Bioamplification of Mercury in Great Skua Catharacta skua Chicks: the Influence of Trophic Status as Determined by Stable Isotope Signatures of Blood and Feathers

Biomagnification of mercury was investigated via combined mercury and stable isotope analysis of the blood and feathers of great skua chicks from two colonies in the north-east Atlantic. There were significant positive correlations between δ15N signatures and mercury concentrations in the blood from chicks at both colonies suggesting that dietary specialization influences intra-specific variability in mercury burdens. The relationships were slightly weaker in feathers and therefore blood is probably a better monitoring unit. Adult blood was also assessed and in terms of biomonitoring may provide an index of mercury intake over the whole breeding season.