the abundance and condition of fish prey species for many seabirds 26 . As a result, the productivity of seabirds has declined in relation to warmer temperatures 27,28 and they may also be vulnerable to more direct negative effects of warming through heat stress 29 . Positive effects of winter temperature upon waterbird abundance may reflect improved survival 30,31 , whilst negative effects of temperature may operate through variation in prey populations 32 .…”